Performance of cows in early lactation fed isonitrogenous diets containing soybean meal or animal by-product meals.

Eighty primiparous cows were assigned to either soybean meal, fish meal, or A and B treatments. Commercial supplement A was a blend of meat and bone, meat, poultry, blood, and feather meals. Commercial supplement B included the same ingredients as A but had a higher amount of blood meal and also a low concentration of fish meal. In vitro undegradabilities of protein were 32.0, 37.8, 38.8, and 42.4% for soybean meal, fish meal, A, and B rations, respectively. Milk yields and body weight changes were not significantly affected by treatments. Because of the lower milk fat content on fish meal diet, FCM yield was lower for cows fed fish meal than soybean meal or B supplements. Milk protein content was 3.19, 3.19, 3.03, and 3.09% on soybean meal, fish meal, A, and B diets, respectively. The calculated protein efficiency (100* output/input) on soybean meal, fish meal, A, and B diets were 47.8, 51.6, 45.9, and 48.7, respectively. The undegraded protein in the fish meal after an 18-h in vitro incubation with protease enzyme (Streptomyces griseus, type V) had a higher concentration of methionine and lysine than the undegraded protein of other supplements. Flavor of milk produced on the soybean and fish meal diets was evaluated. No flavor differences were detected.