Factors influencing the concentrations and yields of milk constituents and their interrelationships

Abstract

SummaryMilk samples from 250 Jersey and Friesian cows were collected and used to investigate the pattern of interrelationships between milk constituents and to test the effects of breed, sire, parity, stage of lactation, season of calving and milking time on them. Breed and sire effects were significant for all constituents. Overall Jersey cows produced significantly higher milk constituent concentrations except lactose, but the test-day yields in Friesians were significantly higher. Milk constituents had varying responses to parity, days in milk and season of calving. Correlation between different constituents and their regression on each other suggested antagonistic relationships. The pattern of association between constituent concentrations in Friesian cows was similar to that between test-day yields, indicating an equilibrium between volume and content of milk.