Effect of season and parity on water buffalo calving distribution throughout the year in Venezuela

Resumo

The aim of this study was to determine the effect of season and parity on water buffalo calving distribution throughout the year in Venezuela. A retrospective study analyzing records of 3,192 crossbred (Murrah/Mediterranean) buffaloes including 7,790 calvings was carried out in Venezuela. Two seasons were evaluated according to the length of the photoperiod: September-February (short photoperiod; autumn-winter) and March-August (long photoperiod; spring-summer). Parity order was categorized in parity 1, parity 2, parity 3, and parity 4. Photoperiod was shorter between September and February in comparison with March-August (11.81 ± 0.08 h/day and 12.42±0.08 h/day, respectively, p < 0.05). Percentage of calving varied between the two seasons
(p < 0.05), and 63.7% (95% Confidence Interval (CI): 62.5%-64.9%) of calving occurred during the season of short photoperiod in comparison with that of the season of long photoperiod (36.3%, 95% CI: 35.1%-37.5%), and this effect was observed in all parities. The proportion of calvings during the short photoperiod season was greater as parity increased. The percentage of calving during the short photoperiod season was lower in primiparous water buffalo cows in comparison with that of multiparous water buffalo cows; conversely, the percentage of calving during the long photoperiod season was higher in primiparous water buffalo cows in comparison with that of multiparous water buffalo cows. Eight percent of water buffalo cows having their first calving in the long photoperiod season had the next calvings during this season. In conclusion, results confirm the seasonal reproductive behavior of water buffaloes with a concentration of calvings during the months with short photoperiod; this seasonality becomes stronger as parity increases; even though a small percentage of water buffalo cows has the ability of calving constantly during long photoperiod.