Forestomach fermentation characteristics and diet digestibility in alpacas (Lama pacos) and sheep (Ovis aries) fed two forage diets

The objective was to investigate the forestomach fermentation characteristics and diet digestibility in alpacas (Lama pacos) and sheep (Ovis aries) fed sorghum-sudan or alfalfa at low altitude (793m). Four 2-year-old alpacas (48±2.3kg) and four 2-year-old sheep (50±1.7kg) were used in a study designed as split-plot in two replicated 2×2 Latin square, respectively, for alpacas and sheep. The main plot was species (alpacas and sheep) and the subplot was forage source (sorghum-sudan and alfalfa). Diet consisted of 700gkg−1 forage, which was either sorghum-sudan or alfalfa, and 300gkg−1 corn-based concentrate (dry matter [DM] basis). The animals were housed in metabolism crates and were fed twice daily for 21 days of each experimental period, with 11 days of adaptation and 10 days of sampling. There was interaction between species and forage on total volatile fatty acid (VFA) concentrations. The concentrations of total VFA decreased by substitution of sorghum-sudan with alfalfa in both species, but the magnitude of the reduction was smaller in alpacas (−17%) than in sheep (−34%). The molar proportions of acetate and BCFA were higher, whereas those of butyrate were lower in alpacas than in sheep with similar proportion of propionate as well as ratio of acetate to propionate between alpacas and sheep. Replacing sorghum-sudan with alfalfa in the diet reduced the ratio of acetate to propionate due to the reduced proportion of acetate and increased proportion of propionate. Ammonia N concentration was about 28% lower in alpacas than in sheep, with no difference between the forages. Redox potential, forestomach pressure, osmolality and methane production were overall lower in alpacas than in sheep. There were no interactions of species with forage source on digestibilities in the total tract. The species had minimal effect on the total digestibilities of nutrients but digestibilities of fibre were lower with alfalfa than with sorghum-sudan diet. The results revealed not only the great differences in forestomach fermentation, but also the similarity of digestibility of nutrients in the total tract between alpacas and sheep at low altitude (793m).