This dissertation has been microfilmed exactly as received 69-4925
LAL, Amrit, 1933- A BIOMETRICAL STUDY OF FERTILITY IN COLUMBIA AND TARGHEE SHEEP.
The Ohio State University, Ph,D., 1968 Agriculture, animal culture
University Microfilms, Inc., Ann Arbor, Michigan A BIOMETRICAL STUDY OF FERTILITY IN COLUMBIA AND TARGHEE SHEEP
DISSERTATION
Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University
By Amrit Lai, B.V.Sc., & A.H., M.Sc.
The Ohio State University 1968
Approved by
t i l d k I?. ^ Adviser Department of Animal Science ACKNOWLEDGEMENTS The author wishes to acknowledge with gratitude the advice, invaluable guidance, and inspirations given by his adviser, Dr. Walter R. Harvey, throughout the course of this study, especially during the course of analysing the data and preparation of dissertation. The writer is grateful to Dr. L.A. Swiger, and Dr. C.F. Parker, his reading committee members, for reading the manuscript and providing valuable suggestions to the departments of Animal and Dairy Sciences, The Ohio State University for providing the data analysed in this study and for providing research associateship during the period of his stay in United States. The author also wants to express his indebtedness to his parents in India, and Dr. Mohan Singh, Dean, Rajasthan College of Veterinary and Animal Sciences, Bikaner, India for their continued encouragements during the entire period of stay in USA. Last but not the least I acknowledge the tireless efforts, encouragements, and understanding of my wife, Jarav, during the course of my entire graduate program. The efforts made by my typist, Mrs. Francine Schaer, towards the preparation of this dissertation are highly appreciated. ii The free computation time provided by The Ohio State
University Computer Centre is highly appreciated. VITA
June 7 5 1933 Born - Khatu Chhoti, Rajasthan,' India 1958 B.V.Sc., & A.H., Rajasthan University Jaipur, India
1958-59 Veterinary Assistant Surgeon, Rajasthan, India
1959-6If Demonstrator, Rajasthan Veterinary College, Bikaner, India 1960-61 Post graduate training in Veterinary Parasitology, Madras Veterinary College, Madras, India 196*+ - continuing Lecturer in Sheep Husbandry. Rajasthan Veterinary College, Bikaner, India 1966 M.Sc. (An. Breed.), The Ohio State University, Columbus, Ohio 1966-67 Research Assistant, Department of Dairy Science, The Ohio State University, Columbus, Ohio 1967-68 Research Associate, Department of Dairy Science, The Ohio State University, Columbus, Ohio
FIELD OF STUDY
Major Animal Breeding
Minors i) Statistics ii) Physiology
PUBLICATIONS
1. A study of feeds and fodders of Rajasthan. C.S. Mathur and A.L. Chaudhry; Camel, i960. 2. Some observations on the Morphology and Pathogenicity of the Larva of Cephalopina titillator (Syn: Cephalopsis titillator, Clark 1816, Cephalomyia
iv maculata, Wiedemann, I83O) in Camels in Rajasthan India. K.R. Lodha and A.L. Chaudhry. Ceylon Vet. J, Vol. X No., k. 1962. 3 . Heterosis in Body Weights and Weight Gains up to Weaning age in Columbia-Targhee crosses (Abstr). A. Lai, W.R. Harvey, and C.F. Parker. J. Anim. Sci. 25:k. 1966. b. Heterosis in Wool Traits in Columbia and Targhee crosses. (Abstr). A. Lai, W. R. Harvey and C.F. Parker. J. Anim. Sci. 26:6. 1967*
v TABLE OF CONTENTS
ACKNOWLEDGMENT ii VITA iv LIST OF TABLES viii
INTRODUCTION 1 REVIEW OF LITERATURE 6
A. Definition and Components of Fertility. B. Reproduction as Affected by Environmental and Physiological Factors. C. Genetic Factors Affecting Reproduction. D. Parameter Estimates for Fertility Components. DATA 31
Recording of Data Flock Management
BIOMETRICAL PRINCIPLES AND STATISTICAL METHODS 38 A. Biometrical Principles 1. Repeatability 2. Heritability 3* Correlations B. Statistical Methods 1. Repeatability 2. Heritability 3. Correlations
RESULTS AND DISCUSSIONS 62
A. Least-Squares Means and Tests of Significance for Fixed Effects B. Repeatability Estimates 1. Fertility 2. Reproduction 3. Prolificacy k. Livability 5. Survival Rate
vi TABLE OF CONTENTS (Continued)
C. Heritability Estimates 1. Fertility 2. Reproduction 3. Prolificacy Livability 5. Survival Rate D. Correlations between Fertility Components and Production Traits.
SUMMARY
APPENDIXES
Appendix A Appendix B Appendix C Appendix D Appendix E
BIBLIOGRAPHY
vii LIST OF TABLES
Table Page 1. Repeatability Estimates of Various Fertility Traits as Published in the Literature. 28 2. Heritability Estimates of Various Components of Fertility as Published in the Literature. 29
3. Classification of Number of Records by Age of Ewe at Lambing and Breed Groups. 35 k. Classification of Ewes by Year of Record and Breed Groups. 35
5* Analysis of Variance Table Showing the Computations of Sums of Squares and Expected Mean Squares. 50 6. Pooled Analysis of Variance for Between and Within Ewes Showing Pooled Sums of Squares and Expected Mean Squares. 51
7- Analysis of Variance Table for Estimating Heritability. 56 8. Least-Squares Means and Standard Errors for Fertility, Reproduction, Prolificacy, Livability, and Survival Rate by Breed- Station Groups and Breeds. 6b
9- Least-Squares Analysis of Variance for Fertility, Reproduction, Prolificacy, Livability, and Survival Rate in Columbia. ' 66 10. Least-Squares Analysis of Variance for Fertility Reproduction, Prolificacy, Livability, and Survival Rate in Targhee. 66 11. Pooled Analysis of Variance for Fertility and Reproduction in Ohio Columbia. 69 12. Pooled Analysis of Variance for Fertility and Reproduction in North Dakota Columbia. 70 13. Pooled Analysis of Variance for Fertility and Reproduction in Ohio Targhee. , 71 lb. Pooled Analysis of Variance for Fertility and Reproduction in Illinois Targhee. 72 vm• • • LIST OF TABLES (Continued)
Table Page 15* Repeatability Estimates of Fertility, Reproduction, Prolificacy, Livability, • and Survival Rate by Breed-Station Groups and Breeds. 75 16. Pooled Analysis of Variance for Prolificacy, Livability, and Survival Rate in Ohio Columbia. 78
17* Pooled Analysis of Variance for Prolificacy, Livability, and Survival Rate in Worth Dakota Columbia. 79 18. Pooled Analysis of Variance for Prolificacy, Livability, and Survival Rate in Ohio Targhee. 80 19. Pooled Analysis of Variance for Prolificacy, Livability, and Survival Rate in Illinois Targhee. 81 20. Least-Squares Analysis of Variance and Heritability Estimates for Fertility and Reproduction in Ohio Columbia. 90
21. Least-Squares Analysis of Variance and Heritability Estimates for Fertility and Reproduction in North Dakota Columbia. 90
22. Least-Squares Analysis of Variance and Heritability Estimates for Fertility and Reproduction in Ohio Targhee. 91
23- Least-Squares Analysis of Variance and Heritability Estimates for Fertility and Reproduction in Illinois Targhee. 91
2b. Least-Squares Analysis of Variance and Heritability Estimates for Fertility and Reproduction in Columbia. 92
25. Least-Squares Analysis of Variance and Heritability Estimates for Fertility and Reproduction in Targhee. 92
26. Least-Squares Analysis of Variance and Heritability Estimates for Prolificacy, Livability, and Survival Rate in Ohio
Columbia. 98’ ix LIST OF TABLES. (Continued)
Table Page 27. Least-Squares Analysis of Variance and■ Heritability Estimates for Prolificacy, Livability, and Survival Rate in North Dakota Columbia. 98 28. Least-Squares Analysis of Variance and Heritability Estimates for Prolificacy, Livability, and Survival Rate in Ohio Targhee. 99 29. Least-Squares Analysis of Variance and Heritability Estimates for Prolificacy, Livability, and Survival Rate in Illinois Targhee. 99 30. Least-Squares Analysis of Variance and Heritability Estimates for Prolificacy, Livability, and Survival Rate in Columbia. 100 31. Least-Squares Analysis of Variance "and Heritability Estimates for Prolificacy, Livability, and Survival Rate in Targhee. 100 32. Heritability Estimates for Fertility, Reproduction, Prolificacy, Livability, and Survival Rate by Breed-Station Groups and Breeds. 105
33* Phenotypic Correlations Between Fertility Components and Production Traits in Columbia. 108 3^-. Phenotypic Correlations Between Fertility Components and Production Traits in Targhee. 109
x INTRODUCTION
In order to obtain maximum net return from a sheep enterprise, the fitness of sheep to a given environment is of major interest. Fitness^as expressed by the reproductive status of animals exposed to a specific environment is the single most important factor affecting
pounds of lamb and wool production (Terrill 1959)* Due to the large effect of fertility on production in sheep, this trait is of high economic value. Hence, the
possibilities of making any progress in fertility through artificial selection should be of paramount importance to sheep breeders. The level of reproduction rate in a flock is of interest for several reasons, e.g., to ensure replacements in breeding flock of fixed size, to provide surplus stock, either for sale or to increase flock size and to ensure as high a selection differential as possible, since a higher level of fertility means retention of a smaller proportion of the total animals available for selection. Permanent improvement in the performance of an animal population for economic traits is dependent upon the effective use of existing genetic variation. Realizing the multifactorial inheritence of the important_ productive traits, various investigators have applied statistical methods to study the hereditary-variation in these traits (Rae, 1956). These methods involve the estimation of heritability of various traits and of interrelationships which may exist between the traits. This information, in turn, is used to formulate an effective selection scheme and an efficient breeding program to change the genetic merit of the population at the fastest possible rate (Lush, 1935; Wright, 1939)* It is well recognized that reproductive performance has some hereditary basis but published literature strongly suggests that it is also highly influenced by factors other than heredity (Reeve and Robertson, 1953? Rae, 1956; Terrill, 1958; Desai and Winters, 1951; Young et al., 1963; Purser, 1965; and Kennedy, 1967). A review of the literature also indicates that there is extensive variability in fertility in sheep. A large proportion of this is due to the complex phenomena with which the nongenetic factors act on fertility. If the proportion of this variability could be estimated more accurately and if the relative importance of the various factors could be determined, progress due to selection for increased fertility in sheep could be estimated more accurately. For many years fertility in sheep has been considered as the proportion of ewes giving multiple births in a given flock, and as such, most of the .studies published give the various genetic and non-genetic parameter estimates for number of lambs born and number of lambs weaned per ewe mated (Reeve and Robertson, 1953;
Terrill, 1958; Rae, 1956; Young et al., 1963; etc.)* In a general sense, reproduction, as applied to the female is its ability to produce viable ova and to provide a suitable environment for fertilization and subsequent developement and finally to give birth to one or more fully developed foetus capable of separate existence. With this elaborate definition of reproduction, breeders may be interested in the parameter estimates for lambing rate of ewes, pre- and post-natal survival rate of lambs, and the overall weaning percent of lambs. Estimates of reproduction parameters in this sense are completely lacking in literature. Although there is general agreement among research workers regarding the low heritability of fertility, some studies have shown that heritability of fertility does change with the age of the ewe (Young .et al., 1963; Singh et al., 1967). This suggests that genetic improvement in flock fertility may be maximized by selecting ewes at an age when heritability is high. Research information on this aspect of sheep fertility is very limited and needs further investigation. The overall productive rate of a flock depends on the amount of quality lamb and wool produced per unit expenses incurred by the farmer. In order to increase the productive index of a flock, the formulation of an efficient selection scheme will require knowledge of the genetic and phenotypic correlations between fertility and production traits. Literature review indicates scanty and extremely variable information on this subject (Young _et al., 1.963; Purser, 1965; Kennedy,' 1967). With the above mentioned background of the problem at hand the objectives of the present study are-- 1. To estimate genetic and phenotypic parameters for the various'* components of reproductive performance in Columbia and Targhee sheep.' 2. To estimate genetic, phenotypic, and environmental correlations between measures of reproductive performance and various important production traits. The term reproductive performance, as applied in this study, will be subdivided into the following components- 1. Fertility - defined as the percent of ewes lambing of ewes bred. 2. Prolificacy - defined as the percent of lambs born of ewes lambing. 3- Livability - defined as the percent of lambs born alive of ewes lambing (Pre-natal livability). ^f. Survival Rate - defined as the percent of lambs weaned of lambs born alive (Post-natal livability). 5 5. Reproduction - defined as the percent of lambs weaned of ewes.bred.
The various production traits included in this study for correlation with reproduction performance are - A. Body Weights
1. Birth weight. 2. 30 day weight. 3 . 90 day weight. Gain in weight from birth to 30 days. 5". Gain in weight from birth to 90 days. 6. Gain in weight from 30 to 90 days.
B. Body Scores
7 . Condition. 8. Conformation. 9- Back conformation. 10. Feet and legs. 11. Pasterns. C . Wool measurements and Scores
12. Face cover. 13. Skin folds (wrinkles). 1^-. Wool uniformity. l^. Staple length. 16. Fibre diameter. REVIEW OF LITERATURE
Effective selection and an efficient breeding program require estimates of the amount of genetic variability and of measurable environmental factors affecting the characters concerned. For the breeder of livestock, there can be no more important economic problem than the reproductive performance of his animals. As defined earlier, reproductive performance as applied to the female is her ability to produce viable ova and to provide a suitable environment for the fertilization, s development of embryo, and giving birth to one or more offspring capable of becoming potential parents of the next generation. A large number of factors are involved in the problem of reproductive performance (Reeve and
Robertson, 1953, Rae, 1956; Terrill, 1958) and these are very closely inter-related. A review of literature reveals that many research workers have been attracted by this complicated problem of sheep fertility. Some excellent review papers (Reeve and Robertson, 1953? Rae, 1956; Terrill, 1958) give a good background of the research on fertility in sheep. For the purpose of this section, the published literature will be reviewed under the following titles-- A. Definition and components of reproduction. B. Reproduction as affected by environmental and physiological factors.
C. Genetic factors affecting reproduction. D. Parameter estimates for fertility components. A. Definition and Components of Reproduction Various measures of reproductive rate are used to estimate flock productivity in the literature, and care must be taken in comparing them, because not all measure the same thing and they cannot always be converted from one to another. Until recent years, fertility was considered as a single composite trait expressed in terms of percent multiple births in a flock. Reeve and Robertson
(1953) reviewed the literature published on factors affecting multiple births in sheep. In this review paper,- they considered fertility as the lambs born of ewes lambing, percent of live lambs born of' ewes lambing, and percent of live lambs born of ewes bred. Sidewell, J3t_al. (19^2) subdivided the term fertility into fertility, prolificacy, and lamb livability. They defined fertility as the number of ewes lambing of ewes bred , prolificacy as number of lambs born of ewes lambing, and livability as the number of lambs born alive of ewes JLambing and number of lambs weaned of lambs born alive. Purser (1965) regarded barrenness and litter size as the two components of ewe-productivity. Probably 8 the most extensive definition of productivity is given by Turner and Dolling (1965). They divided total ewe productivity into the following individual traits. 1. Number of ewes lambing per ewe mated. 2. Number of open ewes per ewe mated. 3- Number of lambs born per ewe mated. 4-. Number of lambs weaned per ewe mated. 5- Number of lambs born per ewe lambing. 6. Number of multiple births per ewe mated. 7- Number of multiple births per ewe lambing. Traits 3 and 5 above were also considered separately for each type of birth and sex.
In various other studies (Kennedy, 1967; Singh et al.. 1967; Desai and Winters, 1951a; 1951b; Rae, 1956) fertility in sheep was considered only as two components, i.e., the number of lambs born and weaned of ewes mated. Turner and Young (1968) defined reproduction rate in two ways depending on the purpose for which it is used. If production of lambs for sale is of primary consideration the number of lambs weaned per ewe mated is of utmost importance; whereas, if the replacement rate of the breeding flock is to be investigated, then the net reproductive rate is of utmost importance i.e., the number of ewes reaching breeding age by each ewe while she is in the breeding flock.
B. Reproduction As Affected By Environmental And Physiological Factors.
The extent to which prolificacy in sheep can be influenced depends upon the degree to which various environmental factors can be controlled in practice and also on the amount of genetic variation available for selection.
Reeve and Robertson (1953) in their review paper on factors affecting multiple births in sheep have summarized the literature published by 1953 for the effects of age of ewe, time of mating, flushing, and breed. The various environmental and physiological factors influencing
fertility of sheep can be discussed under the following headings - 1. Year The effects of yearly variation on reproduction are important. Over a period of time the change in ambient temperature and rainfall, and thus, availability of the quality and quantity of pastures for grazing by sheep are
some of the major sources of yearly effects. Karam (1957) reported highly significant effects of years on multiple births in Rehmani sheep. Sidewell, _et al. (1962) observed significant differences due to years on fertility, prolificacy, and lamb livability. Wiggins, _et_al. (195^) observed yearly variation in the percent of ewes lambing over a period of fifteen years. In this study the ewes lambing in different
years ranged from a low of 87.9% in 19^6 to 93-7% in 1950. The average percent of ewes- lambing over the entire period was 90.7%. Turner, et al. (1962) also observed a yearly trend in the twinning rate of 5-6 year old Merino ewes. They reported a twinning rate,of ^3% in 1952 and 56% in 1953* Vesely and Peters (1965) in a study of fertility, prolificacy, weaned lamb production, and lamb survival ability observed highly significant (P o.Ol) year effects on all four traits. Various other studies quoted by Rae
(1956), Terrill (1958), and Reeve and Robertson (1953) in their review papers suggest that yearly trends are important for the various components of sheep reproduction. 2. Age of ewe at breeding
It is generally agreed that age of ewe at the time of mating influences the fertility level of individuals and that as the ewe gets older the fecundity level increases up to certain limits. In the published literature, age effects have been studied on many components of reproductive performance by different workers on many breeds of sheep. Marshall and Potts (1921) . observed that the frequency of twins in pure-bred Southdown ewes increased with age of ewe up to 5 to 6 years of age. Terrill and Stoehr (1939) reported a similar trend in their study on Columbia, Corriedale, Rambouillet, and Targhee breeds. They reported 109% of lambs born of ewes lambing at 2 years of age and 150% of lambs born of ewes lambing at 9 years of age. The range in percent of live lambs born of ewes bred 11 was from 73% from 2 year old ewes to lbb% from 9 year old ewes. They believe that fertility of ewes -is likely to decrease after 6 years of age. Lopyrin (1938) concluded from work in Russia that ewes of late maturing breeds show the highest number of multiple births at 5 to 6 years of age; whereas, the ewes of early maturing breeds may reach their maximum at 3 years of age. Johansson and Hansson (19^3) in a study of the records of registered flocks in Sweden observed a steady rise in average number of lambs born per birth in all breeds up to 5 - 6 years of age with a gradual regression afterwards. Similar observations were made by Desai and
Winters (1951a)* They concluded that lambing percentage rises as the age increases up to the fifth year of age and then gradually declines at an average annual rate of 0.1*+ lambs, when the year effects were ignored. Karam (1957) found that the number of lambs per birth increased as the ewe grew older, reaching a peak at
5 to 7 years of age. Purser and Young (1959) observed that in the two hill flocks the mortality among lambs born decreased with the age of ewe. Mortality decreased to l*+.3% for lambs from b to 6 years old black face ewes and to 9-b% for lambs of 3 to b year old Welsh ewes. Further, they reported that ewes having their first lambs had a mortality rate twice as great as the mature ewes in the same flock. Campbell (1962) noted a twinning rate of 7.3$ in 2 year old Rambouillet ewes that rose to 27.b% in 5- year olds. The percent of dry ewes was 30.0$ at 2 years of age and varied between 19.8 and 38.1$ in 5 to 10 year old ewes and dropped to from 9-8 to 12.9$ from 3 to 7 years. In 8 to 10 year old ex^es the percent of dry ewes varied from 17A to 21A$. The number of lambs weaned per 100 ewes mated was 67*5$ for 2 year old ewes. It rose to from 97.0 to 105-3$ for 3 to 7 year olds and decreased thereafter to 86-5 and 95-2% for 8 to 10 year old ewes respectively. Losses of lambs from 2 to 9 year old ewes ranged from 9*9 to 16.7$ and rose to 23-8$ in the progeny of 10 year old ewes.
