Measurements of meat pH on 16905 steer carcasses supplied to the Richmond Asian Beef Programme in the 1993/94 and 1994/95 seasons were analysed for variability between suppliers and associations between pH and other carcass attributes. Carcass measurements were made 12 hours or later after slaughter. Factors evaluated included carcass weight, carcass grade, marbling level, age of cattle, mob size, and use of growth promotants. The frequency distribution of meat pH was highly skewed, with 92% of carcasses falling within the range of 5.2 to 5.8, and the remainder forming a long tail above 5.8, ranging to an extreme value of 7.1. For carcasses falling in the pH range of 5.2 to 5.8, pH showed a highly significant positive association with meat colour. As pH rose above 5.8, the slope of the relationship increased and the percentage of carcasses in the darkest meat colour category rapidly approached 100%. In the range 5.2 to 5.8, pH showed highly significant negative (P< 0.0001) associations with degree of marbling and carcass weight. After adjusting for carcass weight and marbling score, pH showed a significant positive association with age of cattle. The percentage of carcasses with a pH above 5.6 was 38% for carcasses with a marbling score of 1. For every unit increase in marbling score (up to 5), the percentage of carcasses above a pH 5.6 specification declined by approximately 5%. However, the proportion of carcasses with pH above 5.8 showed little association with marbling. Similarly, effects of weight and cattle age on pH were much more apparent near the mean pH (5.61) than at pH values at and above 5.8. Mob size had a small but highly significant(P<0.001) effect on the frequency distribution of pH, with smaller mobs tending to have lower pH. The effect of smaller mob size was more evident near the high pH range than in the middle of the frequency distribution. For mobs of 15 or fewer cattle, 94% of carcasses had a pH of 5.8 or less. For mobs larger than 15, 91% of carcasses met this specification.
Proceedings of the New Zealand Society of Animal Production, Volume 56, , 187-192, 1996
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