Date of Award

12-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Animal Science

Committee Chair

Brian Richert

Committee Member 1

J. Scott Radcliffe

Committee Member 2

Paul D. Ebner

Committee Member 3

Marcos H. Rostagno

Committee Member 4

Todd Applegate

Abstract

As demand for oilseeds and grains increase for uses beyond livestock feeds, swine and poultry producers are continually challenged to source alternative feed ingredients or co-products that are traditionally fed to ruminant animals. Many of these alternative feed ingredients have characteristics, such as higher fiber content or inherent antinutritional factors, that may reduce the feeding value for swine and poultry. To help improve the nutrient availability as well as understanding the positive affect that feeding fiber can have on gut health, biotech companies have developed novel enzymes to help breakdown these complex carbohydrate structures to release additional energy or reduce anti-nutritional factors. There are inherent anti-nutritional factors found in some feed ingredients that can illicit an inflammatory response in the gastrointestinal tract (GIT). This inflammatory response can partition energy away from growth and induce an innate immune response, causing an increased energy requirement for maintenance. One such anti-nutritional factor is mannan, which is a carbohydrate structural component of hemicellulose. Hemicellulose is commonly found in several plant species, such as soybeans. Specifically, hemicellulose is predominantly found in the seed coat, known as the hull. When hemicellulose is broken down, subunits of mannan can be recognized by the innate immune system, and trigger an inflammatory response. Furthermore, other proteincarbohydrate- lipid structures like lipopolysaccharides or endotoxins released by microorganisms or ingested with the feed can further exacerbate the inflammatory response. Activating the immune response shifts energy away from the animal’s growth potential. The experiments conducted as part of my doctoral research investigate three novel enzymes and their effects on growth performance, nutrient digestibility and gut health in growing pigs and broilers. The first experiment investigated the effect of β-mannanase (Hemicell HTTM, Elanco, Greenfield, IN) on growth performance of swine, initially weighing 16.3 ± 0.12 kg and fed for 84 days. The second experiment was a metabolism study which investigated fiber digestibility, changes in cecal and fecal pH, and volatile fatty acids (VFA) production in the hindgut of growing pigs fed either 15 or 30% distiller’s dried grains with solubles (DDGS) and with or without endo-1,3 β-glucanase (Elanco, Greenfield, IN). And the third experiment investigated the effects of feeding a novel alkaline phosphatase (ALP) (Elanco, Greenfield, IN) to broiler chickens to improve phosphorus (P) digestibility of diets and how ALP affects gene expression in the broiler GIT. Genes of interest included: sodium-phosphate transporter (NaPi Type IIb), cytokine genes; interleukin-6 (IL-6), interleukin-1B (IL-1B), interferon-gamma (IFN-ɣ), interleukin (IL-10); receptor genes; toll-like receptors 2 and 4 (TLR-2 Type II and TLR-4), and mucin-2 (MUC2).

Results of the first experiment feeding β-mannanase with increased soy hulls for each diet phase showed no difference in growth performance for average daily gain (ADG), average daily feed intake (ADFI), or gain-to-feed ratio (GF) for any phase of growth or overall. The results of this study may have been confounded due to porcine epidemic diarrhea virus (PEDv) outbreak during the grower phases of the study for the pigs being tested.

In the metabolism experiment, there were no differences in growth performance (ADG, ADFI, and GF) between any of the treatment groups. For nutrient digestibility, there was a DDGS x Time interaction for ATTD of dry matter (DM). The ATTD of DM decreased (P < 0.0001) following the diet switch after phase 1, and ATTD of DM was lowered when 30% DDGS diets were fed to pigs compared to when 15% DDGS diets were fed. There was an effect of DDGS (P < 0.0001) on ATTD of nitrogen (N), where pigs that consumed diets with 15% DDGS had greater ATTD of N as compared to diets with 30% DDGS. The ATTD of N was also reduced over time (P < 0.0001) following the diet switch after phase 1. Interaction of DDGS x enzyme (P < 0.02) for cecal digesta pH indicated that pigs fed 15% DDGS with enzyme had higher pH compared to pigs fed 15% without enzyme, and the pigs fed 30% DDGS with or without enzyme were intermediary. Fecal pH was not different amongst treatments, but did have a strong trend (P < 0.06) for a DDGS x Enzyme x Time interaction where pH increased following phase 1, (i.e., 0% DDGS without enzyme, -7 to 0 d) for the pigs fed either 15% DDGS without enzyme, or 30% DDGS with enzyme. During phase 2 (i.e. 15 or 30 % DDGS, with or without enzyme) fecal pH tended to increase by week 3 or week 4 as compared to week 2. Cecal total VFA concentrations were greater (P < 0.05) in pigs fed 15% DDGS diets compared to 30% DDGS diets. There was a trend for effect of Time (P < 0.08) for cecal total VFA concentration to increase over time. Cecal acetate, butyrate, and isovalerate as percentages of total VFA were each greater (P = 0.04; P=0.01; P=0.004, respectively) in pigs fed 15% DDGS compared to pigs fed 30% DDGS. Over time following phase 1 diet switch, percent of acetate (P < 0.003) was greater at weeks 3 or 4 compared to week 1. Valerate percent of total VFA decreased over time (P < 0.0001) at weeks 3 or 4 compared to week 1. We observed increasing trends of isobutyrate (P < 0.08) and isovalerate (P < 0.06) percentages at week 3 compared to weeks 1 or 2. Propionate as a percent of total VFA was not different amongst treatments for any of the main effects or interactions. Fecal total VFA concentrations decreased over time (P < 0.05). Fecal acetate and butyrate concentrations decreased over time (P < 0.05) and were lower by week 4 as compared to week 1. No other VFA concentrations were different amongst treatments for any of the main effects or interactions. Fecal acetate and valerate, each as a percent of total VFA, were lower for 15% DDGS as compared to 30% DDGS treatments. Percent of propionate in feces was greater in pigs fed the 15% DDGS versus 30% DDGS. The percent of isovalerate approached a trend (P=0.102) for time with increasing percent of total VFA by week 4 compared to week 1 or 2. Although no effect of enzyme was observed in this study to improve digestibility of diets containing 15 or 30% DDGS, changes to VFA concentrations and the pH of cecal digesta indicate that DDGS inclusion influence small intestine digestion and gut fermentation of dietary fiber.

The broiler study investigated changes to NaPi type IIb gene expression in the jejunum when supplemented ALP. The results indicated that birds fed deficient P diets (0.13% available P (avP)) and supplemented with 1 or 7 million (MM) Units/kg ALP had decreased NaPi type IIb gene expression as compared to birds fed the P deficient diet and no enzyme (P

In conclusion, providing feed additive enzymes to improve growth performance and nutrient digestibility may be an effective tool to help improve feeding value of lower quality ingredients. However, understanding the characteristics of the feed ingredients and the mechanisms in which enzymes work most effectively are warranted. In these experiments, the results did not improve growth performance in pigs, however, broilers responded with reduced jejunum gene expression of Na-P type IIb, indicating that P was being released from monophosphate esters, and supplementing 7 MM Units/kg ALP may reduce inflammatory response as indicated by downregulation of TLR-2, TLR-4 and IL-6 gene expressions. The study investigating mannanase, pigs experienced illness which may have influenced how the enzyme performed within the GIT of the pigs. The ALP study in broilers was positive and showed that gene expression for phosphorus nutrient transporter was downregulated in birds fed P deficient diets supplemented with ALP and was similar to birds fed the positive control, 0.45% avP diet. The changes in gene expression indicated that ALP was releasing P from monoester-containing substrates, and that the broiler may be absorbing this phosphorus.

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