EFFECTS OF AGE AND OR WEIGHT AT SLAUGHTER ON LONGISSIMUS-DORSI MUSCLE- BIOCHEMICAL TRAITS AND SENSORY QUALITY IN PIGS/

The effect of increasing either age alone through feed restriction, or both age and weight at slaughter, on the quality of the longissimus d orsi muscle (LM) was investigated. Starting at 83 days of age and 32 k g, 80 pigs were allotted within litter to four experimental groups. Al l pigs were free of RYR1 mutated gene. Pigs were fed either ad libitum (A100, A130) or restricted 30% (R100, R130) and slaughtered at either 100 kg (A100, R100) or 130 kg (A130, R130) body weight. Restricting f eed intake in order to increase age at the same weight resulted in slo wer growth, better feed efficiency and increased leanness, whereas inc reasing age and weight simultaneously elicited slower growth, reduced feed efficiency and fatter carcasses. Intramuscular fat (IMF) and musc le collagen concentration were reduced by restricted feeding. Increase in both age and weight of pigs resulted in lower water, and higher pr otein and IMF concentrations. Although pigs were free of RYR1 gene, th e PSE condition (defined as pH1 less than or equal to 5.9) developed i n 25 carcasses, with a higher incidence in restricted pigs. PSE animal s were excluded from the subsequent analysis of meat quality data. Fee d restriction resulted in higher drip loss and lower a and c* (satura tion index) values. Longer myofibril fragments in muscle of restricted pigs on day I post mortem are indicative of slower maturation, while longer fragments on day 4 in heavier pigs, suggest that the extent of post mortem tenderisation could be negatively affected by the elevatio n of slaughter weight. Feed restriction had no significant effect on m eat sensory quality, whereas increase in both age and weight resulted in lower tenderness, chewiness and mouth coating scores. Our results i ndicate that increasing age at a given body weight, via feed restricti on, reduced IMF and collagen concentrations, and the rate of post mort em proteolysis, however, this had no significant impact on pork qualit y assessed after 4 days of ageing. On the other hand, increasing both age and weight at slaughter could alter pork texture, in spite of elev ated IMF concentration. (C) 1998 Elsevier Science Ltd. All rights rese rved.