Estimation of Genetic Parameters for Production Traits of Chios Sheep Using a Multitrait Animal Model

Livestock Production Science 66 (2000) 217±221 www.elsevier.com/locate/livprodsci

Estimation of genetic parameters for production traits of Chios sheep using a multitrait animal model

Ch. Ligdaa,* , G. Gabriilidis b , Th. Papadopoulos b , A. Georgoudis a aDepartment of Animal Production, Faculty of Agriculture, Aristotle University of Thessaloniki, 54006 Thessaloniki, Greece b Agricultural Research Station of Chalkidiki, N.AG.RE.F., 63 200 N. Moudania, Greece Received 10 June 1999; received in revised form 10 January 2000; accepted 23 February 2000

Abstract

Genetic parameters for commercial milk yield, litter size at birth and mean litter weight at weaning of Chios sheep were estimated. The data originated from the Agricultural Research Station of Chalkidiki and included 5343 lactations of 2315 ewes with lambings from 1977 until 1996. Variance components were estimated using restricted maximum likelihood, ®tting a multitrait animal model. The random effects included in the model were the additive genetic effect of the animal, the effect of the permanent environment of the animal and the residuals. Heritability estimates were 0.2360.015, 0.1660.011 and 0.1660.010, for commercial milk yield, litter size at birth and mean litter weight at weaning, respectively. In the same sequence the repeatabilities of the traits were 0.38, 0.18 and 0.16. Genetic correlations were 0.0360.040 between milk yield and litter size, 2 0.7760.036 between litter size at birth and mean litter weight at weaning and 2 0.0660.037 between milk yield and mean litter weight at weaning.  2000 Elsevier Science B.V. All rights reserved.

Keywords: Chios sheep; Multitrait animal model; Genetic parameters; Milk yield; Litter size; Weaning weight

1. Introduction extension of the breed was pursued in collaboration with the Section of the Ministry of Agriculture The Chios sheep breed is widely known for its responsible for the livestock genetic improvement, high milk production and proli®cacy. Since 1977, a by the distribution of superior genetic material for nucleus ¯ock of the breed was established in the the upgrading of several ¯ocks in the country Agricultural Research Station of Chalkidiki (Gabriilidis et al., 1988). Although today, the origi- (A.R.S.C.), within the framework of a nationwide nal nucleus of the breed in the island of Chios has programme for protecting, studying and improving decreased to 500 animals (Ministry of Agriculture, important indigenous sheep breeds (Hatziminaoglou 1999, personal communication), the breed has been et al., 1996). Along with the above programme, the spread all over the Greek mainland. The breed is mainly raised in Chalkidiki and in Central *Corresponding author. Tel.: 130-31-471-256; fax: 130-31- Macedonia, in the region near Thessaloniki. The 998-719. purebred population under milk control is 4500 E-mail address: [email protected] (Ch. Ligda) animals, while the total population including

0301-6226/00/$ ± see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0301-6226(00)00184-6 218 Ch. Ligda et al. / Livestock Production Science 66 (2000) 217 ±221 crossbred animals is | 100,000 heads. The economic lactation records of 2315 ewes. In the ®nal pedigree importance of the Chios sheep breed has led several data ®le a total of 3057 animals were included, of researchers to investigate the characteristics of the which 596 were sires, 2315 were ewes with records breed. Early publications on the Chios breed and 146 were dams without records. concerned the population in the homonymous island Estimates of (co)variances were obtained by re- (Zervas, 1965) and the genetic parameters of the stricted maximum likelihood with a multitrait in- productive and reproductive traits of the breed dividual animal model, using the V.C.E.4.2 software (Mavrogenis, 1982, 1985, 1988; Zervas et al., 1988; (Groeneveld and Kovac, 1994). Standard errors of Georgoudis et al., 1990; Gabriilidis et al., 1995). heritabilities, permanent environment effects and Although a number of publications considered the genetic correlations were also estimated. genetic parameters of the productive and reproduc- The model was: tive traits of the breed and the selection scheme Y 5Year 1 Month 1 Lact 1 a 1 perm applied in Cyprus (Mavrogenis and Constantinou, ijklmn i j k l m

