Location: Livestock Issues ResearchTitle: OmniGen-AF alters rectal temperature (RT) and leukocyte profiles in dairy cows exposed to heat stress (HS) following acute activation of the stress axis Author
|Carroll, Jeffery - Jeff Carroll|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/20/2015
Publication Date: 7/1/2015
Citation: Sanchez, N.C., Carroll, J.A., Mcbride, M.L., Ortiz, X.A., Collier, J.L., Chapman, J.D., Mclean, D., Collier, R.J. 2015. OmniGen-AF alters rectal temperature (RT) and leukocyte profiles in dairy cows exposed to heat stress (HS) following acute activation of the stress axis. Journal of Animal Science Supplement. 93 (E-Supplement 3):323, Abstract#T25. Interpretive Summary:
Technical Abstract: Differences in the response of OmniGen-AF (OG) supplemented dairy cows to a corticotropin releasing hormone (CRH) and vasopressin (VP) or an adrenocorticotropic hormone (ACTH) challenge when housed at different temperature-humidity indices (THI) were studied. Holstein cows (n=12; 162±1 days in milk) were balanced by milk yield, body weight and days in milk into 1 of 2 treatments: 1) OminGen-AF, supplemented with OG at 4.54 g/kg body weight for 70 days; or 2) Control (CON), no supplement. Cows were moved to individual tie stalls in 1 of 2 temperature controlled chambers on day 51 and fitted with indwelling RT devices and jugular catheters on day 52. Initially THI was cycling at thermoneutrality [TN; THI<72 for 24 h/d] for 7 days, followed by HS (THI>72 for 12h/d) for 10 days. Cows were challenged with CRH (0.3 microgram/kg) and VP (1 microgram/kg) at 1000h on day 4 of TN and day 1 of HS, and with ACTH (0.1 International Units/kg) at 1000h on day 5 of TN and day 2 of HS. Blood samples were collected from -2 to 8 hours at 30-min intervals relative to each challenge and analyzed for leukocyte profiles. There was a THI x time interaction (P=0.01) for RT such that RT was greater during HS than TN (2 to 9 hours, and at 11 hours for CRHVP and 4 to 9 hours and 11 to 13 hours for ACTH). Also, RT was greater (P=0.02) in OG than CON cows regardless of challenge. Total white blood cells (WBC) and neutrophils (NT) increased (P<0.01) in response to CRHVP and ACTH. There was a treatment x THI interaction (P<0.01) for WBC during both challenges. Specifically, WBC were decreased in CON during HS compared to TN in response to CRHVP, while WBC were greatest in CON during TN and least in OG during HS in response to ACTH. There was a treatment x THI interaction (P=0.02) for NT in response to CRHVP challenge; NT decreased in CON cows during HS compared to TN. Also, NT were decreased during HS (P<0.01) compared to TN and decreased in OG compared to CON (P<0.01) following ACTH. Lymphocytes were decreased during HS compared to TN (P<0.01) and in OG compared to CON cows (P<0.01) regardless of challenge. These data suggest supplementing cows with OG can reduce the negative effects of HS on leukocyte profiles following activation of the stress axis.