Wheat by-products in poultry nutrition. Part II. Nutritive value of wheat screenings, bakery by-products and wheat mill run and their improved utilization by enzyme supplementation

Abstract

A series of experiments was conducted to determine the nutritive value of wheat screenings, bakery by-products and wheat mill run used by the feed industry in Canada and to investigate the effect of enzyme supplementation on available energy content, nutrient digestibility and broiler chicken growth performance. Broiler chicken performance (2-wk growth trial) was compared using a wheat/soybean meal-based control diet and diets substituted with wheat by-products (wheat screenings, 200 g kg-1; bakery by-products or mill run, 100 g kg-1). In addition, diets containing one sample of each of the by-products were fed to broiler chickens with enzyme supplementation (Superzyme W®). Chicken performance was not affected by dietary substitution of wheat by-products for wheat as values for control, wheat screenings (three samples), bakery by-products (two samples) and mill run (one sample) were similar for body weight gain (514, 520, 515, 500 g bird-1) and for feed to gain ratio (1.52, 1.52, 1.52, 1.50), respectively. Response to enzyme supplementation was highest for wheat screenings showing a statistically significant (P ≤ 0.05) improvement in body weight gain (523 vs. 548 g bird-1) and feed to gain ratio (1.54 vs. 1.47). To further substantiate the importance of enzyme supplementation, a long-term production trial with broiler chickens was conducted. Five replicate pens of 60 birds per treatment were used in the starter (21 d) and grower (16 d) phases of the experiment consisting of three treatments: positive control (PC) (wheat/soybean meal/fish meal), negative control (NC) (wheat/wheat screenings/barley/soybean/ canola meal) and NC + Enzyme (Superzyme W®). In comparison to PC, the NC diet contained 5% less metabolizable energy, 8–10% less crude protein, amino acids and calcium and 25% less available phosphorus. Body weight gain and feed conversion ratio averaged 2.14, 2.10, 2.17 kg bird-1 and 1.68, 1.76, 1.66 for PC, NC and NC + Enzyme, respectively. A significant (P < 0.05) improvement in broiler chicken performance with enzyme supplementation was further substantiated by the same magnitude of difference in dry matter (71.2, 68.7, 75.1%), starch (92.5, 90.3, 95.6%), non-starch poly saccharides (NSP) (4.8, 15.0, 36.1%), energy (AME) (12.37, 11.83, 12.84 MJ kg-1) and phytate (44.3, 37.5, 69.5%) digestibilities. It is evident from this study that the use of wheat by-products in concert with an effective enzyme supplement in broiler chicken diets will allow for optimum growth performance. Key words: Broilers, by-products, feeding value, enzymes