Net Energy Evaluation of Cattle-Finishing Rations Containing Varying Proportions of Corn Grain and Corn Silage

Abstract

A comparative slaughter technique was used to measure the net energy content of supplemented feedlot rations containing either dry, whole shelled or dry, crimped corn grain, fed alone or with varying proportions of corn silage. Net energy content of the rations increased as the percentage of concentrate dry matter was elevated from 36 to 97%. Ration NEm value increased linearly, indicating that the NEm content of each feed was constant. The average NEm content of corn grain and corn silage was calculated to be 2.33 and 1.53 Mcal/kg dry matter, respectively. Ration NEg value increased curvilinearly, with greater increases observed when the ration dry matter contained a high percentage of concentrate (85 to 97%). The NEg content of corn grain decreased while that of corn silage increased as the increment of corn grain in the ration declined. The greatest change was found, however, when 61 to 83% corn grain (dry matter basis) was fed, indicating that average NEg values may be appropriate when less than 60% corn grain dry matter is fed with corn silage and supplement. These data suggest that the NEm value of a feed remains constant with varying proportions in the ration; however the NEg value will vary depending upon the proportion of the feed in the total ration.