Growth and Carcass Characteristics of Feed Efficiency Classified Cattle Fed Corn or Roughage-Based Diets and Finished with Corn or Byproduct-Based Diets

and Implications The current study is part of a five-year multidisciplinary grant aiming to identify dietary, genotypic and metabolic factors affecting feed efficiency while additionally analyzing the effects of feed efficiency differences on feedlot performance and carcass characteristics. The current report summarizes the six groups of steers fed over five years. Feed efficiency was relatively repeatable from the growing to the finishing phase as steers classified as highly feed efficient during the growing phase remained more feed efficient than steers previously classified as mid and lowly feed efficient. Marbling differed due to feed efficiency classification but classification effects on other carcass traits were limited. Relative to other diet combinations, steers grown with roughage-based diets and finished with byproduct-based diets excelled in finishing phase growth rate, final bodyweight and hot carcass weight with no differences detected in feed conversion or marbling score. Introduction Due to increasing production costs in the beef industry as well the inherent feed conversion disadvantage relative to other meat-producing species, it is important that the beef industry continuously strive to improve efficiency. Because individual feed efficiency measurement is expensive and generally only determined once it is important to determine the repeatability of feed efficiency from one production stage to the next. Previous reports note that cattle within a contemporary group maintained feed efficiency rank as little as 33% or as much as 62% of the time. Feedlot animals are typically grown on roughage-based diets and finished on corn-based diets; diets greatly differing in energy, fiber and other nutritional components. This transition in diet type during the feedlot phase further complicates the evaluation of feed efficiency across feeding phases. Although feed conversion is a predominant profitability determinant, it is also important to evaluate the effect of improved feed efficiency on other economically relevant growth and carcass traits. The objective of the current study was to determine the influence of growing phase feed efficiency classification and diet type on feed efficiency, growth performance, and carcass traits of steers finished on corn or byproduct-based diets.