Effects of white-tailed deer population density and supplemental feed on forage abundance and nutritional value in a semiarid environment

Highly proactive white-tailed deer (Odocoileus virginianus) management and habitat enhancement activities are common in southern Texas. Managers may seek high deer densities or provide deer populations with highly nutritious pelleted feed in an attempt to achieve a personal management goal. The purpose of my experiment was to determine if increasing deer density and providing supplemental feed altered forage standing crop and nutritional quality. I used 6, 81-ha controlled-density enclosures on 2 ranches in south Texas with low, medium and high deer densities representative of typical population estimates for the Rio Grande Plains of Texas. One pair of each density of each replicate was provided highly nutritious pelleted feed ad libitum ; the other pair of each density was unfed. Standing crop of forage was estimated in 40 plots/enclosure bi-annually and was harvested in 20 randomly selected plots/enclosure to correct estimates to dry mass.;Feeding did not generally affect forb standing crop (P = 0.096); but, forb standing crop was greater (P = 0.032) in low deer density enclosures during the summer in 2 of 8 years. Forb, browse, and grass standing crop and nutritional quality varied (P < 0.05) with rainfall among years. Enclosures with low deer densities had lower forb nutritional quality than those with higher densities (P = 0.036) during drought years. Enclosures provided pelleted feed tended to have greater browse crude protein than enclosures absent of feed (P = 0.046) in spring. Summer browse NDF was lower (P = 0.002) in low density than in high density enclosures. Variation in annual and seasonal precipitation appeared to have a much larger impact on forage standing crop than did feeding pelleted rations or increasing deer densities.