The effect of feed intake and body weight on purine derivative excretion and microbial protein supply in sheep.

TitleThe effect of feed intake and body weight on purine derivative excretion and microbial protein supply in sheep.
Publication TypeJournal Article
Year of Publication1992
AuthorsChen, XB, Chen YK, Franklin MF, Orskov ER, Shand WJ
JournalJournal of animal science
Volume70
Issue5
Pagination1534-42
KeywordsAllantoin, Animals, Bacterial Proteins, Body Weight, Digestion, Eating, Female, Hypoxanthine, Hypoxanthines, Male, Purines, Rumen, Sheep, Uric Acid, Xanthine, Xanthines
Abstract

Urinary excretion of purine derivatives (PD) was used to estimate the microbial N (MN) supply to sheep in three experiments designed to examine the effects of DMI and BW on the efficiency of microbial N supply (EMNS) to the host animal. In Exp. 1, four sheep of about 45 kg BW were given 328, 656, 984, and 1313 g of DM/d of a hay/concentrate diet in a Latin square design. Excretion of PD per kilogram of digestible organic matter intake (DOMI) increased with intake, and EMNS increased from 12.0 to 28.3 g of MN/kg of OM digested in the rumen (DOMR). In Exp. 2, 19 sheep ranging from 22 to 73 kg BW were all offered 820 g of DM/d of the same diet as that fed in Exp. 1. Although DM digestibility was relatively constant, PD excretion varied from 4.5 to 13.5 mmol/d and EMNS from 8 to 36 g of MN/kg of DOMR, both inversely related to animal BW. In Exp. 3, five sheep of 48 to 57 kg BW were given a different diet at 702, 966, or 1,237 g of DM/d. Purine derivative excretion per kilogram of DOMI increased with the DMI:BW ratio. Calculated EMNS ranged from 23 to 35 g of MN/kg of DOMR. Pooled data from all experiments showed EMNS to be related to the DMI:BW ratio. It is suggested that the DMI:BW ratio defines the ruminal digesta passage rate and hence outflow of microbial protein. The results imply that the EMNS for a given diet is not constant, but changes with intake.

Alternate TitleJ. Anim. Sci.