Post-mortem activity of the glycogen debranching enzyme and change in the glycogen pools in porcine M. longissimus dorsi from carriers and non-carriers of the RN− gene

Ractopamine does not rescue Halothane and Rendement Napole metabolism postmortem

The objective of this study was to determine if ractopamine (RAC) impacts postmortem muscle metabolism and subsequent pork quality in Halothane (HAL) and Rendement Napole (RN) mutant pigs. All RAC fed pigs had increased (P < 0.04) L* values. HAL and RN mutants muscle had lower (P < 0.01) pH values but RAC feeding had no effect. RN mutants had higher and lower (P < 0.05) muscle pH and temperatures, respectfully at 15 min and RN mutant pigs had greater (P < 0.0001) glycogen initially but lactate levels similar to wild type (WT) pigs at 24 h. RAC lowered (P < 0.05) glycogen in RN mutants but not in HAL mutated or WT pig muscle. These data show RAC feeding changes postmortem energy metabolism but does not change pH and pork quality hallmark of two major pig gene mutations and supports our contention that ultimate meat quality traits and their biochemical drivers may be more complex than originally reasoned.

Ractopamine changes in pork quality are not mediated by changes in muscle glycogen or lactate accumulation postmortem

Pork quality is a product of the rate and extent of muscle pH decline paced by carbohydrate metabolism postmortem. The beta-adrenergic agonist ractopamine (RAC) alters muscle metabolism but has little impact on pork quality. The objective of this study was to determine how feeding RAC alters postmortem carbohydrate metabolism in muscle. Muscle pH was higher early postmortem in pigs fed RAC for 2 wks compared to control, while other time points and temperatures were largely unaffected. Early postmortem, muscle lactate levels were reduced (P < 0.05) after feeding RAC for 1 and 2 wks. Similarly, pigs fed RAC for 4 wks had reduced (P < 0.05) glycogen levels early postmortem compared to control pigs, but unexpectedly, L* values (lightness) increased (P < 0.05) after inclusion of RAC in the diet for 4 wk. These data show RAC feeding reduces glycogen content and changes lactate accumulation postmortem, but raise questions about the role glycolytic flux has in driving pork quality development.

Supplementation of sows with L-Arginine during gestating and lactation affects muscle traits of offspring related with postnatal growth and meat quality: From conception to consumption

This study investigated the effect of dietary inclusion of 25 g/day of _L-Arginine (n = 7) or iso‑nitrogenous amounts of alanine (n = 6) from d 30 of gestation to d 28 of lactation of sows on performance, muscle traits and meat quality in offspring. From each litter, heaviest and smallest littermate of both sexes were reared from d 28 and slaughtered at d 140 in accordance with a 2³factorial design. A response to _L-Arginine were obtained on small females where _L-Arginine increased birth weight, however this effect disappeared at weaning. _L-Arginine increased daily gain by 7% and increased the cross-sectional area of the M. semitendinosus in small females by 14%, suggesting an increased lean ratio. Mechanistic studies showed firstly, that small female littermates had increased number of muscle fibres (myogenesis) after _L-Arginine treatment (11%) and secondly increased total DNA (12%) as a consequence of satellite cell proliferation. Traits describing tenderness seem to be affected by _L-Arginine but further studies are needed.

Changes in expression of monocarboxylate transporters, heat shock proteins and meat quality of Large White Yorkshire and Ghungroo pigs during hot summer period

OBJECTIVE

Present study explores the effect of hot summer period on the glycolytic rate of early post-mortem meat quality of Ghungroo and Large White Yorkshire (LWY) pig and comparative adaptability to high temperature between above breeds by shifting the expression of stress related genes like mono-carboxylate transporters (MCTs) and heat shock proteins (HSPs).

METHODS

Healthy pigs of two different breeds, viz., LYW and Ghungroo (20 from each) were maintained during hot summer period (May to June) with a mean temperature of about 38°C. The pigs were slaughtered and meat samples from the longissimus dorsi (LD) muscles were analyzed for pH, glycogen and lactate content and mRNA expression. Following 24 h of chilling, LD muscle was also taken from the carcasses to evaluate protein solubility and different meat quality measurements.

