Fecal nitrogen and 2,6-diaminopimelic acid as indices to dietary nitrogenin white-tailed deer

摘要

Few controlled studies have been conducted to determine how accurately fecal nitrogen (FN) and fecal 2,6-diaminopimelic acid (FDAPA) track changes in diet quality. Additionally, it is assumed that gender does not influence either index and that tannin consumption does not influence FDAPA concentrations, but these assumptions have not been tested. We examined effects of gender and tannin consumption on FN and FDAPA under controlled experimental conditions. In one experiment, we fed white-tailed deer (Odocoileus virginianus) tannin-free experimental diets holding dietary energy constant but varying dietary nitrogen ON) from 1.3 to 4.1%. Fecal nitrogen concentrations tracked changes in DN (P <0.01), but FDAPA did not (P=0.47). Gender did not influence either FN (P=0.56) or FDAPA (P=0.54). In a second experiment, we fed deer 6 experimental diets with 2 levels of DN and 3 levels of tannin in a factorial arrangement. Presence of tannins elevated FN concentrations (P <0.01); however, the effect was more pronounced for animals consuming high nitrogen diets. Fecal DAPA was influenced by DN (P <0.01), but not by tannin level (P=0.45). The apparent response of FDAPA to DN may have been related to dietary energy differences between the low and high nitrogen tannin diets. Fecal nitrogen may be a useful method to monitor DN, provided the potential confounding effects of tannins are recognized. While FDAPA may be a useful method to monitor dietary energy, it should not be used to monitor DN.