Context Profitability of water buffalo systems depends on a calving interval (CI) <400 days. Several factors affect the achievement of this target. However, milk yield at first lactation has received little attention. Aims Determine the effect of milk yield at first lactation, parity, season of calving and farm, on the length of CI and the probability of a CI ≤ 400 days in water buffaloes. Methods A retrospective analysis of milk yield at first lactation and reproductive records of 1459 water buffaloes was carried out. Milk yield was categorised as Group 1 (≤1090 kg), Group 2 (1090–1377 kg), Group 3 (1377–1684 kg) and Group 4 (>1684 kg); parity was categorised as parity 1, 2 and ≥ 3; and month of calving was grouped into three seasons: December–March, April–July, and August–November. Data were analysed using linear and logistic mixed models. Key results CI increased from 425.3 days (95% CI: 418.8–431.8 days) in group 1 to 463.3 days (95% CI: 456–470.6 days) in group 4 (P < 0.05), while the probability of having a CI ≤ 400 days decreased from 0.5 (95% CI: 0.46–0.54) to 0.26 (95% CI: 0.22–0.29), respectively (P < 0.05). CI decreased from 466 days (95% CI: 460.8–471.3 days) in parity 1 to 410.5 days (95% CI: 405.2–415.8 days) in parity ≥3, whereas the probability of a CI ≤ 400 days increased from 0.26 (95% CI: 0.24–0.29) to 0.51 (95% CI: 0.47–0.54) respectively (P < 0.05). Water buffaloes calving in August–November showed significantly shorter CI and, along with those calving between December–March, showed the highest probability of a CI ≤ 400 days. An interaction between milk yield at first lactation and parity on both outcomes was observed. Conclusions Shorter CI and higher probability of a CI <400 days were associated with lower milk yields at first lactation, higher parity and calving between August–November. Higher milk yield at first lactation affected negatively the reproductive performance of water buffaloes, especially at parity 1 and 2. Implications These results highlight the importance of adequate nutritional management to allow water buffaloes to cope with the challenge of the postpartum negative energy balance and have a calving interval less than 400 days.

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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.

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This article aims to review both the economic impact of reproductive failures on the profitability of water buffalo systems and the effect of different factors on the reproductive performance of water buffaloes. Besides, an overview of various non-hormonal alternatives to improve reproductive performance is made. The optimal reproductive efficiency in water buffaloes implies calving to conception interval around 90 days to reach a calving interval of 400 days, with longer calving intervals having a negative impact on profitability. Reproductive efficiency is the consequence of the interaction of genetic and non-genetic factors, and the recognition of these factors by analyzing the reproductive information must be a priority. Although each factor's impact can be of greater or lesser magnitude depending on the conditions of each herd, some factors like nutrition, milk yield, body condition score, negative energy balance, parity, bull presence, low estrus intensity, and season can be considered high-impact factors. Not all factors are common among farms; therefore each farm must implement a program for the identification, control, and prevention of reproductive problems, especially during early lactation, to prevent a long anestrus; and when artificial insemination is used, so that it is done at the correct time with respect to the beginning of estrus to enhance fertility.