RESULTS

LWY exhibited significantly (p<0.01) higher plasma cortisol and lactate dehydrogenase concentration than Ghungroo indicating their higher sensitivity to high temperature. LD muscle from LWY pigs revealed lower initial and ultimate pH values and higher drip loss compared to Ghungroo, indicating a faster rate of pH fall. LD muscle of Ghungroo had significantly lower lactate content at 45 min postmortem indicating normal postmortem glycolysis and much slower glycolytic rate at early postmortem. LD muscle of LWY showed rapid postmortem glycolysis, higher drip loss and higher degrees of protein denaturation. Ghungroo exhibited slightly better water holding capacity, lower cooking loss and higher protein solubility. All HSPs (HSP27, HSP70, and HSP90) and MCTs (MCT1, MCT2, and MCT4) in the LD muscle of pigs inclined to increase more in Ghungroo than LWY when exposed to high temperature.

CONCLUSION

Effect of high temperature on the variation of HSPs and MCTs may play a crucial role in thermal tolerance and adaptation to different climatic conditions, pH regulation, muscle acidification, drip loss, protein denaturation and also in postmortem meat quality development.

Carcass and meat quality traits of four different pig crosses

The study compared properties of Finnish Landrace×Yorkshire crossbred sows mated with Finnish Landrace (FL), Norwegian Landrace (NL), Norwegian Duroc×Norwegian Landrace (NDL), or Swedish Hampshire (SH) boars. The focus was to study the cross-sectional area of loin, cross-sectional area and number of muscle fibres, loin colour and pH value as well as the ratio of water to protein in the loin. The four studied crosses were quite similar having only small differences in carcass and meat quality. The carcass lean content was the lowest in NDL. The loins of FL and NL were longer than the loins of NDL and of SH. The cross-sectional area of loin was the largest in SH. The loin of FL was lighter in colour and the loin of SH was redder than the loins of the other crosses studied. The protein content was lower and the ratio of water to protein higher in loin of SH than in the other crosses.

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

The current experiment was designed to examine if a compensatory feed regimen influenced storage of glycogen forms, activity of proteolytic systems, and meat quality. Female pigs (Large White × Landrace × Duroc cross) with an initial age of 74 d were allocated to 6 feeding treatment groups (n=8 for each group). Groups then consumed feed ad libitum for 40 (A40), 42 (A42), or 82 d (A82). The compensatory growth groups were fed 0.70 of ad libitum intake for 40 d (R40) followed by refeeding for ad libitum intake for 2 (R40A2) or 42 d (R40A42). Pigs were slaughtered at the end of the restriction period (SL1), then after refeeding for 2 (SL2) and 42 d (SL3). The feeding regimen caused restricted animals at SL2 to have a decreased BW (P=0.039), with the refed animals undergoing compensatory growth by SL3 so BW was not different (P=0.829). At SL1 there was a trend for the 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 in R40, which was associated with the R40 having a lower pH at 24 h postmortem (P=0.043). After refeeding for 2 d (SL2), only MG of R40A2 was greater (P=0.030) than A42 and had a trend for a greater difference of decline at 24 h postmortem (P=0.091), which was associated with lower pH at 24 h (P=0.012). The data suggest that the concentrations of ProG are more labile and recovered to the concentrations of pigs fed for ad libitum intake sooner than MG. After full compensation in SL3, there was no difference for MG content (at 0 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, there was no difference in shear force (at SL1, P=0.101; at SL2, P=0.420; at SL3, P=0.167). There were no significant effects of the feeding regimen on micro- and milli-calpain large subunit gene expression (for micro-calpain at 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 2 proteolytic enzymes at any of the slaughter dates (for micro-calpain at SL1, P=0.238; at SL2, P =0.238; at SL3, P=0.222; for milli-calpain at SL1, P=0.296; at SL2, P=0.230; at SL3, P=0.615). In R40 there was a trend (P=0.070) for greater gene expression of caspase 3, 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, at SL3 was less in R40A42 (P=0.019). Although compensatory growth does appear to influence the expression of various proteolytic systems, the changes do not appear to be associated with meat quality as measured by shear force.

The relation between glycogen, lactate content and muscle fiber type composition, and their influence on postmortem glycolytic rate and pork quality

This study examined the relation between glycogen, lactate content and muscle fiber type composition, and evaluated their influence on postmortem glycolytic rate and meat quality. Muscle samples were classified based on their glycogen and lactate content at 45min postmortem. Muscles with low glycogen and high lactate levels showed low muscle pH(45min) and high R-values. However, muscles with low glycogen and lactate levels showed normal rates of postmortem glycolysis and normal meat quality. On the other hand, muscles with high glycogen and lactate content showed rapid postmortem glycolysis, paler surface color, higher drip loss, and higher extents of protein denaturation than muscles with high glycogen and low lactate content. These results may be partially explained by muscle fiber type composition. Muscles with low glycogen and lactate content at early postmortem are composed of significantly higher fiber type I and lower fiber type IIB as compared to muscles with high glycogen and lactate content.