Comparative Analysis of the Porcine IGF2-G3072A Mutation and Reduced Myostatin Function on Carcass and Meat Quality Characteristics

The objective of this study was to determine the relative effects of the porcine IGF2 mutation (IGF2-G3072A) and a novel, gene-editing derived myostatin loss-of-function (LOF) mutation on carcass traits and meat quality in pigs. The hypothesis was that both the IGF2 paternal A allele (Apat) and myostatin LOF mutation would increase muscle growth in pigs, but may potentially reduce loin and belly quality. Pigs were either IGF2 paternal G allele (Gpat) and wild-type (WT) for myostatin (n=13), Gpat and heterozygous (HET) for myostatin (n=10), Apat WT (n=11) or Apat HET (n=10). Pigs were raised in mixed sex pens of 10-15 pigs per pen, given free access to a diet that met or exceeded NRC nutrient requirements, and slaughtered at 175 d (±5 d) of age. Loin eye area and back fat depth was measured. Loin and belly quality was measured on the left side of the carcass. Warner-Bratzler shear force (WBSF) was used to determine tenderness of loin chops d14 postmortem. Data were analyzed using the MIXED procedure of SAS with a model including the effects of sex, IGF2, myostatin, and all interactions; means were separated using the pdiff option and considered different when P≤0.05. Ending live weight and hot carcass weight were similar among all genotypes (P≥0.05). Loin eye area was greater (P≤0.05) in HET pigs regardless of IGF2 genotype compared with WT pigs, and tended (P=0.10) to be greater in IGF2 Apat WT pigs compared with Gpat WT pigs. Back fat depth was similar (P≥0.05) among all genotypes. Longissimus dorsi (LD) muscle weighed less (P≤0.05) in WT Gpat pigs in comparison with all other genotypes, and was larger (P≤0.05) in Apat HET pigs compared with Apat WT pigs. Loins from myostatin HET pigs were paler than those from WT pigs, regardless of IGF2 genotype, as evidenced by an increased L* value of approximately 5 units (P< 0.01). However, L* of IGF2 Apat (52.1) and Gpat (53.9) pigs were similar (P≥0.05). Tenderness (WBSF) was similar (P≥0.05) among all genotypes. Bellies from IGF2 Gpat pigs were firmer as indicated by an increased (P<0.05) flop distance compared with all other genotypes. These data suggest that the partial loss of myostatin (HET) increased lean muscle deposition in pigs but resulted in poorer loin color. The IGF2 Apat mutation also tended to increase lean muscle deposition but did not negatively impact loin color. However, both mutations resulted in poorer belly firmness.

The objective of this study was to determine the relative effects of the porcine IGF2 mutation (IGF2-G3072A) and a novel, gene-editing derived myostatin loss-of-function (LOF) mutation on carcass traits and meat quality in pigs. The hypothesis was that both the IGF2 paternal A allele (Apat) and myostatin LOF mutation would increase muscle growth in pigs, but may potentially reduce loin and belly quality. Pigs were either IGF2 paternal G allele (Gpat) and wild-type (WT) for myostatin (n=13), Gpat and heterozygous (HET) for myostatin (n=10), Apat WT (n=11) or Apat HET (n=10). Pigs were raised in mixed sex pens of 10-15 pigs per pen, given free access to a diet that met or exceeded NRC nutrient requirements, and slaughtered at 175 d (±5 d) of age. Loin eye area and back fat depth was measured. Loin and belly quality was measured on the left side of the carcass. Warner-Bratzler shear force (WBSF) was used to determine tenderness of loin chops d14 postmortem. Data were analyzed using the MIXED procedure of SAS with a model including the effects of sex, IGF2, myostatin, and all interactions; means were separated using the pdiff option and considered different when P≤0.05. Ending live weight and hot carcass weight were similar among all genotypes (P≥0.05). Loin eye area was greater (P≤0.05) in HET pigs regardless of IGF2 genotype compared with WT pigs, and tended (P=0.10) to be greater in IGF2 Apat WT pigs compared with Gpat WT pigs. Back fat depth was similar (P≥0.05) among all genotypes. Longissimus dorsi (LD) muscle weighed less (P≤0.05) in WT Gpat pigs in comparison with all other genotypes, and was larger (P≤0.05) in Apat HET pigs compared with Apat WT pigs. Loins from myostatin HET pigs were paler than those from WT pigs, regardless of IGF2 genotype, as evidenced by an increased L* value of approximately 5 units (P< 0.01). However, L* of IGF2 Apat (52.1) and Gpat (53.9) pigs were similar (P≥0.05). Tenderness (WBSF) was similar (P≥0.05) among all genotypes. Bellies from IGF2 Gpat pigs were firmer as indicated by an increased (P<0.05) flop distance compared with all other genotypes. These data suggest that the partial loss of myostatin (HET) increased lean muscle deposition in pigs but resulted in poorer loin color. The IGF2 Apat mutation also tended to increase lean muscle deposition but did not negatively impact loin color. However, both mutations resulted in poorer belly firmness.