The objective of this study was to evaluate the efficacy of treating sexually inactive bucks with artificial long photoperiod or testosterone on the induction of estrus in anovulatory grazing goats. A total of 91 multiparous mixed-breed anestrous goats were randomly assigned to one of three treatment groups: (1) joining with bucks subjected to 2.5 month of artificial long days (16 h of light/day; n=31), (2) joining with testosterone-treated bucks (n=30), and (3) joining with untreated bucks (control; n=30). There were no differences between the light-treated (100%) and testosterone-treated (93%) bucks in their ability to induce estrus in anovulatory does. On the other hand, none of the goats in contact with control bucks exhibited estrus. The interval from start of mating to estrus was shorter in goats with the light-treated bucks (37.9 ± 4.8 h) compared with does in contact with testosterone-treated bucks (58.3 ± 8.7 h). The overall pregnancy rate in goats joined with light-treated, testosterone-treated and control bucks was 84%, 77% and 0%, respectively, with no difference (P>0.05) between the first two groups. Anogenital sniffing, approaches, mounting attempts, and mounts were highest (P<0.01) in light-treated bucks and lowest in control bucks. It was concluded that testosterone-treated bucks and long-day-treated bucks were equally effective in synchronizing estrus in anovulatory goats and resulted in similar levels of fertility. Given that light-treated bucks are unviable in communal production systems of goats raised by resource-poor farmers, the sexual arousal of bucks with testosterone is a practical and reliable method to induce ovulation in anovulatory goats in pastoral goat systems in hot environments.

No abstract

The aim of this study was to evaluate the possible difference in seminal characteristics of Dorper rams of either high, medium or low social ranks in northern Mexico (26º N). The male’s social status was quantified through a competitive behavioral test in a herd of 36 adult males, the aggressive interactions and their consequences were registered to calculate the success index (SI), where low hierarchy (LH) rams had a SI of 0 to 0.33, medium hierarchy (MH) rams had a SI of 0.34 to 0.66 and high hierarchy (HH) had a SI of 0.67 to 1. Afterwards, the rams were subjected to an estrogenized female (2 mg of estradiol cypionate) for teasing in order to collect a semen sample with an artificial vagina. The semen was evaluated for volume, motility and concentration. The seminal characteristics differences were analyzed using a one-way ANOVA tests and stablishing a p-value of 0.10 as significance level in the SPSS statistical package. Results are shown in table 1. In conclusion, low hierarchy Dorper rams show a statistical tendency to have a lower sperm concentration.

El objetivo de este estudio fue evaluar la respuesta reproductiva de machos cabríos con diferente condición corporal tratados con testosterona al final del periodo de baja actividad sexual en el norte de México (26° N). Se utilizaron 12 machos, divididos en dos grupos (n = 6 c/u), CCA: Condición Corporal Alta (2.2 ± 0.1) y CCB: Condición Corporal Baja; (1.6 ± 0.1), misma que se mantuvo durante nueve semanas (29 de febrero al 31 de abril). Ambos grupos recibieron 25 mg de testosterona, vía intramuscular cada 3er día durante 21 días. Semanalmente se registraron, condición corporal (rango 1-4), intensidad del olor sexual (rango 0-3), circunferencia escrotal, glucosa sanguínea y calidad seminal. Además, se cuantificaron comportamientos sexuales apetitivos y de consumación. El grupo CCA fue superior (P < 0.05) en calidad de semen, circunferencia escrotal y glucosa sanguínea. Asimismo, el grupo CCA mostró superioridad (P < 0.001) en el porcentaje global de comportamientos sexuales apetitivos (57.6 vs. 42.3 %) y de consumación (72.2 vs. 27.7 %) sobre el grupo CCB. Se concluye que un incremento en la condición corporal en machos tratados con testosterona mejora la circunferencia escrotal, olor sexual, glucosa sanguínea, calidad seminal y los comportamientos sexuales apetitivos y de consumación.