Porcine Muscle Properties. B. Relation to Naturally Occurring and Artificially Induced Variation in Heart and Respiration Rates

Abstract

SUMMARYStudies were conducted to: 1) investigate the association between the physiological parameters heart and respiration rates, and the postmortem properties of muscle; and 2) determine the physiological response of the pig to experimentally‐imposed, abrupt changes in environmental temperature immediately prior to slaughter. In the first phase of these studies, observations were made on 55 untreated pigs representing 4 breeds. Heart and respiration rates were determined on restrained animals in standing position, just before slaughter. Abnormally high heart and respiration rates were observed under these conditions in comparison with resting rates. Nevertheless, very high heart and respiration rates, immediately prior to slaughter, were associated with rapid rates of post‐mortem muscle pH decline, low post‐mortem pH values and pale, soft, exudative musculature. In the second phase of these studies, a group of 42 Poland China pigs were subjected to 7 ante‐mortem temperature treatments. Warm treatment resulted in marked increases in respiration rates and wide variations in heart rates. Cold treatments generally decreased both respiration and heart rates. In the combination treatments, a change from warm to cold environment tended to restore respiration rate to pretreatment levels. Both respiration and heart rate tended to increase as muscle temperature increased. Drastic increases in heart rates due to warm treatment were associated with the development of extremely pale, soft, exudative musculature.