Double-Yolk Egg
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id10567781 pdfMachine by Broadgun Software - a great PDF writer! - a great PDF creator! - http://www.pdfmachine.com http://www.broadgun.com ISSN : 0974 - 7532 Volume 4 Issue 4 Research & Reviews in Trade Science Inc. BBiiooSScciieenncceess Regular Paper RRBS, 4(4), 2010 [204-208] ’ Analysis of fitness predominance for Gaoyou duck s double-yolk egg Tangjie Zhang1*, Hui-Fang Li2, Kuanwei Chen2, Yonggao Zhao3, Hong Chang1, Minkai Xue3, Shengfu Zhang3 1College of Veterinary, Yangzhou University, Yangzhou 225009, (CHINA) 2Institute of Poultry Science, Chinese Academy of Agricultural Sciences, Yangzhou 225003, (CHINA) 3Jiangsu Gaoyou Duck Group, Gaoyou 225601, (CHINA) E-mail : [email protected]; [email protected] Received: 13th October, 2010 ; Accepted: 23rd October, 2010 ABSTRACT KEYWORDS One pair of recessive major gene and several modifiers dominated the ma- Gaoyou duck; ’s double-yolk egg. The fitness of double-yolk jor gene of Gaoyou duck Double-yolk egg; egg trait was analyzed by population genetics one the basis of special Fitness; environment and natural geography. The results showed that the double- Gene. yolk egg trait fitness was 8.23 under artificial selection during the year 2000 to 2002. The equilibrium of high intensive artificial selection and natural ’s double-yolk egg. selection resulted in the trait of Gaoyou duck 2010 Trade Science Inc. - INDIA INTRODUCTION predominate in a species. Fitness is a measure of reproductive success. Those Domestication actually is the process of artificial individuals who leave the largest number of mature off- selection. Like natural selection, artificial selection acts spring are the fittest. The maintenance of reproductive by allowing differential reproductive success to indi- fitness in lines subjected to artificial selection is one of viduals with different genetically determined traits in the major problems in animal breeding. The decline in order to increase the frequency of desirable traits in the reproductive performance has neither been predictable population. However, unlike naturally selected traits, from heritabilities and genetic correlations, nor have con- artificially selected traits do not necessarily convey ventional selection indices been adequate to avoid the greater fitness. Instead, artificially selected traits are problem. ’s desires based on what the person breeding animal [4]. The Gaoyou Duck is one of the best duck strains in These traits, which can range from hornless China. Gaoyou duck, distributed Lixiahe district, Jiangsu goats[3,6] to a particular coat color in domestic ani- province and protected in preserve areas and in pre- mals[14], are selected for by allowing only individuals serve farms (Gaoyou Breeder Duck Farm), is excellent that possess the trait to reproduce, while those that in egg production. Gaoyou Duck can be used to make lack the trait are prevented from reproducing. Because processed and salted duck, and is famous for produc- it lacks the control of fitness needing to increase fit- ing double yolk eggs[1,13]. There were 100 000 ducks ness, artificial selection can cause problem traits to in 2002. Age at first laying is 120~160 days. Annual RRBS, 4(4) 2010 Tangjie Zhang et al. 205 Regular Paper egg production is over 200 at 500 days. Average egg little plump and lower feed conversion. [2] size is about 85g. Eggshell color is white and green . Egg production data retrieval Gaoyou duck is a breed of duck that has been bred for egg production, especially double-yolk egg. In the pro- There are 10 populations, 39 lines now. The data cess of selecting for this appearance, a genetic defect for this investigation were taken from egg production has increased in frequency in the population. Usually, a record of 4 closed populations,19 lines in Gaoyou double yolk egg will not even survive to hatch. If it does Breeding Duck Farm during the period 2000 to 2002. Egg production records per year were all number and hatch, the poor ducks are severely deformed, connected ’s age at to one another. Clearly, this condition does not increase double-yolk number from 26th to37th week ’s fitness and would be strongly the double-yolk egg first egg in early spring. selected against by natural selection. However, since Statistical and genetic analysis these ducks have been subjected to artificial rather than Statistical and genetic analysis are based on ’s method of quantitative genetics natural selection for generations, the defect has spread Falconer [4] in the population. The percentage of Gaoyou duck double-yolk egg reaches 2-10%, another high Estimation of double-yolk egg real production ’s poultry breed of double-yolk egg is Shaver percentage Calculation of repeatability star cross 288 hens[7,11]. ’s double-yolk egg is a The trait of double-yolk egg is affected