The long-term influences of birth weight on muscle characteristics and eating meat quality in pigs individually reared and fed during fattening

This study aims to determine whether a low weight at birth may influence muscle characteristics and meat quality traits in pigs at market weight. At 68 days of age, a total of 30 female piglets were assigned within litter to one of the two experimental groups (n = 15 per group): low birth weight (LW: 1.05 + 0.04 kg) or heavy birth weight (HW: 1.89 + 0.02 kg). Pigs were penned individually and fed ad libitum up to slaughter. At 111.8 + 0.8 kg, LW pigs were 12 days older (P < 0.001) than HW pigs. Feed conversion ratio was deteriorated in LW pigs compared to HW pigs (+10%, P< 0.001). A higher proportion of subcutaneous fat (+29%, P < 0.005) and a lower lean meat content (-1.85 point, P < 0.01) were observed in LW carcasses compared with HW ones. Myofiber cross-sectional area was 14% higher in both semitendinosus and longissimus muscles of LW pigs than in HW pigs. Total fiber number was 19% lower (P < 0.01) in the semitendinosus muscle of LW pigs. Lipid content was 25% higher in the semitendinosus muscle of LW pigs compared with HW pigs, but did not differ in the longissimus muscle. The LW pigs exhibited a lower score for loin meat tenderness compared with HW pigs. Tenderness score tended to be negatively correlated (r = -0.34, P = 0.07) with mean myofiber size of the longissimus muscle. Then, birth-weight effect on meat tenderness may be partly attributed to its influence on myofiber hypertrophy.