Influence of sexual behavior of Dorper rams treated with glutamate and/or testosterone on reproductive performance of anovulatory ewes

• Published in: Theriogenology Vol. 106; pp. 79 - 86
• Main Authors: Calderón-Leyva, Guadalupe, Meza-Herrera, Cesar A., Rodriguez-Martinez, Rafael, Angel-García, Oscar, Rivas-Muñoz, Raymundo, Delgado-Bermejo, Juan V., Véliz-Deras, Francisco G.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15-01-2018
• Subjects: Androgens - administration & dosage; Androgens - pharmacology; Animals; Anovulatory-nulliparous ewes; Dorper rams; Female; Glutamate; Glutamic Acid - administration & dosage; Glutamic Acid - pharmacology; Male; Male effect; Ovulation - physiology; Pregnancy; Reproductive outcomes; Sexual Behavior, Animal - drug effects; Sheep - physiology; Testosterone; Testosterone - administration & dosage; Testosterone - pharmacology; Testosterone; Glutamate; Dorper rams; Male effect; Anovulatory-nulliparous ewes; Reproductive outcomes
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/j.theriogenology.2017.10.016

The aim of this study was to determine if exogenous administration of glutamate and (or) testosterone to male rams during the season of reproductive arrest is able to re-activate male sexual behavior and, later on, to promote through the male effect, both sexual and reproductive competence of anovulatory nulliparous ewes. Therefore, an experiment was performed under long-day photoperiods (spring; photo-reproductive arrest, 26°N). Dorper rams were randomly divided into four homogeneous experimental groups (n = 5 males each) regarding live weight (LW), body condition score (BCS), scrotal circumference (SC) and odor intensity (OI). Then, groups were treated with: i) GG (7 mg kg−1 LW of glutamate, every 4d × 30d, im.), ii) GGT (7 mg kg−1 LW of glutamate every 4d × 30d im + 25 mg of testosterone propionate, every 3d × 15d, im.), iii) GT (25 mg of testosterone propionate every 3d × 15d, im, and iv) GC (1 mL of saline, every 4d × 30d, im.). Thereafter, Dorper rams, (n = 4 per group) were selected and exposed to Dorper anovulatory-nulliparous ewes divided in four groups (n = 14 ewes each), and all the appetitive (ASB) and consummatory (CSB) sexual behaviors and indicators of sexual rest (ISR) were registered during the first 48 h of this male-to-females contact. Thereafter, males continued the male-to-female contact for another 8 d, in order to quantify the ewe's sexual and reproductive response through the male effect. During the sexual behavior tests, the GGT rams showed the highest ASB + CSB frequencies (P < 0.05) followed by the GG-rams with the lowest frequencies showed by the GC and GT groups. While the highest ISR behaviors were shown by the GG and GGT groups (P < 0.05) followed by the GC and GT-rams, no differences occurred regarding LW, BCS, and SC along the experimental breeding, with the largest (P < 0.05) OI shown by the GGT-rams and the lowest value observed in the control rams. Regarding the reproductive response of the nulliparous-anovulatory ewes exposed to treated rams, the glutamate + testosterone treated males induced not only an increased (P < 0.05) ovulatory activity and faster (P < 0.05) estrus response but an augmented (P < 0.05) pregnancy rate of the previously anovulatory ewes. To conclude, whereas the GG and GGT treatments generated encouraging sexual and reproductive outcomes, our results are also thought-provoking from a comparative sexual behavior perspective while may embrace potential applications to other animal industries.
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•The effect of glutamate (G) and (or) testosterone (T) upon re-activation of male sexual behavior was evaluated.•We also evaluated if these treated males would promote the reproductive competence of anestrus-nulliparous ewes.•Both G and G + T rams showed the largest appetitive sexual behavior.•The G + T males induced a faster estrus response, while the G-males promoted the highest pregnancy rate.