Duration of estrus and preovulatory surge of LH in Boer x Nubian goats synchronized with various hormones in tropical latitude of Mexico
The objective was to determine the duration of estrus, preovulatory surge of luteinizing hormone (LH), fertility and prolificacy of Boer x Nubian goats in tropical Mexico (19º29’LN) synchronized with fluorogestone acetate (FGA) and prostaglandin F2 (PGF2) combined with gonadotrophin-releasing hormone (GnRH) or equine chorionic gonadotrophin (eCG). The treatments were: T1 (FGA, n = 5), T2 (FGA + GnRH, n = 7), T3 (FGA + eCG, n = 8), T4 (PGF2 + GnRH, n = 5) and T5 (PGF2 + eCG, n = 7). The responses measured were percentage of animals showing estrus, duration of estrus (h), fertility (%), prolificacy (kids/parturition); intervals (h) from end of treatment til estrus and til peak preovulatory LH concentration, from onset of estrus til peak LH; duration of peak LH (h), and LH concentration (ng/mL). Duration of estrus was longest in goats of T3 (35.2 ± 1.4). Onset of estrus differed (P<0.05) between T2 and T3 (27.9 ± 1.2 vs. 17.2 ± 1.2). Use of PGF2 (T4 and T5) delayed onset of estrus compared with T2 and T3. Interval between sponge withdrawal and onset of LH peak was shorter in T3 than T2 (P<0.05), while that from onset of estrus to LH peak was shorter (P<0.05) with eCG, injection than with GnRH. There were no differences in length and breadth neither of the preovulatory LH surge nor in fertility or litter size (P>0.05). The use of GnRH, either with PGF2 or FGA, increased the time from onset of estrus to LH peak, whereas the use of eCG shortened it.