• Digestibility of guajillo for white-tailed deer

      Barnes, T. G.; Blankenship, L. H.; Varner, L. W.; Gallagher, J. F. (Society for Range Management, 1991-11-01)
      A study was conducted from May 1986 to June 1987 with white-tailed deer (Odocoileus virginianus) to determine seasonal nutritive value and nutrient digestibilities of guajillo (Acacia berlandieri) and a pelleted diet. In vivo dry matter digestibility (DMD) of guajillo varied seasonally from 35.2 to 48.1% and was inversely correlated to levels of condensed tannins in the forage. Apparent protein digestibility varied seasonally from 13.7 to 45.8% and was a highly dependent function R2 = 0.97) of the amount of neutral detergent fiber nitrogen (NDFN) digested and the negative impact of condensed tannins. Cellulose and hemicellulose digestibilities also varied seasonally (0.6 to 13.5% and 52.3 to 71.1%, respectively). Nutrient digestibilities of the pelleted diet did not vary by season, sex, or age. Dry matter digestibility of the pelleted diet was 75.6% +/- 0.9 and true protein digestibility was 95.0 +/- 0.04. Results suggest summer is a stressful period for south Texas deer due to low protein and energy digestibility and high levels of condensed tannins.
    • Instantaneous intake rates of 9 browse species by white-tailed deer

      Koerth, B. H.; Stuth, J. W. (Society for Range Management, 1991-11-01)
      Instantaneous intake rate (IIR) and instantaneous nutrient intake rate (INIR) by tame white-tailed deer (Odocoileus virginianus) of 9 common browse species in south Texas were studied to determine if morphological properties of the plants were associated with intake rate, and if IIR and INIR correlated to preference ratings derived from percent time spent foraging a particular species and with total foliage consumed. Mean leaf mass showed a significant (P < 0.05) positive correlation to IIR (r = 0.75), INIR of neutral detergent fiber (r = 0.73), acid detergent fiber (r = 0.73), and acid detergent fiber nitrogen (r = 0.68). Mean leaf length showed a significant (P < 0.05) positive correlation to INIR of crude protein (r = 0.67). Thorn density showed no significant (P > 0.05) correlations to IIR or INIR. Leaf weight/stem weight ratio showed a significant (P < 0.05) positive-correlation to IIR (r = 0.65) and INIR of acid detergent fiber nitrogen (r = 0.81). Rankings of IIR and INIR did not agree with preference indices based on weight of forage removed or amount of time spent browsing. Significant (P < 0.05) positive correlations for all trials between preference indices based on weight removal and time spent browsing (r = 0.73 for new leaf development, r = 0.87 for stem elongation, and r = 0.70 for full leaf development) indicated these 2 techniques closely agreed on species rank.