REGRESSION ANALYSIS OF FACTORS AFFECTING MILK YIELD OF DAIRY COWS

Abstract

By using a forward selection multiple regression technique, 60% of the total sums of squares (SS) in either average daily milk yield (DCA) or average BCA milk among 56 Ontario dairy herds was accounted for by selected feeding and management factors. Herd average body weight had a strong positive influence on both DCA and BCA milk and was associated with higher nutrient intake. High production was associated with shorter calving intervals (CI) and therefore shorter lactations. Whereas average days in lactation had a strong negative influence on DCA, average CI adversely affected both DCA and BCA milk. Differences in feed quality and nutrient intake (primarily energy) accounted for most of the remaining variation in milk yield between herds. The inability of dairymen to monitor intake of energy-dense feeds was an important factor limiting herd yield. Key words: Milk yield, dairy cows, feeding and management factors