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Analogues of PGF2α have been used in boars with positive results on sexual behaviour, but limited impact on semen quality. The objective of this study was to determine whether the administration of Dinoprost tromethamine or D-Cloprostenol enhances the sexual behaviour and semen quality of sexually inexperienced growing lambs during the onset of the breeding season. The study lasted 10 weeks, beginning during the non-breeding season, with 24 sexually inexperienced Katahdin lambs (5.1 ± 0.5 months old). Three groups of eight lambs each received: (1) vehicle treatment (group CON); (2) 10 mg of Dinoprost tromethamine (group DIN); or (3) 0.15 mg of Cloprostenol dextrogy (group CLOP). The treatments were all applied im 5 min before the tests of sexual behaviour, or 20 min before the collection of semen. Sexual behaviour was evaluated twice weekly in a pen test with a non-oestrous ewe, and semen was collected once weekly with an artificial vagina. The latency to begin courtship was significantly shorter in both groups that received analogues of PGF2α than in CON lambs. The number of ano-genital sniffs, flehmens and lateral approaches was greater in both treated groups than in CON lambs (p < .05). Lambs from DIN group mounted significantly more than CLOP and CON lambs, which did not differ. However, CLOP lambs showed significantly greater mating efficiency (i.e. ejaculations/total mounts) than CON lambs, which exhibited significantly greater mating efficiency that DIN lambs. Lambs treated with CLOP produced significantly more semen volume with more mass motility than those treated with DIN and CON (without differences between DIN and CON). Overall, we concluded that the administration of cloprostenol or dinoprost before sexual evaluation in young rams enhances their sexual behaviour. Cloprostenol had greater effects than dinoprost. The administration of cloprostenol before semen collection also triggered the ejaculation of a greater volume of semen, with greater mass motility. These results open interesting possibilities to study deeply the use of simple and cost-effective treatments to improve the reproductive results of young growing rams., (© 2022 Wiley-VCH GmbH.)

The objective of this study was to determine the effect of the weaning method on lamb stress, body weight, sexual behavior, and semen quality of Saint Croix male lambs. The present study was carried out during the late spring and summer of 2018 in the northeast of Mexico. Sixty male lambs born as twins or triplets (3.2 ± 0.6 kg birth weight) and weaned at 60 d of age (19.21 ± 1.8 kg weaning weight) were divided into two weaning methods: complete separation from the dams (CS; the lambs were moved to a pen that was at 500 m of distance from the dams) and separation with contact from the dams (SCD); the lambs were physically separated by a steel mesh that prevented the lambs from having the possibility of sucking milk from their mothers, but they maintained permanent visual and auditory contact. Cortisol levels were determined 3 d before and 7 d after weaning. Lambs were evaluated as 3-month-old lambs for sexual behavior and semen quality for 9 weeks. The effects of the weaning method (M), week (W), and the interaction M × W were significant on body weight and cortisol levels (P<0.001). The SCD lambs had higher cortisol levels at 3, 5, and 7 d after weaning than CS lambs (P<0.001). The CS lambs had higher body weight during the first 4 weeks after weaning than SCD lambs (P<0.001). The weaning method had no effect on scrotal circumference, sexual behavior, and semen quality traits, except for progressive sperm motility, being better for the lambs that were completely separated (P<0.05). The results from this study show that complete separation of lambs and ewes at weaning is an effective method to reduce lamb stress and improve lamb growth after weaning, but it did not have long-term effects on sexual behavior and semen quality of Saint Croix male lambs. [ABSTRACT FROM AUTHOR]

Goats are polygynous seasonal mammals that establish dominant-subordinate relationships, especially in bucks. The aims of this study were to: 1) compare the reproductive development of dominant and subordinate young bucks allocated in dyads, and 2) determine if their previous dominant position affect their response to grouping. Twenty-four young bucks were allocated in dyads when they were 4 mo old, and the dominance position (DP) [dominant (DB) or subordinate buck (SB)] was determined with a test of competition for food. Body weight, scrotal circumference, semen quality and sexual behaviour toward an oestrous ewe were weekly determined during 8 weeks beginning when the bucks were 8 mo old. Body weight, scrotal circumference, and seminal parameters were not affected by DP. Dominant bucks tended to begin sexual courtship earlier than SB bucks (P = .09), but displayed less flehmen (P = .0008) and tended to display less ano-genital sniffings (P = .053). However, DB bucks displayed more lateral approaches (P = .019), attempted to mount, mounted, and mated the oestrous doe more times (P < .0001, P = .0002 and P < .0001, respectively) than SB bucks. In the 9th week, all the bucks were grouped, cortisol and testosterone serum concentrations were measured, and agonistic and sexual behaviour between bucks were recorded during the first day. Semen was collected and evaluated 4 and 9 days after grouping. Cortisol concentration increased (P = .037), but testosterone decreased (P < .0001), after grouping the animals, without differences according to their DP. The DB tended to display more lateral approaches toward other bucks than SB bucks (P = .06), but there were no effects of DP in any other behaviour. Sperm concentration and the total number of sperm in the ejaculate decreased after grouping (P = .01 and P = .009 respectively. In conclusion, in the conditions of this study, dominance relationships affected sexual behaviour but not body or testicular size or semen output in young bucks allocated in dyads. Dominant bucks were more effective displaying sexual consummatory behaviours. Grouping all the bucks together displayed a strong stress response that affected testosterone secretion and sperm output which was of similar magnitude in bucks that were dominant or subordinate individuals before. [ABSTRACT FROM AUTHOR]