A study of growth in four racial stocks of the black-tailed deer, Odocoileus hemionus, has, under captive circumstances with ideal diet, revealed that the traditional expressions of the growth patterns of a species are inadequate. Graphic expression of growth in this species requires the use of four curves; one describes prepubertal growth, a second the actual course of weight change through an annual cycle of growth rate; the third describes the annual progression of maximum weights reached; and the fourth the progression of minimum weights reached. Each of these conveys information essential to an understanding of growth in the species. The formulas of lines 1, 3, and 4 are presented for representative males in each of the experimental stocks. Racial characteristics are demonstrated.
The hormonal regulation of reproduction and the antler cycle was investigated by measuring serum testosterone, testis volume, sperm production, and the antler growth cycle of wild and captive deer. The functional relationships of the testes and accessory sex glands to reproduction and antler growth were also studied by examining these organs histologically.Reproductive activity was maximal in November when the mean serum testosterone level of the adult males was 10 ng/ml, testis volume averaged 30 cm3, and the concentration of sperm in the semen was 100 × 106 to 700 × 106/ml. In winter, the activity of the reproductive organs declined, until a minimum was reached in February or March. The antlers were cast several weeks after the serum testosterone dropped below 1 ng/ml. In spring, a significant increase in spermatogenetic activity occurred, coincident with the initiation of antler growth. The serum testosterone level, however, remained low until velvet shedding, in late summer.These findings support the hypothesis that the maturation of antlers, shedding of the velvet, and the maintenance of antlers in the hard, functional condition are dependent on testosterone. The possible significance of increased spermatogenetic activity in the spring and its relationship to antler growth are also discussed.
WOOD. 1970. The feed intake and heat production of the young black-tailed deer (Odocoileus hemionus columbianus). Can. J . Zool. 48: 275-282. The feed intake, resting heat production, and growth rate of prepubertal black-tailed deer fawns of both sexes have been studied under captive conditions. Comparisons of these hdings with those of other workers on domestic and other wild species are presented. The present results provide some explanation for the unusual growth behavior of this species when reared on a high plane of nutrition. IntroductionEarlier studies (11) from this laboratory have shown that members of the genus Odocoileus follow a cyclical pattern in their growth and development. Under nutritional conditions that afford a near-maximum expression of the genetic growth potential, the weight growth curve displays periods of rapid weight accretion during spring and summer followed by periods of weight stasis or loss in fall and winter. Their nutrient energy intake under ad libitum feeding conditions shows, as would be expected, a parallel cyclical course. Observations on the behavior of these animals suggests that the pattern of energy use does not conform in all details with that which might be expected from their feed intake, particularly after the first year of life.This communication presents the findings from experiments designed to determine the feed intake and resting heat production of the deer over the first year of life.
Methallibure, a non-steroidal inhibitor of gonadotrophin secretion, arrested antler growth and suppressed reproduction. The administration of prolactin, pregnant mares' serum gonadotrophin (PMS), and some androgenic steroids to methallibure-treated deer during June and July failed to stimulate antler growth, but human chorionic gonadotrophin (HCG) did rejuvenate it in one instance. None of these hormones was effective in completely restoring reproductive function, although PMS and HCG were capable of stimulating the production of enough testosterone to induce velvet shedding.During the normal period of antler growth, the testes of methallibure-treated deer did not respond to the exogenous administration of HCG by secreting testosterone, whereas both PMS and prolactin were effective in this respect. After the administration of PMS, HCG was capable of stimulating testosterone production, but it was ineffective in the deer previously treated with prolactin. Also, when methallibure treatment was terminated in the fall, testosterone production and spermatogenesis recovered, but the deer that had previously received prolactin did not produce mature sperm until the next spring. Thus, the testicular response may depend on the temporal sequence as well as on the type of hormonal stimulation. The results of this study support the hypothesis that a gonadotrophin is responsible for stimulating antler growth.
WEST, N. O., and H. C. NORDAN. 1976. Cytology of the anterior pituitary at different t~mes of the year in normal and methallibure-treated male Columbian black-tailed deer (Odocoileus hemionus columbianus). Can. J. Zool. 54: 1969-1978. The application of histochemical staining techniques to the anterior pituitary revealed the presence of seven cell types. Most cell types underwent cyclic changes that could be related to a seasonal pattern of functional activity. The cell type tentatively identified as the interstitial-cellstimulating hormone (ICSH) (luteinizing hormone) cell had the most pronounced seasonal cycle. Hormonal release by these cells, and other cells tentatively identified as follicle-stimulating hormone (FSH) cells, was judged to be greatest in the fall, but some activity was also apparent during the spring and summer. The somatotrophs appeared most active in sprlng and summer, whereas the lactotrophs appeared most active in the fall. With the possible exception of the cort~cotrophs, all the cells of the anterior pituitary showed the least signs of activity inlate winter.The pituitaries of methallibure-treated deer sacrificed in July, November, and December contained ICSH cells and FSH cells that were small and chromophobic, whereas other cell types appeared to be affected little or not at all. This suggests that the main effect of methallibure on the anterior pituitary was to suppress the secretory activity of the gonadotrophic cells. The significance of these findings in relation to the hormonal regulation of reproduction and the antler cycle is discussed. WEST, N. O., et H. C. NORDAN. 1976. Cytology of the anterior pituitary at different times of the year in normal and methallibure-treated male Columbian black-tailed deer (Odocoileus hemionus columbianus). Can. J . Zool. 54: 1969-1978. Des techniques de coloration histocbimiques ont permis de constater la pnisence de sept types de mUules dans l'hypophyse ant*rreure. LA pluport de ces types subissent des changemenfs cycliques relies sernble-1-il h une dquencc saisonniert d'activiti foncrionnelle. Les cellutes identifiees cornme etant sans d o u t~ des ceIluIes 9 ICSH ILH) (gonadorruphine B. hormone Iultini
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