Feed intake variability and performance implications of adjusting for dry matter content of cattle feedlot feed ingredients exposed to the elements

Objectives of this study were: 1) validate on-farm dry matter (DM) testing methods, and 2) determine how as-fed dietary composition adjustment to respond to DM content changes affected performance. Onehundredfifty-one crossbred steers (n = 85; 404 kg initial BW) and heifers (n = 66; 384 kg initial BW) were allocated randomly (4 to 6 hd/pen), within truck loadand sex, to one of two 15-pen rows in a deep-bedded confinement barn. Treatments included control (n = 15pens), where diets were only modified to account for changes in ingredient DM every 28 d or adjusted (ADJ; n = 15 pens), in which diets were modified daily toaccount for changes in ingredient DM. Target composition of diets was (DM basis) hay (3.73%), corn silage (CS; 8.28%), high moisture corn (HMC; 50.86%), drydistillers grains with solubles (DDGS; 11.83%), dry rolled corn (DRC; 20.07%), and a liquid supplement (5.23%). Cattle were fed for 84 d. Dry matter contentof hay was determined daily using a microwave oven and that of CS and HMC were determined using a forced-air dryer every other day upon removal from bunker silos; these methods were validated against DM determination using a forced-air oven set at 105 °C. Hay or corn silage DM measured indirectly was similar (P > 0.10) to that measured using a forced-air oven at 105 °C. Adjusting as-fed dietary composition daily to compensate for changes in ingredient DM had no effect on DMI, ADG, feed conversion or final BW. Withinpen feed delivery residual variance tended to be greater (P = 0.06) for pens managed under ADJ. Within-pen and between-treatment residual DMI variance was not different (P > 0.10). Under the conditions of this study,exposure to the elements did not precipitate in large changes in diet DM composition or content. This resulted in similar performance response whether dietary as-fed composition was adjusted or not.