Evaluation of physiological and blood serum differences in heat-tolerant (Romosinuano) and heat-susceptible (Angus) Bos taurus cattle during controlled heat challenge

• Published in: Journal of animal science Vol. 88; no. 7; pp. 2321 - 2336
• Main Authors: SCHARF, B, CARROLL, J. A, RILEY, D. G, CHASE, C. C, COLEMAN, S. W, KEISLER, D. H, WEABER, R. L, SPIERS, D. E
• Format: Journal Article
• Language: English
• Published: Champaign, IL American Society of Animal Science 01.07.2010
• Subjects: Animal productions; Animals; Biological and medical sciences; Body Temperature - physiology; Body Temperature Regulation - physiology; Cattle - blood; Cattle - physiology; Cholesterol - blood; Creatinine - blood; Fundamental and applied biological sciences. Psychology; Hot Temperature; Leptin - blood; Male; Prolactin - blood; Respiratory Rate - physiology; Species Specificity; Stress, Physiological - physiology; Sweating - physiology; Terrestrial animal productions; Vertebrates; heat tolerance; Evaluation; Farming animal; physiological marker; Tolerance; cattle; Bos taurus; Marker; Blood; Vertebrata; Heat; Mammalia; Serum; Livestock; Artiodactyla; Ungulata
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2009-2551

A study was performed to evaluate differences in thermoregulatory ability of 2 Bos taurus breeds with known differences in heat tolerance. Nine Angus (AG; 304 +/- 7 kg of BW) and 9 Romosinuano (RO; 285 +/- 7.5 kg of BW) steers were transported to the Brody Environmental Center at the University of Missouri. Steers were housed for 18 d at thermoneutrality (TN; 21 degrees C) before initiation of heat stress (HS), which consisted of daily cyclic air temperature (26 degrees C, night; 36 degrees C, day) for 14 d. Rectal temperature and respiration rate were measured 6 times daily throughout the study. Sweat rates at shaved skin sites were recorded on specific days. Blood samples were taken once per week. Angus steers maintained rectal temperature 0.5 degrees C greater than RO at TN (P < 0.001). Likewise, respiration and sweat rates were greater (P < 0.001) in AG than RO at TN (P < 0.05). Rectal temperature increased during HS for both breeds with AG maintaining greater temperatures (P < 0.001). Both breeds increased respiration rate during HS, with AG steers exhibiting the greater rate (P < 0.001). Sweat rate increased more than 4-fold during HS (P < 0.001), followed by reduction after 7 d. Even after HS acclimation, AG exhibited the greater sweat rate (P < 0.001). Breed differences for serum leptin, creatinine, and cholesterol were found throughout the study with AG being greater than RO. Although there were no breed differences (P = 0.21) at TN, only AG steers exhibited a HS-induced increase (P < 0.05) in prolactin, creatinine, and cholesterol concentrations to suggest that an increase in rectal temperature is required for this effect. Use of rectal temperature along with endocrine markers, such as prolactin, may aid in the identification of B. taurus sensitivity to heat.