|ABDELFATTAH, ESSAM - Benha University|
|KAROUSA, M - Benha University|
|SCHUTZ, MICHAEL - Purdue University|
|Lay Jr, Donald|
Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2015
Publication Date: 2/7/2015
Citation: Abdelfattah, E.M., Karousa, M.M., Schutz, M.M., Lay Jr, D.C., Marchant Forde, J.N., Eicher, S.D. 2015. Acute phase cytokines, TAC1, and Toll-like receptor 4 mRNA expression association with housing and health in veal calves. Veterinary Immunology and Immunopathology. 164(3-4):118-26. DOI: 10.1016/j.vetimm.2015.01.008.
Interpretive Summary: Chronic stressors are a major health and well-being issue in animals. Immune status of animals under chronic stress is compromised, thus reducing disease resistance and compromising well-being of the animal. The objective of this study was to determine the influence of group size of veal calves on immune and health status over the 5-month finishing period. Holstein bull calves were housed with 2, 4, or 8 calves/pen (with the same space allowance/calf). Two early immune modulators (interleukin-1 and tachykinin 1) were greater for calves in groups of 8 one month after grouping. This corresponded with the time that calves in groups of 8 had greater coughing scores. White blood cell counts tended to support that calves at 1 month in groups of 8 had more neutrophils (which is both an early indicator of acute stress and is also an early cell response to infections). Therefore, these data support the premise that housing of veal calves in larger groups may lead to greater incidence of respiratory disease and stress and that the stress of larger groups may be the reason for greater susceptibility to respiratory disease.
Technical Abstract: Chronic stressors are a major health and well-being issue in animals. Immune status of animals under chronic stress is compromised, thus reducing disease resistance and compromising well-being of the animal. The objective of this study was to determine the influence of group size of veal calves on immune status and leukocyte mRNA expression of acute phase cytokines, toll-like receptor 4 (TLR4) and tachykinin 1 (TAC1) over the 5-month finishing period. Holstein bull calves (n = 168), 44 ± 3 d of age were assigned to 1 of 3 treatments; 2, 4, or 8 calves/pen (pen space allowance of 1.82 m2/calf). Jugular blood samples were collected at the day of grouping and then monthly for 4 months. The differential leukocyte counts were determined and mRNA was extracted from the leukocytes. Quantitative real-time RT-PCR was used to determine mRNA expression of interleukin-1 (IL-1ß), IL-1 Receptor antagonist (IL-1Ra), tumor necrosis factor (TNF-alpha), TLR4, and TAC1. Health was evaluated before grouping and monthly for 4 months. On d 28 after grouping, veal calves that were housed in groups of 8 have greater expression of IL-1ß mRNA than calves housed in groups of 4 or 2 (treatment × month, P = 0.04). Also, on d 28 the same group tended to have greater TAC1 expression (P = 0.08) than calves housed in groups of 4 or 2. However, the expression of IL-1Ra, TNF-alpha, and TLR4 were not influenced by group size. In the first mo of the trial, calves in groups of 8 coughed more (P < 0.05) than calves in groups of 2 and coughed more than calves in groups of 4 and 2 during the 2nd mo (treatment × month, P = 0.03). Calves housed in groups of 8 tended to have greater neutrophil percentage (P = 0.09), neutrophil to lymphocyte ratio (P = 0.06), and had lower lymphocyte percentage (P = 0.06) than those housed in groups of 4 or 2. In conclusion, the number of veal calves in a group, given the same space during the finishing period did not alter IL-1Ra, TNF-alpha, and TLR4 mRNA expression. However, housing of calves in groups of 8 was associated with greater expression of IL-1ß and TAC1 mRNA in peripheral blood leukocytes, and coughing during the first 2 months after grouping, also associated with neutrophilia, lymphopenia, and greater neutrophil to lymphocyte ratio. Therefore, housing of veal calves in larger groups may lead to greater incidence of respiratory disease and stress.