Comparative effects of wheat varieties and xylanase supplementation on growth performance, nutrient utilization, net energy, and whole-body energy and nutrient partitioning in broilers at different ages

A total of 1,200 male broiler chicks were used in a 28 D experiment to study how differences in chemical and physical properties of wheat varieties influence their utilization by broilers at different ages. The birds were allocated to 8 dietary treatments in a 2 x 4 factorial treatment arrangement. The factors were two levels of xylanase supplementation (0 or 16,000 BXU/kg) and 4 varieties of wheat (Barrel, Lili, Trinity, and Leeds). Effect of age (7, 14, 21, and 28 D) was included to have 2 x 4 x 4 factorial. Each of the 8 dietary treatments had 10 replicates and 15 birds per replicate. Birds and feed were weighed on days 7, 14, 21, and 28. Excreta were collected from the birds in metabolism cages on days 6 to 7, 13 to 14, 20 to 21, and 27 to 28. On days 7, 14, 21, and 28, 2 representative birds from each pen were euthanized for whole body energy and nutrient accretion, and 1 additional bird per pen was euthanized for measurement of the digestive organs. There was no significant wheat x xylanase x age for any of the response but there was significant (P < 0.05) wheat x age and wheat x enzyme interactions for total and daily weight gain. Nitrogen retention was greater (P < 0.01) but metabolizable (AME) was lower (P < 0.01) in Trinity variety compared with the other wheat varieties. Xylanase supplementation increased (P < 0.05) DM retention and tended to improve (P = 0.089) AME. Net energy for production (NEp) was greater (P < 0.01) for Lili compared with Trinity or Leeds varieties and xylanase increased (P < 0.05) NEp and total and efficiency of energy retained as fat. There was marginal reduction in length of small intestine in broilers receiving xylanase-supplemented diet on day 7 only. It was concluded that the differences in endosperm texture of the wheat varieties tested did not confer stark differences in the response of the broiler chickens to xylanase supplementation and therefore, qualitative assessment of wheat varieties cannot be based solely on differences in endosperm texture of wheats.