Cross-sectional studies of ultimate pH in lambs

The ultimate pH of the longissimus muscle was measured in 1536 lambs routinely slaughtered at a meat export works in the southern part of the North Island during the 1981/82 season. The mean ultimate pH of ail samples was 5.60, and 7.2 percent of the carcases had values equal to, or above, 6.00 whereas 85.3 percent of carcases had values below 5.80 which is considered to be optimal. The ultimate pH values of samples from lambs slaughtered during the summer period was significantly higher than those obtained during three other seasonal sampling periods and Perendale lambs had significantly higher ultimate pH values as compared to Iambs of other breeds. There was no statistical association between distance travelled before slaughter and the ultimate pH of carcases but there was a highly significant direct correlation between holding periods of lambs in the stockyards and ultimate pH of their meat. There was also a highly significant inverse correlation between fleece weight and ultimate pH and it is suggested that both this effect and the seasonal pattern of ultimate pH values indirectly reflect the major role that nutrition may play in the development of high ultimate pH meat in lambs. It is further suggested that washing of animals prior to slaughter and the length of subsequent resting periods are important factors in relation to the development of undesirably high ultimate pH values.