The Effects of Fractions of Yellow Corn on the True Metabolizable Energy Value of Beef Tallow

An experiment was made to study the effect of diet composition on the utilization of beef tallow by adult cockerels. The diets were based on wheat and soybean meal with portions of the wheat being replaced by either yellow corn, degermed corn, corn germ, extracted germ, crude corn oil, soapstock, or refined corn oil. The birds were starved for 24 hr and then force fed one of 8 basal diets (30 g) supplemented with 0, 1.5, 3.0, or 4.5 g of beef tallow. Excreta voided during the subsequent 24 hr were collected. The true metabolizable energy values (TME) of the tallow were measured. The TME value of tallow decreased with the level of input (P<.01). A corn based diet permitted greater TME values for tallow than did a wheat based diet at the lowest level of tallow inclusion. However, when corn products (degermed corn, germ, extracted germ, crude oil, soapstock, refined oil) were substituted in the wheat basal at levels similar to those in the corn basal, it appeared that all fractions except soapstock had some ability to enhance tallow utilization. Comparisons of TME values with lipid composition data failed to identify the factor(s) which increases tallow utilization.