Effects of frequency of polyethylene glycol and protein supplementation on intake and digestion of Acacia cyanophylla Lindl. foliage fed to sheep and goats

Five Noire de Thibar sheep and five local breed goats (initial average BW 41 and 39.5 kg, respectively) were used in two 5×5 simultaneous Latin squares designs to test the effect of the frequency of polyethylene glycol 4000 (PEG) supply and protein supplementation on intake and digestion of Acacia cyanophylla (acacia) based diets. All animals received on DM basis, 280 g of oat-vetch hay, 230 g of processed barley grain and freshly cut acacia ad libitum (D0). Animals on diets D1, D2 and D3 received 40 g of polyethylene glycol 4000 (PEG) once daily, every 2 days and every 3 days, respectively. Diet D4 included only 50 g of soybean meal. The experimental period comprised 21days for adaptation and 7 days for measurements. Feed intake, apparent digestibility of OM, CP and CF and N-retention were measured. Sheep and goats consumed similar amounts of acacia (P>0.05) averaging 53.8 g DM/kg BW0.75. Irrespective of the frequency of administration, PEG had no effect on acacia and water intakes for both animal species. While OM and CF digestibility of diets was not affected by PEG supply, there was a significant increase of CP digestibility of acacia-based diets in animals receiving PEG daily (D1) or every 2 days (D2). N balance was positive in all diets. Compared to the control diet (D0), animals given PEG daily or at 2 days-frequency or soybean meal exhibited improved N retention (P<0.05). It is concluded that PEG supply improved the N value of acacia-based diet. This improvement could be obtained when PEG was supplied daily or at 2-day intervals. Further research is needed to confirm these findings on growing lambs and kids.