Absorption of Non-Protein Nitrogen in Guajillo by White-Tailed Deer

Abstract

Guajillo (Acacia berlandieri) is an important forage for white-tailed deer (Odocoileus virginianus), but has high concentrations of non-protein nitrogen (N).  To determine if non-protein N is absorbed by deer, 4 diets with different proportions of guajillo were assigned randomly to 4 male deer in a Latin square design and total balance trials were conducted.  Urea and ammonium N were assayed and subtracted from total urinary N, resulting in a pool of N we called uncharacterized N.  Our hypothesis was if non-protein N was absorbed but not used by the deer, the amount of uncharacterized N in urine would increase with increasing amounts of guajillo in the diet.  Uncharacterized N did not differ among diets (F3,6= 2.37, P = 0.169).  Our data suggest non-protein N must have either not been absorbed in the digestive tract, or was converted to amino acids by rumen microbes prior to absorption.