- Volume 29 Issue 2
DOI QR Code
Variance Components and Genetic Parameters Estimated for Fat and Protein Content in Individual Months of Lactation: The Case of Tsigai Sheep
- Oravcova, Marta (National Agricultural and Food Centre - Research Institute for Animal Production Nitra)
- Received : 2015.02.17
- Accepted : 2015.06.05
- Published : 2016.02.01
The objective of this study was to assess variance components and genetic parameters for fat and protein content in Tsigai sheep using multivariate animal models in which fat and protein content in individual months of lactation were treated as different traits, and univariate models in which fat and protein content were treated as repeated measures of the same traits. Test day measurements were taken between the second and the seventh month of lactation. The fixed effects were lactation number, litter size and days in milk. The random effects were animal genetic effect and permanent environmental effect of ewe. The effect of flock-year-month of test day measurement was fitted either as a fixed (FYM) or random (fym) effect. Heritabilities for fat content were estimated between 0.06 and 0.17 (FYM fitted) and between 0.06 and 0.11 (fym fitted). Heritabilities for protein content were estimated between 0.15 and 0.23 (FYM fitted) and between 0.10 and 0.18 (fym fitted). For fat content, variance ratios of permanent environmental effect of ewe were estimated between 0.04 and 0.11 (FYM fitted) and between 0.02 and 0.06 (fym fitted). For protein content, variance ratios of permanent environmental effect of ewe were estimated between 0.13 and 0.20 (FYM fitted) and between 0.08 and 0.12 (fym fitted). The proportion of phenotypic variance explained by fym effect ranged from 0.39 to 0.43 for fat content and from 0.25 to 0.36 for protein content. Genetic correlations between individual months of lactation ranged from 0.74 to 0.99 (fat content) and from 0.64 to 0.99 (protein content). Fat content heritabilities estimated with univariate animal models roughly corresponded with heritability estimates from multivariate models: 0.13 (FYM fitted) and 0.07 (fym fitted). Protein content heritabilities estimated with univariate animal models also corresponded with heritability estimates from multivariate models: 0.18 (FYM fitted) and 0.13 (fym fitted).
Sheep;Milk Composition;Test Day Model;Variance Ratios;Heritability;Genetic Correlations
Supported by : Ministry of Agriculture and Regional Development of the Slovak Republic
- Ali, T. E. and L. R. Schaeffer. 1987. Accounting for covariances among test day milk yields in dairy cows. Can. J. Anim. Sci. 67:637-644. https://doi.org/10.4141/cjas87-067
- Baro, J. A., J. A. Carriedo, and F. San Primitivo. 1994. Genetic parameters of test day measures for somatic cell count, milk yield, and protein percentage of milking ewes. J. Dairy Sci. 77:2658-2662. https://doi.org/10.3168/jds.S0022-0302(94)77207-6
- Bauer, J., M. Milerski, J. Pribyl, and L. Vostry. 2012. Estimation of genetic parameters and evaluation of test-day milk production in sheep. Czech J. Anim. Sci. 57:522-528. https://doi.org/10.17221/6385-CJAS
- Groeneveld, E., M. Kovac, and N. Mielenz. 2010. VCE User's Guide and Reference Manual, version 6.0. Institute of Farm Animal Genetics, Neustadt, Germany.
- International Committee for Animal Recording. 2011. International Agreement of Recording Practices: Guidelines Approved by the General Assembly Held in Riga, Latvia, June 2010. International Committee for Animal Recording, Rome, Italy.
- Komprej, A., G. Gorjanc, D. Kompan, and M. Kovac. 2009. Covariance components by a repeatability model in Slovenian dairy sheep using test-day records. Czech J. Anim. Sci. 54:426-434. https://doi.org/10.17221/1680-CJAS
- Komprej, A., D. Kompan, and M. Kovac. 2011. Genetic and environmental dispersion parameter estimation by test interval method in dairy sheep. Acta Agric. Slov. 98:5-13.
- Oravcova, M., E. Groeneveld, M. Kovac, D. Peskovicova, and M. Margetin. 2005. Estimation of genetic and environmental parameters of milk production traits in Slovak purebred sheep using test- day model. Small Rumin. Res. 56:113-120. https://doi.org/10.1016/j.smallrumres.2004.03.002
- Oravcova, M. and D. Peskovicova. 2008. Genetic and environmental trends for milk production traits in sheep estimated with test-day model. Asian Australas. J. Anim. Sci. 21:1088-1096. https://doi.org/10.5713/ajas.2008.70700
- Oravcova, M. 2014. Variance components and genetic parameters estimated for daily milk yield in individual months of lactation: the case of Tsigai sheep. Vet. Med. Zoot. 68:55-59.
- SAS Institute Inc. 2009. SAS/STAT User's Guide: Version 9.2. 2nd edn. SAS Institute Inc., Cary, NC, USA.
- Serrano, M., E. Ugarte, J. J. Jurado, M. D. Perez-Guzman, and A. Legarra. 2001. Test day models and genetic parameters in Latxa and Manchega dairy ewes. Livest. Prod. Sci. 67:253-264. https://doi.org/10.1016/S0301-6226(00)00203-7
- Slovak Standards Institute. 1995. Determination of milk composition by infrared absorption instrument (STN 57 0536). Slovak Standards Institute, Bratislava, Slovakia.
- Swalve, H. H. 1995. The effect of test day models on the estimation of genetic parameters and breeding values for dairy yield traits. J. Dairy Sci. 78:929-938. https://doi.org/10.3168/jds.S0022-0302(95)76708-X
- Volanis, M., A. Kominakis, and E. Rogdakis. 2002. Genetic analysis of udder score and milk traits in test day records of Sfakia dairy ewes. Arch. Tierz. 45:69-77.