Scrotum bipartite in sheep as a parameter indicative of adaptation to semi-arid climates: A thermographic and reproductive study

Abstract

With the objective of assessing the influence of scrotum bipartition on scrotum-testiclar thermoregulation and semen quality in sheep native to a semiarid region, 14 adult crossbred rams were placed into groups, GI (7 with bipartition in the scrotum) and GII (7 without bipartition). Images were taken of the caudal scrotum surface using a Fluke (Ti25^®) thermographic camera, for temperature analysis. Two semen collections were made, at an eight-day interval, by electroejaculation, to analyze macroscopic and microscopic parameters. It was observed that the surface temperatures of the proximal, medial and distal regions of the testicle and the epididymis tail did not present significant statistical difference (p > 0.05) between the groups. The GI showed a great ability to regulate the temperature in the tail region of the epididymis (p = 0.062), location of the bipartition, and the difference in temperature between the body surface and the epididymis tail was 0.54 °C much lower than the G2. Although no significant statistical difference (p > 0.05) was observed, the animals with bipartition presented higher means for body surface temperature, showing greater efficiency in heat dissipation and indicating that these animals used peripheral vasodilation on a larger scale to eliminate excess heat and thus had a lower energy expenditure. The semen parameters studied in both groups were within the desirable values for the species, with no differences between the groups (p > 0.05). Higher scrotum testiclar values were observed (scrotum circumference GI = 30.40 cm ± 0.53 and GII = 28.42 ± 1.13 cm, testicle length, right and left, respectively GI = 8.14 ± 0.90 cm, 8.00 ± 0.00 cm and GII = 7.28 ± 0.04 cm, 7.28 ± 0.48 cm) and bodyweight (GI = 44.57 ± 5.25 Kg and GII = 39.85 ± 1.57 Kg) in rams with scrotum bipartition (p > 0.05). It is concluded that scrotum bipartite in rams was shown to be an evolutionary indicator showing that animals with this characteristic dissipate heat more efficiently, have bigger scrotum-testicle biometrical parameters and heavier body weight. However, as the rams with scrotum bipartite presented division of less than 50% of the scrotum length, this degree did not influence the scrotum surface temperature and semen quality, as has been observed in goats with the same characteristic.

Keywords: Morphology; Reproduction; Ruminants; Semi-arid; Temperature.