Numerous other studies (Dalton, 1962; Donald, 1962; Turner, et al., 1962; Coop and Hayman, 1962) were devoted to the study of age of ewe effects on fertility in sheep and similar trends were observed. Dalton estimated age effects on number of lambs born and weaned, and Turner, et al.,(1962) and Coop and Hayman (1962) estimated age trends on twinning rate. Gunn and Robinson (1963) reported that mortality rate in single born lambs from three year old ewes and older ewes was 12$ and 6$ respectively. Further, they observed considerably heavier mortality among lambs from two year old ewes. Purser and Young (196,+) reported a decline in mortality rate among both single and twin born lambs with increasing age of ewe. Joustra (196^) stated that with increasing age of ewe both percent of ewe lamhing and incidence of multiple births increased -in mutton Merinos, Precoce, and Suffolk ewes.
In a more recent report by Turner and Dolling (1965) estimates are given for various characteristics associated with reproductive rate at each age of ewe from 2 to 10 years. In general, reproductive rate rose with increasing age to a peak with a subsequent fall, the ten-year old reproductive rate, however, being in most cases above the two-year old ewes. The peak occured at 5 to 6 years for number of ewes lambing per ewe joined, at 6 years for survival rate of both single and twin lambs and for number of lambs weaned per ewe joined, at 7 years for number of lambs born per ewe joined, and at 7 to 8 years for number of multiple births per ewe joined. Various other studies reviewed also suggest an important age effect on the ewe Vs reproducing ability.
3- Breeding weight of ewe The breeding weight of ewe is believed to have significant effects on its fertility. As is the case with age of ewe, the breeding weight of ewe increases fertility up to a certain level and then fertility decreases. Terrill and Stoehr (19*+2 ) compared the number of lambs produced per 100 ewes lambing in ewes of different body weights in the Columbia, Corriedale, and Rambouillet breeds. In their study they found a general tendency for production to Ik increase with body weight. The number of lambs born per 100 ewes lambing rises with an increase in yearling body weight but the number of.lambs weaned per 100 lambs born does not increase with ewe weight, although the heavier ewes have an advantage in number of ewes lambing and the proportion of live lambs born. The authors concluded that the heavier ewes, which had more lambs, also had the additional milking and mothering abilities to carry the large number of lambs to weaning. The number of lambs born, or twinning ability, appeared'to be more than twice as important as the number of ewes lambing per year, while the loss of lambs at birth and from birth to weaning were least important in bringing about differences among the light and heavy groups of ewes in percentages of lambs weaned.
Johansson and Hansson (19^+3) in their study on Shropshire, Cheviot, and Oxford sheep found no clearly positive correlation between body weight and fertility. Differences in average litter size between the three breeds were very small, but within breeds they found a significant increase in litter size with an increase in body weight, holding age constant. Donald (1962), Coop (1962), Coop and Hayman (1962) and Quinlivan (1963) observed positive effects of body weight at mating on ewe fertility. Coop (1962) reported that lamb mortality (12.0$) in Corriedale flocks was independent of breeding liveweight of the ewe except at liveweight below 90 - 100 lbs., barrenness (6%) was relatively independent of liveweight above 90 - 100 lbs., but below this critical weight barrenness increased rapidly, and twinning increased approximately linearly with increasing breeding liveweight at a rate of the order of 6% per 10 lbs. Coop and Hayman (1962) reported that lamb drop or twinning is significantly and positively correlated with liveweight. The regression of percent twins on liveweight gave values equivalent to increases of 8.2% between groups and b.6% within groups of ewes for a 10% increase in liveweight from 100 to 110 lbs. Joustra (196l+) observed that at a given age heavier ewes tended to have more twins than lighter ewes. Yalcin and Bichard (1961+) reported a 2.7 to 5*1% increase in litter size per 10% increase in mating time body weight of ewes. Polasek (1965) observed that irrespective of age, the incidence of twinning increased from 2.17% for females weighing 30*35 kg.', to ^9 *25% for those weighing 56-50 kg. Various other studies reviewed also supported the general conclusion that fertility of ewe is positively affected by its breeding body weight. Too high or too low weights will tend to show a lower fertility with a nearly linear relationship between fertility and body weight in the middle of the range. 16 b. Nutritional levels
The practice of "Flushing" ewes by improvement of their nutrition for a short time just prior to breeding is often recommended as a method of increasing lamb crop. Marshall and Potts (1921) flushed Southdown ewes with grain and pasture and found that ewes which were flushed
dropped lb-7.kfo lambs per 100 ewes against 128.7^ lambs
per 100 unflushed ewes. Clerk (193*0 indicated an increased ovulation rate of mature ewes due to flushing for a period as short as approximately three weeks in one of two trials.
Miller, Hart, and Cole (191+2) also agree with the ..findings of Clark. In their study they concluded that flushing is beneficial to the ewes if they are thin.
McKenzie and Terrill (1937) and ElShiekh et al. (1935) have shown consistent increases In ovulation rate from higher levels of feeding over an extended period of time. The high level of feeding which was found by El-Shiekh
et al. (1935) to increase ovulation rate was shown, also to increase embroy mortality when measured at ^0 days of gestation. On the contrary, Briggs et. al. (19*+2) in their report did not mention any incidence suggesting
that flushing increases lamb crop. Bell and Parker (1965) specifically designed an experiment to study flushing'effects of pastures on ewe
fertility. They assigned 51 ewes in each of the three 17 groups exposed to three different environments. Conception rate was observed to be similar in all three environments. Lambing percentage was 168.2 on blue grass pasture, 187*7 on Ladino clover pasture, and 156-7 when fed alfalfa hay in a barn. For mature ewes the difference between results on Ladino clover and in the barn was only 3*3$? but for two year olds it was 35$ and for yearlings the difference was 28.8$. The authors concluded that fertility differences between the groups were due to flushing effects. 5- Type of birth Most of the work published in the literature on the effects of type of birth on ewe fertility pertains to the livability or mortality among single or multiple born lambs. Very little research information is published on the fecundity or reproductive performance of ewes born as single or multiples. Kiser and Christagu (19^0) reported that twin born ewes consistently give a higher percentage of lambs than single born ewes. Terrill and Stoehr (19^+2) did not observe any consistent difference in lamb production between ewes born as singles and as twins.
However, Desai and Winters (195la) did observe that the twin born ewes give birth, on the average, to 0.12 more lambs than single born ewes. They also reported more consistency in the higher performance of twin born ewes throughout their productive life. Karam (1957) also observed positive effects for type of birth of ewe on its lambing rate. Dun and Grewal (1963) in their study of fertility (total number of lambs mothered at the first two lambings) in Merinos reported a significant interaction between type of birth and flock. In a single born "weight minus" flock (selected for smaller weaning weight) ewes were more fertile whereas in the other four flocks the difference favored twin
born ewes. Excluding the flock selected negatively for weaning weight twin born ewes showed a highly significant advantage of 16.9$ in percent lambs mothered. This difference could be wholly accounted for by a higher incidence of multiple births.,
The effects of type of birth on total productivity and on lamb livability has been published by many authors. Winters et, al. (19^6 ) found that ewes with twins were about 3*+$ more productive than ewes with single lambs.
Campbell (1962) reported that ewes weaning twins reared
5^.3 lbs. of lamb per head more than those weaning singles. Post-natal mortality among twin born lambs was reported to
be higher as compared to single born lambs by Gunn and
Robinson (1963). Donald et al. (1963) observed that 96$ of the single born lambs survive to weaning as compared to 91$ of the lambs born as twins. Asker (196*+) also reported a higher mortality rate among twin born lambs (20.5$ as against 12.0$ for singles). Purser and Young (196*+) did observe a similar trend for mortality among single and twin born lambs, but they suggested that this could be mainly due to the lower average birth weight of twins. Further, they observed that at the same weight, mortality among twin and single born lambs was similar.
C. Genetic Factors Affecting Reproduction The extent to which reproductive performance depends on various genetic sources such as breed, sire, and ram effects is likely to be variable depending on several factors. According to the published literature, differences between breeds in reproductive performance are very pronounced but within breeds the genetic differences among individuals are believed to be small.
Reeve and Robertson (1953) reviewed the literature concerning the effects of genetic factors on twinning rate in sheep.
The greatest source of genetic variability between fertility levels of two flocks is the breed of flock. Reeve and Robertson (1953) summarized the prolificacy of a few sheep breeds. They reported that the Wilstermarsch, Suffolk, and Kerry Hill breeds were the most prolific breeds with 222$, 202$ and 202$ lambing rates, respectively; while the Merino and Rambouillet breeds were the least prolific with lambing rates of only 103$ and 110$ respectively. The most prolific breeds were reported to give births to 10.5$ singles, 59*7$ twins, 28.0$ 20 triplets, and 2.2% quadruplets. In comparison, the less prolific ewes had 97-3% singles and 2.7% twins born. Rendel (1956) used four breeds of sheep to estimate heritability and repeatability of multiple births. As expected, the estimates obtained varied to a great extent for the different breeds, suggesting differences in the genetic variability among breeds. Desai and Winters (195lt>) also reported similar results on nine lines of sheep.
Foote et. al. (1959a, 1959b), McKenzie and Terrill
(1937) and Clark (193*+) reported breed differences in ovulation rate. McKenzie and Terrill (1937) and Clark (193*0 observed a higher ovulation rate in the English breeds than in the fine wool breeds. Foote et al. (1959a,b) reported different ovulation rates, conception, and survival rates for the Hampshire and Columbia breeds. However, the breed effects on foetal developement were found important only during the later stages of gestation.
Wiggins et, al. (195*0 in a study on fertility in rams reported that Targhee rams had the highest fertility followed by Corriedale, Rambouillet, and Columbia rams. Since most of the published data were analyzed within breeds one does not find too many research reports on breed effects on fertility, but the differences between genetic parameter estimates for the various breeds, presented in tables 1 and 2 strongly suggest differences in the amount of 21 genetic variability existing among breeds for the various components of reproduction.
D. Parameter Estimates For Fertility Components Although, it is generally believed that there are important genetic differences in twinning ability between breeds, very few studies have been made to discover how much of the differences in twinning observed between different breeds reared under their normal conditions are really genetic, or what genetic variation exists within the same breed. All important studies conducted on the estimation of heritability and repeatability of fertility in sheep have been reviewed by Reeve and Robertson (1953), Rae (1956), and Terrill (1958). More recently, Young et al. (1963) reviewed the literature published on this subject since 1958. Estimates obtained for different components of ewe fertility are presented in tables 1 and 2. From tables 1 and 2 it will be noticed that both heritability and repeatibility estimates differ to a great extent. The wide variation among estimates is probably due to differences in the breed of sheep used, sampling errors, environmental conditions, and the method of estimation employed by the different authors. However, it is of interest to note that in the published literature, the heritability estimates 22 range from 0.0 to 0.35 and repeatibility from 0.0 to 0.30.
1. Repeatability
Most of the published data were analyzed either by analysis of variance methods or by daughter-darn relationship techniques. Smirnov (1935) reported that prolificacy in the Romanov sheep appeared to be an individual genetic character. Karam (1957) obtained an estimate of 0.056i O.O^-l for repeatability of number of lambs from the intra-class correlation for ewes with four lambings from 2 to 7 years of age. He also estimated a correlation between first and second lambings of 0.CAf6± 0.067* The correlation between average of first and second lambings with the average of third and fourth lambings was .215^ .086.' The higher repeatability of number of lambs born is expected when averages are used.
Johansson and Hansson (19*+3) estimated the intra- ewe correlation for litter size to be 0.183, the correlation of number of lambs born at two and three years of age was 0.16^, and the correlation of the
average number of lambs per birth at 2 - 3 and \ - 5 years of age was 0.256. This seems to be the first report suggesting that repeatability of fertility might be different at different ages of ewe. Similar 23 results were also found by Young et al. (1963) who obtained repeatability estimates of 0 .15- 0.06 and 0.10± 0.05- for lambs born and lambs weaned at 3 years of age. At both two and four years of age of ewe, the repeatability estimates were lower than at three years of age, but the estimates for two year old ewes were higher than those for four year old ewes for both the traits. They further reported that, pooled over all ages, repeatability of ewe performance for barren and single births is lower than repeatability for single and twin births, suggesting that genetic progress for increased flock productivity is more accurately predicted by selecting for multiple births as compared to selecting against barrenness. The possibility of differences in repeatability estimates from year-to-year was investigated by Inskeep et al. (1967). Various other estimates of repeatability of litter size are 0.073 in the Romney Marsh breed (Youssef, 1956)5 0.010 and 0.073 for two strains of the Texel breed in Holland (Sharafeldin, i960), and 0.079 in the Italian Langhe sheep (Mason and Dassat, 1955-). Felts et_ al. (1957) reported aneestimate of 0.25-3 for repeatability of litter size.
2. Heritability Various heritability estimates reported in the literature are presented in table 2. The low estimates reported by different workers support the general belief that the amount of additive genetic variance is very small as compared to the total phenotypic variance for fertility in sheep. With the exception of only one report (Rendel, 1956). all published data on fertility were analyzed assuming an underlying normal distribution. Rendel (1956) assumed that the number of lambs per litter is not normally distributed but approaches the binomial distribution. Correlation analyses applied to binomially distributed data may lead to serious biases in estimating repeatability and heritability. Several methods that may be applied to estimate heritability for binomially distributed data will be discussed in a later section.
Johansson and Hans son (19^3) obtained an average heritability estimate of 0.21*+ using daughter-darn regression on three lambings, and 0.196 using the paternal half-sib correlation based on two lambings. Estimation of heritability for multiple births by Karam (1957) was made with data that were uncorrected for non-genetic effects and hence, the value reported could be biased. Karam and Ragab (1958) using average number of lambs born per lambing reported an estimate of 0.26- 0.108 for the heritability of lambs born per lambing that was obtained by doubling the overall daughter-dam regression. However, this estimate was also based on data that were uncorrected for either flock or sire effects and could therefore be biased. Further, the estimates are not based on single records. To equate such estimates to a single record basis, information concerning the individuals lambing and the repeatability of litter size would need to be available. Such information was not given by these authors. The literature suggests that heritability estimates also change with the age of ewe .as seems to be the case for repeatability. Young et, al.(1963) reported higher heritability estimates for both number of lambs born and weaned at three years of age than at two years of age, suggesting that mass selection for number of lambs born at three years of age would be expected to lead to appreciably more genetic progress.
Research information in this area is very limited and needs further investigation. Vari-ous other estimates published in the literature fall in the range of 0.0 to 0.3
(Cockerham, 19*+9j Rae, and Ch'ang, 1955"5 Rietz and Roberts,
1915; Joseph, 1931j Turner et al., 1958; Kennedy, 1959)* 3• Correlations In order to formulate an effective selection scheme, a full investigation of the genetic and phenotypic relationships between reproductive efficiency and quality and quantity of lamb and wool production is needed as has been emphasized by several workers. The importance of such an investigation arises from the possibility that selection of extreme deviates for quality and quantity traits, as usually recommended in breeding programs, may result in a decline in fertility (Lerner, 195*0* Correlations between the.number of lambs born and other characteristics of sheep have been reported by several authors. Terrill (195-9), Fail and Dun (1956), Inkster (1956), Quinlivan (1963) and Mullancy (1966) reported both phenotypic and genetic correlations between number of lambs born and face cover scores in different breeds of sheep. All studies showed that higher face cover is associated with a decrease in the number of lambs * born and also that face covering seems to reduce the porportion of twins born rather than the number of ewes lambing. Kennedy (1959) reported a low positive phenotypic correlation between face cover and fertility in the same flock as that studied by Fail and Dun (1956), with data from different years, but this result could be biased because of the method of estimation employed. Positive phenotypic correlations between body weight and fertility were reported by Terrill and Stoehr (195-2),
Young et, al. (1963), Quinlivan (1963), and Purser (1965). Negative phenotypic correlations between fertility and wrinkle scores (skin folds) were reported by Kennedy (1959) Dun (1961), Young et al. (1963) and Fels (196*+), between number of lambs weaned and staple length by Campbell (1962) between number of lambs born or weaned and greasy fleese 27 weight and between number of lambs born and clean-wool weight by Kennedy (1967).
Some authors have also published estimate of genetic correlations between fertility and important lamb and wool traits. Roberts (1957) and Kennedy (1959) reported negative genetic correlations between fertility and clean wool weight. These results were probably biased because of the method of estimation as they estimated correlations by intra-sire daughter-darn correlation analysis, which obviously would not include ewes which did not lamb or produce a male lamb. This type of analysis also introduces bias due to maternal effects. However, Young ,e_t al. (1963) did not observe any genetic correlation between fertility and greasy or clean fleese weight. Kennedy (1957) reported large negative genetic correlations between lambs born and weaned with clean and greasy fleese weight.
Young et al. (1963)5 in an extensive study, reported that fertility was' positively correlated genetically with body weight and staple length and negatively correlated with fibre diameter and wrinkle score. The limited research information available concerning the correlations between reproductive performance and production traits emphasizes the need for further investigation in this area. TABLE 1 REPEATABILITY ESTIMATES OF VARIOUS FERTILITY TRAITS AS PUBLISHED IN THE LITERATURE
No. of Traits Breed Animal s Estimate Method Reference No. of Lambs ^12 d.f. Sire .07±.03 Half-sib Anova . Kennedy(1967) born Merino 785 d.f. Error .18 Regression .ob± .03 No. of Lambs Half-sib Anova weaned Regression Litter size Black face • 19 Intra-ewe Parser (1965) at birth Welsh .2b correlation Barrenness Black face .09 Welsh .08 Lambs born/ Black face .07 mating Welsh .10 No. of Lambs 0.11 Regression Inskeep et al born Hampshire year to year 0.13 (1967) No. of Lambs weaned Lambs born Crossbred 154- d.f. sheep 0.12t.0^ Analysis of Yalein and bjl d.f. error 0 . 10+. 0^ variation Bichard (196^) Lambs weaned No. of Lambs .05-*02 Anova Young et al born Merino .10±.02 Regression (1963) No. of Lambs .08t.03 Anova weaned .08t.02 Regression No. of Lambs Rahmani 279 .06± .04- Intra-ewe Karam (1997) rv> correlation 00 born/birth for ewes. TABLE 2 HERITABILITY ESTIMATES OF VARIOUS COMPONENTS OF FERTILITY AS PUBLISHED IN THE LITERATURE Trait Breed No. of Estimates Method Reference Animals Incidence of Oxford 156 0.17 Daughter-Dam Johansson and Multiple Births Hampshire 4-55 0.26 Regression Hans son (19*13) Cheviot 659 0.0k Multiple Births Ossami 0.04- Ragab and Askar (195*0 Lambing 9 Lines 639 .07±.02 Daughter-Dam Desai and Winters Averages Regression (1951b) Multiple Births Cheviot 12,023 0.22 Paternal Half- Rendel(1956) Hampshire 10,957 0.04- sib ANOVA. Landrace *+,14-8 0.09 Oxford Down 3,861 0.08 Twinning Navajo 4-26 0.12 Daughter-Dam Sidwell(1956) Rates Crossbreed 1,836 0.22 Correlation Navajo Multiple Births Rehmani 279 .08 Daughter-Dam Karam(1957) . Regression Lambs Born/ Texel 3 *+3 pairs 0.22-0.11 Daughter-Dam Karam and Lambing 175 pairs 0.54-±o.l4- Regression Ragab (1958) 0.2910.33 Intra-sire- Dam Regression Half-sib corre- . lation Lambs Born Merino 86 d.f. sires 0 .19*0.10 Half-sib Young et al., Lambs Weaned 528 d.f. Error 0 .0910.09 ANOVA (1963) VO TABLE 2 (Continued)
Trait Breed No. of Estimates Method Reference Animals Litter Size at (l)Blackface 34-2 (1) (2) Half-sib ANOVA Purser (1965) Birth (2) Welsh 156 0.14- 0.16 Barrenness Mountain -0.03 0.03 No.of Lambs Born/ -0.01 0.07 Mating No. of Lambs Born Merino 616 d.f. 0.20-0.10 Half-sib ANOVA Kennedy (1967) No. of Lambs Merino 574- d.f. 0.06-0.08 Weaned Lamb Production 5 Lines of 730 0.19±0.07 Daughter-Darn Singh and Minnesota Regression Rampel (1967)
Lo O DATA
The data analysed in this study were made available by the Department of Animal Science, Ohio Agriculture Research and Development Center, Wooster. The data were collected in a routine procedure on Columbia and Targhee sheep maintained under NC-5 0 > a long range sheep breeding experiment conducted cooperatively by North Dakota, Illinois, and Ohio entitled, "Improvement of Lamb Meat Production Through Breeding." The data used for this study covered a period of six years lambing records from 1962 to 1967? inclusive. Design of Experiment The Columbia, Targhee, and Suffolk breeds, represent ing the basic types of sheep in popular use, were included in this experiment. Each of the three stations maintain two breeds Columbia was maintained at Ohio and North Dakota, Targhee at Ohio and Illinois, and Suffolk at North Dakota and Illinois. Bell et al., (1962, 1965) have discussed the various phases of this experiment which was designed to obtain data on breed, strain, and sire differences under two different environments. For the two breeds (Columbia and Targhee) included in this study, a sampling of each breed was accomplished through selecting a sire from the flock of each of eight
31 principal breeders of each breed in the state. The rams were all unrelated. Each ram was then bred to about 18 ewes each year for two and possibly for three lambings. Thus, the total progeny within each breed represent a total of 16 sire groups. In order to obtain genetic equality, a random one-half of the ewe lambs and four ram lambs in each sire group were exchanged after weaning between the two stations involved. This exchange of lambs started in i960 and continued until 1962 and at the end of this program Wooster had two groups in each breed, i.e., the Ohio and North Dakota Columbia and the Ohio and Illinois Targhees. Random breeding within each breed-station group, the second phase of this experiment, was started in September 1961. A ram of each founding sire line (six rams or lines per breed-station group) was used on eight ewes of pure breeding. According to the original plan, ewes were retained in the breeding flocks for at least two breeding seasons and rams were used for only one season and then replaced. However, all the ewes included in this’ study did not contribute at least two records. A small proportion of the ewes which were mated to a ram of their own breed-station group only once during their ■ entire production years contributed only one record. Secondly, the last record year included in this study is 1967, and ewe lambs born in 1965 and used as replacement 33 breeding stock made their first lambing records in 1967? thus contributing only one record. The number of lambing records used in this study are presented for the age x breed-station group subclasses in table 3- The number of records available on ewes in the different years by the various breed station groups is presented in table *f.
