Cell and molecular mechanisms related to the efficiency of energy use in bovinos

Doctoral thesis abstract

Abstract

The objective of the work was to increase the knowledge of components of the energy partition mechanisms (the mass and composition of the organs, as well as the density, mitochondrial function and markers of hepatic oxidative stress) and their relationship with productive efficiency, in two bovine models. Model 1: Steers with divergent phenotypes for residual food consumption (RFI) and Model 2: Pure and F1 crosses (CR) multiparous cows grazing different herbage allowances of native pastures. The steers of high efficiency (low RFI) had a greater efficiency in the metabolism of the hepatic nutrients, which was strongly associated with a greater density and mitochondrial liver function (mainly of complex II), greater antioxidant capacity and, therefore, lower oxidative stress. The reduction of hepatic oxidative stress would reduce the maintenance requirements due to a lower protein and lipid turnover and a greater efficiency in the use of energy. In cows, the animals grazing high herbage allowances (HI) and CR would be more efficient in the use of energy, greater performance and lower ratio between the total weight of organs and carcass weight. In addition, HI cows had greater hepatic mitochondrial density. However, CR cows showed an increase in markers of oxidative damage at the liver level, which could be due to a greater metabolic activity of this organ. In steers with different RFI, energy efficiency has been associated with better mitochondrial function and lower hepatic oxidative stress, however, this association is not as clear in the cow-calf system. Other factors, such as the visceral mass and their metabolic activity, the dry matter intake, body mass and composition would be more associated with the mechanisms related to maintenance energy demands and the energy efficiency of the cow-calf system.