Effects of rumen-undegradable protein and feed intake on purine derivative and urea nitrogen: comparison with predictions from the Cornell net carbohydrate and protein system

摘要

Six multiparous Holstein cows were used in a 6×6 Latin square to investigate the ability of the Cornell Net Carbohydrate and Protein System to predict ac- Curately rumen microbial yield, plasma urea N, and Milk urea N. Estimations for microbial protein yield Were compared with the measured excretion of purine Derivative N in urine. A 3×2 factorial arrangement Of treatments was adopted. Three concentrations of a Rumen-undegradable protein(RUP)supplement (4.5,14.9, and 29.1/100 of dry matter intake)and two levels of feed restriction(90 and 80/100 of ad libitum intake)were the corresponding factors.