Rumen Microbial Protein Synthesis and Milk Performance in Lactating Dairy Cows Fed the Fortified Corn Stover Diet in Comparison with Alfalfa Diet

摘要

The objective of this study was to compare the rumen microbial protein synthesis and milk performance in lactating dairy cows fed the fortified corn stover diet with alfalfa diet. Twelve multiparous Holstein lactating cows were used in a 3x3 Latin square design involving three diets with different forage ingredients: Alfalfa (AH), Corn Stover Supplemented with starch (CSS) and CSS supplemented with rumen-protected methionine and lysine (CSSAA). The basal diets were isonitrogenous and isocaloric with a ratio of forage to concentrate of 45:55 (Dry Matter (DM) basis). The daily DM intake (p = 0.68) and milk yield (p = 0.20) did not differ among the treatments. Compared with CSS, supplementation of Rumen Protected Amino Acid (RPAA) increased the 4% fat-corrected milk (p = 0.06) and milk efficiency (p = 0.08). Milk protein yield was higher (p = 0.07) for cows fed AH than those fed CSS with CSSAA at an intermediate position. Ruminal ammonia nitrogen concentrations (p<0.01) for AH diet was lower than for CSS and CSSAA. Total volatile fatty acids concentration (p = 0.65), microbial protein yield (p = 0.71) and metabolizable protein (p = 0.61) did not differ among the treatments. Lower N conversion (p<0.01) was detected for CSS than AH and CSSAA. It is indicated that supplementation of starch and amino acid to a corn stover diet achieve a similar lactation performance as the cows fed alfalfa diet.