A total of 1,235 pigs (PIC 337 × 1050; initially 68.4 lb) were used in a 118-d study
to determine the effects of 7.5 and 15% ground or unground soybean hulls on growth
performance and carcass characteristics of finishing pigs raised in a commercial environment.
Pens of pigs were balanced by initial weight and randomly allotted to 1 of 5
dietary treatments in a completely randomized design with 26 to 28 pigs per pen and
9 replications per treatment. Treatments were arranged in a 2 × 2 factorial, and main
effects were soybean hull particle size (unground or ground, 787 and 370 μ, respectively)
and amount of soybean hulls (7.5 or 15%) in corn-soybean meal–based diets.
The fifth treatment was a positive control, a corn-soybean meal–based diet. No particle
size × soybean hull interactions (P > 0.18) occurred. Overall (d 0 to 118), increasing
soybean hulls, regardless of particle size, did not affect ADG but numerically increased
(P = 0.11) ADFI, resulting in poorer (linear, P < 0.02) F/G. Although F/G became
worse, increasing soybean hulls in the diet improved (linear, P < 0.002) caloric efficiency
on an ME and NE basis, indicating that published energy values undervalue
the energy content of soybean hulls. Unexpectedly, grinding soybean hulls to a lower
particle size worsened F/G (P < 0.04) and caloric efficiencies (P < 0.03).