Recording of Data The data were recorded from the flock record books from 1962 through 1967, and all recorded data were put on punch cards for the purpose of analyses. A card was punched for each ewe mated to a ram. The following information was recorded-
1. Year of record 2. Station of origin
3- Breed k. Ewe number
5. Ram number 6 . Type of birth and rearing of ewe
7. Age of the ewe at lambing 8. Birth weight of the ewe (nearest 1/10 pound)
9. 30 day weight of the ewe (nearest 1/10 pound 10. 90 day weight of the ewe ( " 1! 11
11. Conformation score of the ewe (3 judge total n 12. Back conformation (" it 11 11 13- Feet and legs (" 11 11 lb. Pasterns (" 15* Wrinkles 3 judge total 16. Face covering 11
17- Condition score 11 18. Grade of wool 11
19. Wool uniformity score (" " " ) 20. Staple length (" " " )
21. Wo. of lambs born of ewes lambing
22. Wo. of lambs weaned per ewe mated
23. No. of lambs born alive per ewe lambing 2h. Wo. of lambs weaned of lambs born alive 25. No. of ewes lambing of ewes bred 26. Breeding weight of the ewe 27. The three gains (birth to 30 days, birth to 90 days, and 30 days to 90 days) were obtained by subtractions and recorded to the nearest 1/10 of a pound.
All birth weights and 30-day weights of the ewes were obtained at the specified time. The 90-day weights were taken on 90 t 3 days and were adjusted to 90 days. All the weight gains for the respective periods were calculated on computers. Staple length was measured to the nearest one-tenth of a centemeter at weaning. Scoring and grading of the ewe lambs for all the above mentioned subjective body traits was done independently by a committee of three judges at weaning age (90 days) under a 15 point scoring system. For condition, conformation, back conformation, feet and legs and pasterns, the scores ranged 35 TABLE 3 CLASSIFICATION OF NUMBER OF RECORDS. BY AGE OF EWE AT LAMBING AND BREED GROUP. Age of Ewe Breed Group* Total (Years) OC NDC OT IT
2 108 109 127 132 k76 •
3 73 73 83 80 309
b b7. • bb 52 38 181 5 3b 2b b 6 68
6 5 b — — 9 *0C = Ohio Columbia OT = Ohio Targhee NDC = North Dakota Columbia IT = Illinois Targhee
TABLE b CLASSIFICATION OF EWES BY YEAR OF RECORD AND BREED GROUP. .Breed Group* Year OC NDC OT' IT Totals 1962 35 26 31 20 112 1963 b7 >+8 bb 1+h 187 196*+ b8 be b7 bb 189
1965 b7 b7 bQ b7 189 1966 b3 bl b$ *+8 177 1967 b7 b6 b7 ^9 189 *00 = Ohio Columbia OT = Ohio Targhee NDC = North Dakota Columbia IT = Illinois Targhee from one through fifteen, indicating the desirable or undesirable condition of the ewe lambs, low points indicating more desirability for a particular trait. For wool uniformity low points indicate less variability. Similarly for wrinkles, low points indicate smooth body and for face covering, the extent of wool on the head is indirectly proportional to the points scored.'
Flock management The breeding season throughout the course of this study began on September 1, and covered three 17-day cycling periods up to October 22, a total of 51 days. Fertility of each ram was based on an estimate from electro-ejaculated semen obtained in late August and scored for color, sperm concentration, percent motility, rate of mobility, and morphology. Each ram was mated to 8 ewes of his own breed-station group. Rams were used only once and each year a new set of rams was replaced in the breeding flocks. All ewes were fed the same during pregnancy, the 10 day post-natal period, and the nursing period. Ewe management was exactly the same for all breed-station groups. Pregnant ewes were separated by breed and run as a single band until they lambed. Immediately upon lambing the ewe and her lambs were placed in the nursery pen. At 10 days the lambs and ewe were transferred to the rearing pen. At 90 days the lambs were weaned, the ewe going to the dry band and the lambs were placed in the weaned lamb pen (ram lambs and ewe lambs separately). The lambs were not consciously subjected to any form of selection except those which were physically unsound or black colored. Ewes were not culled because of failure to reproduce. To reduce yearly and station nutritional differences, a standard pellet ration was fed to all lambs. The pellets were prepared according to a standard formula and were supplied to each of the three stations by a single manufacturer. (Bell et al., 1961). BIOMETRICAL PRINCIPLES AND STATISTICAL METHODS
The biometrical methods employed for the study of animal and plant populations are relatively new. Although, the basic definition of repeatability, heritability, and correlations in animal populations are well known, a brief summarization of the fundamental concepts would be in order to understand the results obtained by using a specific technique of analysis.
A. Biometrical Principles 1. Repeatability To illustrate the basic idea of repeatability consider a population of organisms. The phenotype of any individual will be determined by its genetic make up, the type of environment provided, and possibly, a joint effect of heredity and environment (genotype x environment interaction). In the case of traits which are expressed more than once, the environmental component can be divided into two portions, the effect which is constant for all expressions of the trait (permanent), and the effect which is variable from one expression to another (temporary). To express this biological phenomenon in mathematical form, let Y represent the phenotypic expression of a particular trait. For example in case of lambs born of ewes lambing, Y would be the number of lambs born in one lambing. Now if y symbolizes the phenotypic deviation of an individual from the population mean (Y), i.e., y = (Y-Y) can be expressed as a linear function of the contributing 38 39 effects such that
U j k = F + hi + pi + tj + HE^ + e.Jk where, is the kfth expression by the i£h individual exposed to the j£2l environment.
p is the overall population mean common to all the individuals in that population. hj_ is an effect of the i£il hereditary makeup or genotype. Pj_ is the effect of the permanent environment effect specific to each individual. This constitutes any environmental effects constant for all the records made by the individual in that population. t^ is an effect attributable to the j-iil temporary J environment. This is common to all the individuals reared or bred in a specific management or environmental conditions.
HEji may be considered as the sum of all the interactions among the particular combinations of genotype, permanent environment, and temporary environment.
eiik as the random error term associated with ijkiil expression of the trait and is assumed to be normally distributed with mean zero and variance 6|. This may be considered as physical source of variation other than the temporary environmental' effects. Now this definition model can be easily expressed in terms of the deviation, y, from the population mean, which is the working model
yijk - ^ ij k - Z1) - + Pj_ + t^ + HE^j + Thus, from this model it can be seen that the deviation of the i— individual from the population mean is a function of its genetic composition, the permanent and >+0
temporary environmental effects, the genetic x environmental interaction component, and the random error. Assuming that the occurrence of genotypes among the various environments is at random, the phenotypic variance, 6y, may he partitioned as
s 2 _ / 2 . , /I . z-2 . / r ‘2. , /"2 6y - 6h + 6p + 6t +he 6 + 6e
With the usual assumption of non-existant of HE
2 2 effects, and for the purpose of convenience let 60 and 6jjE he included in 6^ and designate it 6^,. Thus 6^, includes 6g,2 2 and 6^.2 such that
/-2 _ /;2 . ^2 . /r2 °y ~ h p °e' p In the above equation 6e#, includes all the observed variance other than the portion attributable to constant differences (due to hereditary and environment) between individual organisms. Assuming that each individual has a specific genotype (h) and a permanent environmental effect (p), both h and p can be considered as a joint individual effect, s (sheep effect), so that
6y = 6! + 6§, and Repeatability (R) then, can be expressed as
Repeatability, therefore, is the fraction of the
phenotypic variance that is attributable to constant
differences between individuals. kl
2. Heritability
Once again if the equation is considered where the total phenotypic variance for a trait has been shown as the sum of the variance due to heredity, permanent environment, and the joint effect of temporary environment, and the heredity x environment interaction and random p error term (6|») as 6§ = + 6§ + 6 | The first element (h) in the above model, which is the genotypic effect contributing to the phenotypic expression of a trait, can be further broken down into several components. Let G be the additive genetic effects of each gene summed over all the pairs of genes contributing to the expression of the trait. Let D be the dominance deviation, i.e., D is the sum of the deviations from the
P additive effects for each pair of genes because of dominance effects. Let I be the deviation (h-G-D) because of interactions of non-allelic gene pairs, then the total heriditary component (h) can be expressed as
H = G + D + I 2 and the heriditary variance, 6^, can be partitioned as *2 _ ^2 , *2 . /I 6h " 6G + 6D + 6I p where 6^ is the total heriditary (genotypic) variance and
6§, 6§ and 6j are the variances due to additive genetic effects, dominance deviations, and epistatic effects, respectively (Wright, 1935)* k2 Lush (19^0) partitioned the total phenotypic variance (6y) into several components. The relationship between 6^ and the variances due to genetic and environmental causes may be written as
6y = 6G + 6D + 6I + 6HE + 6E
As before, the deviations due to total environmental effects may be further divided into deviations due to temporary and permanent environments and then
6| = 6G + 6D + 6I + 6HE + (6t + 6P
Lush (191+5) defined heritability as a quantitative measurement of the relative influence of heredity on the observed variation in a trait in a specified population in a particular environment, and in algebric form
v,2 _ 6§ + 6§ + 61 + 6§e i f —
is heritability in the broad sense, and
g2 = ^
6y ■ is defined as heritability in the narrow sense. Permanent improvement from phenotypic selection is proportional to the genic fraction of the observed variance and varies from trait-to-trait (Lush, 1935)- Thus, heritability is important to the breeder as it represents the proportion of gain in selected parents which is passed
on to their offspring. To appreciate the relationships between heritability (both in the broad sense and in the narrow sense) and repeatability consider the equation
6y = 6G + 6D + 6I + 6HE + (6t 6P + where 6 2 represents the permanent environmental effects and Jr p represents the temporary environmental effects. OOO Further, it was also shown above that 6y = 6g + 6^\ , and thus <5§» can be written as aye' = 6^. - , and as defined earlier, <5^, includes <5|jg5 and Thus, the individual sheep variance (<5g) can be written as <5^ = <5q + + 6^ + c5^.
Now with the above breakdown of the various components of variance and the broad definition of heritability
2 and assuming d-nxr to be non-existant ,2 Since 6 is greater than or equal to zero (non- P negative) repeatability (R) cannot be expected to be less than heritability in the broad sense (h^), and hence, repeatability is the upper limit of heritability. The ratio R/h^ is
H/h2 = £ l . 4 = 4 + 4 + 4 * 4
61 {6\ - 6P 6l + 6l + 4
6vM — '— ■ + 1 4 + 4 + 4 2 (assuming is non-existant)
2 4 and R/g2 = -| • 4 4
4 + 4 + 4 + 4
4
4 + 4 + 4
■ =1 + — ? — 6g n (assuming that tfjjg is non-existant) Thus, the extent to which repeatability is greater than heritability in the broad and narrow sense depends on the estimates obtained for the various components above. ^5
3• Correlations
Correlations between two traits in one individual and correlation between two individuals for one trait are the two types of correlations commonly used in animal breeding. Like the phenotypic variance of a single, trait, the phenotypic correlation between any two traits includes both genetic and environmental components. The genetic correlation could arise from the linkage of genes affecting the traits under consideration, or from pleiotropic effects, i.e., the individual pairs of genes affect more than one trait. The contribution to a genetic correlation from linkage would decrease in every generation of random mating and the rate of decrease depends upon the crossing over distance. Thus,except for very close linkage, the contribution from this source is very insignificant in most animal populations. Pleiotropy, on the other hand, is the most important contributor to genetic correlations (Falconer, 1961; Turner and Young, 1968). The environmental correlation results from a common developmental environment shared by the two traits. This component has no effect on the association between the characters in the next generation.
Hazel (19^3) defined the genetic correlation between traits 1 and 2 as -
rG G - cov(GlG2) 1 2 “ CTg ^ cT ^ where: kS cov(G]_G2 ) additive genetic covariance of traits one and two.
<5q -^ and are the additive genetic standard deviations for traits one and two.
The phenotypic correlation between traits one and two, by definition, is
where the covariance and standard deviations are on a phenotypic basis. Now, assuming that the genetic and environmental covariances of traits 1 and 2 are independent, i.e.,
c o v (G]_E2) - c o v (G2E-[_) = 0 then the phenotypic covariance can be partitioned as
cov (P1P2 ) = cov (G1G2 ) + cov (E1E 2 ). From this expression the phenotypic correlation rp p can be rewritten as 1 2
_ cov(^1^2 ) + cov(ElE 2 ) (6?1 . tfp2)
c o v (G]_G2) - rG]_G2Ei^2 + rElE2 ^ “§ 2 ^ This can be seen more readily in the path diagram below • • where rPlp2 - g ^ ^ ^ + ^ rg^ e2 and e1 = [(l-g^|2, and e2 = 2 Searle (1961) examined the relative size of the two correlations under different conditions. He showed that for rp p to be greater than Tq q must also be greater than rQ^Qg- Further, it was shown that the ratio rg 1 “ ^1§2^ x x is greater than ------ B. Estimation Procedures■ Various methods of estimating repeatability, heritability, and correlations from animal data are used in present day animal breeding research (Falconer, 1961). In almost all these methods it is assumed that the trait . k8 or traits under consideration follow an underlying continuous distribution. With this assumption the usual analysis of variance-covariance or regression techniques are employed to obtain the appropriate estimates and their' standard errors. Some attempts have been made to estimate heritability from data which follow more discrete patterns e.g., digits in mice (Wright, 193^)5 resistance to disease in poultry (Lush, 19^8; Robertson and Lerner, 19^9), and others. The most important problem usually encountered in studying animal breeding data is one of missing or unequal subclass frequencies. In such cases the conventional analysis of variance method yields biased estimates due to confounding of the main effects. The least-squares method of fitting constants provides a computational procedure for obtaining unbiased estimates from non-orthogonal data. Least- squares techniques discussed by Harvey (I960, 196*+) were used to analyze the data reported in this study. All analyses were performed by using LSMLGP written in the FORTRAN IV language (Harvey, 1968). 1. Repeatability Two methods of estimating repeatability of all five traits included in this study, were used. The first set a of estimates and their standard errors were obtained by using analysis of variance technique. Let a single observation be represented by the following model. ^9 Yijkmn = V + ai + tj + r ^ + dm + M X i;]kmn~ x) + ei;jkinn where Yijkmn = n"^ record on the m^h ewe of the i— age mated to the k^n ram in the jth year. )i = the overall population mean with equal subclass frequencies. a^ = the i-i& age of ewe effect. -[-■u tj = the year of record effect. = the effect of the kill ram mated to the m-^ ewe in the ji&L year. th dm = the effect due to the m— ewe. b(xijkmn“ x) = regression of the y values on the breeding weight of ewes holding all other variables constant. eijkmn = ^he random error component associated with each observation and is assumed to be distributed normally with mean zero and variance £|. In this model all interactions are assumed to be non-existent. Since the age of ewe and year effects were partially confounded in the present set of data fitting constants for both the year and age effects was not practicable. To eliminate this practical limitation the model was further reduced to a simpler one by completely confounding the age of ewe and year of record effects which also reduced the number of equations to be solved simultaneously. This was achieved by sorting the ewes on their birth-year basis and performing the analyses separately by each birth-year subgroups. In other words, all ewes born In a given year were of the same age in any subsequent year even though they varied in the number of 50 records. Thus, by doing the analyses so tiara tely for each of these birth-year groups confounding of the a-, effects with t_j from the above model was achieved. Thus, the model used for preliminary analyses was as follows yijlon = /■’ + a + rij + U + bU'ijkm-x) -i- e13ta„ With this model the test of significance for year effects will be slightly inflated but this would not effect the estimates of variance components for ewes and error. In the preliminary analyses the effects due to rams within year and the quadratic regression of the five traits studied on ewes breeding weight were found to be statistically insignificant and hence, were dropped from the model for the final analyses. The model used to complete the final analyses between and within ewes v/as as follows: n jk =fi + U + The analysis of variance table for this model is given in table 5 » TABLE 5 ANALYSIS OF VARIANCE TABLE SHOWING THE COMPUTATIONS OF SUM OF SQUARES AND EXPECTED MEAN SQUARES Source df Sum of Squares E(MS) Years (t-1 ) R(ji,t,d,b) - R(yt,d,b) Ewes (d-1 ) R(}i,t,d,b) - R(yijt,b) e a Regression 1 Remainder (n.. -t-d) f f a 2U Y r* 0 M constant «<2 51 Since each breed-station group of ewes was divided into six birth year groups, the pooled sums of squares between and within ewes was obtained as shown in table 6. TABLE 6 POOLED ANALYSIS OF VARIANCE FOR BETWEEN AND WITHIN EWES SHOWING POOLED SUM OF SQUARES AND EXPECTED MEAN SQUARES Source df. Sum of Sauares E(MS) 6 6 2 2 Between Ewes + k'tfd f=i(di-1) f=i(ssd)i ^e 6 6 2 Within ewes 2- 6,- (SSe)^ 6 i=l x i=l 6 e for the ilk birth year group. eq is the degrees of freedom for remainder in the i M group. (SS^)j_ and (SSe)j_ are the sum of squares for between ewes and remainder, respectively, in the iik group. The value of k 1 for the pooled analysis of variance can be obtained as 6 ki(di-l) kt ' -= i=l x x 6 51 (di-1) i=l 1 and the estimate of repeatability was obtained as R = a where I - MS(Between)" MS(Within) d k . The standard error of repeatability was estimated by using the approximate formula given by Swiger et al., (196k) to estimate the variance of an intraclass correlation (7-j-). The formula is written as vt = 2(N-1) (1-t)2 £l + (k-l)tl 2 k2 (N-s) (s-1 ) where N = total number of observations. s =• number of groups (sheep in this case), k =' cofficient for the between ewe component, t = estimated repeatability value. . The second method of estimating repeatability of the various ewe productive traits was the regression method as suggested by Lush (1956) and used by Young _et al., (1963) and others. Lush (1956) pointed out that for the case of number of lambs born per ewe exposed, the regression of the average number of lambs born at future lambing on the number born at the first, or any other lambing is a direct estimate of repeatability. To see that this is true - Let y = mean number of lambs born at future lambing, x = mean number of lambs born at first or any other lambing The regression of y on x is \ r/v = cov(y x) y/x V(x) Expanding the numerator and denominator in the above equation cov(y x) = E [x(yi + 72 + -- + Yn)/n] where y]_, Y^j-'-Yn are observations on n ewes which enter in both y and x. 53 Taking the expected values of both the numerator and denominator separately jcov (y x)j where 62^ = variance between ewes and 62 = total phenotypic variance «y Substituting the expected values of cov(y x) and V(x) in the regression equation above | cov(y xjj L v(x) J which is the direct estimate of repeatability. 