Exogenous application of GnRH after fixed-time artificial insemination (FTAI) and its effect on serum progesterone levels and pregnancy rate in primiparous dairy cows at high altitude environments
2016
Gutiérrez-Reinoso MA | Collaguazo-Gómez VM | García-Herreros M.
The aim of the present study was to determine the effect of the exogenous application of gonadotropin-releasing hormone (GnRH) on day 4, 8 and 12 after fixed-time artificial insemination (post-FTAI) in order to evaluate its influence on serum progesterone (P4) levels and pregnancy rate in primiparous dairy cows maintained at high altitude environments. Four experimental groups (Control-T1, T2, T3 and T4) of Holstein Friesian primiparous dairy cows were used. A single dose of GnRH (day-4 (T2), day-8 (T3) and day-12 (T4)) was applied post-FTAI. Before and after each treatment, blood samples were collected from the different experimental groups to determine P4 serum levels. Statistically significant differences were observed in serum P4 levels when T1 / T2 were compared to T3 and T4, noting also statistically significant differences between these two treatments (p<0,05). Moreover, statistically significant differences were observed in pregnancy rates when T1 / T2 / T4 were compared to T3 treatment (20% higher) (p<0,05). In conclusion, the exogenous application of GnRH post-FTAI had a significant influence on serum P4 levels (T3) in primiparous dairy cows at high altitude environments. In addition, the pregnancy rate was significantly higher when exogenous GnRH was applied on day-8 (T3) postFTAI, being possible to optimise FTAI protocols combined with hormonal treatments post-FTAI, and improving fertility in primiparous dairy cows at high altitude environments.
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