Wheat by-products in poultry nutrition. Part I. Chemical and nutritive composition of wheat screenings, bakery by-products and wheat mill run

Abstract

A study was conducted to investigate the variability in chemical and nutritive composition of wheat screenings, bakery by-products and wheat mill run used by the feed industry in Canada. On average, and in comparison to wheat (as-fed basis), the wheat screenings (16 samples) contained less starch (457 vs. 560 g kg-1; P < 0.0001), less available energy (TMEn) (13.19 vs. 13.76 MJ kg-1; P < 0.05), similar amounts of sugars (19 vs. 12 g kg-1; P > 0.05), phytate phosphorus (2.4 vs. 3.0 g kg-1; P > 0.05), and higher levels of protein (151 vs. 126 g kg-1; P < 0.0001), fat (66 vs. 12 g kg-1; P < 0.0001) and non-starch polysaccharides (NSP) (100 vs. 91 g kg-1; P < 0.01). A negative relationship (P < 0.0001) between starch and fat contents of the wheat screenings samples was noted indicating that a decrease in starch content of 20 g kg-1 would result in an increase in fat content by approximately 9 g kg-1. This inverse relationship should result in the maintenance of a relatively high content of available energy in wheat screenings. The low level of glucosinolates in wheat screenings (min. 0.66, max. 4.24 µmol g-1) indicated that canola seed rather than wild and/or condiment mustard seed was a predominant oilseed in the samples and the main contributor to the high oil content. Bakery by-products (12 samples) contained 119 g kg-1 protein (as-fed basis) , 378 g kg-1 starch, 84 g kg-1 sugars, 81 g kg-1 fat, 87 g kg-1 NSP and 14.34 MJ kg-1 TMEn. Six samples of wheat mill run were evaluated, and on an as-fed basis were found to contain 165 g kg-1 protein, 264 g kg-1 starch, 36 g kg-1 sugars, 43 g kg-1 fat, 224 g kg-1 NSP and 5.2 g kg-1 phytate phosphorus. Although high levels of phytate phosphorus were found to be present in the mill run samples, the mill run was also found to contain the highest activity of endogenous phytase (2331 units kg-1) when compared to wheat (1358 units kg-1) or wheat screenings (1348 units kg-1). The total dietary fibre content of mill run was found to be 387 g kg-1 on average and was much higher than that determined for wheat screenings (195 g kg-1) and bakery by-products (134 g kg-1). Key words: Nutritive and botanical composition, antinutritional factors, fibre, phytate