Effects of lowering dietary NDF levels
prior to marketing on finishing pig growth
performance, carcass characteristics, carcass
fat quality, and intestinal weights

A total of 264 pigs (PIC 327 × 1050, initially 90.1 lb) were used in a 90-d study to determine the effects of withdrawal of high dietary NDF (provided by wheat middlings [midds] and dried distillers grains with solubles [DDGS]) on growth performance, carcass characteristics, carcass fat quality, and intestinal weights of growing-finishing pigs. Pens of pigs were randomly allotted by initial weight and gender to 1 of 6 dietary treatments with 6 replications per treatment. There were 24 pens with 7 pigs per pen (3 barrows and 4 gilts) and 12 pens with 8 pigs per pen (4 barrows and 4 gilts). A positive control diet containing no DDGS or midds and a negative control diet containing 30% DDGS and 19% midds was fed the entire study duration (no withdrawal). The other 4 treatments were arranged in a 2 × 2 factorial with the main effects of with- drawal time (23 or 47 d) and NDF level fed during the withdrawal (low or medium). Pigs on these treatments were fed the negative control diet containing 30% DDGS and 19% wheat midds (19% NDF) prior to their withdrawal treatment. The medium fiber withdrawal diet contained 15% DDGS and 9.5% midds (14.2% NDF). The low-fiber withdrawal diet was the positive control diet without DDGS or midds (9.3% NDF). Increasing the duration of the withdrawal lowered overall ADFI (linear, P < 0.03) and improved F/G (linear, P < 0.004); however, overall ADG was not affected. Withdrawing the high-fiber diet for the last 23 d did not influence (P > 0.61) growth performance. Withdrawing the high-fiber diet improved carcass yield (P < 0.004) with a greater response (P < 0.001) when the low-NDF diet was fed during the withdrawal instead of the medium NDF diet; however, increasing the withdrawal time from 23 to 47 d did not further improve yield (P = 0.11).