Phosophorus Nutrition in White‐Tailed Deer: Nutrient Balance, Physiological Responses, and Antler Growth

Abstract

Phosphorus (P) is considered, except for sodium, to be the most limiting, mineral for growth and reproduction in large mammalian herbivores worldwide and a predictor of ungulate distribution and abundance. Knowledge of phosphorus nutrition and seasonal adaptation to dynamics in mineral needs and availability in wild herbivores is incomplete. This paper reports data on experiments designed to evaluate physiological responses to low dietary P and to determine phosphorus requirements in male white—tailed deer (Odocoileus virginianus), a browsing cervid with presumed elevated mineral requirements during antlerogenesis. Adult (>2 yr) male deer were housed individually and placed on three levels of dietary P (0.14—0.19%, 0.24—0.27%, and 0.34—0.36% of diet dry mass) from June 1989 to September 1991. We conducted balance trials to measure seasonal P retention and to model annual and seasonal dietary P requirements. Data were collected on serum chemistry, endocrine function, antler growth, antler composition, and tail bone composition in two trials designed to test the hypothesis that P is limiting to deer antler growth in southwestern habitats. Phosphorus balance varied by diet and tended to fluctuate seasonally. Retention was highest for the 0.19% P diet and greatest during the fall. The variation in P balance resulted from increased efficiency in P metabolism in animals on the 0.14—0.19% P diet. Dietary phosphorus requirements were estimated at 72.2 mg°kg—0.75°d—1 (0.14% P at study intake rates) on an annual basis, changing seasonally from 94.4 mg°kg—0.75°d—1 (0.16%) during spring to 57.4 mg°kg—0.75°d—1 (0.11%), and 59.6 mg°kg—0.75°d—1 (0.12%) during summer and fall, respectively. Feed consumption, body mass, antler size and composition, and bone composition did not vary by diet. Diet x month interactions were observed in 1990 and 1991 for serum activity of alkaline phosphatase (AP), manifested in higher activity on the 0.14—0.19% P diet during the peak period of antler growth . changes in AP were an indicator of physiological compensation to low dietary P. Other key serum chemistries and hormonal concentrations did not vary by diet. These results suggest that P limitation for antler growth is unlikely for adult browsing cervids. We predict sensitivity of the distribution and abundance of male cervids to P limitation to be a function of feeding strategy and body size.