Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Robert C. Thaler


Antibiotic, Broiler, Essential Oil, Pig, Soybean


Increasing consumer pressure to minimize antibiotic use and the implementation of the Veterinary Feed Directive in 2017 has increased research on alternatives to preventative antibiotics. This thesis focuses on evaluation of Ralco’s Microfused™ Essential Oils (MEO) fed to broilers and soybean meal from low allergenicity soybeans fed to weaned pigs and their potential use as alternatives to antibiotics. Essential oils are known to have antimicrobial, antioxidant, antiparasitic, and digestive stimulant effects. Low allergenicity (LA) soybeans were bred to contain significantly lower concentrations of the following anti-nutritional factors and allergenic proteins: Kunitz trypsin inhibitor, soybean agglutinin (lectin), and P34 (Gly m Bd 28 K; Schmidt et al., 2015). For the poultry experiment, day old broilers (n = 768) were induced with a coccidiosis challenge and fed diets containing either MEO, antibiotics, or no additive for 41 days. The following parameters were measured: growth performance, jejunal villus height, jejunal crypt depth, breast meat pH, and whole breast and ground thigh meat color and lipid oxidation over seven days. Broilers fed MEO at 250 mg/kg performed similarly to the antibiotic-fed, but minimal differences were noted for jejunal histology. MEO did not affect breast pH, but impacted meat color and reduced lipid oxidation levels. For the swine experiment, weaned pigs (n = 36) were housed in individual metabolism crates using three blocks of 12 pigs each. Pigs were fed either a high caseinstarch diet (CAS), conventional soybean meal-starch diet (CON), or LA soybean mealstarch diet (LA) for 10 days and then euthanized. The following parameters were measured: growth performance, fecal energy digestibility, and ileal villus height, crypt depth, mast cell number, expression of IL-4 and IL-10 mRNA, and amino acid digestibility. CAS-fed pigs had significantly higher average daily gain compared to CON and LA-fed pigs (0.103, -0.008, and 0.36 ± 0.014 g; P < 0.0001). Minimal differences were noted for ileal villus height and crypt depth. Mast cell, IL-4, and IL-10 were unable to be quantified. Finally, CAS-fed pigs had greater digestibility of most ileal amino acids over LA-fed pigs and increased fecal energy digestibility over CON-fed pigs.

Library of Congress Subject Headings

Essences and essential oils.
Feed additives.
Soybean meal as feed.
Alternative medicine.
Swine -- Feeding and feeds.
Broilers (Chickens) -- Feeding and feeds.


Includes bibliographical references (pages 63-72)



Number of Pages



South Dakota State University



Rights Statement

In Copyright