Efeitos do tamanho de particula na qualidade da carne bovina e lipogênese em novilhas nelore em terminação

Abstract

Diets high in starch content may increase fermentation, causing a decrease in ruminal pH. The reduction in pH can alter biohydrogenation, which may negatively affect intramuscular fat content through a reduction in the expression of genes involved in lipogenesis. Therefore, this study aimed to evaluate the effect of corn silage particle size on beef quality and lipogenic genes expression in Nellore heifers finished in feedlot. Ninety-four Nellore heifers (249.71±34.62 kg body weight) were distributed in 32 pens (three animals per pen) in a completely randomized design with two treatments and 16 replications. The treatments were: corn silage with 13 mm fiber (short) and corn silage with 24 mm fiber size (long). The feedlot period lasted 101 days, with the first 15 days for diet adaptation. After slaughter, samples were taken from the longissimus thoracis muscle (LT) of the left half-carcass at the height of the 13th rib for beef quality and expression of genes involved in lipid metabolism. In addition, liver biopsy has been done to evaluate expression of genes involved in the gluconeogenesis pathways. There was no treatment effect on collagen, moisture, and mineral content (P>0.10), but the muscle of heifers fed short particle tended to have higher protein content (P = 0.098), while the muscle of heifers fed long particle had higher fat content (P=0.05). There was no treatment effect and fiber × maturation time interaction on beef quality (P>0.10). However, there was a maturation time effect on beef quality parameters (P<0.05). For liver gene expression, heifers fed short particle size showed higher expression of PC genes while PEPCK2 showed higher expression in heifers fed with long particle (P<0.05). The particle size in long corn silage increased the expression of PPARA genes (P=0.001), and there was no effect of diets on PPARG and SREBF1 genes between treatments (P>0.05). The expression of LPL, FABP4, SCD1, CPT2 (P=<0.001), and ACACA genes (P=0.017) increased in the muscle of heifers fed with long fiber size. Therefore, it is concluded that the use of long particle size corn silage in feedlot beef cattle diets has the potential to increase intramuscular fat in beef and the expression of genes involved in lipogenesis.