Location: Livestock Issues Research
Title: Heat-tolerant versus heat-sensitive Bos taurus cattle: Influence of air temperature and breed on the metabolic response to a provocative immune challenge Authors
Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 24, 2013
Publication Date: N/A
Interpretive Summary: This research represents a collaborative effort of scientists from the Livestock Issues Research Unit, the SubTropical Agricultural Research Station, and the University of Missouri to determine the influence of breed on the metabolic response of cattle housed at two different air temperatures (thermal neutral and heat stress). Breed is understood to affect many aspects of production, including reproduction, growth, and immune function. Additionally, certain breeds of cattle are known to possess different traits, such as heat-tolerance. Specifically, the Romosinuano breed is known for its longevity, docile temperament, and adaptation to tropical stressors. As both heat stress and immune challenges can increase the energy requirements of an animal, we utilized two diverse Bos taurus breeds, Romosinuano (heat-tolerant), and Angus (heat-sensitive) to determine if their metabolic response differed when housed at different air temperatures. Results from this study suggest that Romosinuano heifers have greater energy supplies, or are more capable of mobilizing these energy stores, in response to an immune challenge under heat stress conditions. Specifically, Romosinuano heifers had greater concentrations of glucose, insulin, and non-esterified fatty acids prior to and following an immune challenge. Additionally, concentrations of glucose and non-esterified fatty acids were decreased in Angus heifers compared to Romosinuano heifers when housed at heat stress conditions. These data suggest that both breed and air temperatures can affect the metabolic response of cattle to a provocative immune challenge. Additionally, the differences observed in this study may help explain the differences observed in the acute phase response to lipopolysaccharide immune challenge in the same heifers. These data will be of interest to scientists in the field of stress physiology, immunity, and nutrition, as well as cattle producers, and can be used to modify management practices in order to enhance cattle health, growth, and well-being.
Technical Abstract: The response of the immune and stress systems have been assessed in response to a lipopolysaccharide (LPS) challenge, yet the role of metabolism in mediating energy requirements during the acute phase response (APR) has not been sufficiently studied. This study tested heat-tolerant and heat-sensitive Bos taurus breeds at different ambient temperatures (Ta) to determine differential metabolic responses to LPS challenge. Angus (ANG; n = 11; 306 +/- 26 kg body weight) and Romosinuano (RO; n = 10; 313 +/- 32 kg body weight) heifers were housed in stanchions in 4 temperature-controlled chambers. Initially, Ta in all 4 chambers was cycling at thermoneutrality (TN; 18.5 to 23.5 C) for a 1-week adjustment period, followed by an increase in 2 chambers to cycling heat stress (HS; 24 to 38 C) for 2 weeks. On day 19, heifers were fitted with jugular catheters. On day 20, heifers were challenged with LPS (0.5 microgram per kg body weight; 0 hour) and blood samples were collected from -2 to 8 hours and at 24 hours relative to LPS challenge. Serum was analyzed for glucose, insulin, and non-esterified fatty acid (NEFA) concentrations. Pre-LPS glucose concentrations were greater in RO (P = 0.01) compared to ANG heifers and greater in TN housed heifers (P = 0.02) compared to HS. Post-LPS, glucose initially increased before decreasing below baseline concentrations (P < 0.01) in all heifers. In addition, ANG heifers at HS post-LPS had lower serum concentrations of glucose (breed by Ta P < 0.01) compared to heifers at TN. Pre-LPS NEFA concentrations were not affected by breed (P = 0.37) or Ta (P = 0.60). Although post-LPS NEFA concentration was unaffected by Ta (P = 0.78), there tended to be a breed by Ta interaction (P = 0.07) such that NEFA was greater in RO than ANG during HS exposure (P = 0.01), while NEFA in heifers at TN did not differ from each other (P = 0.89) or from heifers at HS (P > 0.12). Pre-LPS insulin concentration was greater in RO than ANG (P < 0.01). Post-LPS insulin increased (P < 0.01), with RO, producing a greater insulin response than ANG (P < 0.01). These data suggest that HS decreases the metabolic response of ANG heifers in response to LPS challenge, thus providing physiological evidence that may explain differences observed in the APR between heat-sensitive and heat-tolerant cattle breeds.