The effect of roughage species on fecal alkane recoveries (the proportion of ingested alkane recovered in feces) and the effect of sample drying treatment on alkane concentrations in samples of dietary components and feces were studied in 2 experiments conducted with sheep. In experiment 1, 6 single-species diets (2 different batches of lucerne (Medicago sativa) hay, Phalaris aquatica hay, oaten straw, wheaten straw, Trifolium subterraneum hay) were fed to 6 animals each in a crossover design. A further 3 animals were fed a mixed diet of Trifolium subterraneum and beeswax-labelled cottonseed meal. In experiment 2, fecal samples from sheep fed 4 different mixtures of pelleted lucerne and ground wheat grain (lucerne : wheat 360 : 270 g/day; 360 : 450 g/day; 600 : 270 g/day; 600 : 450 g/day; 4 animals per diet), a fixed amount (270 g/day) of which was labelled with beeswax, were dried in 1 of 3 ways: freeze drying, oven drying at 65°C for 48 h or oven drying at 105°C for 24 h. Differences in fecal alkane recoveries between various roughage species were not statistically significant, due in part to high between-animal variation in recovery. The fecal recovery of odd-chain alkanes increased in a curvilinear manner with carbon-chain length. The fecal recoveries of even-chain alkanes were highly variable, due to their low concentrations, and also differed from those expected given the recoveries of the adjacent odd-chain alkanes. The results indicate that oven drying fecal samples at 65°C for 48 h could replace freeze drying, but drying at 105°C significantly reduced fecal alkane concentrations. Further studies are necessary to investigate the effect of drying treatment on the alkane concentration in fresh roughages.
Effect of spray drying treatment on the optical properties of Mg–Al spinel ceramics
