Effects of Dry or Ensiled Feeds and Protein Percent on Milk Production and Nitrogen Utilization by Lactating Cow

Abstract

In two 2×2 factorial experiments, 28 cows in first and later lactation (Trial 1) and 28 cows in second and later lactation (Trial 2) were fed rations containing either dry (low nitrogen solubility) or ensiled (high nitrogen solubility) feeds with low (14%) or high (16%) concentrations of crude protein. Rations were formulated with hay or hay crop silage and dry shelled corn or high moisture shelled corn in a 50:50 ratio (Trial 1) or 40:60 ratio (Trial 2) of forage to concentrate in the dry matter. Soybean meal was used to alter the protein content.Protein percent had no effect on milk yield or milk composition in either trial, although nitrogen digestibility was greater on high protein diets. Solids-corrected milk yield and milk fat percent were lower when nitrogen solubility of the ration was increased in Trial 2 but not in Trial 1. Analysis of nitrogen balance data indicated higher conversion of nitrogen of feed to nitrogen of milk for low solubility diets in Trial 1 and high solubility diets in Trial 2.