K Van den Maagdenberg

Effect of the insulin-like growth factor-II and RYR1 genotype in pigs on carcass and meat quality traits

Recently, a new QTN (quantitative trait nucleotide), which is located in the regulatory sequence of the imprinted IGF-II gene was discovered in the pig and is associated with a significant increase in IGF-II mRNA expression in skeletal muscle during postnatal growth. The aim of the current study was to investigate the effect of the IGF-II paternal allele (Apat and Gpat animals that inherited, respectively, the mutant and wild type paternal allele of interest) on carcass and meat quality traits in Nn and NN RYR1 genotypes. A total of 141 animals were measured, almost equally distributed over the IGF-II and RYR1 genotypes and gender. The Apat allele increased carcass lean meat percentage with approximately 4.5% (P<0.001) as a result of decreased backfat thickness. Average live weight daily gain was not affected, hence average daily lean meat gain was significantly higher for Apat compared to Gpat animals. The IGF-II mutation had no noticeable effect on meat quality in contrast with the RYR1 mutation. No interaction effects of both mutations on meat quality were noticed.

Role of proline and hydroxyproline in N-nitrosamine formation during heating in cured meat.

N-Nitrosamines are formed in a multi-step reaction of nitrite with free amino acids and amines in the meat products. The aim of this study was to determine the role of proline and hydroxyproline in N-nitrosamines formation during heating of cured meat. A lean meat model was used with different nitrite concentrations (0, 120, and 480mg/kg), and addition of proline and hydroxyproline (1000mg/kg), followed by heating at different temperatures. Volatile nitrosamines were analyzed with GC-TEA. The nitrosamine content never exceeded 10μg/kg and stayed <LOQ as long as the nitrite level of 120mg/kg was not surpassed. The importance of proline as a precursor for N-nitrosamine formation was confirmed. In contrast, hydroxyproline inhibited NPYR formation (N-nitrosopyrrolidine) because no traces were found after addition of hydroxyproline. NPYR formation was not related to nitrite, but was significantly influenced by temperature (⩾200°C) and proline. NDMA-presence (N-nitrosodimethylamine) in heated meat products was influenced by nitrite and temperatures >120°C.

The effect of mutations in the insulin-like growth factor-II and ryanodine receptor-1 genes on biochemical and histochemical muscle fibre characteristics in pigs

Mutations in IGF-II (insulin-like growth factor-II) and RYR1 (ryanodine receptor-1) increase lean meat content in pigs but with different effects on meat quality. Differences in biochemical and histochemical muscle fibre characteristics between the two mutations can thus be suspected. Therefore, the aim of this study was to investigate the effect of the IGF-II mutation (Apat vs. Gpat) on biochemical and histochemical muscle fibre characteristics in relation to the RYR1 genotype (Nn vs. NN). A prenatal effect of the IGF-II mutation could not be excluded but the increased leanness in both mutations was clearly related to postnatal muscle hypertrophy due to an increase in muscle fibre diameter and a higher proliferative capacity in animals carrying the IGF-II mutation. No effect of the IGF-II or RYR1 mutation was found on fibre type composition and metabolic enzyme activities. Interactions between IGF-II and RYR1 genotypes suggest that the mechanism involved in increased leanness due to the impaired RYR1 receptor might influence the underlying mechanisms of the IGF-II mutation.

Interactions between genes involved in growth and muscularity in pigs: IGF-2, myostatin, ryanodine receptor 1, and melanocortin-4 receptor.

In the swine breeding industry, two economical traits are of particular importance in sires, namely, muscle growth and average daily gain (ADG). These traits are quantitative, which implies that they are under the control of multiple genes. Mutations in these genes, associated with either muscularity or growth, are useful quantitative trait nucleotides (QTN) for unraveling genetic variation of these traits and can be used in marker-assisted selection. Until now, QTN involved in muscle growth and/or ADG in pigs were identified in porcine ryanodine receptor 1 (RYR1), insulin-like growth factor-2 (IGF-2), and melanocortin-4 receptor (MC4R). Recently, a fourth possible QTN was found in porcine myostatin (MSTN). All four QTN have an influence on muscle growth and/or somatic growth, so an influence of one mutation on one or more of the other mutations should not be excluded. However, although the polymorphisms in the RYR1 and the MC4R gene affect the function of the respective protein, the polymorphisms of the IGF-2 and MSTN gene influence the mRNA expression of the respective gene. Therefore, this study investigated possible interactions between the genotypes of MSTN, IGF-2, and MC4R (population 1) or the RYR1, IGF-2, and MSTN QTN (population 2) on IGF-2 and MSTN expression in different muscle types in pigs. In both skeletal muscle and heart muscle growth, the IGF-2:MSTN ratio seems to play an important role. Also, the RYR1 genotype had a significant effect on IGF-2 expression in m. longissimus dorsi. No effect of the MC4R QTN could be seen.