Efficacy of corn dried distillers grains with solubles as a replacement for soybean meal in Boer-cross goat finishing diets

Abstract

Due to increased use of dried distillers grains with solubles (DDGS) in animal feed and accessibility of ethanol plants in the Midwest, the effect of feeding DDGS in place of soybean meal (SBM) on growth, economics, carcass characteristics, backfat fatty acid profiles, and fecal microbiome of Boer-cross goats was evaluated. Forty-eight Boer-cross goats (approximately 70 d of age; 28.21 ± 0.96 kg) were blocked by BW and assigned to 1 of 4 dietary treatments in a completely randomized design. Treatments were 0 %, 33 %, 66 %, or 100 % DDGS replacing SBM, equating to the inclusion of 0 % (0DDGS), 10.3 % (10DDGS), 20.5 % (20DDGS), or 31.1 % (30DDGS) DDGS in the total diet. The inclusion rates of corn and soybean hulls were adjusted to maintain isocaloric and isonitrogenous diets. Goats were provided ad libitum access to feed and water for 47 d. There were 3 goats/pen and 4 pens/treatment. The inclusion of DDGS linearly improved (P = 0.01) average daily gain (ADG) and gain:feed (G:F; P = 0.001), without affecting average daily feed intake (ADFI; P > 0.10) in goats fed DDGS in place of SBM. Feed cost/kg gain decreased (P < 0.0001) with increased inclusion of DDGS, which led to a linear increase in value of gain (P = 0.02) with increased DDGS inclusion. Bacterial and archaeal genera with individual relative abundances greater than 1% in feces that were impacted by 30DDGS were increased Ruminococcus and Methanobrevibacter (P < 0.01) and decreased Lachnoclostridium (P = 0.02). Ruminococcus and Methanobrevibacter most likely increased in goats fed 30DDGS due to greater amounts of soluble fiber passing through the rumen, thus being fermented in the hindgut. While there were no differences detected in overall percentage of phyla Bacteroidetes (P = 0.36) and Firmicutes (P = 0.12) among treatments; the Firmicutes:Bacteroidetes was greater (P = 0.05) in goats fed 30DDGS than those fed 0DDGS. There was no observed impact (P = 0.47) of treatment on β-diversity, although Shannon Index tended to increase (P = 0.09) in goats fed 30DDGS possibly because more soluble fiber was available for fermentation in the hindgut. Polyunsaturated fatty acids over the 12th rib tended to increase quadratically (P = 0.06) with increased DDGS inclusion, yet there was no differences observed in the saturated fatty acid to unsaturated fatty acid ratio (P = 0.93) or iodine value (P = 0.36) with increased levels of DDGS. Up to 100 % of the SBM in a Boer-cross finishing goat ration can be replaced by corn DDGS with no detectable difference in growth performance, fecal microbial populations, carcass characteristics, or fatty acid profile.