Publisher : Asian Australasian Association of Animal Production Societies
DOI : 10.5713/ajas.2002.315
Title & Authors
Genetic Aspects of Persistency of Milk Yield in Boutsico Dairy Sheep Kominakis, A.P.; Rogdakis, E.; Koutsotolis, K.;
Test-day records (n=13677) sampled from 896 ewes in 5-9 (=7.5) monthly test-days were used to estimate genetic and phenotypic parameters of test-day yields, lactation milk yield (TMY), length of the milking period (DAYS) and three measures of persistency of milk yield in Boutsico dairy sheep. Τhe measures of persistency were the slope of the regression line (), the coefficient of variation (CV) of the test-day milk yields and the maximum to average daily milk yield ratio (MA). The estimates of variance components were obtained under a linear mixed model by restricted maximum likelihood. The heritability of test-day yields ranged from 0.15 to 0.24. DAYS were found to be heritable (=0.11). Heritability estimates of , CV and MA were 0.15, 0.13, 0.10, respectively. Selection for maximum lactation yields is expected to result in prolonged milking periods, high rates of decline of yields after peak production, variable test-day yields and higher litter sizes. Selection for flatter lactation curves would reduce lactation yields, increase slightly the length of the milking period and decrease yield variation as well as litter size. The most accurate prediction of TMY was obtained with a linear regression model with the first five test-day records.
Genetic and Environmental Trends for Milk Production Traits in Sheep Estimated with Test-day Model,;;
Asian-Australasian Journal of Animal Sciences, 2008. vol.21. 8, pp.1088-1096
Bizelis, J. A., M. A. Charismiadou and E. Rogdakis. 1993. The effect of number of foetuses on mammary gland in sheep. Anim. Sci. Rev. 17:21-38 (in Greek with English summary).
Bizelis, J. A., M. A. Charismiadou and E. Rogdakis. 2000. Metabolic changes during the perinatal period in dairy sheep in relation to level of nutrition and breed. II. Early lactation. J. Anim. Physiol. Anim. Nutr. 84:73-84.
Fisher, A. 1958. Untersuchungen an württembergischen Fleckviehkühen über die Form der Laktationskurve und deren Beeinflussung durch nichterbliche Faktoren. Zuchtungskunde 30:296-304.
Gilmour, A. R., R. Thompson and B. R. Cullis. 1995. Average information REML, an efficient algorithm for variance parameter estimation in linear mixed models. Biometrics 51: 1440-1450.
Gilmour, A. R., B. R. Cullis, S. J. Welham and R. Thompon. 1999. ASREML reference manual.
Gravert, H. O. and R. Baptist. 1976. Breeding for persistency of milk yield. Livest. Prod. Sci. 3:27-31.
Johansson, I. and A. Hansson. 1940. Causes of variation in milk and butterfat yield in dairy cows. Kungl. Landbr. Akad. Tidskr. 79:1-127.
Jamrozik, J., L. R. Schaeffer and J. C. M. Dekkers. 1997. Genetic evaluation of dairy cattle using test day yields and random regression model. J. Dairy Sci. 80:1217-1226.
Kominakis, A., M. Volanis and E. Rogdakis. 1999. Genetic and phenotypic parameters of milk yield in Sfakia sheep. In: Proceedings of the 15th Scientific Meeting of the Hellenic Zootechnical Society, Chania, Greece, November 3-5, 1999.
Kominakis, A., M. Volanis and E. Rogdakis. 2001. Genetic modelling of test day records in dairy sheep using orthogonal Legendre polynomials. Small Rum. Res. 39:209-217.
Knight, C. H. 1997. Biological control of lactation length. Livest. Prod. Sci. 50:1-3.
Lean, I. J., J. C. Gallard and J. L. Scott. 1989. Relationships between fertility, peak milk yields and lactational persistency in dairy cows. Theriogenology 31:1093-1103.
Leukkennen, A. 1985. Genetic parameters for the persistency of milk yield in the Finnish Ayrshire cattle. Z. Tierz. Zuchtungsbiol. 102:117-124.
Louda, F. and J. M. Doney. 1976. Persistency of lactation in the Improved Valachian breed of sheep. J. Agric. Sci. Cambridge, 87:455-457.
Madsen, O. 1975. A comparison of some suggested measures of persistency of milk yield in dairy cows. Anim. Prod. 20:191-197.
Sanders, H. G. 1930. The analysis of the lactation curve into maximum yield and persistency. J. Agric. Sci. 20:145-185.
Solkner, J. and W. Fuchs. 1987. A comparison of different measures of persistency with special respect to variation of test-day milk yields. Livest. Prod. Sci. 16:305-319.