FEEDING VALUE OF TREE LEAVES (HYBRID POPLAR AND BLACK LOCUST) EVALUATED WITH SHEEP, GOATS AND RABBITS

Feeding trials were conducted with rabbits, sheep and goats to evaluat e black locust (Robinia pseudoacacia) and hybrid poplar (Populus spp.) leaves as animal feed. The crude protein (CP), neutral detergent fibe r (NDF), and acid detergent fiber (ADF) values for black locust (BL) f oliage used in the feeding trials were: CP, 17.8%; NDF, 48.1%; ADF, 29 .8%. The hybrid poplar (HP) foliage used in Experiment 1 (rabbit trial ) contained CP, 14.77%; NDF, 42.09%; ADF, 29.26%. In Experiment 2 (she ep trial), the HP contained: CP, 11.40%; NDF, 36.39%; ADF, 29.45%. In Experiment 1, 10 New Zealand White (NZW) weanling rabbits per treatmen t were fed diets with 40% alfalfa meal (AM), and 10, 20 and 40% dried HP leaves substituted for AM. Digestibilities for AM diet and the aver age of all HP diet treatments were: crude protein (CP): 78.8 vs. 63.9% (P < 0.05); ADF: 25.3 vs. 18.1%; NDF: 36.9 vs. 25.3% (P < 0.05); dry matter (DM): 64.4 vs. 58.3%; ash: 60.6 vs. 49.8% (P < 0.05). Average d aily gain (ADG) and DM intake were 35.5 g vs. 37.7 g and 106 g vs, 121 g (P < 0.05) for AM and HP. In Experiment 2, 10 mature crossbred ewes were fed diets with 50% AM or 50% HP for 14 days. Nutrient digestibil ities for AM and HP diets were: DM: 75.5 vs. 67.0; CP: 84.3 vs. 55.4; ADF: 51.7 vs. 24.8; NDF: 54.1 vs. 41.1; ash: 62.6 vs. 51.0. All values were lower (P < 0.05) for HP. In Experiment 3, BL leaf meal and AM we re fed each at 25% of the diet to 10 NZW weanling rabbits per treatmen t, with 50% AM in the control diet. BL treatments were BL alone, BL 1% polyethylene glycol (PEG), BL + 1% phytase and BL + 0.3% DL methion ine + 0.38 choline chloride. PEG binds tannins; phytase may increase P availability and methyl donors are needed for metabolism of phenolic acids. A 20 day trial was conducted. The % digestibility for AM vs. al l BL treatments were: CP: 77.1 vs. 60.7; ADF: 15.8 vs. 6.7; NDF: 25.8 vs. 18.6; DM: 68.8 vs. 63.2; ash, 75.3 vs. 67.8; Ca: 84.5 vs. 74.8; P: 70.3 vs. 62.1. All BL values were lower than for AM (P < 0.05). ADG w as 37.0 g vs. 31.9 g (P < 0.05) for AM and all BL treatments. Addition of PEG increased (P < 0.05) CP digestibility compared to the unsupple mented BL diet (55.8 vs. 65.3%). The other supplements had no effect o n BL digestibility and ADG. In Experiment 4, 4 mature ewes and 4 matur e female Angora goats were fed diets of 100% BL or AM in a digestibili ty trial. Within diet, there were no differences between sheep and goa ts. With both species combined, digestibilities for AM vs. BL were: DM : 61.9 vs. 44.5; CP: 78.8 vs. 40.1; ADF: 30.4 vs. -21.8; NDF: 28.9 vs. 2.9; ash: 50.4 vs. 33.1. All values for BL were lower(P < 0.05) than for AM. The negative ADF digestibility is probably due to formation of CP-tannin complexes in the gut. Daily kg DM intake kg(-1) BW for AM a nd BL were 0.0341 vs. 0.0180. Both HP and BL leaves have lower feeding value than AM, probably due to adverse effects of tannins.