2 . Heritability- Yarious methods of estimating heritability of quantitative characters in farm animals have been discussed by Lush (19^+9) * In almost all these methods a continuous distribution is assumed. Some observations e.g., number of ewes lambing or number of lambs born etc. are discrete in nature. It is likely, however, that all these characters are polygenic in nature, and hence, for each of these it can be assumed that there is a background normally distributed variable, with a combination of genetic and environmental effects, equivalent to the distribution of • 5*t the phenotypes of a continuous variable (Turner and Young, 1968). ' . . The discrete observations result from a number of thresholds which divide the distribution into sections, and the phenotypic expression can only be changed when a threshold is passed. Hence, discrete variables may be considered as a special type of continous variable...with coarse classification. With this assumption, two methods of estimating heritabilities were employed. In the first method analysis of paternal half-sibs was employed to estimate the sire component of variance and intra-class correlations. Paternal half-sib analyses were preferred over the daughter-darn correlation or regression analyses, because in the later cases ewes which failed to lamb or which gave birth to male lambs would automatically be excluded and such a severe selection of ewes would preculde the other two methods. Preliminary analyses for each of the four breed-station groups (Ohio Columbia, North Dakota Columbia, Ohio Targhee, and Illinois Targhee) were run separately using complete least-squares procedures (Harvey, i960, 196^). The following model was considered appropriate to describe the underlying biology of each observation. Yj jkmn = + ai + + sk + rjm + ^ l ^ i jkmn“x ^ + _ 2 kp^ijkmn''*) + eijkmn 55 where: Y-i jkmn - the mMt ewe horn from the kill sire mated to the mth ram in the jth year when she was ith years old. ji = over all population mean common to all the observations. a^ = effects due to the i£k age of ewe at breeding time. tj = effects due to the jth year on lambing records' of the ewes. s^ = effects due to the k— sire of the ewes. fV, r = effects due to the m— ram mated to the ewes in the jSl year. — . O b-| (X.| and b2 (Xj jkmn-x) are the linear and quadratic regressions of the performance records of ewes on breeding weights of ewes for fertility. eiikmn ~ ^ndom error term assumed to be distributed normally with mean zero and variance In the preliminary analyses the effects due to rams mated to ewes within years and the quadratic regression of breeding weight were found statistically insignificant. ■ Eliminating these elements, the final analyses for estimating heritability were completed using the following model. Yijkm ~ F + ai + tj + sk + -x) + As stated above, complete least-squares procedures as described by Harvey (I960, 196b-) were used to estimate the least-squares constants for the fixed effects, making F tests for fixed effects, and obtaining the variance components for sires and k values for the sire components. The analysis of variance for the above model is presented in table 7 - TABLE 7 ANALYSIS OF VARIANCE TABLE FOR ESTIMATING HERITABILITY Source d.f. Sum of Squares E(MS) Total N-l ij kl ^ i j kl ^ Age of Ewe (a-1 ) R(p,a,t,s) - R(p,t,s) Year (t-1 ) R(VL,a,t,s) - R(p,a,s) Sires (s-1 ) R(ji,a,t,s) - R(p,a,t) d| +kd| Regression 1 Remainder (N-a-t- s + 1 > 4 From this analysis of variance table if can be seen that the variance component for sires (<5g)2 can be computed as <5? ^^Sire - MSerror) - + kd^ - iD — '■ k k and it is known that c* = 1/b 6~ e and 6^ e = 3/^ g + 6*: e under the usual assumptions. Where <5^ = additive genetic variance and = all other variance except additive genetic. Thus heritability was estimated as 0 g = ? <^s + The standard error of heritability was computed by using the approximate formula suggested by Swiger et al. . (196*+) which was given previously. 57 ' The second method of estimating heritability was the one suggested by Robertson and Lerner (19^9). As stated earlier, in more extreme cases where the characters can be expressed in only one of two classes, the data follow a binomial distribution. Methods for estimating heritability for such data have been investigated by Lush et al. (19^8), Robertson and Lerner (19^9) and others. The method used by Lush et al. (19^8) is similar to the analysis of variance, but that of Robertson and Lerner is related to realized genetic change for a trait under selection. Using the case of fertility of ewe as an example, Robertson and Lerner (19^9) defined the genetic value for fertility of n individuals be Gi, G2 , ... Gn with mean G p and variance Uq . In this case the Gj_ value may be thought of as the probability of lambing of the iife genotype. ■ The phenotype (Pi) of the iiil ewe will be (Gi + ei), where ei was defined as the non-genetic contribution to fertility. The value Pi = (Gi + ei) will necessarily be either 0 or 1 i.e., either the ewe lambed or she was open. If G^i is the additive genetic value of the i£h ewe, then the mean additive genotype of the next generation is and the expected value of G^ is approximately e (g a ) = GAj[(Gi + ei)J E[ ^ Gi + ei > ] n(6a + P2) _ 6\ + P2 nP p Assuming E(e^) = ECG^e^) = 0 and E(G) = P, the genetic improvement after natural selection is G - E(Ga ) - P s2 , "pE _ = A P - P = P P Since the genetic gain (AG) for a single trait is expressed • as heritability (g2) times the selection intensity (I), i.e., A G = g2I and, in the present case the mean value for fertility is necessarily equal to 1, the term I is I = 1 - P, therefore A G - (1-P) g2 *2. or ?■ AG _ A s - TTEpy - Pa-p.y Since P is the proportion of ewes lambing in a population, the denominator in the above equation is the variance between individuals in the binomial distribution. Thus the heritability can be estimated by using the sire component from the half-sib analysis and the proportion of ewes lambing in the flock. 59 3- Correlations All the correlations between reproductive performance components and body and wool traits were estimated by correlating two traits on the same individual. Since the components of reproductive performance were defined in such a way that of all the animals included for studying fertility and reproduction, only those ewes which lambed were analysed for estimating the parameters for prolificacy, lamb livability, and survival rate. Thus, separate analyses were run to estimate the correlations for fertility and reproduction with production traits, and for prolificacy, livability, and survival rate, with production traits. a) Phenotypic Correlation - The phenotypic correlation (rp p ) between trait i and i j j was computed b y using the formula - cov(PiPj) cov(G-iGn) + cov(EjEn) covCspsj) + cov(eiej) where: cov(sj_Sj) = sire covariance for traits i and j cov(EiEj) = environmental covariance between traits i and j 2 2 2 2 6 S., 6S ., 6e., 6e . are the sire and paternal half-sib 1 ^ 1 3 variances for traits i and j respectively. 60 The phenotypic correlation computed in this way estimates the correlation between traits i and j in a random mating population., b) Genetic Correlations - As discussed above, the genetic correlation between traits i and j measured on the same individual describes the relationship between the two traits due to additive genetic effects of the genes influencing the two traits. This genic association was estimated using the formula - •G , = oov(s1sp rr'"’3 _ ...... * h % where: cov(sj_sp = sire covariance for traits i and j and <5"s. , cov(ej_ep = cov(Ej_Ej) + 3 A cov(Gj_G;j) covCsiS^) = icov(GiGj) [ A ) = 3 A ^ where: cov(E^E^) = environmental covariance between traits i and j. cov(e^e-;) = residual covariance between traits 0 i and j. Substituting these values in the equation above. [cov(EjEj) + 3A covtG-Aj) - 3A cov(Gj_Gj)] rE±E3 jVli + 3A - 3A )(^e j + 3A <*$.- 3A dg^) cov(Ej_E^) % * E; RESULTS M D DISCUSSIONS The results of the various statistical analyses for the traits under consideration in this study are presented in the following section. For the purpose of convenience in presenting the results, this section will he discussed under the following suh-titles: A.' Least squares means and significance of fixed effects B. Repeatability Estimates 1. Fertility 2. Reproduction 3. Prolificacy b. Livability 5. Survival rate C. Heritability Estimates 1. Fertility 2. Reproduction 3- Prolificacy b. Livability 5- Survival rate D. Correlations 1. Phenotypic 2. Genetic 3- Environmental A. Fixed Effects The environmental effects for which estimates were obtained were six years, five ages at lambing in Columbia ewes and four ages in Targhee ewes, and body weight of ewe at breeding time. These effects were estimated by complete 62 least-squares procedures. Least-squares means and standard errors for the various components of reproductive performance by breed-station groups and breeds are presented in table 8. Least-squares constants and least-squares means for the various traits by age of ewe at lambing and year of record are presented in Appendixes A, B, and C. During the six year period, a total of b22 Columbia and ^99 Targhee matings produce and 365 and ^62 lambing records, respectively. Thus 85-15% of Columbia and 95*0^% of Targhee ewes mated produced one or more lambs. Bennett et al. (1963) observed a 96% conception rate in Targhee sheep and Vesely and Peters (1965) reported 92.b% lambing rate in four breeds of sheep, with no significant differences among the four breeds. Means presented in table 8 also reveal that for each hundred Columbia ewes lambing 138.8% lambs were dropped of which 116.b% were alive at birth and only 77-2% of the live lambs born were reared to weaning. The corresponding figures for the Targhee breed were 150.0, 13^.0 , and 100.3% respectively, which are in close agreement with the published literature. A study of data presented in table 8 reveals that the fertility (lambing rate) among Targhee ewes was about 9*9% higher than Columbia ewes and that Targhee ewes weaned about 31*9% more lambs than Columbia ewes. This big difference is due to the lower weaning percent among North Dakota Columbia ewes which showed the lowest weaning percent TABLE 8 LEAST-SQUARES MEANS AND STANDARD ERRORS FOR FERTILITY, REPRODUCTION, PROLIFICACY, LIVABILITY, AND SURVIVAL RATE BY BREED-STATION GROUPS AND BREEDS. No.of obser Fer Repro No.of obser Pro- Liv- Classification vations tility duction vations lificacy ability Survival Rate Ohio Columbia Mean 259 0.8863 0 .8l*+9 228 1 .5092 1.3223 0.9769 S.E.a 0 .108*+ 0.2*4-17 0.1875 0.2066 0.2387 N.Dakota Columbia Mean 163 0 .88l*+ 0.1+687 137 1.2222 0.9673 0.5519 S.E. 0.1198 0 .2*+58 0 .205*+ 0.2297 0 . 2*+68 Columbia Mean *+22 0.8515 0.6 *+01 365 1*3879 . 1*1639 0.7723 S.E. 0.0772 0.1653 0.1321 0 .1*+68 0.1658 Ohio Targhee Mean 262 0.9197 1.0250 239 1-6385 1.535*+ 1.0812 S.E. 0.1011 0.2325 0.1909 0.1982 0 .232*+ Illinois Targhee Mean 237 0.9628 0.9*+59 223 1. *+206 1.2*+88 0.9916 S.E. 0.0637 0.1791 0.1*+89 0.1522 0.1703 Targhee Mean *+99 0.950b 0.9597 *+62 1**4-997 1-3395 ■ 1.003*4- S.E. 0.05*46 0.1371 0.111*+ 0.1153 0.1316 aStandard error 65 among the four breed-station. groups. Further, it was observed that for prolificacy, livability, and survival rate the Targhee ewes had an advantage of 11.1$, 16.5$ and 23-1$ respectively, over the Columbia ewes. However, the least squares means for the Ohio Columbia are closely comparable with the Targhee breed for all traits. Differences among the means of the two strains of Targhee ewes were not very large. However, except for fertility, the Ohio Targhee ewes did show a consistant advantage over the Illinois Targhee ewes. The differences between the means for livability (live lambs born of ewes lambing), and survival rate (lambs weaned of lambs born alive) give the lamb mortality rate for each of the breed-station groups and breeds. These differences reveal that lamb mortality in the Targhee flock was 33-6$ and in the Columbia flock It was 39-2$. The overall lamb mortality rate in the Ohio Columbia, North Dakota Columbia, Ohio Targhee, and Illinois Targhee flocks was ^t"l. 55 j+5-1+5 and 25-7% respectively. The higher mortality rate in the Ohio Targhee flock could be attributable to its larger litter size and the lowest mortality figures for the Illinois Targhee flock suggests better mothering ability among the Illinois Targhee ewes. Preliminary analyses made to determine the significance of the fixed effects of years, age of ewe at lambing, and breeding weight of the ewe for the two breeds are presented 66 TABLE 9 LEAST-SQUARES ANALYSIS OF VARIANCE FOR FERTILITY, REPRODUCTION, PROLIFICACY, LIVABILITY AND SURVIVAL RATE IN COLUMBIA Mean Squares______Mean Squares Fer Repro- Prolif Liv Survival Source df. tility duction df. icacy ability Rate Groups(G) 1 0.1+79* 1.6if5 1 0.711 0 . if 29 0.281 Age of Ewe(A) 0.062 0.812 if 0. 2if9 0.658 0.599 Years(T) 5 0 .321* 0.61+6 5 0.135 0.637 0.757 Sires/Gl 22 0.09if 0.626 22 0A15* OA79 0.6i+7* Sires/G2 2 if 0.222** 0.712 23 0.176 0.201 0.1+26 G x T 5 0.lif8 0.318 5 0.269 0.31+6 0 A 3O Breeding Wt.of Ewe (Linear) i 0.608* 6.1+52** 1 2.711** if. 1+22** 2 .922** Remainder 359 0.108 0.501 303 0.258 0.319 0.1+07 *Probability due to chance<0.05 **Probability due to chance<0.01 TABLE 10 LEAST SQUARES ANALYSIS OF VARIANCE FOR FERTILITY REPRODUCTION, PROLIFICACY, LIVABILITY AND SURVIVAL RATE IN TARGHEE ______Mean Squares______Mean Squares Fer- Repro- Prolif- Liv- Survival Source df. tility duction df. icacy ability Rate Groups(G) 1 0.016 0.311 1 0 .1+27 O.i+33 0.229 Age of Ewe(A) 3 0.001+ 0.023 3 0.167 0.027 0.01+9 Years(T) 5 0.065 1.656** 5 0 .1+38 O.815* 1.86m-** Sires/Gl 30 0.075 0 .69!+* 30 0.21+5 0.277 0.532 Sires/G2 27 0.01+5 0 .5^2 27 0.21+9 0.263 0.1+18 G x T 5 0.068 0.220 5 0.079 0.088 0.186 Breeding Wt.of Ewe- (Linear) 1 0.078 0. 53^ 1 0.885 1.871* 0.079 Remainder 1+26 0.066 0.1+19 389 0.267 0.286 0.372 ^Probability due to chance<0.05 ^^Probability due to chance<0.01 in tables 9 and 10. Results from earlier analyses suggested that the effects of rams mated to the ewes and the quadratic regression of ewe breeding weight on all traits were insignificant. Hence, these effects were eliminated from these latter analyses. It is interesting to note that the linear regression of breeding weight of ewe is significant or highly significant for all the fertility components in the Columbia breed but it is significant only for pre-natal lamb livability in Targhee ewes. This could be explained by the fast growing and early maturing ability of the Targhee breed. The Columbia is a comparatively smaller breed that grows at a slower rate, reaching its mature size at a later age than the Targhee breed and thus the breeding weight at early ages is important in this breed. These results are in agreement with those published by many workers as given in the review of literature section. The effects of age of ewe at lambing were found to be insignificant for all traits in both breeds. Most of the literature on ewe fertility reviewed in this study was published on the Merino (Turner et al. , 1962*, Young et al., 1963) or English breeds, (Purser, 1965) which are comparatively late maturing and less prolific than the Columbia or Targhee, suggesting that age would be an important factor for ewe fertility. Data published on local breeds (Sidwell el; al., 1962) included a wide range 68 of ewe ages. Insignificance of age effects in this study can be explained by the fact that both the Columbia and Targhee are fast growing breeds and attain their mature size and producing ability comparatively at an early age. Further, most of the records analysed in this study were made by ewes from two to four years old, and hence, within this short range.of ages, the fertility levels of the ewes can reasonably be assumed to follow a steady pattern. Effects due to year of record were found to be, significant on lambing rate in the Columbia breed and on weaning percent and both pre- and post-natal livability of lambs in the Targhee breed. Yearly variation has been reported to be important for fertility traits by Turner et al. (1962), Sidwell et al. (1962) and others as indicated in the review of literature. The constants for age of ewe and year effects for all traits for each of the two breed- station groups and for both breeds are presented in Appendixes A, and the least squares means and standard errors are reported in Appendixes B and C. B. Repeatability Estimates As stated earlier, fertility in sheep has been considered in various ways and care must be taken in comparing the estimates published for the various components by many authors, since all of these do not always measure the same traits. Most of the published literature is on 69 TABLE 11 POOLED ANALYSIS OF VARIANCE FOR FERTILITY AND REPRODUCTION IN OHIO COLUMBIA Fertility Reproduction Source df. SSa MS8 SSa MS8 E(MS) Years 13 1.0016 0.0770 8.2289 0.6329 Between Ewes 125 16A538 0.1317** 7!