The impact of temperature-humidity index on blood morphology and β-hydroxybutyrate in different sheep breeds

Abstract

Climatic variations directly affect the animals, changing their physiology. Several factors such as species, breed, sex, age, nutrition, diseases, physiological stage, and seasonal variations can affect the pattern of haematological values. Quantitative and morphological changes in blood cells are associated with higher temperatures and humidity. Sixty-seven sheep (3 years old, not pregnant, clinically healthy) were used in the study to determine the effect of the temperature-humidity index (THI) and breed on morphological blood indices and β-hydroxybutyrate (BHB). The sheep were divided into groups by the breed (4 breeds) and the THI (2 classes). The blood samples from each animal were collected monthly. Significant differences between the values of leukocytes (WBC), neutrophils (NEU), erythrocytes (RBC), haemoglobin (HGB), haematocrit (HCT), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), lymphocytes (LYM), monocytes (MON) and platelet count (PLT) in THI groups were observed. In THI 1, the mean values of MCHC (5.68%, P < 0.05), MCH (0.52%), and HCT (4.90%, P < 0.05) were higher compared to those in THI 2. Multivariate test showed a significant effect of breed on NEU (P < 0.05), RBC (P < 0.05), HGB (P < 0.05) and MCHC (P < 0.05). The concentration of BHB in group THI 2 was by 12.9% higher (P < 0.05), compared to group THI 1. A significant effect of the breed (P < 0.05) and THI class (P < 0.05) on BHB was determined, whereas the impact of breed interaction with the THI was found to be non-significant. The observations reported in this study suggest that the response to temperature is dependent on animal breed. It was found that both morphological blood indices and BHB were affected by the temperature-humidity index.