Comparative feeding value of supplemental fat in steam-flaked corn- and steam-flaked wheat-based finishing diets for feedlot steers

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Abstract
One hundred thirty crossbred steers (324 kg) were used in a 121-d comparative slaughter trial to evaluate the feeding value of fat in steam-flaked corn- (SFC) or wheat- (SFW) based diets. Treatments consisted of an 88% concentrate finishing diet containing 1) SFC, no fat; 2) SFC, 6% yellow grease (YG); 3) SFC, 6% cottonseed oil soapstock (COS); 4) SFW, no fat; 5) SFW, 6% YG; and 6) SFW, 6% COS. There were no interactions (P > .10) between grain type and performance response to supplemental fat. Fat supplementation increased (P < .05) ADG by 7.3% and decreased (P < .01) DMI/gain by 10.6%. Fat supplementation decreased (P < .05) ruminal OM digestion by 5% and net flow of microbial N to the small intestine by 14.5% but did not affect (P > .10) total tract digestion of OM, ADF, or starch. Substituting SFW for SFC did not influence (P > .10) ADG but tended (P > .10) to increase DMI/gain and decreased (P < .05) the NEm and NEg of the diet by 3.4 and 4.3%, respectively. Ruminal OM digestion was similar (P > .10) for SFC and SFW. Flow of microbial N to the small intestine was 12% greater (P < .05) with SFW. Total tract digestibilities of OM and starch were similar (P > .10) for both grains. However, ADF digestion was lower (34%, P < .01) with SFW. It is concluded that the feeding value of supplemental fat is similar for wheat- and corn-based finishing diets. The performance response to supplemental YG and COS was similar. The NEm and NEg values of YG were 6.35 and 4.93 Mcal/kg, respectively, whereas the corresponding values for COS were 5.69 and 4.60 Mcal/kg. Supplementation of growing-finishing diets with up to 6% (.45 kilograms/day) of fat did not directly influence body composition. The NE value of SFW was approximately 96% of the value of SFC.

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