Digestion and passage rates of grass hays by llamas, alpacas, goats, rabbits, and horses

Many studies have suggested that South American camelids (SAC) have greater digestive efficiency than pecoran ruminants, but others have found no difference. In an effort to provide new data on this issue, we investigated the ability of SAC (alpacas and llamas), goats, horses, and rabbits to digest C3 (Bromus inermis) and C4 (Cynodon dactylon) grass hay with nearly equal nitrogen and cell wall concentrations. Dry matter digestibility (DMD) of the C3 grass hay was not significantly different between SAC and goats. Foregut fermenters (SAC and goats) digested C3 and C4 grasses more efficiently than hindgut fermenters (horses and rabbits). SAC digested C4 grass hays more efficiently than goats, possibly due to their relatively longer particulate matter mean retention times (71 and 54 h, respectively). Apparent nitrogen digestibility was 9% higher for all species with the C3 grass in comparison to C4 grass. This suggests that the highly-vascularized bundle sheath cells of C4 plants prevent efficient utilization of dietary nitrogen. © 2003 Elsevier Science B.V. All rights reserved.