Grain feeding increases core body temperature of beef cattle

Abstract

The core body temperature and post slaughter loin temperatures of steers fed on grass pasture was compared with those of steers fed a grain-based feedlot diet. The feeding treatments were grass for 300 days (Grass), grass for 150 days then feedlot for 150 days (Short Feedlot) and feedlot for 300 days (Long Feedlot). Temperature telemeters were inserted under the peritoneum of the steers and temperature measured at intervals of 1 h for the 300 days, and then at intervals of 1 min for the 48-h period before slaughter. The pH and temperature decline post mortem was also measured. The carcasses of the feedlot steers were heavier and fatter than those from the Grass-fed steers. The core body temperature of the steers from the feedlot treatments was 0.3–0.4°C higher than for the Grass treatment at the time of slaughter. The loin temperature was higher in the feedlot treatments than the Grass treatment at all times measured post mortem as was the temperature at pH 6. Feedlotting can increase the likelihood of ‘high rigor temperature’ conditions of high temperature and low pH occurring in beef carcasses, due to an increase in core body temperature before slaughter, a decrease in the rate of cooling and an increase in the rate of pH decline post mortem. These effects are possibly due to a combination of a direct effect of feed type on body temperature as well as indirect effects on bodyweight and condition score.