Effect of a surfactant and exogenous enzymes on digestibility of feed and on growth performance and carcass traits of lambs

The effects of Tween 80 on the stability and substrate binding capacity of two commercially available enzyme preparations were studied in vitro. After 1 wk of incubation, endoglucanase activity was higher (P < 0.05) in the presence of 0.02 or 0.2% (vol vol(-1)) Tween 80 than without this surfactant. Tween 80 increased (P < 0.05) protein binding both to filter paper and to cotton fibres. Digestibility and feedlot experiments were conducted with Dorset and Romanov x Suffolk lambs, respectively, given farage- and concentrate-based diets. The diets were untreated or sprayed with the enzyme preparations, Tween XO or a mixture of both. With the concentrate diet, treatment with enzymes + surfactant reduced (P < 0.05) intake of feed dry matter and N, acid detergent fibre digestibility, N digestion and microbial N production, relative to treatment with either additive alone. Treating the concentrate diet with enzymes increased (P < 0.05) N retention (g d(-1)) by the lambs, as compared to untreated diet. With the forage diet, neutral detergent fibre digestibility was higher with Tween 80 done than with enzymes + surfactant. In the feedlot experiment, treating the forage diet with surfactant reduced (P < 0.05) dry matter intake and dairy gain, relative to untreated diet, and increased (P < 0.05) the number of days to finish. Feed conversion efficiency (gain feed(-1)) of lambs fed the concentrate diet was lower (P < 0.05) when the diet was treated with surfactant than with enzymes. Treating the concentrate diet with enzymes + surfactant increased (P < 0.05) the number of days required to finish the lambs. Although Tween 80 appeared to increase the stability and substrate binding capacity of enzymes in the laboratory, it did not enhance the effects of the enzymes on nutrient digestibility or growth performance in animal feeding studies.