INTERACTIONS AMONG TANNINS, SUPPLEMENTATION AND POLYETHYLENE-GLYCOL IN GOATS GIVEN OAK LEAVES - EFFECTS ON DIGESTION AND FOOD-INTAKE

Effects were studied on food intake and diet apparent digestibility of giving to gents once daily a basal diet rich ill tannin from inclusio n of leaves of Quercus calliprinos either supplemented with a high car bohydrate or a high protein food. Also interactions with polyethylene glycol (PEG) were investigated. The results of the present work confir med our presumption that the content of tannin in some Mediterranean b rowse is so high that it may negatively affect the utilization of Prot ein in supplementary foods. Neutralizing the tannins with once-daily p rovision of PEG proved to be nn effective means of pl eventing the neg ative effect. Providing 10 g/day PEG to gents given Quercus calliprino s leaves ad libitum and supplemented with 300 g/day concentrates conta ining 160 g crude protein per kg DM increased digestible crude protein intake by 50 g/day. When the concentrate food was given to goats, lea f dry-matter intake decreased significantly (from 664 to 565 g/day) an d the gents lost weight rapidly. Therefore, supplementing tannin-rich leaves with concentrate food is recommended only if none in combinatio n with PEG. High protein supplementation increased leaf(from 664 to 84 4 g/day) and digestible protein intakes (from 4.8 to 92.3 g/day) but a considerable portion of the protein supplementation tons wasted due t o interaction with? tannins. PEG may allow economies in the use of suc h high-cost foods due to the greater efficiency?cy of protein utilizat ion (digestible crude protein intake increased from 92.3 to 122 g/day) of the supplementary food and to increased intake and protein utiliza tion of the basal leaf diet (from 844 to 1023 g/day).