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Continuous exposure to sexually active rams extends estrous activity in ewes in spring.
J A Abecia1, P Chemineau2, J A Flores3
1Departamento de Producción Animal y Ciencia de los Alimentos, IUCA, Universidad de Zaragoza, Zaragoza, Spain.
Theriogenology
|September 3, 2015
Summary
Stimulating rams with artificial light and melatonin extended ewes' breeding season, reducing seasonal anestrus. This research highlights new methods for managing sheep reproduction and increasing estrous expression in small ruminants.
Area of Science:
- Reproductive biology
- Animal science
- Endocrinology
Background:
- Sexual activity in sheep is primarily controlled by photoperiod, influencing seasonal reproduction.
- Environmental factors like conspecific presence can modulate the breeding season's timing.
- Previous studies in goats suggest photoperiod's role in seasonal anestrus may need reevaluation in small ruminants.
Purpose of the Study:
- To determine if sexually active rams, stimulated by artificial photoperiod and melatonin, can reduce seasonal anestrus in sheep.
- To assess the potential for prolonging ovulatory activity in ewes during spring through ram stimulation.
Main Methods:
- Ewes were housed with either treated rams (artificial long days + melatonin implants) or control rams (natural light).
- Rams were vasectomized and treated to induce sexual activity out of season.
- Estrus was monitored daily, and plasma progesterone levels were analyzed weekly to track ovulatory activity.
Main Results:
- Ewes exposed to treated rams showed a higher proportion of monthly estrus compared to control groups (P < 0.05).
- Ewes with treated rams had a significantly shorter anestrous season (26 days) than those with control rams (89 days; P < 0.0001).
- Continuous ovulatory activity was observed in 13 of 15 ewes with treated rams, versus none with control rams.
Conclusions:
- Continuous exposure to sexually activated rams, induced by artificial photoperiod and melatonin, extends ovarian activity in ewes during spring.
- This method effectively increases estrous expression and reduces the duration of seasonal anestrus in sheep.
- Findings suggest a potential for enhanced reproductive management in small ruminants by manipulating ram stimulation.
