Characteristics of first-antler growth in reindeer and their association with seasonal fluctuations in steroid and insulin-like growth factor 1 levels

Growth and development of the pedicles and first antlers were monitored in seven reindeer (Rangifer tarandus tarandus) calves (three males, four femal es) from birth to 1 year of age. Calves were weighed, blood was sampled, an d antler observations and (or) measurements were taken on the day of birth and days 2, 4, and 7 and then at weekly intervals for the remainder of the year. Prior to measurable growth, the frontal lateral crest was carefully p alpated for evidence of pedicle initiation, starting on the day of birth. C alves were born between April 8 and 26, 1994. Pedicle initiation occurred i n all reindeer by day 7. Velvet skin first appeared when calves were 4-6 we eks old, when estimated pedicle height was 3.5 +/- 0.9 cm (mean +/- SD). An tler growth in both sexes followed a sigmoidal pattern, producing a mean an tler length of 33.5 +/- 4.2 and 46.7 +/- 13.8 cm in females and males, resp ectively. Antler growth was complete by week 18 in females and week 21 in m ales. Velvet cleaning was associated with a significant increase in plasma testosterone levels in males and estradiol-17 beta (but not testosterone) l evels in females. Insulin-like growth factor 1 levels were significantly hi gher in males than in females and were positively correlated with the perio d of most rapid antler growth in both sexes. Casting occurred between March 14 and April 17, when steroid levels were at a minimum, and was immediatel y followed by growth of the second antler.