Seasonal levels of serum parathyroid hormone, calcitonin and alkaline phosphatase in relation to antler cycles in white-tailed deer.

Seasonal levels of serum parathyroid hormone (PTH), calcitonin (CT), and alkaline phosphatase (AP) were studied in relation to antler growth cycles in 8 male (2.5-6 years old) white-tailed deer. Feed consumption was recorded weekly, whereas body weight was recorded biweekly. Antler length was measured from the pedicle to the tip after velvet growth was initiated. Serum samples were obtained biweekly while animals were tranquilized with xylazine hydrochloride. Serum Ca was significantly (P less than 0.05) elevated during the summer. Serum P was significantly (P less than 0.05) elevated only during early fall. There was an increase in serum PTH during velvet initiation in April-May, but not thereafter. CT increased during the rapid antler growth period. Serum PTH levels were significantly (P less than 0.05) elevated (0.628 vs 0.884 ng/ml) during post-velvet shedding and decreased (0.602 vs 0.346 ng/ml, P less than 0.05) during post-antler casting. Serum AP activity was highest during rapid velvet antler growth. Feed intake was lowest in early winter, but a compensatory increase was found in late winter. Feed intake peaked in May, then gradually decreased. Body weight was maximum in November and minimum in March. It is concluded that increased PTH during velvet initiation is responsible for Ca absorption and/or mobilization. Increasing PTH levels are related to final mineralization of antlers post-velvet shedding. Higher levels of serum Ca in June-July inhibit continued increase in PTH. Increased CT during rapid antler growth may have prevented excessive bone resorption.