Milk production response to dietary forage:grain ratio

Forty-four multiparous and 49 primiparous Holstein cows were assigned randomly at parturition to one of five diets differing in forage:grain ratio and studied for the entire lactation for effects of diet on milk production and milk composition, body condition, BW gain, health, and reproductive performance. Total mixed rations fed once daily consisted of alfalfa silage, high moisture ear corn, soybean meal, vitamins, and minerals. Percentages of forage in the diet (dry basis) for treatments 1 to 5 were postpartum wk 1 to 12 (38.2, 48.2, 58.2, 68.2, and 98.2); wk 13 to 26 (48.2, 58.2, 68.2, 88.2, and 98.2); and wk 27 to 44 (68.2, 78.2, 88.2, 98.2, and 98.2). Milk production (3.5% FCM in 305 d) was 8295, 8659, 7563, 6849, and 6000 kg for multiparous cows in treatments 1 to 5, respectively, and 7334, 7177, 6976, 6014, and 4750 kg for primiparous cows. Primiparous cows had decreased milk protein, BW gain, DMI and gross feed efficiency as forage increased in the diet. Multiparous cows in treatment 1 had depressed milk fat and lower DMI and gross feed efficiency compared with other treatments. Body condition scores tended to be lower as forage increased in the diet with both age groups. Increased forage in the diet did not cause any adverse effects on health and reproductive performance in either age group.