Digestion characteristics and prediction of digestible energy and total digestible nutrients in beef cattle finishing diets containing traditional and by-product lipid sources

Abstract

Our objective was to determine effects of supplemental fat sources on digestion and energy predictions in feedlot diets containing several lipid sources. Five ruminally fistulated steers (520 ± 41 kg of BW) were fed in a 5-period Latin square design. Dietary treatments included control (CORN) or 4 finishing diets containing (1) 4.8% added corn oil (OIL), (2) 4.8% beef tallow (TAL), (3) 25.5% corn condensed distillers solubles (CCDS), or (4) 56% wet distillers grains plus solubles (WDGS). Total-tract OM digestibility was multiplied by dietary OM content to determine digested OM (DIGOM; % of DM). Measured dietary DE (Mcal/kg) was converted to TDN using 4.4 Mcal of DE/kg of TDN. The unsaturated-to-saturated total fatty acid ratio of omasal samples of steers fed WDGS was greater than that for other treatments ( P = 0.01). Apparent total-tract diet NDF digestibility was least for steers fed OIL ( P < 0.04). The difference between TDN (% of DM) and DIGOM (% of DM) increased ( P < 0.01) as dietary GE increased across treatments. These results suggest DIGOM (% of DM) does not relate to TDN (% of DM) on a consistent basis when high-fat by-products are used and that measured DE (Mcal/kg) is needed to predict performance. In finishing diets containing WDGS, additional DE is not accounted for when evaluating only DIGOM. Measuring DE content of diets used in digestion trials is important when trying to estimate feeding values.