CORN DISTILLERS DRIED GRAINS VERSUS SOYBEAN-MEAL IN LACTATION DIETS

The responses to distillers dried grains were compared with soybean meal using 86 Holstein cows. Diet DM contained 50% ammoniated corn silage and 50% concentrate: negative control (urea), 14.5% CP; soybean meal test diet, 14.5% CP; distillers dried grains with solubles test diet, 14.5% CP; soybean meal positive control, 18% CP; and distillers dried grains with solubles positive control, 18% CP. Daily intake was higher (25.1 vs. 22.2 kg) for the distillers grains test diet than for the negative control but not significantly greater than for the soybean meal test diet (23.7 kg) and positive control (24.0 kg) or the distillers grains positive controls (23.0 kg). Yields of FCM were not significantly different for the soy and distillers test diets. However, the distillers test diet produced 2.3 kg more FCM daily than the negative control compared with 1.7 kg more for the soy test diet. Lactation performance was lowest for the distillers positive control diet. Although blood urea tended to be lower for the lower protein and distillers diets, neither protein source nor level in the diet affected reproductive performance significantly. Thus, these results indicate that dried distillers grains with solubles can be used effectively as a protein source in dairy rations, and yield lactation responses equal to or exceeding soybean meal when the amount in the total ration DM does not exceed 19%.