Effect of semen collection frequency on seasonal variation in sexual behaviour, testosterone, testicular size and semen characteristics of tropical hair rams (Ovis aries)

Abstract

The purpose of this study was to examine the effect of day length on seminal characteristics, testicular size, sexual behaviour and testosterone (T4) concentration in pelibuey rams subjected to different semen collection frequencies. eighteen intact males were assigned randomly to one of two semen collection frequencies: in the high rate (HR) treatment, two ejaculations per week were obtained from each ram; one ejaculation every two weeks was collected under the low rate (LR) treatment. All animals were housed individually in contiguous 5 m x 5 m wire mesh pens and evaluated over a 12-month period. At the beginning of the experiment rams were 20 months old and 40-50 kg in weight. All rams ejaculated and produced semen throughout the year. Semen volume, sperm per ejaculation, testicular circumference and testicular volume were significantly (p < 0.05) greater during short days in all rams, regardless of the semen collection frequency, with the exception of sperm concentration, for which no variation was found in hr individuals, and reaction time and T4 levels, for which no variation was found in IR males. Rams subjected to HR collection were more affected by the short-day photoperiod than rams collected twice per week, exhibiting greater reduction (p < 0.05) in time to achieve their first ejaculation and in sperm per ejaculation, as well as greater increases (p < 0.05) in T4 concentration than IR rams (14.65 +/- 1.22 vs 23.53 +/- 5.34 s, (3.37 +/- 0.17) x 10(9) vs (3.52 +/- 0.20) x10(9) sperm and 8.68 +/- 0.44 vs 6.85 +/- 0.74 ng/ml, respectively). It was concluded that: (a) the magnitude of the seasonal effects was not sufficient to prevent the rams being used for breeding throughout the year, and (b) seasonal variation within variables was affected differently between semen collection frequencies.

Libido and serving capacity of mature hair rams under tropical environmental conditions

“…Although differences were found in reaction time in the four breeds, the overall mean of 37.62 ± 4.89 seconds is within the reported range of 20 to 59 seconds in several sheep breeds , Kheradmand and Babaei 2006, Aguirre et al 2007 and is shorter than the average mentioned for mature hair rams (Chi et al 2009), young hair rams (Godfrey et al 1998, Lezama et al 2003, yearling Targhee rams (Price et al 1991) and for local wool breeds (Pimentel et al 2005). In relation to second and third mating, the overall mean of 136.43 ± 9.13 and 180.95 ± 11.46 seconds, respectively, is similar with the results of Chi et al (2009), but is lower than results reported in yearling Katahdin rams (Lezama et al 2003) and for local wool breeds (Pimentel et al 2005).…”

“…Time from the introduction of the ram and his first mating (reaction time) and latency (refractory period) between the first and second and between the second and third mating were recorded. At no time rams were allowed to copulate the exposed ewes, first due to health reasons and secondly because studies such as Aguirre et al (2007) and Cárdenas-Gallegos et al (2012), show that this method of assessment does not affect sexual behaviour of rams. It was considered as mating when rams mounted, penetrated and ejaculated into an artificial vagina.…”

“…In breeds originated in tropical regions, the photoperiod differences between seasons do not affect the ram reproductive performance as it does with breeds with temperate origin, affecting their sexual activity and sperm production (Aguirre et al 2007, Riders et al 2012. Under commercial conditions, rams need to be ready to perform and farmers have to be sure that their reproductive performance is continuous during the year, avoiding changes in their sexual behaviour and performance which could affect the flock performance (Alexander et al 2012).…”

“…All of these breeds apparently are well adapted to the tropical environmental conditions of high ambient temperature, humidity and rainfall, where it has been demonstrated that hair rams express adequate levels of good quality semen and sexual behavior throughout the year (Godfrey et al 1998, Aguirre et al 2007, CardenasGallegos et al 2012. Unfortunately, information about sexual performance of hair rams is scarce due to non-existent or rarely conducted sexual performance tests as a consequence of unknown or inadequate ram management by breeders.…”

Reproductive behaviour of Saint Croix and Suffolk rams at medium latitudes (19º N) during long days while being exposed to Suffolk ewes in seasonal anestrus

“…On the other hand, hair sheep, a breed originated in the tropics, have been reported to be almost or completely aseasonal (Rosa and Bryant 2002, Aguirre et al 2007, Arroyo et al 2007, and no comparisons have been mande with wooled breeds regarding their mating activity.…”