Influence of bovine somatotropin on the composition and manufacturing properties of milk

Three studies (84, 140, and 200 d) were performed to examine the effect of injecting dairy cows with various doses (0, 320, 640, or 960 mg/28 d; 0 or 640 mg/28 d; 0, 320 mg/14 d, or 320 or 640 mg/28 d) of bST on milk production, composition, and manufacturing properties. Mean bST response among studies on milk production varied from 0 (trial 1) to 7.3% (trial 2) and from 8.5 to 14.2% (trial 3) in relation to feeding conditions. Neither milk fat nor protein percentages in milk at time of maximum response were affected by the use of bST. Distribution of casein and protein in the whey was not affected by the treatments at any time. The nature of fatty acids varied more with time after injection than with bST doses. Neither coagulation time, standard curd firmness, nor soft or pressed cheese yields were affected by the treatments