Nutritional ecology of white-tailed deer in southcentral Oklahoma

Abstract

The effect of season on physiological parameters of 55 adult (>2 years) female white-tailed deer (Qdocoileus virginianus) was evaluated during 1985-86 (Year 1) and 1986-87 (Year 2). Serum variables not affected by season during either year were glucose, triglycerides, non-esterifled fatty acids, thyroxine, urea nitrogen, and phosphorus. Serum total proteins were lower in summer than in fall (P < 0.0219) and spring (P < 0.0030) during Year 1, but were unaffected by season in Year 2. Serum triiodothyronine was highest (P. < 0.0095) in fall of Year 1; fall levels were higher (£ < 0.0022) than summer in Year 2. The rumen acetate/propionate ratio (A/P) was lower (P. < 0.0257) in winter than in summer during both years. All volatile fatty acids were affected (P. < 0.0500) by season. Carcass weight was not affected by season in either year. Kidney fat index was highest (P. < 0.0486) in winter during Year 1, and in fall and winter (£ < 0.0145) during Year 2. Other variables affected (£ < 0.0500) by season were total perirenal fat, packed cell volume, serum electrolytes (sodium, potassium, calcium, phosphorus), and rumen ammonia. Potentially limiting seasons for deer were determined by estimating seasonal energy- and nitrogen-based estimates of carrying capacity. Spring and summer generally were most limiting for both energy and nitrogen. Fall became nitrogen-limiting during Year 2 when deer consumed large quantities of acorns, which were low in nitrogen. Energy calculations produced lower carrying capacity predictions than nitrogen in all seasons except fall of Year 1. Managers in southcentral Oklahoma should concentrate on the capability of spring and summer ranges to meet deer energy and nitrogen requirements. Vitreous humor was evaluated as a medium for measuring urea nitrogen, glucose, and triglyceride concentrations in white-tailed deer. Deer were collected from May through August 198 6 (summer), and during November 1986 and January 1987 (winter). Blood serum was obtained from each animal at time of death (TOD). Vitreous humor samples were taken from each animal at TOD and either 4-hours postmortem or 8-hours postmortem. Mean TOD vitreous urea nitrogen (VUN) levels were lower than serum urea nitrogen (SUN) in summer (£ < 0.0320) and winter (£ < 0.0019). Mean 8-hours postmortem VUN levels were lower (£ < 0.0002) than SUN in summer. Postmortem interval had no effect (£ < 0.5054) on mean VUN levels. Linear relationships were found between SUN and all VUN groups (£ < 0.0331). Vitreous glucose and triglyceride means were lower than their respective serum means at all postmortem intervals. Vitreous glucose and triglyceride levels tended to be poor predictors of serum levels. Mean vitreous glucose and triglyceride levels were higher at 4-hours postmortem (£ < 0.0095) and 8-hours postmortem (£ < 0.032 9) than corresponding TOD levels in summer. Vitreous triglyceride levels were stable to 4-hours postmortem in winter. While use of vitreous glucose and triglycerides may be limited in deer management, vitreous humor appears to provide an accurate and stable medium for measuring urea nitrogen.