Studies upon genetic and environmental factors affecting the cholesterol content of cow milk. I. Relationship between the polymorphic form of beta-lactoglobulin, somatic cell count, cow age and stage of lactation and cholesterol content of milk

摘要

Despite the fact that cholesterol is a comparatively stable component of cows' milk its concentration is, within a certain range, subject to significant variation related to the season (probably the feeding system), lactation stage and somatic cell count in milk. The highest differences (about 25%) in the amount of cholesterol per g milk fat were observed between the first and last lactation stage. Despite the decreasing milk yield with the progress of lactation, the amount of cholesterol secreted with milk increased significantly. In the milk of cows for which the somatic cell count was below 100 thousand/ml the cholesterol content was by about 10% lower than that in milk characterized by a higher somatic cell count. The positive correlation coefficients obtained between the amount of cholesterol expressed as nig/100 ml milk and the per cent of fat and protein indicate that selection conducted for increasing the concentration of nutritive components in milk will result in an increased cholesterolcontent. However, the quantity of cholesterol per 1 g milk fat will decrease. There was observed no correlation between the content of cholesterol in milk and the polymorphic forms of LGB.