by genetic The trait of Gaoyou duck and environmental factors. It shows different repeat- kind of fitness or embodiment of fitness. A double yolk ’t be hatched and would be strongly eliminated ability at different year. Estimation of possible produc- egg can tion are needed by repeatability. through natural selection. But double-yolk egg line re- mains at the condition of artificial selection by the rea- 2 1 n MSb MSw K N i son of human favor of double-yolk egg along the south- r e MSb (K 1)MSw D 1 N ern part of the Jianghuai Plain. In this study, 4 closed populations, 19 lines egg lay- re : repeatability; MSb: square between populations; MSw: ing performance from 2000 to 2002 are statistically and square within population; D: number of determined years; N: genetically analyzed in order to analyze of fitness pre- sum of different population number ’s double-yolk egg. dominance for Gaoyou duck Significance testing is adopted by t-test. Estimation of double-yolk egg real production MATERIALS AND METHODS nre P (Pn P)re(n) P (Pn P) P x 1 (n 1)r Basic investigation of Gaoyou duck population e P : Double-yolk egg real production; : Mean value of all Gaoyou Breeding Duck Farm was built in 1975. x P population double-yolk egg; P : Mean value of individual popu- Since then, a series of breeding methods was carried n lation n time out to establish basic breeding population. As a result Mean value of all population real production and of many year artificial selections, duck body and ap- Estimation of sampling error pearance are basically alike and production performance improves. Annual egg production is 170, 20 more than m ti m i 1 2 at the beginning of the Farm. The age at first egg is Ycl (t t) n i about 170-180d. M m 1 ni SY 2 cl Mmn m 1 The breeding of Gaoyou duck has fast developed j 1 ’s. By combining line for individual selection since 1990 M: all families of all populations; m: families number of random selection with individual selection, egg production of ni sample; t: all number of within-families; n : mean value the selection population is 220 to 240 at 500days and i m egg weight is about 84g by the end of year 2000. There n t were 39 lines more than 20 000 breeding ducks in 2002. i of different families; t 1 mean value of sample The strain lay high quality and double-yolk egg, but a m ’ 206 Analysis of fitness predominance .for Gaoyou duck s double-yolk egg RRBS, 4(4) 2010 Regular Paper Calculation of double-yolk egg fitness under arti- x = {q3(1 q)+q2(1 q)2}/2(1 q2){1 (1 q)2(1 w)} q2 / 2 ficial selection Supposing double-yolk egg frequency is in equilib- Supposing that trait of no double-yolk egg (H) via rium between adjacent two generation, when x = 0, double-yolk egg (h) is complete dominant, the trait of the equation of which could be expressed: above turns double-yolk is recessive inheritance, all ducks laying to: double-yolk egg are with recessive gene(h), drake is 1 q x W 1 heterozygote Hh, female duck is heterozygote Hh, all 2 ’h’ in filial generation shows “double yolk”. h’h’ is a (1 q)(1 q) (1 x)(1 x ) h ’t be 1 theoretically sex in that double yolk egg can 1 denotes fitness predominance for double-yolk hatched. w q representation double-yolk egg gene frequency, egg under artificial selection in this period. x is double-yolk egg frequency. Because male and fe- male duck theoretically have the trait of laying double- RESULTS yolk egg, x = q2 w denotes relative selection proportion of no Early egg production record of 19 Gaoyou duck double-yolk egg via double-yolk egg (0<w<1), namely, families fitness predominance for no double-yolk egg under ar- Egg production records of 4 Closed populations, tificial selection. 19 Gaoyou duck families shows in TABLE 1 during the Increment of double-yolk egg frequency over one year 2000 to 2002. The record was at the age from 26 generation to 37 week. TABLE 1 : Early records (26-37 week-age) for egg production of 19 Gaoyou duck families during the year 2000 to 2002 2000y (tenth generation) 2001y (eleventh) 2002y (twelfth) C.P. F. F.D.Nu. E.Nu. D.Nu Perc. F.D.Nu. E.Nu. D.Nu Perc. F.D.Nu. E.Nu D.Nu Perc. A 5 50 3161 47 1.49 50 3263 27 0.83 50 3837 61 1.59 B 4 40 2950 43 1.46 40 2516 25 0.99 40 2806 36 1.28 C 6 60 4076 45 1.10 60 3803 44 1.16 60 4510 35 0.78 D 4 40 2474 30 1.21 40 2754 23 0.84 40 3113 37 1.19 C.P.: Closed populations; F.: Families; F.D.N: Female duck number; E.N.: Egg number; D.N: double-yolk egg number; P: Percentage of double-yolk egg P =1.23; P =1.20 P =1.08 P =1.12 re A B C D Populations mean real production of double-yolk MSb MSw r 0.26 trait and sample error e MSb (K 1)MSw 2 2 m 2 1 (n 1)re 1 re ti Vre 0.1444 n(n 1)(D 1) i 1 Ycl 1.15 S 0.08 n x ni V 0.1444 0.38 re re j 1 re 0.26 Fitness predominance of double-yolk egg trait t 0.68 1.96 0.38 (=1%, value of t ), no sig- re under artificial selection nificant difference at 0.