Behavioral and physiological responses to short-term cold exposure in calves carrying the SLICK1 allele.

The SLICK1 genetic variant, originally identified in Senepol cattle, enhances heat tolerance in association with a short hair coat. The improved heat tolerance is linked to an increased ability to lose heat, which may lead to increased cold susceptibility in colder, winter environments. Our objective was to measure the thermoregulatory responses of Friesian-Jersey crossbred SLICK1 carriers and control calves during short-term, controlled, cold challenges over 2 yr. These were allocated into groups of 4 (2 slicks and 2 controls), penned individually, and subjected to acute cold temperatures (-4.5°C) for 6 h with a dry coat and repeated with a wet coat at 1 wk of age (n = 12 slicks vs. 12 controls) and at 5 wk (n = 12 slicks vs. 12 controls). Behavioral observations (lying, shivering, and piloerection), rectal temperature and skin (eye, nose, rump, leg) surface temperature were measured pre- (baseline) and post- (recovery) experiment and at hourly intervals during the cold challenge. Temperature data were analyzed using a repeated measures mixed model. The skin surface temperatures (eye, nose, rump, and leg) remained similar between the genotypes and relatively stable (after an initial fall) throughout the 6 h cold challenges in wk 1, with no differences observed between treatments (dry or wet coats). The temperature of the eye surface showed the smallest change (∼-1 to 2°C) at both 1 and 5 wk. A reduction in rectal temperature of <0.25°C was recorded over the first 2 h of the cold challenge at 1 and 5 wk with no difference attributable to genotype or dry/wet treatment. All calves returned to baseline temperatures within 1 h following removal from the cold environment and feeding warm milk. Slick calves were more often seen shivering during the cold challenge relative to control calves at both 1 and 5 wk of age. The frequency with which shivering was seen was lower in control calves at 5 wk of age but remained high in slick animals. All calves showed an increased frequency of lying at 1 wk of age relative to 5 wk. No difference was observed between genotypes in the frequency of piloerection. Hair length measured at the neck, shoulder, and pin bone during the first 2 wk of life was shorter overall in slick calves compared with controls (20.0 ± 4.3 vs. 26.4 ± 6.4 mm; mean ± SEM). Results indicate that slick calves can effectively regulate their body temperature during short-term cold exposure in a controlled environment; however, they show a greater inclination to shiver, relative to control calves.