Effect of compensatory growth on forms of glycogen, postmortem proteolysis, and meat quality in pigs

Abstract

The current experiment was designedto examine if a compensatory feed regimen influencedstorage of glycogen forms, activity of proteolytic systems,and meat quality. Female pigs (Large White ×Landrace × Duroc cross) with an initial age of 74 dwere allocated to 6 feeding treatment groups (n = 8 foreach group). Groups then consumed feed ad libitum for40 (A40), 42 (A42), or 82 d (A82). The compensatorygrowth groups were fed 0.70 of ad libitum intake for40 d (R40) followed by refeeding for ad libitum intakefor 2 (R40A2) or 42 d (R40A42). Pigs were slaughteredat the end of the restriction period (SL1), thenafter refeeding for 2 (SL2) and 42 d (SL3). The feedingregimen caused restricted animals at SL2 to havea decreased BW (P = 0.039), with the refed animalsundergoing compensatory growth by SL3 so BW wasnot different (P = 0.829). At SL1 there was a trend forthe R40 pigs to have less intramuscular fat than A40 (P= 0.084). There was a trend for macroglycogen (MG; P= 0.051) and a significant effect for proglycogen (ProG;P = 0.014) to be greater at slaughter in R40 than A40,along with a greater postmortem decline in both MG(P = 0.033) and ProG (P = 0.022) over the first 2 h inR40, which was associated with the R40 having a lowerpH at 24 h postmortem (P = 0.043). After refeeding for2 d (SL2), only MG of R40A2 was greater (P = 0.030)than A42 and had a trend for a greater difference ofdecline at 24 h postmortem (P = 0.091), which was associatedwith lower pH at 24 h (P = 0.012). The datasuggest that the concentrations of ProG are more labileand recovered to the concentrations of pigs fed for adlibitum intake sooner than MG. After full compensationin SL3, there was no difference for MG content (at0 h, P = 0.721; at 2 h, P = 0.987; at 24 h, P = 0.343),ProG content (at 0 h, P = 0.879; at 2 h, P = 0.946;at 24 h, P = 0.459), and muscle pH (at 45 min, P =0.373; at 24 h, P = 0.226). At all slaughter points, therewas no difference in shear force (at SL1, P = 0.101; atSL2, P = 0.420; at SL3, P = 0.167). There were nosignificant effects of the feeding regimen on micro- andmilli-calpain large subunit gene expression (for microcalpainat SL1, P = 0.450; at SL2, P = 0.171; at SL3,P = 0.281; for milli-calpain at SL1, P = 0.666; at SL2,P = 0.123; at SL3, P = 0.617) or the activity of the 2proteolytic enzymes at any of the slaughter dates (formicro-calpain at SL1, P = 0.238; at SL2, P = 0.238; atSL3, P = 0.222; for milli-calpain at SL1, P = 0.296; atSL2, P = 0.230; at SL3, P = 0.615). In R40 there wasa trend (P = 0.070) for greater gene expression of caspase3, whereas in R40A2 the increase was significant(P = 0.009) relative to pigs consuming feed ad libitum.However, gene expression of the E3 ligase, MuRF1, atSL3 was less in R40A42 (P = 0.019). Although compensatorygrowth does appear to influence the expressionof various proteolytic systems, the changes do notappear to be associated with meat quality as measuredby shear force. ©2011 American Society of Animal Science. All rights reserved.