Environmental factors affecting milk, fat and protein yields in Jersey cattle in Zimbabwe
A study was carried out to establish the factors affecting milk, butterfat and protein yields in Zimbabwean Jersey cattle. A total of 10,986 unedited 305-day lactation records were obtained from Zimbabwe Livestock Identification Trust containing 25 herds, with cows calving in the period 1996–2008. The general linear model procedure of the Statistical Analysis Systems version 9.1.3 was used to determine the environmental factors. Herd-year-season, calving interval, days dry and both the linear and quadratic effects of age at calving fitted as covariates significantly (P < 0.0001) affected the milk, fat and protein yields. Herd-year-season accounted for 36%, 36% and 35% to the total variation in milk, fat and protein yields, respectively. Milk, fat and protein yields increased with an increase in calving interval. The optimum dry period for milk, fat and protein yields obtained was 60–75 days dry. The relationship between the production traits and age at calving was both linear and quadratic, implying that milk, fat and protein yields increase with the age of the animal. It is thus necessary to preadjust data for these environmental factors when carrying out genetic evaluations of production traits in dairy cattle.
KeywordsNon-genetic factors Herd Season Calving interval Days dry
The authors thank Mr. NB Mware and his colleagues of Zimbabwe Livestock Identification Trust (LIT) for providing them with data that was used in this study.
- Amimo, J.O., Wakhungu, J.W., Inyangala, B.O. and Mosi, R.O., 2007. The effects of non-genetic factors and estimation of genetic and phenotypic parameters and trends for milk yield in Ayrshire cattle in Kenya. Livestock Research for Rural Development, 19: 1Google Scholar
- Bormann, J.M. and Wilson, D.E., 2010. Calving day and age at first calving in Angus heifers. Journal of Animal Science, 88, 1946–1957Google Scholar
- Missanjo, E.M., 2010. Genetic and phenotypic evaluation of Zimbabwean Jersey cattle towards the development of a selection index (unpublished MSc thesis, University of Zimbabwe)Google Scholar
- SAS® 9.1.3 Qualification Tools User’s Guide Copyright © 2004 SAS Institute Inc., Cary, NC, USA.Google Scholar
- USDA, 2009. Agro-climatic zones in Zimbabwe (United States Department of Agriculture)Google Scholar
- Vierhout, C., 2008. Selection of dairy cow families for superior fertility (unpublished PhD thesis, North Carolina State University)Google Scholar