The Importance of Different On-Farm Feeding and Management Practices on Milk Protein Concentration and Yield

Abstract

The objective of this project was to identify the most important factors which influence milk protein concentrations and yields on farms. Data collected on approximately 300 DairyMis farms were subjected to statistical evaluation by regression analysis, analysis of variance and factor analysis. The range in protein concentrations was 12% of the mean value compared to a variation in protein yield of 86% of the mean. The range in milk yield was 90% of the mean value.

Initially data from 1995 were analysed. The regression model used only accounted for 4% of the variation between farms in milk protein concentration but for over 97% of the variation in milk protein yield. Milk protein yield was highly correlated with milk yield.

Confining the analysis to Spring-calving herds only in 1995 (n=128) gave similar results but including genetic data in the regression model, for those spring-calving herds for which it was available (n = 36), explained approximately 25% of the variation in protein concentration.

Analysis of variance on the spring-calving herd data (for 1994, 1995 and 1996) divided into quartiles on the basis of protein concentration indicated that higher protein concentration was associated with later calving, a higher proportion of milk produced on pasture and lower milk yield per cow.

Factor analysis on all herds in 1994, 1995 and 1996 indicated that higher protein concentration was associated with Spring-calving herds, larger herds and with grass based milk production. These three factors accounted for 8% of the observed variation in milk protein concentration.