+.9693 0.5998* c5e2+1.9839 Remain der 123 10.0150 0 .08A 57A378 0 A 670 <3e2 ♦Probability due to chance-<0.05 ♦♦Probability due to chance <40.01 aSS = Sum of Squares (pooled) 6mS = Mean Squares (pooled) Fertility 0-2 = 0.1317 - 0.08l5 = 0.0253 a i.9«39 ,<•2 Repeatability = d = 0.0253 - q 2S7? ^2 +rr2 0 .0253+0 .081^ * d e 1/2 q p -r2(267-1)(1-0.2372)2tl+(1.9839-l)0-2372}2l L (1.9832)2(267-131)(131-1) = 0.082 Renroduction <5ci2 = 0 • 5998-0.^670 = 0.0669 1.9839 x2 Reneatability = = 0.0669 - n x-2 .+(<2 0 .0669+0.^670 d e q p _r2(267-1) (1-0 .1253)2a + ( 1 -9839-1)0.1253} 211 2 bmh" "L (1.9832)2(267-131) (131-1) J = 0.086 70 TABLE 12 POOLED ANALYSIS OF VARIANCE FOR FERTILITY AND REPRODUCTION IN NORTH DAKOTA COLUMBIA Fertility Reproduction Source df. SSa MSb SSa MSb E(MS) Years 15- 2.0265- 0.15-5-7 8.7261 0.6233 Between Ewes 125- 13.5569 0.1093 65-. 5505 0.5206 oe2+1 .8830a2 Remain der 110 11.91^1 O.IO83 52.3978 0 .5-763 tie2 k* = I.883O Fertility Repeatability = 0.00053 = .005-9 O.IO83+ .00053 1/2 o p _ r 2(255-1) (1-0.00^9 )2 y 1+(1.883-1)0.00^+93 21 ' ' L (l.883)^(255- 130)C130-1 ) J = 0.135- Reproduction «a2 = °-?2° ^ g 3°-tt'763 = 0.0235 Repeatability = °"d2 = 0.023JL__ = 0 05-70 cr,2+(r2 0 .0235+0 .4-763 Cl @ s E = E 2(255— 1) (1-0.05-70) U+(l. 883-1)0.05-70)2 1 1/2 L (1.883)2(25^-130)(130-T) : J = 0.093 71 TABLE. 13 POOLED ANALYSIS OF VARIANCE FOR FERTILITY AND REPRODUCTION IN OHIO TARGHEE • • Fertility Reproduction Source df. SS MS SS MS E(MS) Years 11 0.6587 0.0599 6.455^ O .5869 Between Ewes 143 12.8449 0.0898 66.6648 0.4662 o-e2+1.7‘tl3oa2 Remain der 106 6.5079 0.0614 43.9612 0.4147 Fertility <5^2 = 0.0898 -0.0619 = 0 .OI63 a 1.79-13 Repeatability = °d2 , . .0-P.163__r = 0.2101 0.0163+0.0614 2 -,1/2 S.E. = r 2(266-1) (1-0.2101)2 1 _!+(!.7^13-1)0.210!l) 2 1 L (1.7413) 2 (266 -149) (1^9-15 -* = .092 Reproduction CTd2 = ° - ^ 2 - 0..I+1.I+Z = 0.0296 1. /4lj Repeatability = —°d2 = Q-.Q2.9_6 _ = 0.0665 dd2+Oe2 0.0296+0. *+147 1/2 q w = \ 2(266-1) (1-0.0665)2ll+(1.71+18-l)0.0665>2 1 ^ L (1.7413)2(266-149)(1+9-1) J = 0.311 72 TABLE Ilf POOLED ANALYSIS OF VARIANCE FOR FERTILITY AND REPRODUCTION IN ILLINOIS TARGHEE Fertility Reproduction ■ Source df. SS MS SS MS E(MS) Years 10 0.5085- 0.0508 6.2788 0.6279 Between Ewes 6.1221 0.05-98 60.6851 0.5-935- c A l 813( 123 0 Remainder 100 5.32^9 0.0532 39.6379 0.3965- kJ = 223.0005- - 1.8130 123 Fertility cn2 = °rQi+98 - 0,.053.2 = -0.0019 d ± 7 E ii Repeatability = °d2 = -0.0019 = 0 cr 2+cr 2 -0.0019+0.0^32 d e Reproduction crd2 = Q '^9^ a i 30 '3-9"- = 0.0535 Repeatability °d2 _ 0.0531-.,.- = 0.1189 crd2+oe2 0.0535+0.3965- 2 t £ S.E. = V 2(239-1) (1-0.U 8 9 ) 2Cl+a. 813-1)0.Il89>2 ] I (1.813)2(239-129)C129-1J J = 0.098 73 number of lambs born and .number of lambs weaned on a per mating basis. Since fertility components in this study have been classified in a slightly different manner, estimates obtained for some of the components may not be comparable with the ones available in the literature. Repeatability estimates for the various components of fertility reported in this study were obtained by pooling the between and within sums of squares for ewes and degrees of freedom over all birth-year groups within each breed- station group. Pooled estimates for each of the two breeds were obtained by pooling over the two strains for each breed and a single estimate for each fertility component was obtained by pooling over the two breeds. For the purpose of analysis, every ewe mated to a ram within each of the four breed-station groups over the entire period (1962-1967) of this study contributed a record. Thus, possible biases in the estimates due to selection of ewes which did not lamb or the ewes which gave birth to a ram lamb was eliminated. By definition, for the estimation of parameters for prolificacy, livability, ahd survival rate only those ewes contributed records which lambed at least one lamb. Since these two sets of data were analysed separately within each breed-station group, results for these two sets of repeatabilities will be discussed separately. 7h 1. Fertility and Reproduction The repeatability estimates for fertility (ewes lambing of ewes bred) and reproduction (lambs weaned of ewes bred) are presented by breed-station groups in tables . 11, 12, 13 , and l^f. Pooled estimates for each of the two breeds and across the two breeds are reported in table 15. Mean squares for years, ewes, and the error lines obtained from the separate analyses for each of the birth-year groups within the breed-station groups for both traits are summarized in Appendix D. - - a. Fertility Comparision of values obtained for repeatability of fertility in this study with the estimates for general fertility levels in sheep summarized in table 1 shows a close agreement between the two sets of results. Since fertility in this study is defined in a slightly different manner than in the published literature, the estimates obtained in this study are not exactly comparable with those reported in the literature review section of this study. However, these estimates are in the general range of the tabulated values in table 1. Repeatability in both the Ohio Columbia and the Ohio Targhee is reasonably high but in both the non-Ohio groups the estimates are not significantly different from zero and significantly less than in either Ohio group. Table 15 gives overall values of 0.2*+ and 0.21 for repeatability o f TABLE 1^ BEPEATABILITY ESTIMATES OF FERTILITY, REPRODUCTION, PROLIFICACY, LIVABILITY, AND SURVIVAL RATE BY BREED STATION GROUPS AND BREEDS Traits Ohio N .Dako ta Ohio Illinois Columbia Columbia Columbia Targhee Targhee Targhee Pooled Fertility Repeatability 0.237 0.005 0.125 0.210 0 0.111 0.113 Standard. Error 0.082 0 .13*4- 0.062 0.092 0.069 0.0^6 Reproduction Repeatability 0.125 0 .0^7 0.088 0.067 0.119 0.095 0.085 Standard Error 0.086 0.093 0.063 0.311 0.098 0.069 0.0^7 Prolificacy Repeatability 0.201 0.259 0.217 0 0 -0.12^ 0.056 Standard Error 0.092 0.097 0.06>+ 0.053 Livability Repeatability 0.173 0 .2^8 O.I3U 0 0 -0.163 -0.002 Standard Error 0.093 0.099 0.067 Survival Rate Repeatability 0.081 0 .1^3 0.100 0 0.126 0.018 0.063 Standard Error 0.135 0.105 0.068 0.106 0.077 0.053 v-n-<] 76 fertility in the Ohio Columbia and Ohio Targhee groups. The higher standard error associated with the estimate for the North Dakota Columbia and the negative ewe component for the Illinois Targhee indicate large sampling errors in these two groups. Although, the pooled estimates for each of the two breeds and across the two breeds presented in table 15 look very reasonable with fairly small standard errors, the validity of pooling the estimates when the values for the two groups within ea.ch of the two breeds are significantly different from each other is questionable. Further, the repeatabilities for the North Dakota Columbia and the Illinois Targhee are smaller than their respective breed estimates and the pooled estimates over the two breeds. The low estimates of repeatability for fertility in the North Dakota Columbia and the Ohio Targhee are indicative of the fact that life-time gains In fertility by selection of ewes in these two groups are likely to be small. Barrett and May (1958) working with fine wool Merino also concluded that selection for fertility on a ewe's early performance would not raise life-time production; they compared the lambing frequencies over a number of years, b. Reproduction Although, the repeatabilities obtained for the various breed groups are very low, these estimates are in close agreement with those reported by Young et al. (1963), 77 Yalcin and Bichard (196H0, Inskeep et al. -(1967), and Kennedy (1967). Comparison of the values for each of the breed-station groups with their respective breeds and the overall average value for both breeds as presented in table 15, do not reveal any important differences. As for the lambing rate, the progress due to selection for lambs weaned can be expected to be of a very small magnitude, because from table 15 it will be noticed that for each lamb weaned per ewe exposed in one season only 0.12, 0.07, 0.05, and 0.12 lambs are weaned in the next season for the Ohio Columbia, Ohio Targhee, North Dakota Columbia, and Illinois Targhee groups, respectively. The comparable estimates for the Columbia, Targhee, and averaged over the two breeds are 0 .0 9 , 0.10 and 0 .08, respectively. In the literature, repeatability estimates for reproduction have been reported to range from O.Ok^O.03 to 0 .13 . Estimates presented in table 1 also show that values obtained by analysis of variance technique are consistantly smaller than the ones obtained by using regression estimates. In the present study the Ohio Columbia and the Illinois Targhee breed groups have yielded higher repeatability values than the North Dakota Columbia and Ohio Targhee groups. However, the pooled estimates for each of the two breeds are very similar and not different from the overall pooled estimate for the two breeds. 78 TABLE 16 POOLED ANALYSIS OF VARIANCE FOR PROLIFICACY, LIVABILITY AND SURVIVAL RATE IN OHIO COLUMBIA Prolificacy Livability Survival Rate Source df. SS MS SS MS SS MS Years 13 6.65^6 0.5H9 8.9763 0.6905 8.7812 0.6755 Between 115 3^.9711= O.3O68 51.7128 0.3659 53.5222 0.5686 Ewes Remain 101 21.0121 0.2080 26.5237 0.2626 50.5521 0.5015 der 5(di-l) 115 Prolificacy ^2 _ 0..1068-0.2080 _ q 0523 c[ 1.886 dr Repeatability = 0 -°%3„ = 0.2010 0-2 + o-2 0.0523+0.2080 d e 212 q -r, _ r 2(2.34— 1) (1-0 .2010)2{l+Cl.886-1 )0 .2010^21 L (1 .886)2(235-120)(120-1 ) J = 0.092 Livability d§ = P • 3.85.9 ~Q • .2626 = 0 .05^8 u 1.006 Repeatability _ A P. • = 0.0558 c<2 + ^2 0.0558+0.2626 d e n „ _r2C23^-l)Cl-0.1726')28l+(l.886-1)0.1726)2!*2c 2-ii S-E* "L— ---- (1.8 86) 2 (23V 120) (120-1") J = -093 Survival Rate ^2 0.5686-0.5015 - 0 0856 d 1.886 2 Repeatability = -3 ^ 2 = 0 .03g6°o ^013 = d e S e - f 2 (2 35-1) (1 -0. 8l5) [ 1+ (1. 8 86 -1) 0.0 8l5S,2]^ ** (1 . 886)^(23^-120) (120-1 ) = 0.135 79 • TABLE 17 POOLED ANALYSIS OF VARIANCE FOR PROLIFICACY, LIVABILITY AND SURVIVAL RATE IN NORTH DAKOTA COLUMBIA Prolificacy Livability Survival Rate Source df SS MS SS_____ MS_____ SS______MS Years V+ 4-. 5117 O .3223 4-.9065 0.3505 6.1752 0.4-4-11 Bet ween Ewes 117 39.9634- 0.34-16 ^0.3126 0 . 34-4-6 54-.3883 0.4-64-9 Remain- . der 84- 17.9383 O .2136 23.8769 0.28^2 30-3581 0.3614- k .= I 4 $ ± 3 3 k L = 200,.5,l4hZ = . 71-r s(di-l) 117 1.7130 Prolificacy cTd^ = .Q_-.3-1t46 - 0^ 2136, = 0.074-7 Repeatability = °d^ = 0.074-7 = n 2591 crd2+c^2 0.074-7+0.2136 S.E. = T 2(221-1)(1-0.2591)2U+C1.7138-1)0.2591>211/2_ oq7 L (1 .7138)2 (221-123) (123-1 ) J Livabllity ^ 2 _ 0.34-4-6-0^284-2 _ q .0935 Repeatability = °d2 = 0-0935 = n 24-76 crd2+c^2 0.0935+0.284-2 — -- <— S.E. = f 2(221-1) (1-0.24-76)2U + (1 .7138-1 )0.24-7632]1/,2=q .099 L (1.7138)2(221-123)(123-1) J Survival Rate _ 2 0.4-64-9-0.3614- ^ °d = 1.7136 = 0-0601+ Repeatability = °d2 = 0.0604- = 0.14-31 0-^2+ cr 2 0.0604^-0.3614- 9 1 /2 S.E. = f 2(221-1)(1-0.14-31) £l+(l.7138-1)0.14-3^^1 _n in- L (1.7138)2(221-123) (123-1) J 80 TABLE 18 POOLED ANALYSIS OF VARIANCE FOR PROLIFICACY, LIVABILITY AND SURVIVAL RATE IN OHIO TARGHEE Prolificacy Livability Survival Rate Source df SS_____ MS SS - MS SS______MS Years 11 6.8625 0.6239 8.2284- 0.74-80 ^.8265 0.4-388 Bet ween Ewes 137 30.-784-5 0.224-7 30.2525 0.2208 4-9.1033 0.3584- Remain der 89 23.80I2 0.2675 27.9383 O .3139 36.9235 0.4-14-9 v '_ ? (di-Dki = 226.0014- = 1 .6^96 ?(di-l) 137 Prolificacy ^ 2 = 0.224-7-0.2675 _ n m QQ Q ! 1.64-96 Repeatability = °d^ = -0.0199^ = 0 ^ 2 + ^ 2 -0.0199+0.2675 Livability ^ 2 _ 0.2208-Cu3139 = -0.0564- Repeatability = qd2 = -0.0564- - 0 (Td^+o'e2 -0.0564+0.3139 Survival Rate m 2 = 0.3584— 0.4-14-9 - -0.034-3 °d 1.64-96 Repeatability = = -0.034-3 . - 0 ^ 2 + ^ 2 - 0 .034-3+ 0 .4-14-9 81 TABLE 19 POOLED ANALYSIS OF VARIANCE FOR PROLIFICACY, LIVABILITY AND SURVIVAL RATE IN ILLINOIS TARGHEE Prolificacy Livability Survival Rate Source df SS MS SS MS SS MS Years 10 3.5216 0.3522 A.9655 0.5966 7.3909 0.7391 Bet ween Ewes 135 38.5615 0.2859 38.3315 0.2839 55-807^ 0.5135 Error 89 31.6551 0.3556 30.7011 0.3559 29.6925 O .3336 k' fCdi -1 ) 135 Prolificacy ^ 2 _ O.OSA^O35-9-0.3 A556 = -0.0^26 1.6593 Repeatability = -0.0^-26-0.05-26 __ _ q -0.05-26+0.3556 Livability *-2 _ 0.2839-0.35-5-9 _ n mc o ------od - 1.6593 " u.ujbo Repeatability = -0.0368 = q -0.0368+0.3^9 Survival Rate ^ 2 =0 • 5135-0 A.336 = 0.058l Repeatability - 0.0581 _ n i ^ a O.OkBl+O'.W --0*1250 • S.E. = r 2(250-1)(1-0.1260)2$1+(1.6593-1)>1260}21 1/2 L (1.6 593)2 (250-15-1 )(l5l-l) -1 = 0.106 82 2. Prolificacy, Livability, and Survival Rate The repeatability estimates obtained for prolificacy (lambs born of ewes lambing), livability (lambs born alive of ewes lambing), and survival rate (lambs weaned of lambs born alive) are presented by breed-station groups in tables 16, 17, 18, and 19. Pooled estimates for each of the two breeds and across the two breeds are summarized in table 15 and mean squares for years, ewes, and the error lines for each of the six birth-year groups in each of the four breed- station groups are presented in Appendix E. A brief look into table 15 indicates that these estimates show a definite pattern among the four breed- station groups and with such big differences between the estimates for each'of the two breeds, the feasibility of pooling the estimates across the two breeds seems doubtful, a. Prolificacy In the literature, repeatability for prolificacy (litter size) has been reported to range from O.OCiO.O^ in Rehmani sheep (Karam, 1957) to 0.2R for Welsh sheep (Purser, 1965). Although, the estimates obtained for the two breeds in this study are significantly different from each other, the values obtained for the Ohio Columbia and the North Dakota Columbia, are in agreement with published results. The significant differences in these estimates for the two breeds could be suggestive of the fact that there could be some real differences among the two breeds. The larger repeatability values for the Columbia sub-breeds indicate that the accuracy of predicting future performance is reasonably high and that progress could be achieved by the selection of ewes giving multiple births. . For both strains of the Targhee breed, analysis of variance revealed negative ewe components and, hence, the negative repeatability values. It is a bit difficult to conceive of a biological situation where the ewe component obtained by an analysis of variance between and within ewes should be negative. Thus, the negative ewe component should be due to chance. Further, a combined estimate of -0.124- for the Targhee breed is considerably less than zero and this supports the doubt that this could be real value and the possibility of large sampling errors in the two groups of Targhee breed, b. Livability It is interesting to note that the repeatability estimates for livability follow exactly the same pattern as that of prolificacy. Although, livability (number of live lambs born per ewe lambing) has not been studied exactly in this form, the repeatability for number of lambs born have been reported to range between 0.0*+ to 0.24- in various breeds. Thus, a close comparison of results obtained in this study for livability with the published estimates is not possible but the values obtained for repeatability do fall within the range of the published 8>t results for general fertility levels in sheep. As in the case for litter size, the higher repeatability estimates obtained for the Columbia breed and its two strains are indicative of the fact that pre-natal lamb livability in Columbia ewes is fairly repeatable and the future performance of these ewes can be predicted with greater accuracy, as compared to the Targhee ewes. The negative estimates for Targhee and the strains of Targhee are little doubtful and could have been influenced by large sampling errors. The pooled estimate of 0.13^0.067 can reasonably be considered as the best estimate for repeatability of livability in Columbia ewes, but the pooled estimate for the- Targhee breed is significantly less than zero and does not seem to be of any practical value. Since the estimates for the two breeds are different from each other averaging of the two estimates to obtain a single estimate is of little value, c . Survival Rate Survival rate measured as the number of lambs weaned of the lambs born alive is not directly comparable with the number of lambs weaned as reported in the literature. In .the reviewed literature repeatability for weaning rate has been reported to range between 0.04- in Merino (Kennedy, 1967) to 0.13 in Hampshire (Inskeep et al. 1967). The higher estimates reported by Inskeep et. al. (1967) 'were obtained by regressing the later record on earlier record in successive years and since the adjacency of two successive records was only one year, this value could be slightly larger than expected. Results presented in table 15" are in very good agreement with the published estimates. It should be noted, however, that repeatability estimates for survival rate obtained in this study are expected to be slightly higher than the estimates for lamb weaning percentages as considered in the literature, because the present values are estimated on the basis of lambs weaned of live lambs born, where as the published estimates are on the basis of lambs weaned of ewes bred. With the large standard errors associated with each of the breed-station g.roup estimates, it is reasonable to assume that the trend shown by these estimates may not be real and that these estimates do not differ significantly from each other. Under these circumstances it is also reasonable to get a pooled estimate for each of the two breeds and across the two breeds. Once a live lamb is born, within a breed of sheep, rearing of lambs up to weaning age depends on the mothering ability of individual ewe, percent multiple births in a flock, and the management practices followed. Thus, the prediction of future performance of the ewes for survival rate is influenced by these factors and hence, a low repeatability estimate is expected for survival rate. 86 The value of 0.06 observed in this study appears to be a reasonable estimate for this trait. 