Efficacy of Ovsynch protocol with antiprolactin treatment for timed artificial insemination during non-breeding seasons in yaks (Poephagus grunniens L.).

An attempt was undertaken to investigate the efficacy of Ovsynch protocol for timed artificial insemination (TAI) with or without Norprolac (antiprolactin) treatment during non-breeding season (winter months) in yaks (n = 25). During non-breeding season, plasma prolactin profile has been reported high due to cold and nutritional stress. The Norprolac dose of i.m. administration was standardized for prolactin suppression. Three different doses viz. 2.5, 5.0 and 7.5 mg were attempted and the dose of 7.5 mg Norprolac i.m. per animal was found to be suitable for suppression of prolactin levels up to 30 h. Ovsynch treatment with Norprolac induced more number of oestrous symptoms per animal (4.8 vs 2.1), higher LH peak concentration (24.01 vs 16.16 ng/ml), longer duration of LH surge (6.8 vs 5.2 h) and higher conception rate (70 vs 30%) in Ovsynch plus Norprolac treated animals compared with animals treated with Ovsynch alone. Therefore, this study clearly indicates the opportunity for practical application of the Ovsynch plus Norprolac protocol for TAI in yaks during non-breeding seasons.

Plasma concentrations of 13, 14-dihydro-15-keto-prostaglandin F2alpha, progesterone and cortisol during periparturient period in yaks (Poephagus grunniens L.).

An attempt was made to determine plasma concentrations of, 13, 14-dihydro-15-keto-prostaglandin F(2alpha) (PGFM), cortisol and progesterone during periparturient period in yak. Plasma PGFM level showed an increasing trend beginning day 5 prior to parturition (0.48 +/- 0.14 ng/ml) and increased steeply thereafter to reach a peak level (17.16 +/- 1.31 ng/ml) on the day of parturition. The levels, then, declined sharply on day 1 postpartum to reach 1.20 +/- 0.40 ng/ml and thereafter declined gradually over the days to reach 0.28 +/- 0.09 ng/ml on day 20 postpartum and this level was maintained with fluctuation within narrow limits thereafter till conclusion of the blood sampling on day 90 post-calving. The plasma progesterone concentration on days 7 and 6 before parturition was high (2.10 +/- 0.10 and 2.12 +/- 0.10 ng/ml, respectively). The level then decreased gradually and abrupt fall was observed 1-2 days before parturition and became basal on day of parturition (0.24 +/- 0.04 ng/ml). This basal level was maintained till the end of the blood sampling on day 90 postpartum. Plasma cortisol level showed an increasing trend beginning day 2 prior to parturition (2.36 +/- 0.65 ng/ml) and increased steeply thereafter to reach a peak level (26.65 +/- 5.28 ng/ml) on the day of parturition. The levels, then, declined gradually over the days and touched 2.36 +/- 0.25 ng/ml on day 3 postpartum and this level was maintained with fluctuation within narrow limits thereafter till day 7 post-calving.

Application of sensitive enzymeimmunoassay for determination of testosterone in blood plasma of yaks (Poephagus grunniens L.).

As an alternative to radioimmunoassays, a simple, highly sensitive and quick enzymeimmunoassay (EIA) for determination of testosterone in blood plasma of yaks on microtitreplates using second antibody coating technique and testosterone-horseradish peroxidase as a label has been developed for the first time. The wells of the microtitreplate were coated with affinity-purified goat immunoglobulin (antirabbit IgG) that binds the hormone specific antibody. The EIA was carried out directly in 20 mICROl of plasma after 1:10 dilution with assay buffer. The testosterone standard curve ranged from 0.2 to 200 pg/well. The sensitivity of the assay was 0.20 pg/well. Testosterone standard curve in buffer showed parallelism with serially diluted yak plasma containing high endogenous testosterone. Intra- and inter-assay coefficients of variation (CV) determined using pooled plasma was found 5.24 and 8.54%, respectively. Recovery of known concentrations of added testosterone in charcoal stripped plasma was linear (r=0.98). For biological validation of testosterone enzymeimmunoassay, the blood samples were collected from yak cows at -2h before and thereafter at 2h interval until 24h. after gonadotropin releasing hormone (GnRH) administration. There was a rapid increase (p<0.01) of luteinizing hormone (LH) and testosterone 2 and 6h after GnRH administration. Plasma testosterone concentration in normal adult yak bulls was found to be 0.52+/-0.09 ng/ml. In conclusion, the EIA developed in this study is simple, highly sensitive, valid and sufficiently reliable method for estimation of testosterone directly in yak plasma.

