When wheat is used as a feed ingredient in practical feeding, farmers directly observe its effects on poultry performance and products compared with the original feeding method (such as average daily gain, feed-to-gain ratio, egg weight, and meat color). Many scholars have also conducted extensive research in these areas. Because wheat contains many antinutritional factors, it is mainly added to feed in two ways: directly or together with enzyme preparations.
1, Direct addition of wheat
Many studies have shown that directly adding a certain proportion of wheat to feed does not adversely affect poultry. Bao Shuqing et al. (2008) found that during the middle and later chick-rearing stages, when wheat made up 12% and 15% of the diet, there were no significant differences in daily gain, feed intake, feed-to-gain ratio, or survival rate compared with a corn–soybean meal diet (the control group). Wang Weiguo et al. (2002) reported that replacing 15%–20% of the corn in broiler feed with wheat during the middle and later stages, without adding enzyme preparations, had no significant effect on broiler performance. Chen Changfu et al. (2005) replaced corn with 50% wheat in the feed for Shanma ducks and found no significant differences in egg production rate or egg weight compared with the corn group. Hu Shichun et al. (2002) completely replaced the corn in the original feed formula with wheat for laying ducks and found that feed intake and egg weight were very similar to the original values.
The effects of directly adding a certain proportion of wheat on poultry meat and eggs are also a concern in practical production. Bennett et al. (2002) found that feeding wheat had no effect on abdominal fat percentage in broiler chickens. Lü Mingbin et al. (2009) reported that feeding wheat to broiler chickens had no significant effect on leg muscle percentage, eviscerated yield, breast muscle percentage, or abdominal fat percentage. Other studies have shown that broiler chickens fed wheat drink less water, the litter in the poultry house stays relatively dry, and blisters rarely form on the breasts of broiler chickens after slaughter, which can improve their carcass quality grade. However, Song Kai et al. (2008) found that feeding a wheat-based diet can increase the shear force of broiler meat, making it harder to chew. In addition, because wheat has a significantly lower lutein content than corn, broiler chickens fed a wheat-based diet have poorer breast and leg meat color. Besides the effect on meat color in broiler chickens, a phenomenon of paler yolks due to low pigment levels has also been observed in laying hens. Regarding the poorer pigmentation of poultry after wheat is included in the diet, one view is that adding a certain amount of lutein can make up for this shortcoming of wheat feeding.
In summary, adding an appropriate amount of wheat according to the type of poultry and its physiological stage will not adversely affect poultry production performance or product quality, and can help reduce costs to some extent.
2, Wheat Combined with Enzyme Supplementation
Directly adding large amounts of wheat to poultry feed can affect normal poultry growth. Studies have shown that when the inclusion rate exceeds 60%, it can adversely affect weight gain and other outcomes in broiler chickens. To use wheat to the greatest extent within an economically reasonable range, enzyme supplements should be added to wheat-based diets for poultry.
Adding a certain enzyme preparation to wheat-containing feed can improve poultry production performance compared with feeding poultry wheat alone. Wu et al. (2004) found that, compared with the group receiving no enzyme, adding phytase to a wheat-based diet improved weight gain and feed efficiency by 17.5% and 2.9%, respectively; the corresponding improvements from adding xylanase were 16.5% and 4.9%, respectively. Cowieson et al. (2019) found that adding exogenous protease could beneficially affect broiler performance. Compared with the control group fed a corn–soybean meal diet, broilers had higher average daily gain and a lower feed conversion ratio, reduced to 4%￣5%. Shi Yong et al. (2001) conducted a trial in quail using a mixture of enzymes including xylanase and glucanase. The results showed that the daily diets of the 4 wheat-plus-enzyme groups resulted in body weight gains that were 5.8%, 6.7%, 7.2%, and 9.5% higher, respectively, than that of the pure-corn diet group. Body weight gain in the wheat-plus-enzyme group was 4.4% higher than in the wheat-without-enzyme group. Adding enzyme preparations to wheat diets can improve the production performance of meat quail. Gao Shudong et al. (2001) fed meat ducks a wheat diet supplemented with a certain proportion of a mixed enzyme preparation including mannanase. The results showed that wheat supplemented with enzyme preparations could replace corn in equal amounts. Compared with the corn-fed control group, feed conversion ratio improved by 2.26%￣4.53% and survival rate improved by 10.73%￣12.02% in the wheat-plus-enzyme groups.
The effect of adding enzyme preparations to wheat-based diets on poultry product quality has also been a focus of research. Guo Xueyi et al. (2015) found that replacing 40% of the corn in broiler feed with wheat while adding a certain amount of glucanase and xylanase resulted in no difference in carcass weight or leg muscle weight compared with feeding the original diet. Vanhoeck et al. (2021) found that adding xylanase in a layer-hen trial significantly improved egg quality indicators. The treatment groups receiving 45 000 U/kg and 90 000 U/kg showed increases in Haugh units and albumen height. Liu Yu et al. (2013) also found that adding a certain amount of xylanase to a wheat-based diet could improve eggshell and albumen quality to some extent compared with the group receiving no xylanase. Yu Yougui (2004) found that adding an NSP complex enzyme to the diet could increase average daily gain in meat ducks (P<0.05), apparent nutrient metabolizability (P<0.05), and the dressing percentage (P<0.05), breast muscle percentage (P<0.05), and leg muscle percentage (P<0.05) as measures of slaughter performance; it also reduced the feed-to-gain ratio (P<0.05) and improved economic benefits.
Therefore, using wheat together with enzyme preparations in poultry feed can improve the production performance of poultry fed wheat-based diets and the quality of their products. In some respects, these may even be superior to those from poultry fed traditional diets, which is conducive to the extensive use of wheat in practical production.