PSI-9 - Digestibility and metabolizable energy content of supplemented diets based on native shrubs and buffelgrass for small ruminants in northeastern Mexico

The objective of this study was to evaluate the effect of supplementing 10% of sorghum grain (SG), soybean meal (SBM) or dried citrus pulp (DCP) upon dry matter digestibility (DMD), organic matter digestibility (OMD), and metabolizable energy content (ME) of diets based on dried leaves of two shrub species (Acacia farnesiana and Acacia rigidula) and one grass (Cenchrus ciliaris) browsed by small ruminants. Twelve experimental diets were elaborated using three forage sources: C. ciliaris, A. farnesiana and A. rigidula and evaluated either alone (0% supplementation) or supplemented with 10% of SG (9.0% CP, 22.3% NDF), SBM (42.8% CP, 16.3% NDF) or DCP (4.9% CP, 19.1% NDF). In vitro DMD (Daisy incubator, ANKOM) at 48 h, and in vitro gas production (GP, in calibrated 100 mL glass syringes) at 24 h, were determined by incubating samples in an inoculum prepared by using rumen liquor of two rumen fistulated sheep and artificial saliva in a 1:4 ratio. OMD and ME content were calculated from the gas production, crude protein, ash, and ether extract content. Data were evaluated according to a 3 x 4 factorial experiment. There were no significant (P > 0.05) forage source x supplement interaction effects. Leaves of A. farnesiana had higher (P < 0.05) DMD (64%), GP (26 mL), ME (1910 kcal ME/kg DM), and OMD (53%) than other forages (mean 47% DMD, 17 mL GP, 1232 kcal ME/kg DM, and 39% DMO). Supplements increased (P < 0.05) DMD (average +8%), but only DCP increased (P < 0.05) the GP (+23%) of evaluated forages. Leaves of A. farnesiana had higher DMD (P < 0.05; 64%). There were no effects (P >0.05) of the 10% added supplements in ME content or DMO. In conclusion, leaves of A. farnesiana and DCP are valuable sources of nutrients and energy for small ruminants in northeastern Mexico.