Nutritional Evaluation of Low-Grade Corn for Ruminants

Abstract

Two experiments, involving in vitro evaluations and one metabolism study, were conducted to determine the digestibility and utilization of low grade corn (corn that suffered germ discoloration because of respiration damage). Seven samples of corn grain containing various percentages of total kernel damage (TKD) were obtained either from a grain exchange or a grain elevator in the Texas High Plains. Diets evaluated contained: 1) No. 1 grade, 2% TKD; 2) No. 2 grade, 4.8% TKD; 3) No. 5, 11.8% TKD; 4) sample grade (SG), 18.6% TKD; 5) SG, 20.1% TKD; 6) SG, 41.6% TKD; and 7) SG, 55% TKD. In vitro DM and OM digestibilities and pepsin digestible protein (PDP) did not differ (P > 0.05) among the seven samples. Moreover, the samples were similar in ash, CP, ADF, and starch content and readily available starch. Ether extract values were less (1.5 to 2.2%) than commonly reported for corn and increased (P < 0.05) linearly as TKD increased. In a metabolism study with sheep, four treatments were evaluated: 1) 75% No. 1 grade corn; 2) 37.5% No. 1 and 37.5% SG; 3) 18.75% No. 1 and 56.25% SG; and 4) 75% SG corn. Digestibilities of dietary DM and OM, ADF, and nitrogen (N) as well as retention of dietary N in growing wethers did not differ (P > 0.05) when No. 1 corn was replaced with SG corn. Therefore, SG is a nutritionally viable alternative to No. 1 corn in ruminant diets.