A total of 1,360 pigs (PIC 337 × 1050, initially 53.0 lb) were used in a 125-d study
to determine the effects of dried distillers grains with solubles (DDGS) withdrawal
post-immunocastration (IC; Improvest, Pfizer Animal Health, Kalamazoo, MI) on
growth performance and carcass fat quality of growing-finishing pigs. Pens of pigs
were randomly allotted by initial weight and gender (barrows or IC) to 1 of 3 dietary
treatments with 8 replications per treatment for a total of 48 pens with 27 to 29
pigs per pen. Treatments were arranged in a 2 × 3 factorial with the main effects of
gender (barrow or IC) and diet (0% DDGS throughout, 30% DDGS throughout, or
30% DDGS through d 75 then withdrawn to 0% to d 125). Boars were injected with
Improvest on d 39 and 74 of the study. Dietary treatments were corn-soybean meal–
based diets and fed in 5 phases. No gender × diet interactions (P > 0.18) were observed
except for a tendency for F/G (P < 0.07) during the second phase (d 25 to 53), when
1 of the 2 barrow groups fed 30% DDGS had an increase in ADFI resulting in poorer
F/G. For the entire period before the second Improvest injection (d 0 to 74), barrows
tended (P < 0.08) to have increased ADG (1.98 vs. 1.95 lb) and increased (P < 0.001)
ADFI (4.32 vs. 3.91 lb) but were less efficient (P < 0.001) than boars (2.19 vs. 2.01).
During the same time period, pigs fed 30% DDGS had reduced (P < 0.002) ADG and
poorer feed efficiency.
