Large White x Landrace boars (n = 48) were used to determine the effect of dietary magnesium aspartate supplementation (MgAsp) on subsequent stress and meat quality indicators. Dietary MgAsp supplementation increased plasma magnesium levels compared with pigs fed the control diet. Pigs fed the MgAsp-supplemented diet had lower norepinephrine concentrations at slaughter than pigs fed the control diet. Pigs fed the MgAsp-supplemented and the control diet had similar glycogen concentrations in the longissimus thoracis (LT) and biceps femoris (BF) muscle, whereas pigs fed the MgAsp-supplemented diet had lower lactic acid in the LT and BF muscle compared to pigs fed the control diet. Negative handling of pigs before slaughter reduced muscle glycogen in the LT and the BF muscle and increased the lactic acid levels in the LT and BF muscle compared to when pigs were minimally handled at the abattoir. Comparison of meat quality traits indicates that MgAsp supplementation to pigs raised the muscle pH in the LT muscle at 40 min and 24 h after slaughter. Pigs that were fed the MgAsp-supplemented diet had lower percentage of drip loss, lower surface lightness L, and had no PSE carcasses compared to pigs fed the control diet. Also, pigs that were fed the control diet and negatively handled at the abattoir before slaughter had the highest percentage of drip loss and incidence of PSE compared to other treatment groups. The results indicate that dietary MgAsp supplementation to pigs can significantly improve ultimate meat quality and reduce the incidence of PSE meat.
A major constraint to protein deposition in the pig is energy intake. Ractopamine (RAC) isa b-agonist which has been shown to increase protein deposition under both ad libitum and restrictive feeding regimes. To assess the interactions between energy intake, sex, and dietary RAC, 104 crossbred pigs (52 boars and 52 gilts) were used in a slaughter-balance experiment conducted over the growth phase of 60-90 kg liveweight. To obtain initial body composition, 4 pigs of each sex were slaughtered at 60 kg. The remaining 96 pigs were allocated to a 2 6 2 factorial experiment. The respective factors were sex (boar or gilt), dietary digestible energy (DE) intake (21·2, 24·7, 28·2, 32·7, 36·7MJ DE/day and ad libitum), and dietary RAC (0 and 20 mg/kg of ractopamine.HCl). Average daily gain increased with DE intake and was faster for boars than gilts. Dietary RAC increased averagedaily gain in both boars and gilts independent of DE intake. Neither dietary RAC nor sex had any effect on ad libitum feed intakes while effects on feed : gain ratio reciprocated growth rates. Protein deposition increased with DE intake and was higher in boars than in gilts. Although protein deposition was increased by dietary RAC in both boars and gilts across the range of DE intakes investigated,ad libitum feed intakes were necessary to maximise protein deposition. Fat deposition increased with DE intake and was greater in gilts than in boars. Whereas dietary RAC had no effect on the rateof fat deposition or backfat depths, the fat content of the empty body was lower due to increased protein deposition and lower fat : protein ratio. Dietary RAC improves growth performance and carcass composition in both boars and gilts independent of DE intake. However, ad libitum feed intakes maybe necessary if responses are to be maximised.
Twelve Large White × Landrace sows nursing litters of 6 boars and 6 gilts were used in this study. Six litters suckled the sow only, whereas the other 6 litters received supplemental liquid skim milk (200 g/L) ad libitum from Day 10 until Day 20. On Day 20 the 4 heaviest pigs of each sex were allocated to 2 pairs and were weaned. Each pair was offered either pelleted or pelleted plus liquid feed. For the first 2 days post-weaning, each pair of liquid-supplemented pigs received liquid skim milk (250 g/L). On Day 23, pelleted feed was added to the milk. The ratio of liquid to pelleted feed was adjusted daily until, on Day 28, pigs were provided with pelleted feed only until 41 days of age. Supplemental skim milk increased growth (223 v. 291 g/day, P < 0.001) between Days 10 and 20 of age so that by weaning supplemented pigs were 10% (6.13 v. 6.74 kg, P = 0.038) heavier than unsupplemented pigs. Skim milk intake increased linearly from 190 to 600 g/day per pig over the 10 days of supplementation. Supplemental milk feeding did not alter sow liveweight change (−31.9 v. −30.3 kg for sows nursing litters with and without supplementation, respectively, P = 0.894) or change in P2 backfat thickness (−5.3 v. −4.2 mm, P = 0.279) between farrowing and Day 20 of age. Pigs weaned onto skim milk and pellets ate more (257 v. 30 g dry matter (DM)/day, P < 0.001) and grew better (213 v. −151 g/day, P < 0.001) over the first 2 days post-weaning than pigs weaned onto only pellets. Piglets provided with liquid feed after weaning continued to grow faster beyond Day 22, resulting in the benefit of weaning onto liquid feed being maintained until at least 41 days of age (14.1 v. 12.8 kg, P < 0.001). In conclusion, skim milk feeding before and after weaning can result in cumulative improvements in growth performance in the nursery.
Thirty-six crossbred (Large White × Landrace) boars were used to investigate the effect of positive and negative handling of pigs on-farm over a period of 5 weeks, and the effect of minimal and negative handling just prior to slaughter at the abattoir on the level of stress and meat quality of the carcass. There was no significant difference in adrenal gland weight and plasma cortisol concentration measured at slaughter between pigs negatively and positively handled on-farm. Pigs negatively handled on-farm had lower muscle glycogen 5 min and 40 min post slaughter in the Longissimus thoracis (LT) but muscle paleness and percentage drip loss of the LT were similar compared with pigs positively handled on-farm. Pigs negatively handled at the abattoir had lower muscle glycogen 5 min post slaughter in the LT; however, muscle paleness, percentage drip loss, ultimate pH, and incidence of pale, soft, exudative meat were similar compared with pigs that were minimally handled at the abattoir. This study has shown how the interaction between pigs and humans on-farm can influence the pig’s ‘stress’ response to pre-slaughter handling and, potentially, meat quality.
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