The relationship between body-mass and puberty in young red deer (Cervus elaphus) hinds: Evidence of early-life effects on permissive live-weight thresholds

This study, based on the analysis of growth and reproductive records of 6158 young red deer hinds, tested the hypothesis that the nutritional environment in early life influences the permissive body mass threshold for puberty at around 16 months of age. Live-weight at 3 months (i.e. weaning weight) was a proxy for their nutritional environment between birth and weaning, live-weight at 14 months was the indicator of pre-mating body mass, and pregnancy status at 18–19 months was a proxy for entry into puberty. Data were obtained for two sub-populations of hinds, the commercial stud herds, across four consecutive years. The modelled relationships between pre-mating live-weight and the predicted pregnancy rate demonstrated between-year variation for the logistic curves for the commercial herd for the live-weight range from 50 to 90 kg (P < 0.001). For the stud herd, the predicted pregnancy rate at any given live-weight did not vary significantly between years (P > 0.05) and the pregnancy rates for live-weights <90 kg were higher than for the commercial herd. The regression of average weaning weight on probability of pregnancy showed significant positive associations (P < 0.05) at 60 kg, 70 kg and 80 kg (R2 = 0.513, 0.517 and 0.439, respectively). There were no significant regressions at pre-joining live-weights at 90 kg or above (P > 0.05). The study supports the central hypothesis of early-life influences on the permissive body mass threshold for entry into puberty.