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

Authors: MATEESCU, RALUCA - UNIVERSITY OF FLORIDA; Sarlo Davila, Kaitlyn; HERNANDEZ, AAKILAH - UNIVERSITY OF FLORIDA; NUNEZ ANDRADE, ANDREA - UNIVERSITY OF FLORIDA; ZAYAS, GABRIEL - UNIVERSITY OF FLORIDA; RODRIGUEZ, EDUARDO - UNIVERSITY OF FLORIDA; DIKMEN, SERDAL - ULUDAG UNIVERSITY; RAFIQ, FAHAD - UNIVERSITY OF FLORIDA; OLTENACU, PASCAL - UNIVERSITY OF FLORIDA

Submitted to: Frontiers in Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2023
Publication Date: 5/9/2023
Citation: Mateescu, R.G., Sarlo Davila, K.M., Hernandez, A.S., Nunez Andrade, A., Zayas, G., Rodriguez, E., Dikmen, S., Rafiq, F., Oltenacu, P. 2023. Impact of Brahman genetics on skin histology characteristics with implications for heat tolerance in cattle. Frontiers in Genetics. 14. Article 1107468. https://doi.org/10.3389/fgene.2023.1107468.
DOI: https://doi.org/10.3389/fgene.2023.1107468

Interpretive Summary: This study identified significant differences in skin properties related to heat exchange ability between Brahman and Angus cattle. 85% of cattle’s heat exchange ability occurs through sweating. This study looked at microscopic skin differences between Angus and Brahman cattle and their crossbreds that impact sweating and heat exchange. Epidermis thickness decreased as the percentage of Brahman genetics increased and Angus cattle had a significantly thicker epidermis compared to Brahman cattle. Sweat gland length increased as the Brahman percentage increased, while the sweat gland depth showed an opposite trend, decreasing from the and Brahman percentage increased. Brahman animals had more sebaceous glands than Angus animals. This study identified significant differences in skin properties related to heat exchange ability between Brahman and Angus cattle.

Technical 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 only a few of the many variables that determine the efficacy of evaporative cooling. Sweating is a significant heat dissipation mechanism, being responsible for 85% of body heat loss when temperatures rise above 86°F. The purpose of this study was to characterize significant morphological parameters in Angus, Brahman, and their crossbred cattle, including skin layer thickness, depth and area of sweat glands, and number and area of sebaceous glands. Skin samples were taken during summer of 2017 and 2018 from a total of 319 two-year old heifers from six breed groups ranging from 100% Angus to 100% Brahman. Breed group had a statistically significant effect on all skin properties in this study except dermis thickness. Epidermis thickness decreased as the percentage of Brahman genetics increased where the 100% Angus group had a significantly thicker epidermis (P<0.05) compared to the 100% Brahman animals. A longer epidermis layer was identified in Brahman animals as a result of 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. The breed group with 50% Brahman genes was intermediate between Brahman and Angus group and the 25% and 0% Brahman groups had the smaller sweat gland area. There was a significant linear breed group effect on sweat gland area indicating an increase of 86.20 mm2 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 the 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). 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 encouraging and indicative that selection for these skin traits would result in improvement of heat exchange ability in beef cattle. Further, selecting beef cattle for these skin traits would lead to increased resilience to heat stress without disruption of production traits.