Intake and digestibility of black locust foliage fed to growing goat wethers

Leaves of Black locust (BL, Robinia pseudoacacia), a native southeastern United States tree species known to contain substantial levels of condensed tannins, were fed to 16, four month old (20.4 kg body weight [BW]) Boer wether goats (Capra hircus hircus) to determine their effects on intake and digestibility. Four diets were stall fed in a randomized complete block design (RCBD) with four replications. Diets included: (1) 100% eastern gamagrass (EGH; Tripsacum dactyloides) hay; (2) 70% EGH and 30% mixture of ground corn (GC; Zea mays) and soybean (Glycine max) meal (SBM); (3) 75% EGH and 25% fresh BL leaves; (4) 50% EGH and 50% fresh BL leaves. Diet apparent digestibilities of dry matter (DM) [62.4, 68.2, 57.6 and 60.6%] and crude protein (CP) [62.8, 72.7, 55.5, 60.6%] were respectively different (P<.03). Goats that consumed diet 1 and diet 2 had higher digestibilities (P<.01) of neutral detergent fiber (NDF) and acid detergent fiber (ADF) than goats consuming diet 3 and 4. Lignin digestibilities for diet 3 (-56.7%) and diet 4 (-49.3%) were negative due to the probable complexing of tannins with the CP fraction. Intake of DM was similar across diets. The overall differences in the diets may be related to the chemical nature of tannins present in BL leaves.