The experiment investigated the impact of heatwaves (HWs) on the physiology, postmortem muscle metabolism and meat quality of lambs. Seventy-two second-cross lambs (Poll Dorset × (Border Leicester × Merino)) were selected and exposed to either 1, 3 or 5 days of HWs or thermoneutal (TN) (28-38 °C and 40-60% relative humidity, RH; 18-21 °C, 40-55% RH) conditions in climate-controlled chambers. Lambs exposed to 1-5 days of a HW exhibited higher respiration rates (RRs), rectal temperatures (RTs), skin temperatures (STs) and heart rates (HRs) compared to lambs exposed to an equal duration of TN conditions. However, HWs had no significant effects on muscle metabolism (rate and extent of pH decline, muscle glycogen and lactate content) and meat quality (cooking loss and shear force). Similarly, there were limited impacts of 1-5 days of HW on the colour (L*, a*, b* and R630/580) and drip loss of the longissimus thoracis et lumborum (LTL) and semimembranosus (SM) muscles for 4 days' overwrap retail display. Results suggest that short-duration HWs (1-5 days) had significant negative effects on animal physiology but had no effect on the muscle metabolism and meat quality.
Keywords: heat stress; lamb meat; physiological performance; retail display.