87 C. Heritability Estimates Heritability estimates for each breed-station group were obtained by using paternal half-sib analysis of variance technique. As in the case of repeatability ' estimation, because of the nature of data, analyses for the five fertility components were made in two different sets and the results for each of the breed-station groups are presented in tables 20-31. Similar to the repeatability analyses each ewe mated to a ram within each breed-station group over the entire period (1962-67) of this study contributed a record for fertility and reproduction analyses. However, a small proportion of records was not included in these analyses due to missing sire number, or when a sire group was represented by only one observation. Estimates for prolificacy, livability, and survival rate were obtained by using only those ewes which gave birth to at least one lamb. A small portion of the total records was dropped out of these analyses also due to the above mentioned two reasons. The least-squares analyses of variance made for each breed-station group and breed to estimate the between and within sire components were slightly different from the ones used to estimate the between and within ewe components for repeatability estimations. Since, sires were cross classified both across years and age of ewe, 88 direct adjustments for both the year and age effects on the various fertility components was possible by least- squares procedures. Thus, instead of separate analyses for each birth-year group within each of the breed-station group , only one analysis was made for each breed-station group . Heritability estimates for both the breeds were obtained by separate analyses on the combined data of both the strains for each of the two breeds. The sum of squares and degrees of freedom for sires and error lines for each of the two breeds were pooled to estimate the single' heritability value for each of the components of reproductive performance. 1. Fertility and Reproduction The least-squares analyses of variance and heritability estimates for fertility and reproduction for all the four breed-station groups and both the breeds are presented in tables 20-25* Pooled estimates across the two breeds for both the traits are reported in table 32. a. Fertility Heritability estimates for fertility in Ohio Columbia, North Dakota Columbia, Ohio Targhee, and Illinois Targhee were found to be -0.027, 0.1+855 -0.012, and -0.096 respectively. The combined values for the Columbia and Targhee breeds were estimated to be 0.23 -0.035 respectively and when averaged over the two breeds the heritability of fertility was found to be 0.117t0.03. From table 32 it can be noticed that the three negative estimates for the Ohio Columbia, Ohio Targhee, and Illinois Targhee breeds cannot be significantly less than zero and hence, it may be infered that additive genetic variance for fertility in these three strains is not very important. A large heritability estimate (0.4-85) in North Dakota Columbia is associated with a fairly large standard error suggesting that this estimate could have been, influenced by a large sampling error. The combined estimates for the Columbia and Targhee breeds are significantly different from each other and were found to be in the opposite directions. However, the negative estimate for Targhee breed was not significantly different from zero and assuming that the trend shown in these results has been influenced by sampling errors pooling of the two breed estimates could be of practical value. The pooled heritability estimate of 0.117-0.030 for fertility in the Columbia and Targhee breeds appears to be a reasonable estimate. Although, heritability estimates for fertility, as defined in this study, have not been published in the literature, the reported estimates on ewe fertility range between -0.03 (litter size; Purser, 1965) to 0.51i“0.11+ (lambs born/lambing*, Karam and Ragab, 1958). Comparison of estimates obtained in this study with those published 90 in literature and summarized in table 2 reveals the close agreement between the two sets of estimates, b. Reproduction Heritability estimates for reproduction (lambs weaned of ewes bred) for Ohio Columbia, North Dakota Columbia, Ohio Targhee, and Illinois Targhee were found to be 0.079? 0.2^5? 0 .288, and 0.109 respectively. Comparision of the estimates for the two strains within each of the two breeds revealed no significant difference, and hence, pooled values of 0.202 and 0.2*+! for the Columbia and Targhee breeds may be the appropriate estimates of heritability for the two breeds. Further, it was noticed that the heritabilities of reproduction in the two breeds are nearly the same, a combined estimate of 0 .205± 0.036 was obtained for the two breeds. In the literature, heritability estimates for weaning percent have been reported to range between 0.09^0.09 in the Merino (Young et al., 1963) and 0.19- 0.07 in five lines of Minnesota (Singh and Rampel, 1967)* Young et al. (1963) reported heritability estimates of 0.15-0.10 and 0.29±0.l8 In three year old Merino ewes using two methods of estimations. Comparison of published estimates with the results obtained in this study revealed close agreements between the two sets of heritability estimates. Comparing the heritability estimates for each of the 91 TABLE 20 LEAST-SQUARES ANALYSIS OF VARIANCE AND HERITABILITY ESTIMATES FOR FERTILITY AND REPRODUCTION IN OHIO COLUMBIA Mean Squares Source ■ df. Fertility Reproduction Age of Ewe 0.0502 0.5613- Years 5 0 . 15-35- 0 . 8l*+8 Sires 22 0.0963 0.6132 . Ewe Breeding Weight(Linear) 1 0 .791+8** 2 .9122* Remainder 226 0.1031 0.5128 k = 9-7607 * = Probability due to chance <0.05 ** = Probability due to chance<0.01 1+6? Heritability for Fertility =---— = -0.027=0 Heritability of Reproduction = 0.079-0*15-1 TABLE 21 LEAST-SQUARES ANALYSES OF VARIANCE AND HERITABILITY ESTIMATES FOR FERTILITY AND REPRODUCTION IN NORTH DAKOTA COLUMBIAS Mean Squares Source df. Fertility Reproduction Age of Ewe 5- 0.0823 0.3715 Years 5 0.2903* 0.5-2 50 Sires 25- 0 .2080* 0.675-8 Ewe Breeding .Weight(Linear) 1 0.0210 3.5-75-1 Remainder 128 0.1177 0.5-9 55- k = 5.5538 * = Probability due to chance <0.05 ** = Probability due to chance <0.01 b<5^ Heritability of Fertility = - ^ - 5- = 0.^85±0.295- s e Heritability of Reproduction = 0.25-5*0.259 . 92 TABLE 22 LEAST-SQUARES ANALYSES OF VARIANCE AND HERITABILITY ESTIMATES FOR FERTILITY AND REPRODUCTION IN OHIO TARGHEE Mean Squares Source df. Fertility Reproduction Age of Ewe 3 0.0320 O .3878 Years 5 0.1797* 0.9085 Sires 30 0.0762 0. 65*+5* Ewe Breeding Weight(Linear) . 1 0.1200 0.3085- Remainder 222 0.0780 0 A 125- k = 7.65-17 ‘^Probability due to chance < 0.05 L./f2 Heritability of Fertility = — — = 0.012 0 + °i Heritability of Reproduction = 0.288^0.191 TABLE 23 LEAST-SQUARES ANALYSES OF VARIANCE AND HERITABILITY ESTIMATES FOR FERTILITY AND REPRODUCTION IN ILLINOIS TARGHEE Mean Squares Source df. Fertility____ Reproduction Age of Ewe 3 0.0326 0.5633 Years 5 0.01^6 1.1585- Sires 27 0 . 0¥f 5 0.5067 Ewe Breeding Weight(Linear) 1 0.0000+ 0.1196 Remainder 200 0.0531)- 0.5-225- k = 7.135-0 Heritability of Fertility = . -S— - = -0.096=0 cfs i + d e l Heritability of Reproduction = 0.109^0.173 TABLE 2b LEAST-SQUARES ANALYSES OF VARIANCE AND HERITABILITY ESTIMATES FOR FERTILITY AND REPRODUCTION IN COLUMBIA Mean Squares Source df. Fertility Reproduction Age of Ewe 4- 0.0519 0.7263 Years 5 0 .3221* 0.9Lt-8)+ Sires b7 0.1622* 0.7129* Ewe Breeding Weight(Linear) 1 0.6!+00* 6.2995** Remainder 364- 0.1086 0.4-984- k = 8.1102 ^Probability due to chance <0.05 ^^Probability due to chance<0.01 Heritability of Fertility = — — - = 0.230±0.139 4 + 4 Heritability of Reproduction = 0.202±0.136 TABLE 25 LEAST-SQUARES ANALYSES OF VARIANCE AND HERITABILITY ESTIMATES FOR FERTILITY AND REPRODUCTION IN TABGHEE Mean Squares Source df. Fertility Reproduction • Age of Ewe 3 O.OO69 0.04-85 Years 5 0.1062 1.724-8** Sires 58 0.0617 0.6293* Ewe Breeding Weight(Linear) 1 0 .051+1+ 0.6305 Remainder ^31 0.0662 0.4-175 k = 7-925^ ^Probability due to chance<0.05 ^^Probability due to chance <0.01 b6% Heritability of Fertility = — * ~ = -0.035=0 s + dr e Heritability of Reproduction = 0.24-li0.130 four strains, from table 32 it can be noticed that the standard errors associated with the estimates for Ohio Columbia, North Dakota Columbia, and Illinois Targhee are larger than the respective heritability values, suggesting that the trend shown 'by these estimates may have been influenced by sampling error. Although, the values obtained for the different strains within each of the two breeds are slightly different from each other, the pooled estimates for both the Columbia and Targhee breeds and averaged over the two breeds do suggest that selection based on higher weaning percentage will increase the genetic merit of individuals in these two breeds. A feature of the results, also present in many other published literature but not discussed by them, is that heritability of fertility and reproduction is larger in some of the breed-station groups and breeds. Young et al. (1963), Kennedy (1967), and Karam (1957) reported higher heritability estimates in Merino, and Rehmani sheep than the respective repeatability estimates for lambs weaned and multiple births respectively.- In the present study, comparison of results presented in tables 15 and 32 will reveal that heritability estimates of fertility and reproduction are higher than repeatability estimates for both the breeds and averaged over the two breeds. An explanation of this is suggested by Turner and Dolling (1965) that there are marked changes in the reproductive performance of ewes with increasing age. The reproductive performance of 2 year old ewes' is principally a measure of the number of ewes which lamb, since multiple births are infrequent at this age. Using beef cattle data Koch and Clark (1955)5 reported heritability and repeatability estimates to be, giving heritability first and repeatability second, 0.35 and 0.26 for birth weight, 0 .2*+ and 0 .3*+ for weaning weight, 0.21 and 0 .3*+- for gain from birth to weaning, 0.18 and 0.22 for weaning score, 0.*+7 and 0.20 for yearling weight, 0.39 and 0.09 for gain from weaning to yearling age and 0.27 and 0.02 for yearling score. With these results, obtained by maternal and paternal half-sib analysis of variance, they concluded that maternal environment has little importance for yearling gain and score or is even negatively related to the genes directly influencing these traits. In another study on gestation length in beef cattle Wheat and Riggs (1958) reported heritability estimates for gestation length to be 0.22, O.36, and 0.50 estimated by maternal half-sib, full-sib, and paternal half-sib correlation methods. The repeatability of gestation length was 0.21 and 0.19 for maternal sibs and full sibs, respectively. In their study, they also noticed that the sire component was 2.2*+ times as large as the dam component but, with the large over lapping confidence levels, 96 sampling error could have caused the observed difference in the two components. Since the dam component had a comparatively smaller fiducial limits, they concluded that heritability estimated by maternal half-sib correlation was more reliable. However, heritability based on the maternal half-sib correlation, theoretically, falls between heritability in broad sense and heritability in narrow sense as it includes the variance caused by the additive effects of genes plus a fraction of the variance due to epistatic gene action. Its interpretation depends partly on the extent to which gestation length is a characteristic of the offspring or of the dam. In this study, since all the matings within each breed-station group were purely random, any biases due to non-random matings were eliminated. Further, in each breed station group the number of records were fairly consistant. However, the number of sire groups within each breed- station group were not very large, and moreover , number of ewes within each sire group was very small and greatly variable. In view of the last two reasons, the heritability estimates for fertility and reproduction, obtained in this study are in good agreement with the published estimates and the differences between the estimates are within the range of sampling errors. 2. Prolificacy, Payability, and Survival Rate Least-squares analyses of variance and heritability ’ 97 estimates for prolificacy, livability, and survival rate for all the four breed-station groups and both the breeds are presented in tables 26-31* Pooled estimates across the two breeds for all the three traits are reported in table 32* a. Prolificacy Heritability estimates for prolificacy (number of lambs born of ewes lambing) were found to be 0.259-, -O.308, -O.O76, and -O.O96 in Ohio Columbia, Worth Dakota Columbia, Ohio Targhee, and Illinois Targhee, respectively. Pooling the estimates over two strains for each of the two breeds gave the values of 0.137 for the Columbia, and -0.010 for the Targhee breed. With the large standard error associated with the estimate for Columbia breed and a very small negative estimate for Targhee breed, it is reasonable to assume that heritability for prolificacy in these two breeds is essentially zero and that the negative or positive trends revealed by the estimates for these two breeds may be due to random chance. This assumption is supported by the pooled estimate of 0.010 for the two breeds presented in table 32. Estimates for prolificacy, as obtained in this study, are not directly comparable with those published in the literature. Prolificacy in the literature has been considered either as number of lambs born of ewes bred (Young et al., 1963; Purser, 1965; Kennedy, 1967) ov as 98 •TABLE 26 LEAST-SQUARES ANALYSIS OF VARIANCE AND HERITABILITY ESTIMATES FOR PROLIFICACY, LIVABILITY, AND SURVIVAL RATE IN OHIO COLUMBIA Mean Squares Source df. Prolificacy Livability Survival Rat Age of Ewe H- 0.1361 0.5-910 0 . 5^5- Years 5 0.2611 I.2030** 1.3171** Sires 22 0.5-065-* 0.5-558 0.65-81 Ewe Breeding Weight(Linear) 1 1-3571* 2 .5623** 0.3687 Remainder 195 0.2551 0.3097 0.5-135 k = 8'. 5756 *Probability due to chance <0.05 **Probability due to chance < 0.01 Heritability of Prolificacy = --- -— — = 0.259-0-197 + <1 Heritability of Livability = 0.209^0.187 Heritability of Survival Rate = 0.25-810.195 TABLE 27 LEAST-SQUARES ANALYSES OF VARIANCE AND HERITABILITY ESTIMATES FOR PROLIFICACY, LIVABILITY, AND SURVIVAL RATE IN NORTH DAXOTA COLUMBIA Mean Squares Source df. Age of Ewe 5- 0.2165 0.5-312 0.5-835- Years 5 0.2053 0.3059 0.665-6 Sires 23 0.1795 0.1305- 0.3925- Ewe Breeding Weight(Linear) 1 1.35-58* 1.6763* 3.5723** Remainder . 103 0.2721 0.35-01 0.3927 k = 1+. 7626 *Probability due to chance <0.05 ^Probability due to chance < 0.01 Heritability of Prolificacy -■— - = -0.308=0 « l + Heritability of Prolificacy = -0.5-07=0 Heritability of Survive.! Rate =-0.001=0 99 TABLE 28' LEAST-SQUARES ANALYSES OF VARIANCE AND.HERITABILITY ESTIMATES FOR PROLIFICACY, LIVABILITY, AND. SURVIVAL RATE IN OHIO TARGHEE Mean Squares Source______df. Prolificacy Livability Survival Rate Age of Ewe 3 0.5966 0.5020 0.33^7 Years 5 0.3209 0.4-083 0.6897 Sires 30 0.2116 0.2066 0 .4-891 Ewe Breeding 1 0.0786 0.10>+0Weight(Linear) 0.0179 Remainder 199 0.2^31 0.2620 0.3603 k = 6.974-3 Wg Heritability of Prolificacy = ™ ---- = -0.076=0 TABLE 29 LEAST-SQUARES ANALYSES OF VARIANCE AND HERITABILITY ESTIMATES FOR PROLIFICACY, LIVABILITY, AND SURVIVAL RATE IN ILLINOIS TARGHEE Mean Squares Source df. Prolificacy Livability Survival Rate Age of Ewe 3 0.0573 0.2336 0. 5984- Years 5 0.34-15 O .5988 1.3931** Sires 27 0.24-29 0.2774- 0.3980 Ewe Breeding Weight(Linear) 1 0.9759 2.514-4-** 0.0^62 Remainder 186 0.2885 0.3010 0.3772 k - 6.7158 ^^Probability due to chance <0.01 >2 Heritability of Prolificacy = - _o.096=0 Cf2 + (?2 s e Heritability of Livability = -0.04-7=0 Heritability of Survival Rate = 0.033^0.169 100 TABLE 30 LEAST-SQUARES ANALYSES OF VARIANCE AND HERITABILITY ESTIMATES FOR PROLIFICACY, LIVABILITY, AND SURVIVAL RATE IN COLUMBIA Mean Squares Source______df. Prolificacy Livability Survival Rate Age of Ewe 4- 0.2185 0.4-4-86 0.6005 Years 5 0.1977 1.195-8** 1.5-809** Sires 4-6 0.3238 0.3557 0.615-7* Ewe Breeding Weight(Linear) 1 2.5-5-06** 4.2887** 2 .8330** Remainder 308 0.2583 0.3190. _ 0.5-075- k = 7.14-97 ♦Probability due to chance <0.05 ♦♦Probability due to chance<0.01 4- 1 Heritability of Prolificacy = --- = 0.137-0.15-2 + < 1 Heritability of Livability = 0.06310.131 Heritability of Survival Rate = 0.266±0.l60 TABLE 31 LEAST-SQUARES ANALYSIS OF VARIANCE AND HERITABILITY ESTIMATES FOR PROLIFICACY, LIVABILITY, AND SURVIVAL RATE IN TARGHEE Mean Squares Source df. Prolificacy Livability Survival Rate Age of Ewe 3 0.1550 0.0113 Years 5 0.4-7 0.8573* Sires 58 0.2598 0.2633 Ewe Breeding Weight(Linear) 1 0.85-4-3 ' 1.985-2** Remainder 0.26^6 0.2836 , , 39k „ k = 7.34-23 ♦Probability due to chance <0.05 ♦♦Probability due to chance<0.01 0 Heritability of Prolificacy = ---- —- = 0.010=0 s e Heritability of Livability = -0.039=0 Heritability of Survival Rate = -.137-0.125 101 twinning rate (Ragab and Askar, 195*+; Rendel, 1956; Sidwell, 1956; Karam, 1957)- Since, prolificacy, as considered in the literature, is a function of ewes lambing or multiple births of the ewes bred, rather than being an estimate of lambs born of ewes lambing, the published heritabilities can be expected to be slightly higher than the values obtained in this study. Heritability estimates for prolificacy, as published in the literature and summarized in table 2, range between 0 and 0.29- Of all the estimates reported in table 2 only one study by Karam and Ragab (1958) on lambs born per lambing in Texel breed is directly comparable with this study. Karam and Ragab (1958) obtained an estimate of 0 .29^0.33 for heritability of lambs born per lambing using half-sib correlation method. In view of the large standard error for this value this estimate could have been influenced by large sampling error. Thus, it is evident that the heritability of prolificacy obtained in this study is in reasonable agreement with the estimate reported by Karam and Ragab (1958). Further, the results of this study support the general belief that additive genetic effects for prolificacy in Columbia and Targhee breeds are not very important and that genetic progress due to selection on the basis of this trait cannot be expected to be of much importance. 