Effect of short-term radiation stress on physiological and hematological parameters in Pelibuey sheep in Cuba

Abstract

Projections of warming temperatures as a consequence of climate change will have impacts on food production globally. This heat stress coupled with increased solar radiation, will affect the well-being of livestock. In many regions of the world, local breeds are reared as they demonstrate improved tolerance to local conditions resulting in minimal effects on production when compared with commercial breeds. However, it is still critical to assess the consequences of increased heat and radiation stress on local breeds to ensure that on-farm productivity is not adversely affected. This short communication describes the effects of radiation intensity during daylight on Pelibuey sheep (intact male calves). Three treatments were tested: control (no shade; ≈ 50 lux at 14:00 h), one layer of shade mesh (≈ 35 lux at 14:00 h), and two layers of shade mesh (≈ 15 lux at 14:00 h). Increasing radiation resulted in a decline in sheep body weight from 18 kg to 16 kg. Only animals exposed to 15 lux were capable of gaining in body weight. Exposure to elevated radiation increased the respiratory rate of animals from 130 respirations per min at the lowest exposure level to a maximum of 170 respirations per min in animals kept at 50 lux. The rectal temperature of animals remained consistent (approximately 40 °C) irrespective of the level of radiation. In contrast, the temperature measured at the head, back and thigh were all similarly affected by radiation. In terms of the hematological parameters measured, radiation stress did not affect the concentrations of hemoglobin or hematocrit. There was a non-significant decrease in the concentration of lymphocytes from 58% to 52%. However, neutrophils showed an increasing trend from 42% in animals at the lowest radiation level to a maximum of 51% in animals exposed to the highest stress level. The concentrations of leukocytes were similar in animals kept at 15 and 35 lux and were significantly elevated in those at 50 lux. Serum proteins and CAT concentrations were not affected by the different levels of radiation tested. However, SOD specific activity significantly declined from 11 to 8 U mg−1 protein in animals exposed to 15 and 50 lux respectively. To the best of our knowledge, this is the first report on the response of Pelibuey sheep to short-term radiation stress under Cuban conditions.