Oestrus induction in buffaloes during low and peak breeding season, along with determination of follicular development, ovulation time and fertility

Abstract

Background: In buffaloes, delayed puberty, seasonality of calving, long postpartum anoestrus, weakness of oestrus signs, low conception rate and long calving intervals greatly affect the reproductive efficiency. Artificial insemination (AI) has proved as the most important tool for genetic improvement in dairy cattle. However, its use in buffalo is very low due to poor conception rates achieved through AI especially with frozen semen. In order to improve reproductive capability, there is a need to focus on understanding reproductive endocrinology of buffalo to develop methods for controlled breeding. The present study was designed to monitor the effect of the Ovsynch treatment on plasma LH and progesterone (P4) levels during peak and low breeding seasons of the dairy buffaloes. Secondly conception rate was studied in buffaloes after treatment with oestrus synchronization protocols (CIDR vs Ovsynch) during low and peak breeding seasons under controlled condition and under field conditions with farmers. Materials and Methods: Twelve Nili Ravi buffaloes were treated with the Ovsynch protocol in November and December of 2007 (i.e. the peak breeding season of buffalo). The buffaloes used for heat synchronization during peak breeding season were kept non pregnant and same were used for studying the effect of the Ovsynch during low breeding season (May 2008). Heat detection was continued in these animals to determine their cyclic status from peak into low breeding season. In the Ovsynch protocol, buffaloes were administered GnRH analogue (50 μg lecirelin) (day 0) followed by prostaglandinF2α (PGF2α) analogue (150 μg cloprostenol, day 7) and again GnRH analogue (day 9). Blood sampling for P4, was done on day 0, 4, 7, 11 and then once weekly for 8 weeks. For LH, sampling was started 12 h after PGF2α injection at 3 h interval up to 108 h. At each occasion 10 ml blood was collected in a heparinized vial. For the frequent sampling for LH an intravenous catheter was placed in jugular vein. Blood samples were immediately centrifuged at 3000 rpm (1006g) for 15 min. Plasma was stored at -20 °C until analyzed. LH was determined by using an ELISA LH DETECT® specific for buffaloes. The assay was a sandwich type assay using two polyclonal antibodies produced from the same antigen, buffalo LH. Plasma P4 was estimated by using commercial ELISA kit. Assays for each sample were conducted in duplicate. For fertility trial the Ovsynch treatment was applied and timed AI was done at 12 hour and again at 24 hour after 2nd GnRH. In CIDR (Controlled Internal Drug Release device) treatment EAZI BREED CIDR was inserted into vagina (day 0) followed by PGF2α analogue (day 6). CIDR was removed on day 8 and buffaloes were artificially inseminated at 24 and 36 hours post CIDR removal. Pregnancy test in buffaloes was performed via palpation per rectum 45 days after insemination. Animals repeating/showing spontaneous heat’ 21 to 42 days after timed AI were inseminated again. Fertility under controlled conditions were performed during May, 2009 for low breeding season and in December 2009 for peak breeding season. Number of animals used during low breeding season in the controlled study was 9 (Ovsynch), 10 (CIDR), and 4 (Control) and number of animals used during peak breeding season was 10 (Ovsynch), 11 (CIDR), and 4 (Control). Control animals were given no treatment but were watched for oestrus and were inseminated if found in heat. Since CIDR protocol worked better than the Ovsynch protocol for oestrus induction during low breeding season in buffaloes, CIDR was used for oestrus induction under field condition (n = 20) during May 2010. Similarly the Ovsynch protocol was applied during peak breeding season (n = 24) in December 2010. Inseminations in all the animals were performed using freshly collected chilled semen diluted in skim milk. Results: LH peak was noted at 39 h after PGF2α in all the animals in which blood sampling could be accomplished during peak breeding season, however, 87.5% animals were considered as responsive when progesterone levels were taken into account. The range of LH peak was 4.43-19.37 ng/ml with a mean ± SEM of 10.38 ± 5.54 ng/ml during peak breeding season. Over low breeding season 63.6% buffaloes became acyclic and 36.4% buffaloes responded to the Ovsynch protocol during low breeding season. Only 14.3% buffaloes with ceased heat activity responded to the Ovsynch protocol during low breeding season. The range of LH peak during low breeding season was 4.42-13.60 ng/ml with a mean ± SEM of 7.38 ± 3.74 ng/ml. A significantly higher number of buffaloes responded to the Ovsynch protocol during peak breeding (87.5%) season as compared to animals in low breeding season (36.4%) (P<0.05). Under controlled conditions the Ovsynch proved to be a better management tool during peak breeding season when 70.0 % buffaloes became pregnant after the treatment. However, CIDR worked better during low breeding season where 30 % conception rate was achieved as compared to the Ovsynch (0.0 %.). When these results obtained from controlled conditions were applied at farmer’s level then a conception rate of 52.6 % was achieved with CIDR in low breeding season and 66.7% with the Ovsynch during peak breeding season. Conclusion: In the light of progesterone and LH analyses it was observed that the Ovsynch worked better during peak breeding season as compared to low breeding season. The Ovsynch and CIDR protocols both were found effective for oestrus synchronization and fertility in buffaloes during peak breeding season, however, only CIDR was able to induce fertile heat in a portion of buffaloes during low breeding season, whereas, the Ovsynch was unable to induce fertile heat during low breeding season. From this study it was recommended that CIDR can be effectively used in both seasons.