1991; Mavrogenis, 1995, 1997), the breeding objec- 1 eijklmn tive of the breed and the development of appropriate selection schemes, under Greek conditions, have not where Yijklmn is the observations' vector for the three been studied extensively yet. traits (commercial milk yield, litter size and mean In the present study, data on commercial milk litter weight at weaning), Yeari is the ®xed effect of yield, litter size at birth and average litter weight at the productive period (i 5 1,...,20),Monthj is the weaning of Chios ewes were analyzed, since the ®xed effect of the lambing month ( j 5 1,...,6)and main revenues of the farmers are from the milk Lactk is the ®xed effect of the parity (k 5 1,...,4). production and the lambs weaned per ewe. The The random effects included in the model were, the purpose of this paper is the estimation of the genetic additive genetic effect of the animal (al , l51,..., parameters and especially the genetic correlations 3057), the permanent environmental effect (permm , between the above traits using a multitrait animal m 5 1,..., 2315) and the residual (eijklmn ). model, taking into account all known relationships between animals. 3. Results and discussion

2. Materials and methods The descriptive statistics for the three traits analyzed are given in Table 1 and the means and The data used in this study were collected from standard deviations by productive year are presented 1976 to 1996 at the Agricultural Research Station of in Table 2. During the period from 1977 till 1996, an Chalkidiki (A.R.S.C), in the framework of the re- average annual increase of 2.4 kg for milk yield, cording scheme for production and reproduction 0.01 lambs and 0.04 kg for the mean litter weight traits. Commercial milk yield was calculated using was observed. The estimates of the variance com- the Fleischmann method, from test day records taken at 28-days interval, starting in the ®rst week after Table 1 weaning. Litter size was de®ned as the number of Descriptive statistics for commercial milk yield, litter size and lambs born alive per ewe lambing. Lambings mean litter weight at weaning occurred from October till March. The suckling Commercial Litter Mean litter period of the lambs was 42 days, followed by a milk yield size at weight milking period of circa 190 days. Records of ani- (kg) birth at weaning mals, with less than 50 kg of commercial milk (kg/ewe) and/or were milked less than 70 days, were excluded Observations 5343 5343 5343 from the analysis. Moreover, only the records with Mean 198.8 1.9 14.5 observations in all three traits investigated were used S.D. 85.2 0.78 2.7 in the analysis. The ®nal data set included 5343 C.V. (%) 43 41 19 Ch. Ligda et al. / Livestock Production Science 66 (2000) 217 ±221 219

Table 2 Means and standard deviations of the traits analyzed by productive year Productive Numbers Commercial Litter Mean litter weight year milk yield (kg) size at weaning (kg) Mean S.D. Mean S.D. Mean S.D. 1977 55 187.8 81.98 1.8 0.79 13.9 3.05 1978 163 146.9 59.99 1.6 0.73 14.8 2.50 1979 245 132.2 50.12 1.8 0.83 14.0 2.79 1980 298 207.4 85.78 1.9 0.78 14.1 2.78 1981 283 164.0 72.18 1.9 0.80 14.2 2.72 1982 272 212.5 90.21 2.0 0.79 14.1 3.08 1983 257 230.6 85.51 1.9 0.75 14.3 2.74 1984 317 193.7 77.97 2.0 0.78 14.0 2.69 1985 307 215.0 85.62 2.0 0.84 14.3 2.57 1986 238 207.4 89.30 2.0 0.80 15.0 2.49 1987 289 194.3 84.03 1.9 0.82 14.3 2.94 1988 340 179.5 76.97 1.9 0.73 14.8 2.54 1989 323 185.4 84.40 1.9 0.71 15.1 2.36 1990 287 215.0 89.63 1.9 0.72 15.4 2.49 1991 266 221.5 80.32 2.0 0.77 14.8 2.44 1992 265 214.7 84.88 2.0 0.81 14.4 2.53 1993 230 222.6 90.98 1.9 0.76 14.8 2.90 1994 325 219.8 89.90 1.9 0.82 15.3 2.61 1995 269 202.8 82.71 2.0 0.83 14.5 2.46 1996 314 195.9 74.42 2.0 0.81 14.2 2.81

