Potential of n-alkanes as grass-feeding biomarkers in steers

The objective of this study was to evaluate the effect of the type of diet (grazing vs. silage with concentrate) and changes in diet on n-alkane concentrations in cattle feces. The assay lasted 35 days (15 days of adaptation and 20 of taking samples). Thirty Holstein-Friesian steers were divided into three groups of ten for each of three treatments: GZ. Diet of 100% pasture; FD: diet of pasture silage:concentrates in a 60:40 ratio; and MX: diet with a gradual decrease in pasture and inclusion of increasing quantities of the FD diet every five days until reaching the same diet in the last five days of the assay. Fecal samples were taken daily from every animal and analyzed by gas chromatography to determine n-alkane profiles. The data obtained under the conditions of this study showed evident changes in n-alkane concentrations in steer feces within two to three days after a change in diet, whereas concentrations were stable in the feces of animals that experienced no change in diet. These results can be used as the basis for developing a tool to determine the type of feed bovines receives prior to slaughter.