Linear mixed model analysis of milk production in six Sri Lankan dairy farms under varying management and environmental conditions.

Milk production in cattle is influenced by multiple factors, evaluation of which is essential for resource optimization and sustainable dairy production to maximize economic profitability. This study analyzed the impact and magnitude of such factors considering the Jersey × Friesian crossbred cattle, reared under six different commercial dairy farms in Sri Lanka. The analysis considered five key fixed effects (farm associated system of production, parity, age at first calving, calving year, and calving season) and individual cow associated random effects, focusing on 305-day milk production up to the fourth parity. Linear mixed effect model was employed for the quantification of the magnitude of the effects. The results revealed significant effects of all five fixed effects considered on milk production explaining 41% of the variation in 305-day milk production. Individual cow associated variability accounted for additional 17% of the variation in 305-day milk production. The remaining unexplained variability in 305-day milk production (40%) likely arises from environmental and biological factors within farms and individual animals that were not explicitly measured or modeled. This is due to the lack of detailed management data and subtle variations across individual animals and lactations resulting from minor adjustments in management practices. This study reveals how the management practices and environmental conditions in a dairy production system could influence on the productivity of cattle and, provides valuable guidance for target strategy development and resources allocation to improve dairy production efficiency in Sri Lanka.