Effects of switching from corn distillers dried grains with solubles- to corn- and soybean meal-based diets on finishing pig performance, carcass characteristics, and carcass fatty acid composition.

Corn distillers dried grains with solubles (DDGS) are known to negatively impact carcass yield and fat quality, thus finishing pigs may need to be switched from diets containing DDGS to corn-soybean meal (CSBM) diets before marketing (DDGS withdrawal). A total of 860 finishing pigs (PIC C48 or L42 × 327; initially 66.2 kg body weight, BW) were used in a 76-day experiment to evaluate the effects of DDGS withdrawal periods at increasing intervals before harvest. Pen served as the experimental unit, and there were seven replicate pens per treatment with 23 to 25 pigs per pen. Pens were blocked by BW and allotted to one of five dietary treatments differentiated by the DDGS withdrawal period: 76, 42, 27, 15, or 0 day before harvest. Diets contained 40% DDGS from 22 to 66 kg prior to the experiment, 0% or 35% DDGS during the experiment from ~66 to 82 kg, and 0% or 30% DDGS until the completion of the trial. Diets were not balanced for net energy. Linear and quadratic response to time following dietary switch was evaluated using PROC GLIMMIX. For the overall period (day 76 prior to market to day 0), as withdrawal period increased, average daily gain (ADG) and final BW increased (linear, P < 0.002) and feed efficiency (G:F) improved (quadratic, P = 0.019). Average daily feed intake increased (quadratic, P = 0.030) as withdrawal period increased. There was an increase (linear P = 0.010) in hot carcass weight (HCW), with a marginally significant increase in carcass yield (linear, P = 0.094) with increasing withdrawal period. Loin depth and lean percentage did not demonstrate any evidence for treatment differences (P > 0.132). Backfat increased (linear, P = 0.030) with increasing withdrawal period. Finally, iodine value (IV) of belly fat was decreased (linear, P = 0.001) with increased withdrawal period. In conclusion, switching from a DDGS-based diet to a CSBM-based diet for longer periods before slaughter increased ADG and improved G:F, resulting in increased HCW. After diets were switched from DDGS to CSBM, pigs demonstrated an increase in intake, likely due to the ability to consume high volumes of feed after consuming high fiber (DDGS) diets. Belly fat IV was decreased as the length of time after dietary change was increased, with the lowest IV resulting from pigs that consumed CSBM for the entire experimental period.