DRY-MATTER INTAKE, MILK-YIELD AND COMPOSITION, AND NITROGEN USE IN HOLSTEIN COWS FED SOYBEAN, FISH, OR CORN GLUTEN MEALS

Soybean meal, Atlantic menhaden fish meal, and corn gluten meal feeds varying in CP degradability and amino acid pattern were evaluated as supplements for high milk yield. Forty multiparous Holstein cows were fed a basal diet of corn silage:grain (blended, .8% urea, 12% CP, DM basis) ad libitum in wk 1 to 18 of lactation. During wk 1 to 3 of lactation, diet DM was 16% CP (basal plus soybean, fish, and corn gluten meals; each source contributed equal CP). On d 22, 10 cows were assigned to each of four diets: basal, 12% CP, DM basis or a diet containing 16% CP, DM basis with either soybean, fish, or corn gluten meal providing the supplemental CP. Cows readily ate all diets. Peak milk yields occurred later and were higher for cows fed soybean (wk 8, 38.9 kg/d) and fish meals (wk 9, 41.6 kg/d) compared with those fed the basal diet (wk 4, 31.0 kg/d) or corn gluten meal (wk 5, 37.5 kg/d). Milk protein yield was greater for cows fed soybean and fish meals. Fish meal decreased milk fat test (3.3 to 2.8%); however, due to differences in milk yields, fat yields were similar for cows fed soybean and fish meals. Productive N (milk + retained N) was greater and BW loss was less for cows fed soybean and fish meals. These data indicate the importance of CP degradability and amino acid pattern on performance.