Resumen

RINCON-DELGADO, Romana Melba et al. The male effect stimulus increases reproductive activity of mexican criollo goats irrespective of the photoperiodic regime. Rev. Chapingo ser. cienc. for. ambient [online]. 2011, vol.17, n.spe, pp.147-161. ISSN 2007-4018.  https://doi.org/10.5154/r.rchscfa.2010.08.062.

Influence of a sexually-active male buck was evaluated on the onset of reproductive function (hypothalamic and ovarian activity) and estrous cycles progression in Criollo goats from the northen Mexican desert, exposed to an alternated (decreasing/increasing) artificially controlled photoperiod fluctuating within 13.4 to 10.6 light hours per day until fulfilling 6 photoperiodic cycles of 90 d each cycle: ascending (n=3); and descending (n=3). Mexican-native Criollo goats (n=30) were randomly assigned into 2 treatment groups: 1) goats exposed to a sexually-active male buck (n=15); 2) goats not exposed to a male buck (absence of a male buck; n=15). Each experimental group of goats included ovariectomized goats (OVX, n=5), ovariectomized and estradiol-implanted goats (OVX + E2, n=5), and intact-ovaries goats (Control, n=5). Blood samples were taken from OVX and OVX + E2 goats, every four weeks, during 6 h at 15 min intervals (i.e., 24 samples/day), to determine frequency (FREQ), amplitude (AMP), and concentration (CONC) of luteinizing hormone (LH). For Control goats, blood samples were taken twice every week in order to quantify serum-progesterone levels through radioimmunoanalysis (RIA). Goats implanted with E2 (OVX + E2-goats) showed an increased LH pulse frequency compared to OVX-goats without an E2 implant (2.0 ± 0.5 vs. 0.7 ± 0.1 LH pulses/ 6 h). Presence of a sexually-active male buck increased frequency, amplitude and concentration of LH in OVX goats compared to goats not exposed to males (Frequency: 3.2 ± 0.4 vs. 0.7 ± 0.1 pulses/6 h; Amplitude: 1.6 ± 0.1 vs. 0.8 ± 0.3 ng·mL-1; Concentration: 5.3 ± 0.6 vs. 2.0 ± 0.9 ng·mL-1) (P<0.001). In Control goats (intact ovaries), male exposure increased luteal activity and estrous cycle progression refected as a greater number of days in luteal activity (44 ± 9.05 vs. 32.3 ± 20.6); a reduced number of days in anestrous (4.0 ± 4.8 vs. 51.9 ± 28) and a greater number of luteal phases (15.7 ± 4.4 vs. 11.3 ± 8.7) without compromising serum progesterone levels (6.8 ± 0.8 vs. 7.3 ± 0.5) (P>0.05). In conclusion, presence of a sexually-active male buck induced a greater ovarian activity in Criollo goats, shortening seasonal anestrous even during an ascendent controlled-photoperiod. Such strategy, using a sexually-active male buck might be helpful to increase ovarian activity and reproductive function during the seasonal anestrous of Criollo goats from dry and arid areas of northern Mexico and similar regions of the world.

Palabras llave : Goats; photoperiod; progesterone; ovarian activity; male effect.

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