Table 3 ponents are presented in Tables 3 and 4. The Estimates of variance components, heritabilities, permanent en- heritability estimates were 0.2360.02, 0.1660.01 vironment effect and repeatabilities for the three traits and 0.1660.01 for commercial milk yield, litter size Commercial Litter size Mean litter weight and average litter weight at weaning, respectively milk yield (kg) at birth at weaning (kg) (Table 3). These results are close to the results of a 2 s a 1370.4 0.09 1.14 2 previous investigation with a subset of the Station's s c 900.7 0.017 0.04 2 data with a single trait animal model. However, in s e 3805.6 0.48 5.79 2 the previous study the total number of lambs born s p 6076.7 0.587 6.97 2 hd 0.225 0.153 0.163 was considered (Georgoudis et al., 1990). The c2 0.148 0.028 0.0057 estimates for milk yield of Chios sheep raised in r 0.373 0.181 0.169 Cyprus, are higher ranging from 0.29 to 0.39 (Mav-

Table 4 Estimates of covariance components and phenotypic, genetic and permanent environment correlations for the three traits Commercial milk Commercial milk yield Litter size at birth yield and litter and mean litter and mean litter size at birth weight at weaning weight at weaning sa 0.38 22.17 20.25 sc 20.264 5.03 0.016 se 4.337 2.723 20.829 sp 4.453 5.583 21.063 rg 0.0360.04 20.0660.04 20.7760.04 rc 20.0660.10 0.7860.22 0.5860.27 re 0.10260.01 0.01860.01 20.49860.01 rp 0.07 20.03 20.53 220 Ch. Ligda et al. / Livestock Production Science 66 (2000) 217 ±221 rogenis, 1982, 1988; Mavrogenis and Constantinou, production compared with ewes with only one lamb, 1991). Heritabilities for milk yield in other dairy no signi®cant difference was observed between the sheep breeds, obtained also by REML, are within the two groups regarding the commercial milk yield. The same range as those obtained in the present study. authors explained these results, by the diminishing of Kominakis et al. (1998) using transformed or un- the suckling stimulus effect of twin lambs after transformed data of milk yield in Boutsiko dairy weaning. sheep reported heritability that varied from 0.18 to The high negative genetic correlation between 0.30. Serrano et al. (1994) estimated heritabilities of litter size and mean litter weight at weaning (20.77), 0.29 and 0.33 for normalised and total milk yield, re¯ects the fact that lambs born in large litters are respectively, in the Manchega sheep breed. The weaned at lower weights. Contrary to these results, a heritability of milk yield in Churra sheep is 0.25 (de high positive genetic correlation (0.48) between litter la Fuente et al., 1995). size and weaning weight of the lambs was reported Heritability of litter size (0.16) was higher than by Analla et al. (1997), analyzing data of the the values reported for other sheep breeds. For the Segurena sheep with a model that included the litter Boutsiko mountain breed, the values for litter size size as a ®xed effect. However, they pointed out that varied from 0.06 to 0.07, depending on the model the net phenotypic values for weights of lambs from and the use of transformed or untransformed data multiple births would be smaller than those of lambs (Kominakis et al., 1998). Analla et al. (1997) born as single, due to the systematic effect of type of reported for the Segurena sheep a heritability of 0.08, birth. The estimated genetic correlation between milk while Puntila and Nylander (1998), analyzing data yield and average litter weight at weaning was from a Finnsheep nucleus, reported estimates of 0.08 20.06 indicating the absence of a genetic relation- and 0.03 for litter size at birth and at weaning, ship between the two traits. respectively. Similar values are reported by Davis et The repeatabilities of milk yield, litter size and al. (1998) analyzing data of New Zealand sheep. average litter weight at weaning were 0.38, 0.18 and Bradford (1985) pointed out that heritability of litter 0.17, respectively, and were at the same levels with size is quite low and summarizing over 30 estimates values reported in the literature. Repeatability of for different breeds and methods of estimation milk yield varied from 0.31 to 0.40 (Moioli and reported a range from 20.15 to 0.35 and a mean of Pilla, 1994; Serrano et al., 1994; de la Fuente et al., 0.10. 