The aim of this study was to determine whether the sexual activity of local male Creole goats in subtropical Mexico can be induced during the non-breeding season by a long-day treatment followed by insertion of two melatonin implants. The experiment was carried out in the Laguna region in the State of Coahuila, Mexico (26 degrees N). Fourteen male goats were allocated to two balanced groups (n = 7 each) according to body and testicular weights. Males were kept together in two separate groups and fed lucerne hay for ad libitum intake and 300 g of commercial concentrate and had free access to water and mineral blocks. The control group remained in open sheds under natural photoperiod and ambient temperature conditions. The experimental group was placed in a light-proof building and exposed to 2.5 mo of long days (16 h of light/d) from November 1 to January 15. On January 16, each male received two s.c. melatonin implants and was exposed to natural photoperiodic changes in an open shed. In the control group, testicular weight exhibited seasonal variations; the highest value occurred on May 30 (146 +/- 10 g). Treated males reached maximum testicular weight earlier (March 15; 147 +/- 11 g), and sperm quality from January to March was higher than that observed in the control group (P < 0.05). Treatment caused an increase in LH pulse frequency (2.0 +/- 0.5 vs 0.3 +/- 0.2 pulse/8 h in February, 4.6 +/- 1.1 vs 0.1 +/- 0.1 pulse/8 h in March; experimental vs control group, respectively). In the control group, plasma testosterone remained low until mid-June and increased thereafter to remain elevated until the end of the study. In the experimental group, elevated plasma testosterone was observed from February to April and from July to November. Treating male goats in subtropical latitudes with artificial long days and melatonin can induce an intense sexual activity during the natural nonbreeding season.
The effects of body condition score of does and exposure to sexually active bucks after exposure to long-day artificial photoperiod were examined in mature anovulatory French Alpine goat in Northern Mexico. In June, goats in good (2.3 +/- 0.2, scale 1 to 4; n = 10) or poor (1.6 +/- 0.3; n = 10) body condition were exposed during 15 day to sexually active bucks, which had been exposed to long photoperiod (16:8-h light-dark cycle, starting in December). A third group of goats in good body condition was exposed to bucks kept under the natural photoperiod of this region (26 degrees N). All goats in good body condition exposed to bucks treated with prolonged photoperiod exhibited estrus behavior, whereas only 50% of the does in poor body condition showed estrous behavior during the 15-day buck exposure. None of the does in good body condition showed estrus when exposed to bucks under natural photoperiod. These results revealed that a good body condition is required for maximum estrus response in anestrous Alpine goats and that exposure of bucks to long photoperiod in winter is essential for an adequate stimulus to reestablish estrus cycles in anovulatory Alpine does in Northern Mexico.
In seasonal goats and sheep breeds, onset of puberty is modified by the season of birth. As adult does and bucks from subtropical Mexico display seasonal variation in their reproductive behaviour, this study was carried out to determine the effect of season of birth on puberty. Three groups of each sex born in January, May and October were used. During the seasons, does and bucks were weaned at an age of 30 days and offered ad libitum alfalfa hay and 100 g of commercial concentrate. In the female kids, the onset of ovulatory activity was determined by progesterone plasma concentrations once in a week from 3 months of age until the onset of puberty. In the male kids, the onset of puberty was individually recorded by observing the ability to mount and intromit an induced oestrous female goat aged 3 months and the presence of spermatozoa in the ejaculate obtained in an artificial vagina 1 week after the first mount. In female kids, there was an effect of the season on the date of first ovulation (P < 0.001). In the May group, ovulatory activity commenced at an earlier age (201 ± 3 days) compared with January (264 ± 5 days) and October (344 ± 5 days) groups (P < 0.001). In the January group also, the ovulatory activity commenced earlier than the October group (P < 0.001). In males, an effect of the season of birth on the first mounting was observed (P < 0.001). The male kids that were born in May (111 ± 3) and October (112 ± 5 days) attained puberty earlier than those born in January (131 ± 4 days; P < 0.001). The time of onset of puberty did not differ between groups of May and October. All males showed the presence of spermatozoa in the first ejaculate obtained 1 week after the first mount. The spermatozoa in all ejaculates were immobile. It was concluded that the season of birth modified the onset of puberty in both genders, but these modifications were more pronounced in the female than in the male kid goats.
Reproductive seasonality is observed in some breeds originating from or adapted to subtropical latitudes. In 'photoperiodic flexible breeds', such as Australian cashmere goats, the annual breeding season can be manipulated through nutrition, whereas in 'photoperiodic rigid breeds', such as Creole goats from subtropical Mexico, sexual activity can be controlled by altering the photoperiod. In males from the latter breed, artificial long days, whether or not accompanied by the administration of melatonin, stimulate sexual activity during the non-breeding season. These treated males are able to induce the sexual activity of anoestrous females through the male effect under intensive or extensive conditions. Photoperiodic treatments and the male effect can be easily integrated into different breeding management systems in subtropical latitudes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.