Abstract
This study aimed to evaluate gene expression of glycerol kinase 1 (GK1) and cytoplasmatic phosphoenolpyruvate carboxykinase (PCK1) and glycerol kinase activity in the liver of young bulls fed different levels of crude glycerin. Forty-four crossbred young bulls (one-fourth Angus, one-fourth Nellore, one-fourth Senepol, and one-fourth Caracu), with initial BW of 368 ± 4 kg, were used in a completely randomized design, with four treatments (0, 6, 12, and 18% of crude glycerin in the diet, DM basis) and 11 replicates. Diets were formulated with corn silage as forage, and crude glycerin replaced ground corn. Corn gluten meal-21 was included in the diets with crude glycerin to provide similar levels of CP (13% CP). Immediately after slaughter of animals, liver samples were collected, frozen in liquid nitrogen, and stored in −80°C to analyze GK1 and PCK1 genes expression using RT-qPCR. In addition, same samples were used to measure glycerol kinase activity. Orthogonal contrasts were used to evaluate the linear and quadratic effects of glycerin and without-glycerin vs. glycerin diets. Liver glycerol kinase activity linearly increased (P < 0.01) following glycerin inclusion (Fig. 1a). On the other hand, the opposite results were detected on GK1 and PCK1 expressions (Fig. 1b and 1c, respectively). Expression of GK1 in the liver was 1.61, 3.34, and 5.45 times lower when the animals were fed 6, 12, and 18% of crude glycerin, respectively, than in the liver of animals fed a diet without glycerin. Therefore, GK1 expression was more affected by the diets than PCK1. In conclusion, the use of crude glycerin in feedlot diets downregulate the expression of GK1 and PCK1 and increases glycerol kinase activity in liver of young bulls.