1995), while repeatability of litter size and average The heritability for the average litter weight at litter weight varied from 0.07 to 0.20 (Analla et al., weaning (0.16), although higher, in general is com- 1997; Davis et al., 1998; Kominakis et al., 1998; parable with values found in the literature. From data Puntila and Nylander, 1998). The low values of the on total litter weight at weaning of the Chios sheep permanent environmental variance in litter size at in Cyprus, Mavrogenis (1985, 1988) estimated birth and mean litter weight (0.028 and 0.0057, heritability of 0.11 and 0.13. Puntila and Nylander respectively) indicate, that these traits are in¯uenced (1998), in a Finnsheep nucleus, estimated heritability to a small extent by non-additive genetic effects and for the total and average litter weight at weaning of the permanent environment. 0.11 and 0.10, respectively. The genetic correlation between milk yield and litter size was estimated at 0.03. This value is in 4. Conclusion agreement with the results reported by Barillet et al. (1988), who using Henderson's III method reported Estimated genetic parameters indicate the possi- estimates of genetic correlation between milk yield bility of genetic progress. Even though the genetic and litter size of 0.16 with a sampling error of 0.28. correlation between commercial milk yield and litter The heritabilities estimated for milk yield and litter size at birth was low, the combination of litter size size at birth were 0.24 and 0.03, respectively. with the milk yield in a genetic evaluation procedure Mavrogenis and Economides (1980) pointed out that is expected to result in the genetic improvement in while ewes with twin lambs have higher total milk both traits. In addition the mean litter weight at Ch. Ligda et al. / Livestock Production Science 66 (2000) 217 ±221 221 weaning should be included in the breeding goal to Hatziminaoglou, I., Georgoudis, A., Zervas, N., Boyazoglu, J., avoid decrease in the total lamb weight, due to its 1996. Proli®c breeds of Greece. In: Fahmy, M.H. (Ed.), Proli®c Sheep, CAB International, UK, pp. 73±92. high negative correlation with litter size. Neverthe- Kominakis, A., Rogdakis, E., Koutsotolis, K., 1998. Genetic less the decrease of weaning weight due to the parameters for milk yield and litter size in Boutsiko dairy increase of litter size is counterbalanced by the sheep. Can. J. Anim. Sci. 78, 525±532. increase of the total lambs sold per ewe. In the index Mavrogenis, A.P., 1982. Environmental and genetic factors in- planning to be applied, the three traits included will ¯uencing milk production and lamb output of Chios sheep. Livest. Prod. Sci. 8, 519±527. be weighted by their economic weights and the Mavrogenis, A.P., 1985. The fecundity of Chios sheep. In: Land, overall selection response is expected to be the most R.B., Robinson, D.W. (Eds.), Genetics of Reproduction in pro®table for the farmer. Sheep, Butterworths, London, pp. 63±67. Mavrogenis, A.P., 1988. Genetic improvement of sheep in Cyprus by selection and/or crossbreeding. In: Thompson, E.F., Thompson, F.S. (Eds.), Increasing Small Ruminant Productivi- References ty in Semi-arid areas, ICARDA, Netherlands, pp. 189±194. Mavrogenis, A.P., 1995. Breeding systems and selection strategies Analla, M., Munoz-Serrano, A., Serradilla, J.M., 