Abstract
During the pre-slaughter period, sheep may experience acute stress and extended periods of feed deprivation. Studies in slaughter cattle have shown a moderate impact on plasma non-esterified fatty acid (NEFA) concentration in cattle but a larger acute stress immediately prior to slaughter, demonstrated by marked increases in plasma glucose and lactate. Sheep undergo similar pre-slaughter management to cattle in Australia, thus we hypothesise that lambs will have a similar metabolic profile at slaughter. Blood was collected at exsanguination from 1,536 lambs (mean age at slaughter 298±57 days) from the Sheep Co-Operative Research Council Information Nucleus Flock. The lambs were managed on two research stations (Katanning, Western Australia and Armidale, New South Wales) and were assigned to ten slaughter groups based on carcass weight targets for the desired market. Lambs were yarded the day prior to slaughter, held in curfew on-farm for 2 hours, weighed and then transported to commercial abattoirs where they were held in lairage for an average of 17 .9±1. 79 hours. Blood was collected at exsanguination and the plasma was analysed for non-esterified fatty acids, glucose and lactate. Plasma metabolite concentrations differed markedly between slaughter groups (P<0.05). Across all of these groups the mean plasma NEFA, glucose and lactate concentrations were 1.57±0.45 mmol/1, 4.05±0.56 mmol/1 and 2.94±1.74 mmol/1. Contrary to our hypothesis, NEFA concentrations were markedly higher at slaughter in lambs compared with cattle. Alternatively lactate and glucose concentrations were lower than concentrations in slaughter cattle. This suggests that different mechanisms may exist between sheep and cattle in terms of their metabolic response to feed deprivation and acute stress during the pre-slaughter period.