Document Type

Thesis - Open Access

Award Date

2018

Degree Name

Master of Science (MS)

Department

Animal Science

First Advisor

Tofuko Woyengo

Keywords

DDGS, digestibility pigs, predigestion, pretreatment, WS

Abstract

Corn dried distillers’ grains with solubles (DDGS) can be a good alternative feedstuff to the traditional corn soybean meal diets since it has high fat and protein content. However, it has a high fiber content, which is not well digested by pigs and can reduce nutrient utilization by encapsulation. The nutritive value of fibrous feedstuffs like DDGS can be improved by supplementation with fiber-degrading enzymes. However, fiber-degrading enzymes have not been effective in improving digestibility of DDGS. The overall goal of this thesis research to was to unravel why pigs poorly digest DDGS and to develop strategies that can increase the digestibility of DDGS in pigs.
Objective 1: to determine the effects of supplemental cocktail of fiber-degrading enzymes (multi-enzyme) on porcine in vitro porcine digestion and fermentation characteristics of corn DDGS and wet distillers’ grains (Wet DG). With the goal of determining whether or not the drying of Wet DG into DDGS results in reduced digestibility of DDGS by pigs, and in reduced effect of fiber-degrading enzymes on digestibility of DDGS by pigs. Samples of DDGS and wet DG without or with the supplemental multi-enzyme in 2 × 2 factorial arrangement were hydrolyzed in 2 steps using pepsin and pancreatin. Undigested residues were incubated in a buffer solution with minerals and fresh pig feces as inoculum for determination of volatile fatty acid production and kinetics of gas production. The DDGS and Wet DG did not differ in porcine in vitro digestibility and fermentability. In addition, multi-enzyme did not affect porcine in vitro digestion and fermentation characteristics of DDGS or Wet DG. Thus, it appears that the drying of Wet DG into DDGS does not affect the digestibility of DDGS by pigs, and that effect of fiber degrading enzymes on the digestibility of DDGS by pigs is not influenced by drying of Wet DG into DDGS.
Objective 2: To determine the effects of pretreatment and predigestion technologies on in vitro digestion and fermentation characteristics of whole stillage (WS; slurry material that remains after distillation of fermented corn mash, which is subsequently centrifuged to obtain Wet DG that is dried into DDGS); thus, establishing if the poor digestibility of corn DDGS’ fiber can improve the digestibility of the DDGS in pigs. This is because pretreatment and predigestion technologies can increase susceptibility of (the otherwise highly indigestible) fiber to digestion or fermentation. The WS was either untreated or pretreated with heat (at 160°C and 70 psi for 20 min) alone or in combination with citric acid (10 g/L; CA), sulfuric acid (90 mM; H2SO4) or ammonia (1%; NH3). Untreated WS and pretreated WS were un-predigested or predigested with multi-enzyme (for 24 h) in 5 × 2 factorial arrangement to give 10 treatment combinations. Predigested samples together with untreated and pretreated samples were freeze-dried and subjected to porcine in vitro digestion and fermentation as described in Objective 1. Pre-treatment of WS with heat, CA, H2SO4 or NH3 increased (P < 0.01) in vitro digestibility of DM (IVDDM) by a mean of 13.2%. Also, multi-enzyme predigestion of untreated or pretreated WS increased (P < 0.01) IVDDM by a mean of 13.9%. Pretreatment of WS with heat, CA, or NH2 did not affect total gas production. However, pretreatment of WS with H2SO4 decreased (P < 0.01) total gas production. Pretreatment of WS with heat, CA, H2SO4 or NH2 decreased (P < 0.01) total VFA production. The results showed that the poor digestibility of DDGS fiber by pigs could be due to recalcitrance of DDGS fiber to enzymatic hydrolysis or fermentation, and that pretreatment and predigestions technologies can be used to improve nutritive value of WS and hence DDGS. Heat and CA pretreatment technologies can be attractive methods of improving the digestibility of DDGS because heat pretreatment is relatively cheaper than alkali or acid pretreatment, and CA is less corrosive than H2SO4 or NH2.
Objective 3: to determine the effects of pretreating WS heat or CA on nutrient digestibility of the resulting DDGS for growing pigs. The WS was untreated or pretreated with heat (160°C at 70 psi for 20 min) alone (heat) or with the heat plus CA (12 g/L; heat+CA). Untreated and pretreated WS were paddle-dried before their inclusion in diets. Five diets were fed; they included cornstarch-based containing DDGS, untreated WS, heat-pretreated WS, or CApretreated WS as the sole source of protein; and N-free diet. The DDGS diet was included for comparison. The 5 diets were fed to 10 ileal-cannulated barrows (57 ± 1.53 kg BW) in a replicated 5 × 5 Latin square to give 10 replicates/diet. Untreated WS had greater (P < 0.001) apparent ileal digestibility of GE than DDGS. Pretreatment of WS with heat or CA improved (P < 0.001) apparent ileal digestibility of GE, CP, and ether extract in diet. Pretreatment of WS with heat or CA reduced (P < 0.001) standardized ileal digestibility of most AA. Thus, pretreatment and drying of WS at conditions employed in the current study can improve energy digestibility, but reduce AA availability of the resulting DDGS for pigs. Overall, it appears that the low digestibility of DDGS by pigs and limited effect of fiberdegrading enzymes on the digestibility of DDGS by pigs. Mainly because of recalcitrance of DDGS fiber in corn to enzymatic hydrolysis, and not because of drying of Wet DG into DDGS because pretreatment technologies that increase susceptibility of fiber to enzymatic degradation improved the digestibility of DDGS. Heat and CA pretreatment technologies can be attractive methods of improving the digestibility DDGS, but optimal conditions for the pretreatment of WS with heat and CA, and for drying the pretreated WS need to be identified.

Description

Includes bibliographical references (pages 100-116)

Format

application/pdf

Number of Pages

129

Publisher

South Dakota State University

Rights

In Copyright - Non-Commercial Use Permitted
http://rightsstatements.org/vocab/InC-NC/1.0/

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