Impact of Brahman genetics on skin histology characteristics with implications for heat tolerance in cattle

Abstract

Cattle lose heat predominantly through cutaneous evaporation at the skin-hair coat interface when experiencing heat stress. Sweating ability, sweat gland properties, and hair coat properties are a few of the many variables determining the efficacy of evaporative cooling. Sweating is a significant heat dissipation mechanism responsible for 85% of body heat loss when temperatures rise above 86⁰F. The purpose of this study was to characterize skin morphological parameters in Angus, Brahman, and their crossbred cattle. Skin samples were taken during the summer of 2017 and 2018 from a total of 319 heifers from six breed groups ranging from 100% Angus to 100% Brahman. Epidermis thickness decreased as the percentage of Brahman genetics increased where the 100% Angus group had a significantly thicker epidermis compared to the 100% Brahman animals. A more extended epidermis layer was identified in Brahman animals due to more pronounced undulations in this skin layer. Breed groups with 75% and 100% Brahman genes were similar and had the largest sweat gland area, indicative of superior resilience to heat stress, compared to breed groups with 50% or lower Brahman genetics. There was a significant linear breed group effect on sweat gland area indicating an increase of 862.0 µm2 for every 25% increase in Brahman genetics. Sweat gland length increased as the Brahman percentage increased, while the sweat gland depth showed an opposite trend, decreasing from 100% Angus to 100% Brahman. The number of sebaceous glands was highest in 100% Brahman animals which had about 1.77 more sebaceous glands (p < 0.05) per 4.6 mm2area. Conversely, the sebaceous gland area was greatest in the 100% Angus group. This study identified significant differences in skin properties related to heat exchange ability between Brahman and Angus cattle. Equally important, these differences are also accompanied by significant levels of variation within each breed, which is indicative that selection for these skin traits would improve the heat exchange ability in beef cattle. Further, selecting beef cattle for these skin traits would lead to increased resilience to heat stress without disrupting production traits.

Exploring the genetic control of sweat gland characteristics in beef cattle for enhanced heat tolerance

“…The level of biological variation identified in this study within a relatively uniform groups of cattle suggests a range of genetic potential that, if strategically targeted through selection and management, could lead to significant improvements on these traits for heat stress management. This biological diversity is similar to that found in a population ranging from 100% Angus to 100% Brahman, where a coefficient of variation of 49.77% was found for sweat gland area across five breed groups [ 8 ].…”

“…As air temperatures reach 30 °C, evaporative cooling by sweating is the primary mechanism for heat dissipation in cattle, however, some breeds have a greater potential for heat loss than others [ 4 ]. Recent research identified significant differences in skin properties related to heat exchange ability between Brahman and Angus cattle [ 8 ]. Studies on the possible genetic control of natural variations in sweat gland properties in beef cattle are not currently available.…”

Pre and Post-Weaning Growth and Survivability of Three Genotypes of Cattle at TALIRI Tanga, Tanzania

“…This might be due to physiological and morphological modifications that crossbred animals experience in comparison to their exotic parents, which help them adapt to hot, humid environments that are typically characterized by high temperatures and humidity. Such changes include changes in body size, hair coat, hide texture, and hematological characteristics, which allow them to have unique features that allow them to regulate their body temperature more effectively, resulting in less heat stress than pure Bos taurus [50]. In contrast to Boran cattle, exotic breeds lack natural resistance to tropical diseases like Anaplasmosis, Theileriosis, Cowdriosis, and other parasites and diseases transmitted by ticks.…”

Thermographic Profiles in Livestock Systems under Full Sun and Shaded Pastures during an Extreme Climate Event in the Eastern Amazon, Brazil: El Niño of 2023

“…Research shows that high or very low temperatures tend to hinder thermoregulation, leading to various physiological reflexes, such as increased heart and respiratory rates, sialorrhea and metabolic or reproductive problems, such as an increase in cortisol, glucose and a reduction in the animals’ digestion process, as well as a reduction in the quality of female oocytes and spermatogenesis, causing losses. In this sense, cattle regulate the excess solar radiation that comes into direct contact with their bodies by seeking shade, shelter or water to mitigate heat stress [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ].…”