Seasonality in Saint Croix male lamb reproductive development in northern Mexico

Abstract

ContentsThe aim of this study was to determine the influence of the season of birth on the body weight, testicular size, testosterone concentrations, semen output and sexual behaviour in Saint Croix male lambs. Thirty-three lambs were born in spring (n = 10), summer (Sum; n = 12) or autumn (n = 11). Body weight and the scrotal circumference were weekly recorded; semen was also weekly collected by electroejaculation; and sexual behaviour towards oestrous ewes was weekly evaluated. Data were recorded from 15 to 33 weeks of age. The reproductive development of Saint Croix male lambs differed according to the period in which they were born. More lambs born in spring than in summer and autumn achieved puberty during this study and were also more precocious in semen production and displayed sexual behaviour earlier. Lambs born in summer delayed their semen production; however, season-related negative effects were less pronounced at the end of the study than in autumn born lambs born.In conclusion, despite the apparently low seasonality of the breed, Saint Croix male lambs showed in this study a seasonal pattern in their reproductive development at least until they achieve the puberty. K E Y W O R D Spuberty, semen, sexual behaviour, sheep, testosterone | 399 SÁNCHEZ-DÁVILA Et AL.

Sexual performance and semen quality of pubertal lambs treated with different weaning methods

“…It is also important to note that the second stage of this study was carried out at the start of the natural breeding season (June-August) when lambs may express higher sexual activity. The study carried out by Sánchez et al (2019) showed that the reproductive performance of Saint Croix male lambs born in spring was better than that of lambs born in summer and autumn. The results reported by Santos et al (2015) and Sanchez et al (2019) suggest that there is a significant effect of an interaction between birth season and weaning method on the sexual behavior and semen quality of male lambs, and this should be a matter of future research.…”

“…This difference may be explained by an early intake of fibrous components in the diet that favored the development of the rumen (Urbano et al, 2017), which in turn could increase the assimilation of nutrients that favored the development of this characteristic in the ejaculate (Blache and Martin, 2009). Another possible explanation for not finding significant effects of the weaning method on sexual behavior and semen quality is that regardless of the weaning method, male lambs are less stressed than females (Freitas-de-Melo and Ungerfled, 2020), in such a way that other possible factors are involved in this reproductive process (Sánchez-Dávila et al, 2019). For example, Saint Croix lambs are reported to be sexually precocious (Wheaton and Godfrey, 2003) and adapted to different environments; therefore, it is considered that although the SCD lambs were more stressed, and developed more slowly, this was not an impediment for them to develop sexually in a similar way to the CS lambs.…”

“…Stress caused at weaning can negatively impact the overall health and production of the lamb as shown in decreased growth rates and food intake (Schichowski et al, 2008;Pascual-Alonso et al, 2015;Barnard et al, 2016), changes in physiologic, endocrine and immune responses, and increased susceptibility to disease and infection (Orgeur et al, 1999;Backes et al, 2015;Destrez et al, 2017) manifested in the post-weaning period. Effect of stress at weaning on future reproductive performance of ram lambs has not been reported, but other factors such as maternal stress during late pregnancy (Henrique et al, 2020) and birth season (Sánchez-Dávila et al, 2019) have been reported to influence post-weaning sperm quality and sexual development of ram lambs.…”