Hematological Responses of Brahman, Gyr, and Romosinuano Cattle to the Colombian Lowland Tropical Environment

Abstract

To compare the hematological response of Bos indicus cattle (Brahmán – BRA, and Gyr – GYR) to a Colombian native breed, Bos taurus (Romosinuano – ROM), under lowland tropical conditions, 32 uncastrated males were sampled at Embriotecno facilities in Montería, Colombia. Sampling was carried out during the last week of the month during two climatic seasons: drought (DRY–March 2023) and rainy (RAIN–August 2023), and at two time periods: at 6:00 AM and 1:00 PM. Hematocrit (HR), hemoglobin (HB), red blood cells (RBC), white blood cells (WBC), neutrophils (NEU), and lymphocytes (LYM) were quantified. RBC, HB, RBC, and NEU were higher in BRA and GYR (p<0.05). The time of day effect showed higher values ​​(p<0.05) in PM for WBC and NEU. RBC and HB in BRA and GYR breeds increased significantly from DRY to RAIN (P<0.05). RBC and WBC increased from DRY to RAIN in BRA and GYR (P<0.05). LYM increased between climatic seasons in BRA and GYR breeds (P<0.05), indicating greater adaptation to the tropical climate. On the other hand, WBC and NEU were higher for all three breeds during the PM period compared to the AM throughout the experiment, an effect explained by the higher temperatures in PM (p < 0.05). Heat stress induces an inflammatory response leading to nonspecific leukocytosis and neutrophilia as part of the immune response (Sejian et al., 2018). BRA and GYR breeds during DRY presented elevated RBC and WBC (p < 0.05). The results presented here are within the reference ranges (Merck's Veterinary Manual), except for NEU, which was increased for all three breeds, BRA and GYR having the highest values, suggesting that ROM animals can adapt to Colombia's lowland tropical climate similarly to Zebu breeds.