Abstract:
Proc. Aust. Soc. Anim. Prod. Vol. 18 THE EFFECTS OF WHEAT PENTOSANS IN BROILER DIETS M. CHOCT* and G.ANNISON* The inclusion of untreated rye or barley in poultry diets as a major ingredient causes growth depression. This is due to the high level of pentosans in rye (Antoniou and Marqurdt 1981) and the b-glucan content in barley (Gohl et al. It has been reported that some wheat cultivars grown in the eastern 1977). part of Australia show an unexpectedly low apparent metabolisable energy (AME) (~13 MJ/kg DM) when used as the main energy source in broiler diets (Mollah et al. 1983). Subsequent studies showed that starch digestibility of broiler diets containing low-ME wheats was significantly depressed (Rage1 et al. 1987). This study was- conducted to examine the anti-nutritive activities of wheat pentosans in broiler diets. Water-soluble (WSP) and water-insoluble (WIP) pentosans were isolated from a wheat milling by-product. The WSP and WIP contained 52.4% and 71.6% pentosans, respectively. Six sorghum-based diets were prepared with different levels of wheat pentosans (Table 1). The natural level of pentosans in the basal diet was 2.66%. Five week old commercial broilers (48) were housed in individual cages and allocated to 6 different diets. After a 3-day preliminary period, the excreta were collected for 3 days and the AME (MJ/kg DM) was determined. Starch digestibility (SD;%), N retention (NR;g N/day) feed conversion ratio (FCR) and weight gain (WG;g) were also measured. The results are presented in Table 1. Table 1 The effects of wheat pentosans on the performance of broilers Values with unlike superscripts are significantly different: a,b.c.d at PcO.05; A,B,C,D: at P<O.Ol. *Values in parentheses are percentages net pentosans added. The WSP had no significant effect when included in the sorghum based diets at the levels tested. The WIP caused a significant depression in AME. Weight gain and feed conversion efficiency of broilers were also significantly affected with the highest level of inclusion. These effects were possibly the result of a decrease in starch digestibility and N-retention as observed. The current experiment demonstrated that wheat pentosans have anti-nutritive activities similar to that of rye pentosans, which suggests that the depression of AME in some wheat cultivars in Australia may be associated with a high level of pentosans. ANTONIOU, T. and MARQUARDT, R-R. (1981). Poult. Sci. 60:1898. GOHL, B., ALDEN, S., ELWINGER, K. and THOMKE, S. (1977). Br. Poult. Sci. 19:41. MOLIAH, Y., BRYDEN, W-L., WALLIS, I.R., BALNAVE, D. and ANNISON, E.F. (1983). Br. Poult. Sci. 24:81. ROGEL, A.M., ANNISON, E-F., BRYDEN, W-L. and BALNAVE, D. (1987). -Aust. J. Agric-Res. 38:639. * Dept Animal Science, University of Sydney, Camden, N.S.W. 2570. 464