|Schwertner, Luke -|
|Galyean, Michael -|
|Ballou, Michael -|
Submitted to: Livestock Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 18, 2011
Publication Date: October 10, 2011
Citation: Schwertner, L., Galyean, M., Hulbert, L.E., Carroll, J.A., Ballou, M. 2011. Effects of dietary source and intake of energy on immune competence and the response to an infectious bovine rhinotracheitis virus (IBRV) challenge in cattle. Livestock Science. 141(2-3):259-266. Interpretive Summary: A collaborative study was conducted involving scientists from the Livestock Issues Research Unit and Texas Tech University to evaluate the potential interactions of dietary energy concentration and source on the immune response of beef calves. Specifically, the objective of this study was to evaluate the effects of preconditioning diets varying in energy intake and source of energy on innate immune competence and the response to an infectious bovine rhinotracheitis virus (IBRV) challenge in crossbred beef steers. Results of this experiment indicate that a higher-energy diet (lower in roughage) might be the most appropriate diet to feed preconditioning and stressed, newly received cattle. The more aggressive acute-phase response could benefit cattle by allowing the rapid recognition, recruitment, and elimination of a potential pathogen. Moreover, a more visual display of signs associated with infection and disease would allow the cattle to be detected, removed from their pen, and administered appropriate medical treatments. In addition, the observation that steers previously fed a 70% restricted diet were able to return to feed more quickly when being group penned needs to be further investigated, as this could be a management strategy employed during the preconditioning period that could help cattle cope with the social stress on entering a feedlot. The results of this research will be of particular interest to beef cattle feedlot managers, veterinarians managing the health of feedlot cattle, and scientists, whether from industry, academia, or industry, working in the area of beef cattle production, health, well-being, and alternative management practices.
Technical Abstract: Objectives were to evaluate how dietary energy intake and source affect immune competence and response to an infectious bovine rhinotracheitis virus (IBRV) challenge in cattle. Forty-eight crossbred beef steers were stratified by body weight within 2 periods and randomized to 1 of 3 dietary treatments (8 steers/treatment within period). Treatments were: a 70% concentrate diet fed ad libitum (70AD); a 30% concentrate diet fed ad libitum (30AD); and 70% concentrate diet restricted to the net energy for gain intake of 30AL (70RES). Ex vivo immune responses were evaluated after treatments were applied for 28 d, after which cattle were moved into individual pens (d 28 to 40) and intranasally challenged with IBRV on d 30. On d 34, all cattle were offered a 50% concentrate diet ad libitum until d 50. Both energy source (P < 0.02) and intake level (P < 0.04) affected peripheral blood mononuclear cell synthesis of tumor necrosis factor-a, with cell culture supernatant concentrations averaging 2,264, 1,887, and 1,241 pg/mL for 70AD, 70RES, and 30AD, respectively. Neither whole blood killing of Mannheimia haemolytica nor neutrophil oxidative burst in response to M. haemolytica was affected by treatments. Rectal temperature following IBRV peaked 3 d after the IBRV challenge and returned to baseline by d 6, but it was not affected by treatment. No differences were observed in dry matter intake among treatments while the cattle were individually penned and fed a 50% concentrate diet from d 4 to 10 after the IBRV challenge. When cattle were group-penned from d 40 to 50 of the study (d 10 to 20 after the IBRV challenge), the 70RES cattle had greater DMI (P < 0.04) than cattle in the other 2 groups. Following the IBRV challenge, serum glucose concentrations did not differ among treatments; however, the 70AD cattle had greater blood urea N concentrations (P < 0.01). There was a treatment x time interaction (P < 0.01) for non-esterified fatty acids, such that cattle fed the 70AD had increased non-esterified fatty acids on d 3 and 5 after the IBRV challenge. Results indicate that cattle fed diets with a greater energy concentration and to an extent a greater percentage of concentrates had a more pronounced pro-inflammatory response, but other aspects of innate immune responses were not influenced by intake or source of energy.