Performance, Rumen and Blood Metabolites in High-Yielding Cows Fed Varying Protein Percents and Protected Soybean

Abstract

Three groups of 20 multiparous high-yielding cows were fed during the first 122 days after calving diets containing 16, 16, and 20% crude protein. Protein of soybean meal in the diet of only the first group was protected with formaldehyde. The calculated crude protein intakes, including maintenance, per kilogram of milk, were 71, 76, and 96 g. Average 122-day milk yields of cows were 40.4, 38.9, and 38.4 kg/day, but solids-corrected milk yields were almost identical. Rumen liquor ammonia and urea concentration in blood plasma were 8.6, 10.0, and 17.3 mg/100 ml liquor and 8.4, 8.8, and 15.4 mg/lO0 ml plasma. Cows fed the protected soybean diet had lower total volatile fatty acid concentrations in rumens and higher molar percentages of propionate but lower percentage of butyrate than cows of the two other groups. Likewise, during wk 7 to 17 after calving, cows of the protected soybean group had a lower fat and protein milk content. Conception rates were 69, 56, and 44%, and open days were 84, 98, and 102.