Location: Livestock Issues Research
Project Number: 3096-32000-008-16-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Jan 1, 2018
End Date: Dec 31, 2019
The objective of this study is to determine if activation of the stress axis in live cattle is associated with post-mortem meat quality.
Forty dairy steer calves uniform in weight, age, and with no prior health treatments will be acquired by a calf ranch in the Texas Panhandle and transported no more than 120 km to the USDA-ARS Livestock Issues Research Unit’s Liberty Farm in Lubbock, TX (d -6). Upon arrival calves will be weighed, fitted with an indwelling rectal temperature monitoring device (Reuter et al., 2010), and placed in individual pens within an enclosed, environmentally controlled barn with ad libitum access to feed and water. On d -4, calves will be weighed, 2 whole blood samples will be collected via jugular venipuncture for serum (9-mL vacutainer with no additive) and complete blood cell analysis (4-mL vacutainer containing EDTA), and a muscle biopsy sample collected. Calves will then be returned to their individual pens. Calves will be given 3 days to rest and recover from the muscle biopsy procedure. On d -1, calves calves will be weighed, fitted with jugular catheters and returned to their individual pens. Based on body weights on d -1, calves will be separated into treatments: 1) ACTH, administered 0.1 IU ACTH per kg BW at 0 h on d 0, or 2) Saline (Control), receive a similar volume of saline per kg BW at 0 h on d 0. On d 0, a 9-mL whole blood sample will be collected in a monovette tubes with no additive from each calf for the isolation of serum at 0.5-h intervals from -2 to 6 h relative to ACTH or saline administration at 0 h. Serum will be stored at -80C until analyzed for cortisol concentrations via ELISA. Additionally, a second 4-mL blood sample will be collected into a vacutainer containing EDTA every 2 h from -2 to 6 h relative to ACTH or saline administration for the determination of complete blood counts using the ProCyte DX Hematology Analyzer (IDEXX Laboratories, Westbrook, ME). Relative to the ACTH/saline challenge, calves will be humanely euthanized at 6h, 12h, and 24 h for collection of muscle tissue for measurement of SHSP. At each necropsy, blood samples for serum and complete blood counts will be collected, and a body weight will be collected.