Measurements of microbial N flow to the duodenum and urinary excretion of purine derivatives in bulls

摘要

Accurate determination of microbiai protein synthesis in the rumen is essential in ruminant nutrition and various procedures have been used in the past. Now, purine derivatives excreted in urine represents an attractive alternative technique for thispurpose (Chen et al, 1990, Br J Nutr, 63, 197). An experiment was carried out on six ruminally and duodenally fistulated Belgian White Blue bulls (initial live weight 287 ± 17 kg) in order to determine the relationship between microbial N flow to the duodenum and purine derivatives (PD) excretion in urine. The bulls were fed twice a day (8h30 and 20h30) in equal meals a mixed ration consisting of concentrates (75 % of DMI) and meadow hay (25 % of DMI). Two levels of intake (55 and 85 g of DM/kg W~(0.75) were tested in two 9d measurement period following a 21 d adaptation period, according to a cross-over design.