EFFECTS OF TALLOW AND ESCAPE PROTEIN ON LACTATIONAL AND REPRODUCTIVE-PERFORMANCE OF DAIRY-COWS

Experiments were performed to determine the effect of energy source an d proportion of escape protein on lactational performance, body measur ements, and reproductive activity. Sixty-eight lactating Holstein cows were assigned to one of four dietary treatments during wk 2 to 12 pos tpartum: 1) high fat (3% tallow), high escape protein (5% feather meal :blood meal, 85:15, DM basis); 2) high fat, low escape protein (0% fea ther meal:blood meal); 3) low fat (0% tallow), high escape protein; an d 4) low fat, low escape protein. Diets were similar in energy and CP contents. Overall mean milk yield (32.9 kg/d) was not affected by diet , but efficiency of FCM yield was highest with high fat and high escap e protein. Daily DMI and net energy balance were greater for cows fed the diet low in fat and low in escape protein, but days to first ovula tion were not different among groups. Total cholesterol in plasma incr eased as DIM increased, and concentrations were greater for cows fed t he high fat diets than for cows fed the low fat diets after 35 DIM. Co ncentrations of luteal phase progesterone and follicular phase estradi ol tended to be greater for cows fed the high fat and low escape prote in, but conception rate from first AI was greatest for cows fed the hi gh fat and high escape protein. Supplemental tallow and escape protein did not consistently affect lactational performance but did improve e fficiency of FCM yield and conception rate from first AI.