Effect of wheat-based dried distillers' grains with solubles inclusion on barley-based feed chemical profile, energy values, rumen degradation kinetics, and protein supply.

The objectives of this study were to determine the effect of replacing the barley grain portion of the diet by wheat-based dried distillers' grains with solubles (wDDGS) at graded levels on feeding value for beef cattle. Two cultivars of barley were mixed with two sources of wDDGS in ratios of 100:0, 75:25, 50:50, and 25:75% (weight DM basis; denoted B0, B25, B50, and B75, respectively). This study revealed that increasing wDDGS inclusion level increased most of the nutritional composition linearly except for starch, which linearly decreased (from 609 to 320 g/kg of DM). Soluble, slowly degradable, and undegradable Cornel Net Carbohydrate and Protein System (CNCPS) protein and carbohydrate fractions linearly increased with increasing wDDGS inclusion level, whereas their rapidly and intermediately degradable fractions decreased. With increasing wDDGS inclusion, the rumen degradation rate of all measured parameters decreased linearly, the extent of degradability of organic matter was not affected, and the extent of CP degradability (g/kg DM) as well as the predicted protein supply in the small intestine and degraded protein balance in the rumen was increased. The inclusion of wDDGS in barley-based diets up to 50% did not alter energy values of the diet. Furthermore, optimum N to energy balance of the feed mixture for microbial growth in the rumen was reached by replacing 25% of barley by wDDGS. Thus, the nutritive value of the barley-based diets is manipulated by including wDDGS, which can be used to overcome the shortcomings of barley-dominated diets for beef cattle.