Studies On The Exogenous Nucleic Acid Metabolic Regulation Of Lambs And Fawns

Four lambs and four fawns with pre-rumen were used to study exogenous nucleic acid metabolic regulation. Nucleic acids(RNA and DNA, 6:4) dissolved in milk were fed to the animals at 5 levels (from 2.55 to 12.73mmol purines/d).The results showed that dry matter, organic matter and N apparent digestibility for lambs (97.90,98.11 and 97.06%, respectively) were higher than for fawns (97.14, 97.39 and 95.28%, respectively ) (P < 0.05), but N retention (2.69g/d) was lower than for fawns (3.64g/d) (P<0.01). Nucleic acid apparent digestibility for lambs(92.15%) and for fawns (89.74%) did not differ significantly (P>0.05).Total purine derivative excretion (including allantoin, uric acid, hypoxanthine and xanthine) (Y;mmol/d) in the urine increased with increasing exogenous purine inputs (X;mmol/d) by lambs, its linear equation was: Y=0.752+0.662X(r 0.995, P<0.001) and here 0.662 represented recovery of exogenous purines in the urine, which was similar to the recovery of purines in adult sheep(0.695), indicating that nucleic acid metabolism in the pre-rumen lambs is similar to adult sheep .Total purine derivative excretion (including allantoin, uric acid, hypoxanthine and xanthine) (Y;mmol/d) in the urine by fawns increased with increasing exogenous purine inputs(X';mmol/d), its linear equation was: Y'=0.559+0.326X'(r 0.990, P<0.01) and 0.362 represented the recovery of purines in the urine. Different nucleic acid metabolic patterns were found between lambs and fawns. The equation for the microbial nitrogen flow in the duodenum estimated by the total purine derivative excretion was temporarily determined: Microbial nitrogen (g/d) = -0.923 + 1.814X, and here X (mmol/d) represented the the total purine derivative excretion of in the urine of fawns.Uric acid equivalents (Y;mmol/d) in the urine of iambs increased with increasing exogenous purine inputs(X;mmol/d), and its linear equation was: Y=--0.913+1.506X(r 0.994, P<0.01). The method may be used to investigate the nucleic acid metabolism of lambs. As the exogenous nucleic acid metabolism was similar in adult and young sheep, microbial nitrogen flow in the duodenum of sheep might be estimated by the uric acid equivalents as follows: microbial nitrogen flow (g/d) = 0.417 + 0.396X, and here X (mmol/d) represented the uric acid equivalents in the urine of lambs.Similarly uric acid equivalents (Y;mmol/d) in the urine of fawns increased withincreasing exogenous purine inputs(X;mmol/d) and its linear equation was: Y=3.380 +0.477X (r 0.992, P <0.01). The equation for the microbial nitrogen flow in the duodenum of deer estimated by the uric acid equivalents was temporarily determined as follows: microbial nitrogen flow (g/d) = -4.137 + 1.245 X, and here X (mmol/d) represented the uric acid equivalents in the urine of fawns.