Sheep genotype, age and muscle type affect the expression of metabolic enzyme markers

Abstract

The objective of this study was to determine whether genotype, age (4, 8, 14 and 22 months), sex (ewe and wether) and muscle type influence ovine (n = 587) muscle metabolic characteristics. The genotypes represented were Poll Dorsetgrowth × Border Leicester Merino, Poll Dorsetgrowth × Merino, Poll Dorsetmuscling × Merino, Merino × Merino and Border Leicester × Merino. Between 4 and 22 months of age, myoglobin concentration within all muscles and all genotypes doubled, with the bulk of this response occurring between 4 and 8 months of age. Levels in the longissimus thoracis et lumborum (LT) and semimembranosus muscles were double those seen in the semitendinosus (ST) muscle, and Merinos had the lowest myoglobin concentrations of all genotypes. The other aerobic indicator, isocitrate dehydrogenase, had lower activity in the ST compared with the LT, was lower in 22-month-old sheep compared with all other ages, and decreased as selection for leanness increased. Both phosphofructokinase and lactate dehydrogenase activity tended to increase with age, were lower in the ST compared with the LT, and had higher activity in the Border Leicester × Merino sheep. The correlation between the percentage of total myofibre area comprising type 2X myofibres and metabolic markers was far higher for the oxidative indicators isocitrate dehydrogenase and myoglobin, which both decreased as relative area of type 2X fibres increased. However, the strongest correlations were with the relative area of type 2A myofibres, which were consistently high for both oxidative and glycolytic metabolic markers implying positive coregulation with both energy producing pathways.

Opportunities and challenges in meat production from sheep

“…Berge et al (2003) reported a simple correlation of 0.66 between lamb age and muscle pigment content for 446 lambs from 22 different European production systems, with ages ranging from 1-12 months. Not surprisingly, the age was closely related to weight in that study (r = 0.88) as it would have been in the first experiment of the current work where myoglobin concentrations in all four muscles tested increased with age, particularly between ages of 4 and 8 months (Gardner et al 2007). In contrast, when weight at slaughter was controlled at 32 kg, Ledward and Shorthose (1971) found only a low correlation between muscle myoglobin concentration and age (r = 0.26) for lambs aged from ~100 to 300 days.…”

Short term supplementation rates to optimise vitamin E concentration for retail colour stability of Australian lamb meat

“…This result aligns with work by both Lanari et al (2002) and Yang et al (2002) who found supplemented cattle had a better colour stability than pasture fed animals. Different muscles may vary in initial colour due to differing pigment concentrations (myoglobin), associated with variation in fibre type (Gardner et al, 2007). However in this study, the fibre type of pasture fed lambs is unlikely to have changed significantly compared to other treatments over such a short feeding period.…”

“…concentration from low in the ST, to medium in the LL and high in the SM (Gardner, Hopkins, Greenwood, Cake, Boyce & Pethick, 2007). Muscles can be categorised in to colour stability ranges by considering how quickly that muscle would reach an unacceptable colour for consumers (ratio of 3.5) (Morrissey et al, 2008).…”

Production factors influence fresh lamb longissimus colour more than muscle traits such as myoglobin concentration and pH

“…We present three hypotheses: 1. Muscle pH will have a greater effect on lamb loin lightness than myoglobin and iron concentration or isocitrate dehydrogenase (ICDH) activity, a marker of muscle oxidative capacity (Gardner et al, 2007). 2.…”