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Nitrogen Metabolism in Dairy Cattle. I. The Influence of Grain and Meadow Crops Harvested as Hay, Silage, or Soilage on Efficiency of Nitrogen Utilization

Departments of Dairy and Agronomy, Ohio Agricultural Experiment Station, Wooster

ABSTRACT

Efficiency of nitrogen utilization was studied in four experiments involving varying proportions of silage and hay, comparisons of silage and freshly cut meadow crop (soilage), effects of grain feeding, and feeding different ratios of roughage to grain. Feces and urine were collected separately and nitrogen balance and milk nitrogen determined. In all trials, lactating cows were allowed to eat roughage ad lib. No differences in nitrogen efficiency or urine losses were observed in cows fed different proportions of hay and silage. The nitrogen utilization response from freshly cut forages was different from that obtained with ensiled forages. Below 15% protein equivalent in the total ration, silage and soilage nitrogen were used with the same efficiency. Silage nitrogen declined in efficiency at higher levels, whereas soilage nitrogen was used as efficiently at the highest levels of protein equivalent measured as at the lowest. Adding grain to forage rations increased the efficiency of nitrogen utilization markedly, but increases in the grain content which raised the amount of grain from a 3:1 ratio of roughage to grain to a 2:1 ratio were without further effects.