Reproductive seasonality of hair rams under tropical conditions: an alternative for non-seasonal lamb production?

Systematic review of hormonal strategies to improve fertility in rams

“…This reproductive symphony is controlled by the photoperiod (see Figure 3 ). In the cited literature, it is confirmed that rams are less affected than ewes, but maintain their fertility ( Santos et al, 2015 ; Zaher et al, 2020 ; Hedia et al, 2020 ; Kleeman et al, 2021), especially in hair rams (Sánchez-Dávila et al, 2020; de Sá Geraldo et al, 2024 ). However, different hormonal strategies have been evaluated to improve the sexual activity of rams in and out of the breeding season, which are described in the following sections.…”

“…Consequently, woolly sheep breeds are characterised by different photoreactivity, where the effect of seasonality and circadian variations on sexual behaviour and semen quality in rams has been studied from tropical latitudes to both poles of the earth ( Godfrey et al, 1998 ; Mamontova et al, 2021 ). On the other hand, with regard to hair rams, recent studies have been carried out on the influence of seasonality on their reproductive physiology, where it was found that they can show variations, such as in semen quality, but not reach zero values, for example in Pelibuey and BlackBelly rams ( Aguirre et al, 2007 ; Cárdenas-Gallegos et al, 2012 ), Saint Croix rams ( Sánchez-Davila et al, 2020 ) and Santa Inés rams (de Sá Geraldo et al, 2024 ); all studies concluded that the seasonal dimension was not sufficient to prevent rams from being able to cover and gestate ewes at different times of the year. Similarly, in terms of sexual behaviour, large differences can be found between wool and hair breeds, where wool rams can reach no or low sexual activity ( Avdi et al, 2004 ; Mamontova et al, 2021 ) compared to hair rams, which are mainly used at latitudes below 22° and show significant variations in sexual behaviour when there are high ambient temperatures and relative humidity ( Aké-Villanueva et al, 2019 ; Sánchez-Davila et al, 2020 ; de Sá Geraldo et al, 2024 ).…”