Social rank during pre-pubertal development and reproductive performance of adult rams.

In sheep, access to receptive females is affected by dominance relationships. The aim of the first experiment was to determine how the presence of high- or low-ranking rams affects sexual behavior of medium-ranked rams toward non-estrual ewes in pen tests. A complementary objective was to determine whether the presence of 1 or 2 rams has stronger effects. Social rank of 13 rams was determined using the food competition test. The number of courtship behaviors, mounts, and ejaculations was recorded in pen tests with non-estrual restrained ewes. In the first experiment, medium-ranked rams were subjected to 5 tests with: (1) the ewe alone, (2) the ewe and 1 restrained tied high-ranked ram, (3) the ewe and 2 restrained tied high-ranked rams, (4) the ewe and 1 restrained tied low-ranked ram, and (5) the ewe and 2 restrained tied low-ranked rams. The number of high- or low-ranked rams (1 or 2) present in the tests did not affect the results. There were no differences on courtship behaviors, but the number of mounts and mounts with ejaculation was greater when low-ranked rams were present. In a second experiment, it was determined whether the presence of medium- or low-ranked rams stimulates sexual behavior of high-ranked rams. The high-ranked rams were tested with: (1) the ewe alone, (2) the ewe and 1 restrained tied medium-ranked ram, and (3) the ewe and 1 restrained tied low-ranked ram. No differences were recorded in relation to presence of other rams during the tests. It was concluded that the presence of low-ranked rams stimulates sexual behavior of medium-ranked rams toward non-estrual ewes in pen tests. This effect was not related with the number of rams included in the test. The presence of medium- or low-ranked rams did not alter the sexual behavior of high-ranked rams toward non-estrual ewes.

Sexual behavior of medium-ranked rams toward non-estrual ewes is stimulated by the presence of low-ranked rams

This study analyzed seasonal variations in the testes, the concentration of sex hormones, the parameters of fresh and thawed semen, and the sexual behavior of male Alpine goats from a temperate region in a tropical climate and possible interference with fertility. The maximum and minimum temperature and luminosity were recorded daily, while seminal, hormonal, and behavioral assessments were carried out every fortnight. The maximum and minimum temperature (°C) and luminosity (h) were recorded daily always at 17.00 h. The [...]

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Seasonal variation in the reproductive activity of male goats raised under tropical climate conditions

Changes in melatonin concentrations in seminal plasma are not correlated with testosterone or antioxidant enzyme activity when rams are located in areas with an equatorial photoperiod.

SUMMARY The objectives of the present study were to evaluate the libido and serving capacity of Pelibuey (PB), Blackbelly (BB), Dorper (DR) and Katahdin (KA) hair sheep rams in three seasons under tropical environmental conditions. Twenty-eight mature rams were individually exposed for 10 minutes to an immobilized, oestrous-induced ewe twice per season. The total number of sexual behaviours, reaction time to first mating and latencies between mating were recorded. Reaction time and latencies were affected by breed effect (P  0.05). All rams attained at least one ejaculation during testing. The overall mean (± S.E.M.) of reaction time and latencies to second and third mating were 37.62 ± 4.97s, 136.43 ± 9.75 and 180.95 ± 11.87 seconds, respectively. PB, BB and KA rams were faster than DR in reaction time and latency to second mating (P < 0.05). For latency to third mating, PB and KA rams were faster than BB and DR (P < 0.05). The libido activities that rams performed most frequently were anogenital sniffing and foreleg kicks. It was concluded that under tropical environmental conditions PB, KA and BB rams showed better serving capacity than DR, with shorter reaction time and latency to second mating. Hair rams exhibited more frequencies of anogenital sniffing and foreleg kicks.

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Libido and serving capacity of mature hair rams under tropical environmental conditions Libido y capacidad de servicio de carneros machos adultos de pelo bajo condiciones ambientales tropicales

The purpose of this study was to examine the effect of day length on seminal characteristics, testicular size, sexual behavior and testosterone concentration (T4) in dominant and subordinate Pelibuey rams. Six groups of three animals were evaluated every 2 weeks over a 12 month period. Dominant (D), medium (M) and subordinate (S) animals in each group were identified through a food competition test every 15 days. All rams ejaculated and produced semen throughout the year. A linear hierarchy was clearly established and maintained during the year. S rams had lower levels (P   0.05) by their social position. D rams were more affected by the photoperiod, decreasing (P < 0.05) reaction times, increasing (P < 0.05) T4 and producing more (P < 0.05) sperm per ejaculation than S rams during short days (14.65 ± 1.22 vs 26.92 ± 1.65 s; 8.68 ± 0.44 vs 7.37 ± 0.40 ng/mL and 3.37 ± 0.17 vs 2.04 ± 0.16 sperm/109, respectively). Semen volume and sperm concentration were significantly (P < 0.05) greater during short days in all rams, regardless of their social status, with the exception of sperm concentration in D rams where no variation was found. M rams displayed variable values in the range between the D and S rams. It was concluded that the magnitude of the seasonal effects was not sufficient to prevent the rams being used for breeding throughout the year and that seasonal variation within the variables affected the social ranks differently.

Seasonal variations in sexual behavior, testosterone, testicular size and semen characteristics, as affected by social dominance, of tropical hair rams (Ovis aries)

Virginio Aguirre

Papers

Seasonal variations in sexual behavior, testosterone, testicular size and semen characteristics, as affected by social dominance, of tropical hair rams (Ovis aries)