Estimated energy, protein, and phosphorus balances of a south Texas white-tailed deer population : a dissertation

Abstract

A study was conducted to determine the nutritional status of white-tailed deer in South Texas on a monthly basis between March 1979 and April 1980. Food habits of deer were determined by examining rumens microhistologically. Important species were analyzed for in vitro digestible dry matter (DDM), crude protein (CP), phosphorus (P), and gross energy (GE). Digestible energy, crude protein, and phosphorus models were constructed for 5 age and sex classes, and sensitivity analyses were conducted by changing variables by percentages based upon precision and data base of the variables. Digestible energy and phosphorus were probably the nutritional factors which limited deer growth and survival. The balance of all nutrients was highest in the spring. Energy balances were lowest during the summer because of high maintenance requirements and consumption of low quality browse. Crude protein balances were positive in all months of the year for all age and sex classes because browse high in CP was consumed. Phosphorus balances were below minimum requirements most of the year. Brush was the major component of the diet. Deer consumed larger amounts of evergreens when availability was limited. Changes in intake rates had the greatest overall effect on DE balance because intake rate was changed by a larger percentage than other variables in the sensitivity analysis. Energy required for maintenance affected DE balance greatest during periods of high maintenance requirements and resulted in the largest single deviation from baseline conditions. Energy and protein models failed to predict observed nutritional stress in the winter-spring period of 1979-80 due to a hypothesized severe reduction in intake from lack of available forage caused by an extended drought. Possible behavioral and physiological adaptations to counter nutritional deficiencies are explored. Recommendations for improving white-tailed deer quality included reducing the relative proportion of blackbrush, ceasing treatment of unshredded sandy sites adjacent to shredded areas, shred or roller chop every 3-5 years to increase available forbs and browse, do not attempt control treatments on shallow ridge range sites or drainages, maintain high buck:doe ratio, remove inferior bucks, and always have mineral supplements available free choice as a P source.