Author:

Keywords:

bison, non-invasive endocrinology, gestation, progesterone, sexual behavior, seasonality, Science & Technology, Life Sciences & Biomedicine, Reproductive Biology, Veterinary Sciences, BODY CONDITION, REPRODUCTIVE SUCCESS, WOOD BISON, OVULATION, STRATEGIES, PREGNANCY, BULLS, LEVEL, COWS, Animals, Bison, Breeding, Copulation, Estrus, Feces, Female, Ovulation, Progesterone, Seasons, Sexual Behavior, Animal, Time Factors, 06 Biological Sciences, 07 Agricultural and Veterinary Sciences, 11 Medical and Health Sciences, Dairy & Animal Science, 30 Agricultural, veterinary and food sciences, 31 Biological sciences, 32 Biomedical and clinical sciences

Abstract:

This study provides endocrine data in relation to behavioral events during the transition of the non-breeding into the breeding season in American bison (Bison bison). Fecal progesterone metabolite patterns (20-oxo-P) were obtained in 13 adult female American bison and hormonal data were correlated with behavioral observations; i.e. copulation, male tending, female tail-up behavior and gestation length. Based on fecal progesterone metabolite patterns, the breeding season started between the middle of July and early August. Predictable short cycles reflected the transition from non-breeding to the breeding season; the luteal phase of these cycles was 4.10+/-0.86 days. Copulations and female tail-up behavior were reliably associated with the hormonally detected ovulation. Male tending behavior was more loosely associated with hormonally detected ovulation. The observed hormonal pattern in the study females indicated that 9 of 10 pregnant cows conceived during the second ovulatory period in the breeding season. One other cow conceived during her third ovulatory period, and one cow did not conceive until later in the breeding season by beginning of October. Gestation duration was on average 266.30+/-1.00 days. In summary, this study confirmed that the bison is a seasonally polyestrous species; the transition from the non-breeding into the breeding season was characterized by short cycles with low progesterone metabolite values.