The effect of red clover proportion in timothy silage on nitrogen utilization in lactating dairy cows

Summary

Three multiparous cannulated dairy cows were used to test the effect of including 0, 23 % and 46 % red clover (RC) on dry matter (DM) basis in timothy (T) silage on nitrogen (N) intake, utilization and excretion. The cows were offered a fixed ration; 13 kg silage and 7 kg concentrate DM. The N intake and urine N excretion increased with increasing silage clover proportion. Milk yield was higher in the clover containing silages than in the pure grass silage, probably due to higher organic matter digestibility in RC containing silages. The efficiency in converting feed N into milk N, however, was higher in cows fed the timothy silage than in cows offered grass/clover silages. The efficiency in microbial protein synthesis in the rumen and the proportion of microbial N of the total N flow to duodenum was higher on the T diet than on the RC containing diets. However, the clover diets gave a slightly higher proportion of bypass N originating from the feed. So, the total flow of N to duodenum was the same for all three diets. In conclusion, increased proportion of RC in T silage did not improve the N utilization.