Nitrogen Metabolism of White-Tailed Deer

Urea kinetics were examined in two captive white-tailed deer fawns with 14C-urea. The fawns were fed diets ranging in dietary protein content from 5.14 to 26.00%. Urea pool size and urinary urea excretion rate increased as dietary protein content and plasma urea concentration increased. The percent of urea recycled ranged from 92.3% to 40.6% as dietary protein content increased from 5 to 26%. Endogenous urinary nitrogen was estimated as 0.115 g/kg BW0·75/day. The average biological value of the dietary protein fell from 87.30% to 54.80% as the dietary protein content increased from 5.14 to 26.00%. The true protein digestibility (93.7%±8.4) and metabolic fecal nitrogen excretion (7.55 ±3.36 g N/kg dry matter intake) for white-tailed and mule deer consuming natural forages were calculated from the results of digestion trials reported in the literature.