102 b. Livability Heritability estimates for livability (lambs born alive of ewes lambing) were found to be of the order of 0.209, -O.^-O?, -0.125, and -O.OH'/ in the Ohio Columbia, North Dakota Columbia, Ohio Targhee, and Illinois Targhee breeds, respectively. Analyses for each breed gave heritabilities of O.O63 for the Columbia and -0.039 for the Targhee breed. As in the case of prolificacy with the large standard error for heritability in the Columbia breed, and a very small negative estimate for the Targhee breed, it may be assumed that heritability of livability in these two breeds is essentially zero. The pooled heritability estimate presented in table 32 is in agreement with this assumption. Although, estimates of heritability for livability in sheep are not available in literature, in view of the insignificant values obtained in this study, it may be reasonably concluded that livability in the Columbia and Targhee breeds is not a genetic trait. Further, it may be said that once a ewe is conceived, the possibility of her giving birth to one or more live lambs is more dependent on management of the pregnant ewes, nutritional and environmental conditions, and elimination of infections or contageous diseases causing early abortions or foetal deaths. 103 c . Survival Rate Although, survival rate (lamb weaned of lambs born alive), as defined in this study, is not directly comparable with any of the reported studies in the literature, numerous workers (Young et al., 1963; Kennedy, 1967; Singh and Rampel, 1967; and others) have published on heritability estimates of number of lambs weaned per mating basis in different breeds of sheep. In the published literature, heritability for number of lambs weaned ranges between 0.06±0.08 (Merino) and 0.19-0.07 (5 lines of* Minnesota). Heritability estimates for survival rate in this study were found to be 0.2h8, -0.001, 0.195 and 0.033 in the Ohio Columbia, North Dakota Columbia, Ohio Targhee, and Illinois Targhee breeds. Pooled analyses for each of the two breeds gave values of 0.266 for the Columbia and 0.137 for the Targhee breed. With such a close agreement between the estimates for these two breeds, a single value of 0.155-0*037 was obtained for both the breeds. Heritability estimates and their standard errors are presented by breed-station groups and breeds in table 32. Comparison of estimates for survival rate obtained in this study with the ones published in literature reveal a very close agreement. Further, on the basis of this study, it can be stated that survival rate in Columbia and Targhee breeds is influenced, at least, to some extent by 10^- the additive gene effects, and that selection on the basis of lamb production will increase the flock production index to reasonable limits. As in the case of heritability for fertility and reproduction, comparison of results presented in tables 15 and 32 indicate that heritability of survival rate is higher than repeatability of this trait. This discrepancy in results, which was also noticed by Young et al. (1963), Kennedy (1967)5 and Karam (1957) can be reasoned on the basis of reports by Turner and Dolling (1965)5 Koch and Clark (1955)? and Wheat and Riggs (1958) and could have occurred due to sampling error. An interesting feature of the results obtained in this study is revealed by comparing-the pooled estimates presented in table 32 with the published estimates. Heritabilities for fertility, reproduction, and survival rate obtained in this study are in close agreement with most of the reports reviewed in this study. Estimates for prolificacy and livability, as defined in this study are not comparable with any of the earlier reports. Thus, on the basis of this study, it could be concluded that prolificacy and livability are individual ewe characteristics and that the remaining three components of fertility have some genetic basis. TABLE 32 HERITABILITY ESTIMATES FOR FERTILITY, REPRODUCTION, PROLIFICACY, LIVABILITY, AND SURVIVAL RATE BY BREED-STATION GROUPS AND BREEDS Ohio N .Dakota Columbia Ohio Illinois Targhee Pooled Traits Columbia Columbia Targhee Targhee Fertility Heritability -0.027 0.485 0.230 -0.012 -0.096 -0.035 0.117 Standard Error 0.29*+ 0.139 0.093 Reproduction Heritability 0.079 0.245 0.202 0.288 0.109 0.241 0.205 Standard Error 0.l4l 0.259 0.136- ■ 0.191 0.173 0.130 0. 102 ■ Prolificacy Heritability 0.259 -0.308 0.137 -0.076 -0.096 -0.010 0.010 Standard Error 0.197 0.142 0.085 Livability Heritability 0.209 -0.V-07 0.063 -0.125 -0.047 -0.039 ■-0.003 Standard Error 0.187 0.131 Survival Rate Heritability 0.25-8 -0.001 0.266 0.195 0.033 0.137 0.155 Standard Error -.195 0.160 0.189 0.169 0.125 0.094 ' H . O vn. 106 D. Correlations An attempt was made to estimate phenotypic, genetic, and environmental correlations between the five components of fertility, as defined in this study, and some of the important production traits. Since, grading, scoring, and weighing of lambs at various ages was first started in 1962, for the purpose of estimating correlations only the ewe lambs born in 1962 onwards were included in these analyses. The ewe lambs born in 1962 had their first lambing records in 196*+. Thus, all the ewes which had their first lambing records in 1962 and 1963 had to b e . dropped out of these analyses in want of their weaning and pre-weaning weights and weight gains, and grades and scores for the various body and wool traits. As in the case of repeatability and heritability analyses, because of the nature of fertility components included in this study, separate analyses were made for the two sets of fertility components for 'each breed group'. For each ewe, two cards, carrying information on production traits when she was a lamb and her reproductive performance were merged and a new card was punched on computer carrying both the lamb and adult information. Thus, a total of 14-9 and 207 records were analysed for estimating correlations of fertility and reproduction with production traits in the Columbia and Targhee breeds respectively. Correlations between prolificacy, livability, and survival rate and the production traits, included in 107 this study, were estimated from 135 and 19*+ records in the Columbia and Targhee breeds respectively. Since, the number of records within each breed-station group for each of the two breeds was very small, no attempts were made to estimate correlations within each breed-station group. Phenotypic, genetic, and environmental correlations between fertility components and production traits in Columbia and Targhee breeds were estimated by using half- sib analysis of variance technique. A total of 31 sires in the Columbia and 38 sires in the Targhee breed were represented over the four year period (196^-1967) of this study. Since, genetic correlations estimated on these sets of data on Columbia and Targhee breeds were associated with a larger standard error than the estimate' itself, these estimates could not be considered of any practical value , and hence, will not be discussed in this section. Phenotypic correlations between the fertility components and production traits in the Columbia and Targhee breeds are presented in tables 33 and 3^ respectively. Since, the scoring of all the subjective traits was done in reverse direction, i.e., the desirability for a particular trait was inversely related to the points scored, the signs preceding the correlation coefficients for conformation, back conformation, feet and legs, pasterns, condition, skin folds, face cover, wool grade, and wool 108 TABLE 33 PHENOTYPIC CORRELATIONS BETWEEN FERTILITY COMPONENTS AND PRODUCTION TRAITS IN COLUMBIA Fertility Reprodu Prolifi Livabi Surviv< ction cacy lity Rate Reproduction 0.507 Livability O .877 Survival Rate 0.522 0.613 Birth Weight 0.013 -0.188 -0.182 -0.182 -0.191 30 Day Weight 0.04-1 -0.233 -0.195 -0.180 -0.276 90 Day Weight -0.005 -0.191 -0.15-1 -0.17R -0.187 Gain Birth to 30 Days 0.05-3 -0.205 -0.165 -0.15-7 -0.259 Gain 30 to 90 Days -0.007 -0.175- -0.121 -0.156 -0.167 Gain Birth to 90 Days -0.031 -0.123 -0.077 -O.131 -0.093 Conformation 0.132 0.122 0.008 -0.005 0.076 Back Confor mation 0.115 0.035- -0.05-1 -0.04-9 -0.017 Feet and Legs 0.070 0.002 -0.086 -0.111 -0.123 Pasterns -0.05-5 -0.053 -0.238 -0.222 -0.037 Condition 0.081 0.235 0.050 0.095 0.259 Skin Folds 0.05-8 -0.030 -0.229 -0.230 -0.059 Face Cover -0.05-6 -0.15-5 -0.067 -0.067 -0.153 Wool Grade -0.051 -0.033 -0.020 -0.012 -0.052 Wool Uniformity-0 .079 0.085 0.155 0.112 0.133 Staple Length -0.013 -0.132 -0.05-7 -0.122 -0.137 109 TABLE 3k PHENOTYPIC CORRELATIONS BETWEEN FERTILITY COMPONENTS AND PRODUCTION TRAITS IN TARGHEE Fertility Reprodu- Prolifi- Livabi- Survival ction cacy lity Rate Reproduction 0.V22 Livability O .786 Survival Rate 0.529 Birth Weight -O.OV9 -0.111 -0.155 -0.111 -0.098 30 Day Weight -O.I38 -0.039 -0.076 -0.078 -0 .01V 90 Day Weight -0.077 -O.O9V -0.14-3 -0 .1V5 -0.079 Gain Birth to 30 Days -0.14-5 -0.004- -0.031 -0.051 0.055 Gain 30 to 90 Days -0.072 -0.078 -0.122 -0.132 -O.O65 Gain Birth to 90 Days 0.000+ -0.092 -0.127 -0.127 -0.110 Conformation 0.089 0.025 0.0V8 0.063 -0.028 Back Con formation 0.013 0.052 -0.030 -0.037 0 .0V2 Feet and Legs 0.003 -0.066 -0.115 -0.119 -0.083 Pasterns 0.012 -0.059 -0.069 -0.082 -0.088 Condition 0 .05V O.O69 0.101 0.101 0.057 Skin Folds -0.123 -0.107 -0.120 -0.101 -0.068 Face Cover -0.068 -0.017 0.037 o.oVV 0.016 Wool Grade -0.031 -0.010 0.100 0.02 V 0.001 Wool Uniform ity 0.027 0.069 0.086 0.075 0.06 V Staple Length -0.113 -O.IV7 -0.136 -0 .08V -0.113 110 uniformity in tables 33 and 3^ should be reversed. Although, it is difficult to put any reliability on estimates obtained from such a small sample of data, from tables 33 and 3^ it can be seen that in both the breeds the five fertility components are highly correlated among themselves. Further, it can be noticed that irrespective of the signs for the coefficients, correlations between fertility components and production traits were found to be of very small magnitudes in both the breeds. However, it is rather difficult to explain the negative signs for almost all the correlation coefficients between the fertility components and weights and weight gains during the respective periods upto weaning age in both the breed groups, except on the basis of sampling error which could play quite an important role i n .such a small sample within each breed. Terrill (19*+9), Fail and Dun (1956), Inkster (1956), Quinlivan (1963) and Mullancy (1966) observed negative phenotypic correlation between face cover and number of lambs born. Further, they observed that face covering seems to reduce the proportion of twins born rather than the number of ewes lambing. Comparing these results with the estimates obtained in this study indicates that, although, the estimates are of very small magnitude, present results are in contradiction with the published estimates. In Columbia breed all the five fertility Ill components are positively correlated with the extent of face covering, however, in Targhee breed fertility and reproduction are positively associated with face cover and prolificacy, livability and survival rate are negatively related to the wool blindness. Thus, the results obtained in this study are similar in sign to those published by Kennedy (1959) in Merino. A very close agreement between the results of this study and published estimates is seen in the sign for the correlation between fertility components and staple length. Although, of not very large magnitude, the association of fertility components with staple length was found to be negative in both.the breeds and is in agreement with the report by Campbell (1962). However, results of this study are in disagreement in sign for the relation ship between fertility components and wrinkle scores reported by Kennedy (1959)> Dun. (1961), and Young et al.- (1963). Although, in the beginning it was Intended to compute correlated responses in the various fertility components due to selection for production traits and vice versa, with the estimates obtained for genetic correlations in this study such computations would hardly be of any practical value. However, it could be quite informative to recompute these correlations using larger amount of data and then estimating the correlated responses between fertility and ' 112 production traits when selection is based on one trait at a time. SUMMARY Repeatability and heritability of fertility, reproduction, prolificacy, livability and survival rate for each- of the two strains in Columbia and Targhee breeds were estimated by least-squares procedures. A total of 259) 163) 262, and 237 lambing records on the Ohio Columbia, North Dakota Columbia, Ohio Targhee, and Illinois Targhee ewes, respectively, collected over a period of six years (1962-1967) were analyzed in this study. Least-squares means obtained for the two breeds revealed 85-15% and 95-Oh-% lambing rates in the Columbia and Targhee breeds respectively. Further, for each hundred Columbia ewes lambing 138.8% lambs were dropped of which 116.b% were alive at birth and only 77-2% of the live lambs born were reared to weaning. The corresponding figures for Targhee breed were 150.0%, 13^-0%, and 100.3$ respectively. Lamb mortality rate among each of the four breed-station groups is presented. Averaged over the entire period of this study, lamb mortality in the Targhee flock was 33.6% and in the Columbia flock it was 39-2%. Repeatability estimates for each breed-station group , and pooled estimates for each of the two breeds and across the two breeds were estimated. Because of the 113 11*+ partial confounding of age of ewe and year of record effects, analyses were made by birth-year groups within each breed- station group separately. Ewe and error components of variances were estimated by pooling the sums of squares and degrees of freedom across all the birth-year groups within breed-station groups, adjusted for the confounded age and year effects. Fertility, reproduction, prolificacy, livability, and survival rate were found to be 23*72%, 12.53%; 20.10%, 5.5-8%, and 8.15-% respectively, repeatable in the Ohio Columbia group, and 0.5-9%, 5-.70%, 25*91%; 25-.76%, and 15-.31% respectively, in the North Dakota Columbia ewes. The comparative figures for the other two breed-station groups were 21.01%, 6.65%, 0.0%, 0.0%, and 0.0% respectively for the Ohio Targhee ewes, and 0.0%, 11.89%, 0.0%, 0.0%, and 12.60% respectively for the Illinois Targhee group. Pooled estimates for each of the two breeds and across the two • breeds have been reported. Heritability estimates for all the traits for each of the breed-station groups and breeds were estimated by half-sib correlation method. Heritabilities for fertility, reproduction, prolificacy, livability, and survival rate were estimated to be -0.027, 0.079, 0*259, 0.209, and 0.25-8 respectively in the Ohio Columbia, and 0.5-85, 0.25-5, -0.308, -0.5-07, and -0.001 respectively in the North Dakota Columbia group. The comparable estimates for the two Targhee groups 115 were -0 .012, 0 .288, -0 .076, -0 .125) and 0.195 respectively in the Ohio Targee, and -O.O96, 0.109, -O.O96, -0.09-7, and O.O33 respectively in the Illinois Targhee breed. Pooled analyses separately for each of the two breeds gave heritability values of 0 .230, 0 .202, O.I37, O.O63, and 0.266 for fertility, reproduction, prolificacy, livability, and survival rate respectively in the Columbia breed. The comparable estimates for all the five traits in the Targhee breed were found to be -0.035, 0.29-1, -0.010, -0.039, and 0.137 respectively. Averaged over both the breeds, the estimates revealed that fertility, reproduction, and survival rate are influenced, at least, to some extent by genetic effects, and that prolificacy and livability could be considered as individual traits rather than having any genetic basis of inheritance. Phenotypic correlations between all the five fertility components and 16 important production traits were estimated separately for both the breeds, using four year records from 1969- to 1967, inclusive. In both the Columbia and Targhee breeds, the fertility components as defined in this study were found to be highly correlated positively. . Correlation coefficients between fertility components and production traits were found to be very small with variable signs in both the breeds. Although, very small but negative phenotypic correlations between fertility components and weights and weight gains during different periods up to 116 weaning age in both the breeds could be indicative of large sampling errors in both the breeds. Further investigations using larger samples is emphasized. Appendix A Least-Squares Constants for Age of Ewe, and Year Effects on Fertility, Reproduction, Prolificacy, Lamb Livability, and Survival Rate by Breed Station Groups and Breeds. l' Classification OC* NDC* Columbia GT* IT* Targhee A. FERTILITY 1) Age ofEwe 2 years 0.0908 -0.0b-2*+ 0 .05b-2 0.0127 -0.0*+07 -0.0262 3 " 0 .031!+ -0 .067!+ -0.0098 -0.0393 0.0201 -0.0130 !+ " -0.0070 0.l!+52 0.0088 -0.0087 -O.OO87 O.OO93 5 " -0.0917 -0.0712 -0.0526 0.0352 0.0293 0.0299 6 " -0.0235 0.0358 -0.0005 — • — 2) Years 1962 -0.1080 -0 .03^3 -0.1021 -0.1917 -0.0117 -0.1123 1963 0.069*+ 0.1851 0.1088 0.0160 0 .007b- 0.0302 196b- -0 . Ob-02 -O.O723 -0.0159 0.0270 -0.0326 0.0030 1965 -0.0023 0.1793 0 .ob-38 0.0639 0.0015 0. Ob-06 1966 -0.0312 -0.175*+ -0.08*+b- -0.018b- 0.0377 0.0052 • 1967 0.1123 -0.0821 O.Ob-97 0.1032 -0.0022 0 .033b- Appendix A (Continued) Classification______PC*______NDC*____Columbia______OT*______IT*_____Targhee B. REPRODUCTION 1) Age of Ewe 2 Years 0.0279 0. *+270 0.3160 -0.0322 0.0958 0.055-2 3 !t 0.0135 0.2182 0.135-6 -0.085-3 0.1168 0.0502 5- 11 0.1736 0.0696 0.15-75 -0.205-5- 0.2239 0.0097 5 M -0. 