Abstract
The study examined the effects of botanical factors and fermentation-based, high-level dilution of co-product feeds in maize–soybean growing-pig diets on enzymatic insoluble fibre hydrolysis and fermentation. Feed insoluble fibre residues that were recovered after pepsin-pancreatin digestion were subjected to Roxazyme ® G2 (Roxazyme) versus Viscozyme L ® V2010 (control) hydrolysis, and to 64-hour fermentation using pig faecal inoculum. The control diet was a 13 MJ metabolizable energy, 141 g total dietary fibre/kg dry matter maize-meal/hominy chop-soybean diet, which was diluted with maize cob, soybean hulls, barley brewer’s grains, lucerne hay or wheat bran in 12 MJ metabolizable energy, 246 g total dietary fibre/kg dry matter iso-nutrient, single co-product test diets. Fermentable insoluble fibre was employed in a computerized iterative selection of ingredients in two iso-nutrient 11 MJ metabolizable energy 319 total dietary fibre/kg dry matter mixed fibre test diets for maximal contrast (high (HF) versus low (LF)) in fermentability. Insoluble fibre extractive pepsin-pancreatin digestibility differed between feed ingredients, and the single co-product test diets, and between the HF and LF mixed co-product diets. Fibre digestibility depended on both the origin and enzyme, with interaction, whereby carbohydrases expressed similar low (0.04 - 0.05) insoluble fibre digestibility for maize cob, moderate (0.12) digestibility for wheat bran and brewer’s grain, with inferior Roxazyme G2 digestibility for maize hominy chop (0.02 vs 0.10) and meal (0.04 vs 0.16), dehulled soybean meal (0.02 vs 0.17), lucerne hay (0.08 vs 0.18), and soybean hulls (0.05 vs 0.33). Co-product-enzyme affinities were expressed in single fibre diets. Low Roxazyme-basal fibre affinity limited its comparative single co-product (0.03 - 0.07 vs 0.16 - 0.22) HF (0.07 vs 0.17) and LF (0.4 vs 0.20) dietary fibre digestibility. Screening for HF/LF did not affect enzymatic digestion, though enzyme combination increased HF, but not LF digestibility. Gas and short chain fatty acid production predicted fermentability proportionately in the declining order of dehulled soybean ≥ maize ≥ soy hulls ≥ maize hominy chop > wheat bran >lucerne hay ≥ brewer’s grain = maize cob. Induced HF and LF contrast was significant. Co-product fibre enrichment decreased fermentability for all except the soy hull and HF diets. Cereal fibre yielded proportionately less acetate, with more propionate and butyrate, and a greater butyrate shift for maize fibre. The HF fibre induced more ACE and less butyrate. Biomarkers of deleterious proteolytic fermentation were high for lucerne (iso-butyrate) and soy hulls (iso-valerate). In conclusion, high-level and fermentation based co-product feed dilution into maize-soybean growing pig diets altered enzymatic insoluble fibre hydrolysis and fermentation in relation to botanical origin. Roxazyme expressed weak hydrolytic potency on maize and soybean insoluble fibre. Keywords: fermentation gas, fermentation kinetics, fibre fermentability, insoluble non-starch polysaccharides, non-starch polysaccharide degrading enzymes, proteolytic fermentation, short-chain fatty acids
Highlights
The processing of food grains into flour, vegetable oil, alcohol and biofuels offloads quantitatively variable, chemically diverse non-starch polysaccharides (NSP) into co-products (Bach Knudsen, 2014).Rapidly increasing human demand and random adverse climate change-related events are disrupting global grain markets, forcing producers into greater dependency on co-products for sustainable, cost-effective pig feeding strategies
The study examined how botanical factors and fermentation-based dilution of co-product feeds into high fibre maize-soybean growing-pig diets affect exogenous enzymatic and fermentative insoluble dietary fibre degradation, with the goal to improve the nutritional efficacy of such complex diets
In the study test feed range, chemical variation in NSP was generically indicated by different neutral and acid detergent fibre, hemi-cellulose, ADL, cellulose, soluble versus insoluble fractions, with the quantitative fibre occurrence reflected in the total dietary fibre (Tables 1 & 2b)
Summary
The processing of food grains into flour, vegetable oil, alcohol and biofuels offloads quantitatively variable, chemically diverse non-starch polysaccharides (NSP) into co-products (Bach Knudsen, 2014).Rapidly increasing human demand and random adverse climate change-related events are disrupting global grain markets, forcing producers into greater dependency on co-products for sustainable, cost-effective pig feeding strategies. The processing of food grains into flour, vegetable oil, alcohol and biofuels offloads quantitatively variable, chemically diverse non-starch polysaccharides (NSP) into co-products (Bach Knudsen, 2014). Chemical and quantitative heterogeneity in co-product fibre and the consequent variable impact on nutrient extraction (Bach Knudsen, 2014; Swiatkiewicz et al, 2016) disturb established precisionfeeding systems, imposing risks on animal productivity and the environmental footprint (Zijlstra & Beltranena, 2013; Woyengo et al, 2014). Strategic co-product feeding primarily involves targeting maximal fermentable fibre (Anguita et al, 2006; Gutierrez et al, 2013; Iyayi & Odeola, 2015) to offset fibre-induced nutrient and digestive metabolic energy wastage (Noblet & Le Goff., 2001). SCFA modulate nutrient transporter gene expression (Daly & Shirazi-Beechey, 2006)
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