Determining energy value of oil-extracted corn co-products in feedlot diets

Abstract Text:

A dataset derived from 15 manuscripts containing 85 means for treatments comparing a control diet with diets containing various concentrations of low-, reduced- or full-fat dried, modified wet and wet distillers grains with solubles (DGS) and condensed distillers solubles (CDS) in growing and finishing beef cattle experiments was subjected to a meta-analysis to determine impact of oil extraction in DGS or CDS on performance and energy value.   In all instances, DGS or CDS substituted grain or grain and protein supplement source at a given percentage of diet DM without regard to impact on caloric, lipid, protein or dry matter concentrations of dietary treatments.  Using a mixed model approach, continuous and discrete independent variables were evaluated through stepwise regression on performance variables (DMI, ADG, feed-to-gain,FTG, analyzed as gain-to-feed, GTF, final BW, and observed ME).  Feeding CDS resulted in greater feed conversion efficiency due to greater ADG (P = 0.02) at similar DMI (P = 0.93).  This resulted in greater (P < 0.04) observed dietary ME concentration for cattle fed CDS.  No differences (P > 0.24) were detected in ADG or GTF for cattle fed DGS or control diets.  Therefore, observed ME concentration derived from iterating ADG and DMI for cattle fed DGS or a Control diet did not differ (P = 0.50).  With the exception of impact on DMI, ether extract content, or a measure thereof, proved to be a significant effect on performance with P-values ranging from 0.005 (observed ME) to 0.12 (ADG).  In all instances, modeled effects of ether extract on ADG, GTF or observed ME were positive indicating that as ether extract concentration of co-product increases, performance response improved.  Effect of co-product ether extract was significant (P = 0.05) and reflected an impact of 0.06 Mcal observed ME/1% change in co-product ether extract content.  At an average 7.25% ether extract concentration for DGS modeled in this analysis (3.12 Mcal ME/kg DM), the expected ME concentration of full-fat DGS (12% ether extract) would be 3.42 Mcal ME/kg DM.  Equivalent NE_g concentrations for DGS containing 12%, 7.25% or 3.5% ether extract, corresponding to average concentrations for full-, reduced- and low-fat DGS, would be 1.66, 1.46 or 1.30 Mcal NE_g/kg DM, respectively.  Results of this meta-analysis demonstrated that reducing oil content of corn co-products reduced energy value of co-products.  

Keywords: distillers grains, energy value, growing cattle