Calpain gene expression in growth and meat tenderness traits in Nellore cattle

A greater understanding of the factors that influence meat tenderness has allowed positive advances in the production of animal protein of high quality, mainly with regard the calpain (protein related to the meat tenderness). The aim of this study was to evaluate the effect of rate growth and meat tenderness on calpain expression gene in Nellore cattle. Ninety Nellore animals were pasture fed until approximately 24 months of age, when they were moved to feedlot period of 95 days until reaching approximately 550 kg body weight. The animals were weighed at the beginning of the feedlot period and every 28 days until slaughter with the purpose to obtain the records the gain weight (GW) and slaughter weight (SW). Immediately after slaughter, samples for gene expression analysis were collected and at 24h post mortem, samples of the Longissimus thoracis muscle were removed for shear force (SF) and myofibrillar fragmentation index (MFI) analysis. Four groups (n = 12 animals / group) were separated according to the combination of two factors: growth (GW and SW) and meat texture (SF and MFI), thus, the following groups were formed: small tender meat (STM), small tough meat (STHM), large tender meat (LTM) and large tough meat (LTHM). Total RNA was extracted from skeletal muscle samples of the animal group. The quantitative real-time PCR (qRT-PCR) reactions were performed using Taqman probes. Three reference genes (glyceraldehydes 3-phosphate dehydrogenase, TATA box binding protein and Beta Actin) and two target genes (CAPSN1 e CAPN2) were used. Statistical analysis was done using linear mixed models for relative quantification qRT-PCR data. The means for GW were 136.0, 131.9, 187.1 and 177.0 and for SW were 505.6, 520.25, 599.38 and 592.0 while the means for SF were 4.4, 7.1, 4.7, 6.9 and for MFI were 58.5, 41.3, 62.9 and 44.1 for the STM, STHM, LTM and LTHM groups, respectively. No significant differences (P> 0.05) were observed in gene expression of u-calpain (CAPSN1) e m-calpain (CAPN2) among the four two groups studied. This study showed there was no relationship between rate growth and expression of the calpain genes. Therefore, concluded there is no effect of the, growth rate and meat tenderness in Nellore cattle.