1997. Analysis for sheep improvement in Cyprus. In: Proceedings of the joint of the genetic relationships between litter size and weight traits FAO/CIHEAM Network on Sheep and Goats, Subnetwork on in Segurena sheep. Can. J. Anim. Sci. 77, 17±21. Animal Resources, 26±28 March, Tunisia, Cahiers Options Barillet, F., Elsen, J.M., Roussely, M., Belloc, J.P., Casu, S., Mediterraneennes,ÂÂ Vol. 11, CIHEAM, Zaragoza, pp. 17±26. Carta, R., Poivey, J.P., 1988. Selection lait viande en brebis Mavrogenis, A.P., 1997. Comparative performance of purebred laitiers. In: 3rd World Congress on Sheep and Beef Cattle and crossbred sheep in three different production systems. In: Breeding, 19±23 June, INRA, Paris, Vol. 2, pp. 469±490. Proceedings of the joint FAO/CIHEAM Network on Sheep Bradford, G.E., 1985. Selection for litter size. In: Land, R.B., and Goats, Subnetwork on Animal Resources, 9±11 March, Robinson, D.W. (Eds.), Genetics of Reproduction in Sheep, Toulouse, France, Cahiers Options Mediterraneennes,ÂÂ Vol. 33, Butterworths, London, pp. 3±18. CIHEAM, Zaragoza, pp. 181±186. Davis, G.H., Morris, C.A., Dodds, K.G., 1998. Genetic studies of Mavrogenis, A.P., Constantinou, A., 1991. Selection index and proli®cacy in New Zealand sheep. Anim. Sci. 67, 289±297. expected genetic progress in Chios sheep. In: Technical de la Fuente, L.F., Baro, J.A., San Primitivo, F., 1995. Breeding Bulletin 131, Agricultural Research Institute, Nicosia, Cyprus, programme for the Spanish Churra sheep breed. In: Proceed- p. 7. ings of the joint FAO/CIHEAM Network on Sheep and Goats, Mavrogenis, A.P., Economides, S., 1980. Relationships between Subnetwork on Animal Resources, 26±28 March, Tunisia, ewe milk production and lamb growth. In: Technical Bulletin Cahiers Options Mediterraneennes,ÂÂ Vol. 11, CIHEAM, 33, Agricultural Research Institute, Nicosia, Cyprus, p. 9. Zaragoza, pp. 165±172. Moioli, B.M., Pilla, A.M., 1994. Genetic evaluation of dairy sheep Gabriilidis, G., Zervas, N., Hatziminaoglu, J., Georgoudis, A., with an animal model for annual or partial lactation production. Boyazoglu, J., 1988. The Chios sheep. Data collected at the J. Dairy Sci. 77, 609±615. Station during 1977±1986. In: Special Bulletin, Ministry of Puntila, M.-L., Nylander, A., 1998. Genetic relationship between Agriculture, Agricultural Research Station of Chalikidiki, mature weight and productivity traits in Finnsheep ewes. In: Greece, p. 25. Paper presented to the 49th Annual meeting of the E.A.A.P., Gabriilidis, G., Ligda, Ch., Georgoudis, A., 1995. Estimation of 24th±28th August, Warsaw, Poland. certain phenotypic and genetic parameters for growth traits of Serrano, M., Perez-Guzman, M.D., Montoro, V., Jurado, J.J., 1994. the Chios lambs. Anim. Sci. Rev. 21, 5±16, In Greek with Genetic parameters estimation and selection progress in the English abstract. selection program of ovine Manchega breed. In: Paper pre- Georgoudis, A., Hatziminaoglou, J., James, J.W., Demp¯e, L., sented to the 45th Annual Meeting of the E.A.A.P., 5±8 1990. Estimates of genetic parameters for production and September, Edinburgh, Scotland. reproduction traits of Chios sheep. In: Paper presented to the Zervas, N.P., 1965. In: Contribution to the Phenotypic and Genetic 41st Annual meeting of the E.A.A.P., 8±12 July, Toulouse, Study of Dairy Production of the Chios Breed, Agricultural France. School of Athens, Greece, p. 120, Dissertation; in Greek. Groeneveld, E., Kovac, M., 1994. VCE Ð a multivariate mul- Zervas, N.P., Hatziminaoglou, J., Georgoudis, A., Boyazoglu, J.G., timodel REML (co)variance component estimation package. In: 1988. Characteristics and experiences of Chios breed. J. Agri. Proceedings of the 5th World Congress on Genetics Applied to Sci. Finland 60, 576±584. Livestock Production, Guelph, Vol. 22, pp. 47±48.