1*122 -0.1208 -0.1835 0.3209 -0.5-366 -0.115-1 6 n -0.2828 -0.59^-1 -0.5-15-6 — — ----- 2) Years 1962 -0.2902 -0.65-57 -0.5-123 -0.5267 -0.3275 -0.5-615- 1963 -0.3119 -0.3565- -0.35-65- -0.315-2 -0.5-773 -0.3756 1965- 0.15-66 -0.0556 0.0380 0.1573 0.0811 . 0.1137 1965 0.1135- 0.115-5 0.1278 -0.0058 0.0035 0.0031 1966 O .0929 0.3277 0.1900 0.1865- 0.1993 0.2355- 1967 0.25-93 0.6155- 0.5-030 0.5030 0.5210 0.5-85-8 Appendix A (Continued) Classification______OC____ NDC_____ Columbia______OT______IT+_____ Targhee C. PROLIFICACY 1) Age of Ewe 2 Years -0.0356 0.1759 0.0238 -0.3061 0.0059 -0.1187 3 ” -0.1300 -0.1063 -0.0891 -0.2331 0.0628 -O.OM-92 b " -0.006*+ -0.1063 -0.0320 -0.1515 0.0229 -0 .0^15 5 " -0.0162 0.0716 -0.0718 0.6907 -0.0916 0.2095 6 " 0.1883 -0.03^9 0.1691 ------— 2) Years 1962 -0.1^19 -0.3558 -0.1996 0.0827 -0.1563 -0.0383 1963 -0.1219 -0.1105 -0.1553 -0.0371 -O.IO98 -0.0999 196!+ 0.0568 -0.0709 -0.0115 -0.0099 -0.1356 -0.0810 1965 0.0857 -0.1006 0 .065*+ -0.1525 -0.1313 -0.1331 1966 -0.0835 0.2785 0.0578 -0. 0*+93 0.1973 0.0983 1967 0 .20*+9 0.3592 0 . 2*+31 0.1661 0-3357 0.25*+l Appendix A (Continued) Classification o c NDC Columbia OT IT Targhee D. LIVABILITY 1) Age of Ewe 2 Years O.l^fl 0 A 0 3 5 0.2267 -0 .2^08 0.1712 0.0201 3 " -0 .122+1 0.0372 -0.0166 -0.2090 0.1109 -0 .0002+ Lj. ti -0.0161 O.OO83 0.0138 -0.1523 0.0771 -0.0202 5 " -0.1133 0.1703 -0.1018 0.6022 -0.3592 0.0005 6 " 0.1095 -0.6193 -0.1222 — — -- 2) Years 1962 -0.2006 -0.5089 -0.2968 O.OO98 -0.2755 -0.1598 1963 -0.2+520 -0.3171 -0.^91 -0.1726 -0.327^ -0.2915 1 9 6 ^ 0.0967 -O.O389 0 .012+3 -O.OI32+ -0.0925 -0.0625 1965 0.1736 -0.0398 0 .12+35 -0.1388 - 0 . 0 9 8 1 -0.1078 1 9 6 6 0 .02+50 O.368I 0.1650 0.0280 0.2828 0.1969 1967 0.3373 0.5365 0 A 230 0.2870 0 . 5 1 0 8 0. ^-22+7 Appendix A (Continued) Classification OC NDC Columbia OT IT Targhee E. SURVIVAL RATE 1) Age of Ewe 2 Years 0.1208 0.5583 0.2979 -0.0152 0.1327 0.0910 3 " -O.O38O 0.2836 0.1385 -0. OifOl 0.0979 0.0633 ^ " 0 .23^6 . -0.13^7 0.1611 -0.2018 0.2350 0.0012 5 " -0.0389 -0.039^ -0 .1if82 0.2571 -0.1+657 -0.1555 6 11 -0.2785 -O.6678 -O.M+93 — — — 2) Years 1962 -0.1615 -0.7070 -0.3396 -0.3577 -0.2929 -0.3^29 1963 -0. if071 -0.5956 -0 .1+996 -0.3691 -0.5019 -0.1+305 196b 0.2160 O.Oib-9 0.0713 0.1293 0.1297 0.1190 1965 0.0923 -0.0976 0.0927 -0.0706 0.0016 -0.0357 1966 0.1308 0.5931 0.2899 0.2198 0 .1^15 0.2221 1967 0.1295 0.7922 0.3853 0. ^+8*+ 0.5220 OA679 *0C = Ohio Columbia OT = Ohio Targhee NDC = North Dakota Columbia IT = Illinois Targhee 121 i Appendix B Least-Squares Means and Standard Errors for Fertility, Reproduction, Prolificacy, Livability and Survival Rate for Ohio Columbia, North Dakota Columbia and Columbia Ohio Columbia North Dako ta Columbia Columbia Classification INo. Mean S.E. IMo. Mean B.E. . h o . Mean S.E. 259 163 5+22 A. FERTILITY 1) Age of Ewe 2 Years 103 0.957, 0.05+3 72 0.839 0.056 175 0.906 0.031 3 71 O .898 0.067 51 0. 8l5+ 0.085 122 0.85+2 0.05+9 5+ " 5+7 0.859 0.108 27 1.027 0.157 75+ 0. 860 0.082 5 " 33 0 . 775+ 0.155 9 0.810 0.195 5+2 0.799 0.117 6 " 5 0 .8V 3 0.265+ 5+ 0.917 0.299 9 0.851 0.188 2) Years 1962 35 0.783 0.205+ 25 0.85+7 0.275 60 0.75+9 0.156 1963 5+7 0.936 0.17^ 22 1 .066 0.225+ 69 O.96O 0.130 1965+ 5+6 0.826 0.15+9 23 - 0.809 0.163 69 0.836 0.106 1965 5+6 0.865+ 0.108 29 1.061 0.15+0 75 0.895 0.078 1966 h i 0.835 0.081 31 0.706 0.082 72 0.767 0.055+ 122 1967 5+5+ 0.979 0.058 33 0.799 0.088 77 0.901 0.05+7 V Appendix B (Continned) Ohio Columbia North Dako ta Columbia Columbia Classification No. Mean S.E. No. Mean S.E. No. Mean S.E. 259 163 k22 B. REPRODUCTION 1) Age of Ewe 2 Years 103 1.052 0.096 72 0.919 0 .11k 175 0.965 0.067 3 " 71 0.828 0.150 51' 0.697 0.175 122 0.775 0.106 ^ .. • by 0.988 0 .2kl 27 0.528 0.321 7k 0.789 0.175 5 " 33 0.673 0.3^5 9 0.326 0.399 k2 0 .k56 0.251 6 » 5 0.532 0.589 k -0.126 0 .61k 9 0.225 0.k03 2) Years 1962 37 0.525 O A 5 5 25 -0.192 0 . 56k 60 0.228 0.335 1963 b7 0.503 0.389 22 0.105 0.k59 69 0 .29k 0.278 196k b6 0.961 0.332 23 0.395 0.33^ 69 0.678 0.228 1965 b6 0.928 0 .2kl 29 0.578 0.288 75 0.768 0.167 1966 b l O .908 0.181 31 0.813 0.168 72 O .830 0.117 • 1967 kk 1.06k 0.129 33 1.113 0.181 77 1 .0k3 . 0.102 LOIV) Appendix B (Continued) Ohio Columbia North Dakota Columbia Columbia Classification No. Mean S.E. No. Mean S.E. No. Mean S.E. 228 137 365 C. PROLIFICACY 1) Age of Ewe 2 Years 92 1.576 0.071 .58 1.553 0.091 150 1.5-12 0.051 3 " 65 1.379 0.112 53 1.130 ' 0.15-8 107 1.299 O.O83 1+ 1! b l 1.503 0.189 25 1.102 0.263 66 1-356 0.150 5 " 26 1 A 9 3 0.272 8 1.261 0.325 35- 1.316 0.199 6 » 5 1.697 0.558 3 1.176 0 . 5 H 8 1.557 0.317 2) Years 1962 29 1.367 0.355 17 0.822 0.5-71 5-6 1.188 0.267 1963 55 1.387 0.301 19 1.101 O.38I 65 1.232 0.220 1965 39 1.566 0.259 20 1.122 0.271 59 1.376 0.180 1965 38 1.595 0.186 27 1.121 0.235 65 1*5-53 0.132 1966 35 1 .526 0.139 23 1.530 0.15-8 58 1.556 0.095 1967 b2 1 .7 1 b 0.095 31 1.637 0.15-2 73 1.631 0.076 Appendix B (Continued) Ohio Co 11101131 a North Dakota Columbia Columbia__ Classification No. Mean S.E. No. Mean= S.E. No. Mean S.E. ______228______132______263______D. LIVABILITY 1) Age of Ewe & 1 — 2 Years 92 1.5-66 0.079 58 1 .5-22 0.102 1 1.391 0.057 tf H O IN 3 eh 1.198 0.123 5-3 1.020 0.167 1.15-7 0.093 5- tl 5-i 1.306 0.208 25 O.96O 0.297 66 1.178 0.155 5 11 26 1.209 0.299 8 1.099 0.365- 35- 1.062 0.222 11 6 5 1.5-32 0 .5-95- 3 0.33^ 0.572 8 1.05-2 0.352 2) Years 1962 29 1.122 0.392 17 0.5-07 O .526 5-6 O .867 0.297 1963 5-5 0.870 0.332 19 0.638 0.5-26 65- 0.715 0 .2V+ 1965- 39 1.5-19 0.285 . 20 0.895 0.303 59 1.178 0.201 1965 38 1.5-96 0.205 27 O .927 0.263 65 I .307 0.15-7 1966 35 1.367 0.155- 23 1.369 0.165 58 1.329 0.106 1967 5-2 1.660 0.105- 31 1.568 0.159 73 1.587 0.085- rv> vn. Appendix B (Continued) Ohio Columbia North Dakota Columhia Columhia Classification No. Mean S.E. No. Mean S.E. No. Mean S.E. 228 137 365 E. SURVIVAL RATE 1) Age of Ewe 2 Years 92 1.098 0.091 58 1.117 0.110 150 1.070 0.065- 3 " 65- 0.939 0.15-2 *+3 O .838 0.178 10? 0.911 0.105 5- " 5-1 1.211 0.25-0 25 0.5-15 0.316 66 0.933 0.176 5 " 26 0.938 0.35-6 8 0.507 0.319 3*+ 0.625- 0.251 6 " 5 0.695 0.571 3 -0.118 0 .61^ 8 0.323 0.398 2) Years 1962 29 0.815 0.5-53 17 -0.162 0 .565 1+6 0.5-33 0-336 1963 5-5 0.570 0.385- 19 -0.05-5 0.5-78 65- O .273 0.276 196*+ 39 1.193 0.330 20 0.562 0.325 59 0.85-5- 0.227 1965 38 I.O69 0.237 27 0 . ^ 0.283 65 0.865 0.166 1966 35 1.108 0.178 23' 1.15-9 0.178 58 1.062 0.120- 1967 5-2 1.106 0.120 31 1.353 0.171 73 1.158 . 0.095 Appendix C Least-Squares Means and Standard Errors for Fertility, Reproduction, Prolificacy, Livability and Survival Rate for Ohio Targhee, Illinois Targhee and Targhee Ohio 1'arghee Illinois Targhee Targhee ~ Classification No. Mean S.E. No. Mean S.E. No”. Mean S.E. ______262______237______^99______A. FERTILITY 1) Age” of Ewe 2 Years 125 0.932 0.030 121 0.922 0.028 2k6 0.92k 0.021 3 ii 82 0.880 0.066 7k 0.983 O.okQ 156 0.937 O.O38 it 51 0 . 9 H 0.126 36 0.95^ 0.078 87 0.959 0 .066 CO O ON 0 5 11 if 0.955 0.2lf5 6 0.992 . 0.155 10 • 0.13^ 6 ii _ _ _ — — — -- - - 2) years 1962 31 0.728 0.220 12 0.951 0. llf2 ^3 O .838 0.116 CO 0 ON 1 — 1963 if8 0.936 0.191 38 0.970 0.108 86 1 0.097 196if if5 O.9U-7 O.llflf k-7. 0.930 0.091 92 0.953 0.078 1965 if8 0.98if 0.097 If6 0.96if 0.070 9h 0.991 0.057 1966 i+5 0.901 0.058 k-7 1.000 0.0lf9 92 0.956 O.O38 1967 if 5 1.023 0.077 11-7 0.961 O.Qlf6 92 0.98if 0.039 Appendix C (Continued) Ohio Targhee Illinois Targhee Targhee______Classification No. Mean S.E. No. Mean S.E. No. Mean S.E. 262 237 599 B. REPRODUCTION 1) Age of Ewe 2 Years 125 0.993 0.069 121 1.05-2 0.079 256 1.015 0.052 3 " 82 0.951 0.153 75- 1.063 0.135 156 1.010 0.096 5 '» 51 0.821 0.289 36 1.170 0.221 87 0.969 0.165 5 " i+ 1-356 0.565- 6 0.509 0.535 10 0.856 0.337 6 " — — — — — — Years 1962 31 0.5-98 0.505 12 0.618 0.500 53 0.598 0.292 1963 58 0 . 7 H 0.5-38 38 0.5-68 0.303 96 0. 585 0.253 1965 i+5 1.182 0.330 1+7 1.027 0.257 92 1.073 0.195 1967 58 1.019 0.222 56 0.959 0.197 95 0.963 0.152 1966 55 1.211 0.135 5-7 1.155 0.137 92 1.195 0.095 1967 55 1.528 0.177 5-7 1.157 0.129 92 1.555 0.099 ro OD Appendix C (Continued) Ohio Targhee Illinois Targhee Targhee______Classification No. Mean S.E. 'No. Mean S.E. No. Mean S.E. ______239 ______223______562______C. PROLIFICACY 1) Age of Ewe 2 Years ill 1.332 0.056 111 1.5-26 0.068 222 1.381 0.053 3 " 75 1 A 05 0.128 72 1.583 0.112 157 1.550 0.079 5 " 59 1.587 0.237 35- 1.553 0.185 83 1.558 0.135 5 " 5 2.329 0.556 6 1.329 O.36I 10 1.709 0.273 6 » “ *"* Years "" 1962 23 1.721 0.5-22 11 1.265 0.333 35 1.561 0.251 1963 1+1+ 1.601 0.365 37 1.311 0.251 81 1.500 0.198 196*+ 5i 1.629 0.269 5-2 1.285 0.215 83 1.519 0.159 1965 55 1. *+86 0.182 5-3 I .289 0.165 ‘88 1.367 0.116 1966 b l 1-589 0.107 55 1.618 0.115 86 1.598 0.077 1967 55 1.905 0.15-1 55 1.756 0.107 90 1.755 . 0.080 1—1 ro M3 Appendix C (Continued) Ohio Targhee Illinois Targhee Targhee______Classification No. Mean S.E. No. Mean S.E. No. Mean S.E. 239 223 k-62 D. LIVABILITY 2 Years 111 1.295 0.058 ill I.h20 0.069 222 1.359 O.Ohh 3 M 75 1.326 0.133 72 1.360 ■ O.llh lh7 1.339 0.082 h M h9 1.383 0.2^5 3h 1.326 0.188 83 1.319 0.139 5 If h 2.138 0.h73 6 O .889 0.369 10 1.3^0 0.282 6 II — _ ------2) Years 1962 23 l.5h5 OA 38 11 0.973 0.3h0 3h 1.180 0.250 1963 hh 1.363 0.378 37 0.921 0.257 81 1.0h8 0.205 196h h i 1.522 0.279 h2 1.156 0.220 83 1.277 0.l6h 1965 1.397 0.189 h3 1.151 0.169 88 1.232 0.120 1966 hi 1.563 0.111 *+5 1.531 0.116 86 1.536 0.080 1967 h5 1.822 0.lh7 h5 1.759 0.110 90 1.76h O.O83 H OJo Appendix C (Continued) Ohio Targhee Illinois Targhee Targhee______Classification ho. Mean S.E. ho. Mean S.E. ho. Mean S.E. 239 223 *4-62 E. SURVIVAL RATE 1) Age of Ewe 2 Years ill 1.066 0.068 111 l.*4-20 0.069 222 1.09*4- 0.051 3 " 75 1.0*4-1 0.156 72 1.359 0.11*4- 1*4-7 1.067 0.093 b " ^9 0.879 0.288 3^ 1.326 0.188 83 1.005 0.158 5 M 1.338 0.555 6 O .890 0.369 10 0.8*f8 0.322 6 " “ “ “ ~ “ “ “ “ Years 1962 23 0.723 0.513 11 0.973 0 .3*4-0 3^ 0.661 0.285 1963 *f*4- 0.712 0.¥f3 37 O .921 0.257 81 0.573 0.23*4- 196*4- *+1 1.210 0.327 ■ b2 1.156 0.220 83 1.122 0.187 1965 - *4-5 1.011 0.221 ^3 1.151 0.169 88 0.968 0.137 1966 *4-1 1.301 0.130 *4-5 1.532 0.116 86 1.226 0.091 1967 ^5 1.529 0.172 *4-5 1.759 0.120 90 l.*4-71 0.09*4- 132 APPENDIX D LEAST SQUARES ANALYSES OF VARIANCE FOR FERTILITY IN OHIO COLUMBIA Birth-Year Between'Years Between Ewes Remainder Groups df MSa df MS df MS k value 1 3 0.1585 35- 0.1635* *+8 0.0908 2.4118 2 5- 0.1036 30 0.1355- 5-6 0.0956 2.5333 3 3 0.0163 18 0.2122 17 0.1097 1. 9W 2 0.0000 7 0,115-3** 5 0.0000 1.7153 5 1 0.0625 23 0.0978 7 0.0625 1.305-3 6 - 13 0.0000 0 --- 1.0000 k 1 - = 2HZ.v9.B¥t = 9q39 f-(di-l) 125 *Probability due to chance 0.05 **Probability due to chance 0.01 aMS = Mean Squares LEAST-SQUARES ANALYSES OF VARIANCE FOR REPRODUCTION IN OHIO COLUMBIA Birth-Year Between Years Between Ewes Remainder df MSa df MSa CO Groups df MSa (—1 CM 1—1 1 3 0.905-0 35 0.65-60 5-8 0.5-331 • 2 5 0.5556 30 0.75-55 5-6 0.5568 2.5333 3 3 0.0600 18 0.6188 17 0.2933 1.955-5- 5 2 0.0260 7 0.5908 5 0.5229 1.715-3 5 1 3.0625* 23 o .31+51 7 0.5-911 1.305-3 6 13 7.5286 0 ----- 1.0000 k' = 1.9339 : * = Probability due to chance 0.0? aMS = Mean Squares 133 APPENDIX D (Continued) LEAST-SQUARES ANALYSES OF VARIANCE FOR FERTILITY IN NORTH DAKOTA COLUMBIA Birth-Year Between Years Between Ewes Remainder Groups df MB- df MS df MS k value 1 5 0.0798 27 0.1768 4-2 0.1379 2.5366 2 3 0 .2223* 25 0.0593 36 0.0671 2 .4-4-00 3 3 0.1377 19 0.0909 12 0.14-61 1.6316 4- 2 0.2738 22 0.14-71 12 0.079*+ 1.5*155 ' 5 1 0.0000 21 0.1113 8 0.1250 I.38IO 6 10 0.0000 1.0000 = 1 .8830. LEAST SQUARES ANALYSES OF VARIANCE FOR REPRODUCTION IN NORTH DAKOTA COLUMBIA Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 5 0.4-4-17 27 0.7179 4-2 0.6031 2.5366 2 3 1.6179** 25 0.1+312 36 0.3629 2 .4-4-00 3 3 0.14-72 19 0.5839 12 0.6715 1.6316 5+ 2 0.5833 22 0.5862 12 0.3750 l.5*+55 5 1 0.0556 21 0.3566 8 0.1806 1.3810 6 10 0.2909 1.0000 k' = 1.8830 13^ ArPENDIX D (Continued)' LEAST-SQUARES ANALYSES OF VARIANCE FOR FERTILITY IN OHIO TARGHEE Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 2 0.1093 30 0.1790 30 0.1038 2.0000 2 3 0.0385 35 0 .0768** 35- 0.0309 1.9715- 3 3 0.0322 15 0.2053** 15- 0.05-07 2.0000 2 0.0371 22 0 .05-23 16 0.0579 1.7273 5 1 0.1538 29 0.0338 12 0.0705 1.5-138 U 13 0.0000 1.0000 k 1 = 1 .75-13 LEAST-SQUARES ANALYSES OF VARIANCE FOR REPRODUCTION IN OHIO TARGHEE Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 2 0.7015 30 0.5-319 30 0.5310 2.0000 2 3 0.5-887 35 0.5-995 35- 0.3981 1.9715- 3 3 0.1250 15- 0.6399 15- 0.5-792 2,0000 2 0.6635- 22 0.3715- 16 0.2608 1.7273 5 1 1.885-6* 29 0.5-220 12 0.3013 1.5-138 6 , 13 0.5275 1.0000 k 1 = 1.75-13 135 APPENDIX D (Continued) LEAST-SQUARES ANALYSES OF VARIANCE FOR FERTILITY IN ILLINOIS TARGHEE Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 2 0.0278 19 0.0991 22 0.0732 2.1579 2 2 0.0000 16 0.0000 18 0.0000 2.1250 3 3 0.1301 38 0.0736 *+2 0.0780 2.1053 *+ 2 0.0000 8 0.0000 11 0.0000 2.3750 5 1 0.0625 23 0.021*+ 7 0.0625 1.30*4-3 6 - 19 0.0500 ------1.0000 k' = 1.8130 LEAST- SQUARES ANALYSES OF VARIANCE FOR REPRODUCTION IN ILLINOIS TARGHEE Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 2 1.6111 19 OA705 22 0.7^75 2.1579 2 2 0 .920*+ 16 0.3398 18 0.3977 2.1250 3 3 0 .18*4-7 38 0.6232** *+2 0.2626 2.1053 *+ 2 0.2997 8 0.5635 11 0.32*+3 2.3750 5 1 0.0625 23 0.3009 7 0.205*+ l . 30*+3 6 - 19 0.5895 ------1.0000 k' = 1.8130 136 APPENDIX E LEAST-SQUARES ANALYSES OF VARIANCE FOR PROLIFICACY IN ILLINOIS TARGHEE Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 2 0.0967 18 0.3719 19 0.384-6 2.0556 2 2 0.2579 24 0.2750 18 0.3510 1.7500 3 3 0.3781 38 0.34-58 3? 0.3724- 1.9211 4- 2 0.5176 14- 0.1759 11 0.284-7 1.7857 5 1 0.64-29 23 0.2100 6 0.3095 1.2609 6 — 18 0.2632 ------1.0000 LEAST-SQUARES ANALYSES OF VARIANCE FOR LIVABILITY IN ILLINOIS TARGHEE Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 2 0.84-74- 18 0 . 2^34- 19 0.4-196 2.0556 2 2 0.6106 24- 0.2824- 18 0.3766 1.7500 3 3 0.1238 38 0.2959 35 0.3132 1.9211 4- 2 O .5176 14- 0.1759 11 0.284-7 1.7857 5 1 0.6429 23 0.2100 • 6 0.3095 1.2609 6 - 18 0.4795 __ ------1.0000 LEAST-SQUARES ANALYSES OF VARIANCE FOR SURVIVAL RATE IN ILLINOIS TARGHEE Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 2 2.0714-* l8 0.4-889 19 0.5714- 2.0556 2 2 0.9204- 24 0.3336 18 0.3977 1.7500 3 3 0.174-1 38 0 .4-592 35 0.2113 1.9211 4- 2 0.2997 14- 0.4-153 11 0.324-3 1.7857 5 1 0.2857 23 0.2633 6 0.1190 1.2609 6 18 0.5380 — — -- — — — — 1.0000 k' = 1.6593 * = Probability due to chance 0.05 ** = Probability due to chance 0.01 137 APPENDIX E (Continued) LEAST-SQUARES ANALYSES OF VARIANCE FOR PROLIFICACY IN OHIO TARGHEE Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 2 0.0072 26 0.1855 23 0.35^ 1 .88^6 2 3 0.2353 0.2602 31 0.2^-61 1.9118 3 3 0.5106 13 0.1723 11 0.3759 1 .8^-62 !+ 1 1.7370** 22 0.1682 1*+ 0.1090 1 .636^ 5 1 1.1361* 29 0.1957 10 0 .236^ 1 .3 A 8 6 — 13 0A231 ----- —- 1.0000 LEAST--SQUARES ANALYSES OF VARIANCE FOR LIVABILITY IN OHIO TARGHEE Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 2 0.1805 26 0.1596 23 OA553 1 .88^6 2 3 0.3729 3 if 0.2827 31 0.321+1 1.9118 3 3 0.5106 13 0.1723 11 0.3759 1 ,8*+62 b 2 2 .0^01** 22 0.1528 l b -0.0657 1 .636^ 5 1 1 .136M- 29 0.1957 10 0 .236^ 1.3¥f8 6 — 13 0.4011 - -- — — — 1.0000 LEAST--SQUARES ANALYSES OF VARIANCE FOR SURVIVAL RATE IN OHIO TARGHEE Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df. MS k value 1 2 0.2^18 26 0 .321^ 23 0.5007 1.88^6 2 3 0.5801 3>+ 0.3^22 31 0.^22^ 1.9118 3 3 0.1676 13 0.3258 11 0.5376 1.8J+62 1+ 2 0.*+8l8 22 0.2738 lL- 0.2883 1.636^ 5 1 1.136^ 29 O A 137 10 0 .236^ 1.3^8 6 — — — - — — 13 0.5275 — - -- — — 1.0000 k' = I.6V96 138 APPENDIX E (Continued) LEAST-SQUARES ANALYSES OF VARIANCE FOR PROLIFICACY IN NORTH DAKOTA COLUMBIA Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 5 0.2626 St- 0 A 295 31 0.2571 2.271!+ 2 3 0.7937* 25 0.3090 31 0.2081 2. 2t-00 3 3 O.lt-30 19 O.t-115 8 0.1756 l.t-211 t- 2 0.0515 20 0.2^98 8 0 .17t-6 1 .1+000 5 1 0.2857 19 0.2071 6 0.1190 1.3158 6 — —————— 1- 0.2182 ---- —————— 1.0000 LEAST-SQUARES ANALYSES OF VARIANCE FOR LIVABILITY IN NORTH DAKOTA, COLUMBIA Birth-Year Between Years Between Ewes Remainder Groups df MS df MSdf MS k value 1 5 0.22t-0 2k 0.603t- 31 0.2956 2.271!+ 2 3 O .9896 25 0.2M+5 31 0.3612 2.21+00 3 3 O.lt-30 19 0.1+115 8 0.1756 1.1+211 4 2 0.0515 20 0.21+98 8 0 .17^6 1 .1+000 5 1 0.2857 19 0.2773 6 0.1190 1.3158 6 — 10 O.I636 — — —————— 1.0000 LEAST-SQUARES ANALYSES OF VARIANCE FOR SURVIVAL RATE IN NORTH DAKOTA COLUMBIA Birth-Year Between Years Between Ewes Remainder >ups df MS df MS df MS k value 1 5 0.2712 St- 0.5395 31 0.5057 2 3 1.0755* 25 0.^285 31 0.2991 2.2 *+00 3 3 0.1+077 19 0.6331 8 0.2638 l.t-211 k 2 0.181+7 20 0.5^70 8 0.2872 l.t-000 5 1 0.0000 19 0.2553 6 0.1667 6 ------10 0.2909 — ------ k' = 1.7138 139 APPENDIX E (Continued) LEAST-SQUARES ANALYSES OF VARIANCE FOR PROLIFICACY" IN OHIO COLUMBIA Birth-Year Between Years Between Ewes Remainder Groups df MS df. MS df MS k value 1 3 0 .257k 31 0.4-115* 39 0.2152 2.2581 2 4- 0 .8522** 29 0.3622+* 37 0.2007 2.2759 3 3 0.4-515 12+ 0.2209 14- 0.1532 2.0000 2+ 2 OA167 0.1250 5 0.2667 1.8333 5 1 0.2857 21 0.2213 6 0.2857 1.2857 6 — — - — — — 13 0.22+73 — — 1.0000 LEAST-SQUARES ANALYSES OF VARIANCE FOR LIVABILITY IH OHIO COLUMBIA Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS 1 3 1.1521* 31 0.5^56 39 O .2789 2.2581 2 4- O.9923** 29 0.3572 37 0.2576 2.2759 3 3 0.12+2+0 1*+ 0.3591 14- 0.2192 2.0000 4- 2 0.4-167 6 0.1250 5 0.2667 1.8333 5 1 0.2857 21 0 .2692+ 6 0.2857= 1.2857 6 — ------— 13 0 . 22+73 — — — — — - — 1.0000 LEAST-SQUARES ANALYSES OF VARIANCE FOR SUR SURVIVAL RATE IN OHIO COLUMBIA Birth-Year Between Years Between Ewes Remainder Groups df MS df MS df MS k value 1 3 1.3052* 31 0.4-723 39 0.4-017 2.2581 2 2+ 0.7117 29 0.5937 37 O.2+32+3 2.2759 3 3 0 . 0602+ 14- 0 A 192+ 14- 0.22+90 2.0000 b 2 0.0260 6 0.4-809 5 0.5229 1.8333 5 1 1.7857 21 0.2560 6 0.4-524- 1.2857 6 — — 13 0.57A — — —————— 1.0000 k' = 1.8860 BIBLIOGRAPHY Askar, A.A., (1965-) Some economic -characters of Awassi sheep in Iraq. 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