Effect of farming region and calving season on complete-lactation production traits in simmental cows

Abstract

The present research focused on analysing the effect of farming region, calving season and their interaction on complete-lactation milk performance traits (lactation length, milk production, milk fat production, and milk fat content) using the generalised linear model based on the least squares method (the GLM procedure). The research involved 253 cows with a total of 827 lactations in three farming regions (Aranđelovac (74 cows with 263 lactations), Kraljevo (87 cows with 249 lactations) and Toponica (92 cows with 315 lactations)). In all three farming regions, the average lactation length (the overall mean) was 316.98 days, milk production – 4926.82 kg, milk fat production – 194.37 kg, and milk fat content – 3.94%. Milk and milk fat production and milk fat content showed very significant differences (P<0.01) depending on farming region, whereas the difference in lactation length was significant (P<0.05). Calving season had a significant effect (P<0.05) only on milk fat production, whereas the farming region x calving season interaction significantly affected only the milk fat content. The other milk performance traits were not significantly affected (P>0.05) by either calving season or the farming region x calving season interaction. Therefore, the coefficients of determination were low and very significant (P<0.01), ranging from 0.15 for complete lactation length to 0.30 for milk fat content.