Effects of energy and protein levels on attainment of puberty and steroid hormone production in captive female white-tailed deer

Abstract

Twenty-four female fawns, weaned at 3.5 months of age, were divided into three groups and randomly assigned to one of four treatments with that group. High energy-high protein (HEHP), high energy-low protein (HELP), low energy-high protein (LEHP), and low energy-low protein (LELP) diets were the treatments used in 2x2 factorial design. High energy diets contained an average of 3064 kcal/kg digestible energy while low energy diets contained an average of 2507 kcal/kg digestible energy. Crude protein levels for high and low protein diets averaged 18.19 and 9.60 percent respectively. Eighteen fawns were included in the final analyses. Five fawns died of various causes during the course of the experiment while one fawn begun late on experiment was not included in any analysis. Fawns tended to reduce food consumption while weight gains decreased slowly during the course of the experiment. High energy diets caused a significant (p<0.05) increase in progestin concentrations over low energy diets. Progestin concentrations were significantly (p<0.05) higher during January (especially the first ⅓ of January) than any other month examined. Nine of 11 high energy animals and 0 of 8 low energy animals had progestin levels of at least 1.00 ng/ml during the experimental period. This was interpreted as indicating a higher incidence of ovulation and puberty in high energy animals. Protein level had no apparent effect on incidence of ovulation and puberty. Estrogen analysis was unsuccessful because of extremely low levels of estradiol in these fawns’ plasma.