MICROBIAL NITROGEN PRODUCTION, NITROGEN BALANCE AND EXCRETION OF URINARY PURINE DERIVATIVES IN CORRIEDALE EWES UNDER WATER DEPRIVATION

The objective of this study was to determine microbial N production, and urinary excretion of PDs in Corriedale ewes under water deprivation. Nine Corriedale ewes (average BW=45 +/- 4.5 kg) were individually fed diets based on maintenance requirements in metabolic crates. Ewes were assigned to three treatment groups according to a 3x3 Latin square design for 3 periods of 21 days duration. The treatments were free access to water (FAW), 2h water deprivation (2hWD), and 3h water deprivation (3hWD) following feeding. Daily water intake decreased linearly as water deprivation time following feeding increased. Feed intake and fecal excretion were not different among the treatment groups. Urine weight and volume were higher in FAW than water deprived groups. Nitrogen balance including urinary N, retained N, urinary N/intake N, and retained N/intake N were lower in FAW group than other treatment groups, whereas no differences were observed in intake N, fecal N, digestible N, and fecal N/intake N among the treatment groups. Allantoin concentration tended to be higher in FAW group than 2hWD and 3hWD groups while no differences were observed in uric acid, xanthine+hypoxanthine and creatinine concentrations. Microbial N production per DOMR was higher in 2hWD and 3hWD groups than FAW group whereas no differences were observed between 2hWD and 3hWD groups. Index of PDC decreased linearly with water deprivation. It is concluded that water deprivation following feeding, especially 2h water deprivation in ewes improved microbial N production.