Mammary and Renal Excretion of Purine Metabolites in Relation to Energy Intake and Milk Yield in Dairy Cows

摘要: This investigation was conducted to quantify the purine excretion of cows and evaluate milk allantoin as an estimator synthesis microbial protein in rumen. Concentrations plasma uric acid their urine were determined using 16 Holstein at 21 315 d lactation yielding 8 36 kg/d milk. The mean daily intake a 55:45 roughage concentrate diet 16.3 kg DM with 106 MJ NEL 13.8 16.0% CP. Total collected over 24 h, samples four times, twice on same day. Analyses metabolites performed HPLC. On average, about 294 4.1 mmol/d for 35 1.1 acid. Excretion correlated concentration (r = .84). As yield increased, percentage increased from .6 2.4% total .85). correlations .80) .84) similar. Daily .78) .95). We concluded that determination is useful, noninvasive method monitor rumen synthesis.