Strategies to optimize reproductive efficiency by regulation of ovarian function in yak (Poephagus grunniens L.).

Ovulatory response to the first GnRH of Ovsynch is the critical determinant for successful synchronization of ovulation in animals. An attempt was made in this study to design a pre-Ovsynch hormonal strategy in yaks to increase the ovulatory response to the first GnRH injection of Ovsynch so that overall synchronization rate to Ovsynch could be improved. Non-lactating cyclic yak cows (n=33) were assigned to receive either no treatment before Ovsynch (control) or 0.375 mg of PGF2alpha (PreP) followed 2 d later by 10 microg of GnRH (PreG), administered 4 (G4G), 5 (G5G), or 6 (G6G) d before initiating the Ovsynch protocol. Rectal palpation was performed to assess ovulation and blood samples were collected to measure progesterone concentrations during pre-treatment, treatment and post-treatment periods. All the animals received timed AI 12 and 24h after the final GnRH of Ovsynch. Diagnoses for pregnancy were performed by rectal palpation and profiles of plasma progesterone 35 d after AI. Percentage of yak cows that ovulated in response to the first GnRH injection of Ovsynch, synchronized to Ovsynch treatment, had a functional CL at PGF2alpha of Ovsynch, had circulating concentrations of P4 at PGF2alpha of Ovsynch and likely to be pregnant after 35 d after AI, were greater in G6G and G5G compared with control, whereas G4G did not differ from controls. In addition, animals that ovulated in response to first GnRH of Ovsynch had greater response to PGF2alpha of Ovsynch and greater synchronization rate to the overall protocol than those that did not ovulate. In summary, PGF2alpha-and-GnRH-based pre-Ovsynch strategies consisting of 5 or 6-d interval between PreG and first GnRH of Ovsynch resulted in a greater ovulatory and luteolytic response to first GnRH andPGF2alpha of Ovsynch, respectively, compared with control animals. These, in turn, optimized synchronization rate to Ovsynch in yaks.

Season of the year influences semen output and concentrations of testosterone in circulation of yaks (Poephagus grunniens L.).

Seasonal changes in plasma testosterone concentration and semen quality were evaluated in yak bulls throughout a 1-year period. Blood samples were collected every week from adult yak bulls (n=15). These blood samples were analyzed for testosterone using a highly sensitive enzyme-linked immunoassay. Ejaculates were collected from five representative bulls each week. Ejaculate volume, progressive motility, live sperm count and sperm concentrations were determined. Mean testosterone in plasma was 1.03+/-0.25 ng/ml. Concentrations of testosterone changed throughout the year (P<0.05) and were found to be highest during the winter. It was also higher during the autumn than in summer and spring (P<0.05). Mean ejaculate volume, progressive motility, live sperm count and spermatozoa concentration were 2.7+/-0.3 ml, 72.8+/-1.4%, 82.3+/-0.9% and 968+/-233 x 10(6)ml(-1), respectively. Ejaculate volume and sperm concentration were higher (P<0.05) in autumn than in other seasons. To conclude, a highly sensitive EIA for testosterone was developed and validated for yak plasma. Seasonal changes in semen quality were associated with changes in the concentration of testosterone in plasma from yak bulls.