Available at: https://digitalcommons.calpoly.edu/theses/2936
Date of Award
12-2024
Degree Name
MS in Agriculture - Animal Science
Department/Program
Animal Science
College
College of Agriculture, Food, and Environmental Sciences
Advisor
Siroj Pokharel
Advisor Department
Animal Science
Advisor College
College of Agriculture, Food, and Environmental Sciences
Abstract
The increasing regulation of antimicrobial use in agriculture has driven the search for alternative solutions that support livestock health and production. Essential oils (EO) and prebiotics have recently gained attention as potential alternative supplements due to their antimicrobial properties (benefits for gut health) and ability to improve production parameters in livestock. This study evaluates the impact of a commercially available blend of EO and prebiotics on laying hen production parameters, egg quality, and Gastrointestinal microbiota composition as a possible substitute for antibiotic growth promotors (AGPs). Sixty Hy-Line W-80 laying hens, aged 60 weeks, were divided into four dietary treatment groups: 1) a corn-soybean meal-based basal diet (control), 2) the control diet mixed with 0.5 kg EO (low EO), 3) the control diet mixed with 1.0 kg EO (High EO), 4) the control diet supplemented with 0.5 kg prebiotics (prebiotic). Each diet was administered for 12 weeks, and phased feeding did not occur. Egg production and feed intake were measured weekly, egg quality was measured biweekly, bird body weight was measured monthly, and microbiome samples from both the ileum and ceca were collected at the conclusion of the feeding trial. Repeated measures ANOVA was used to analyze the data for egg production, egg quality, and feed intake using the GLIMMIX function in SAS (9.4). Microbiome samples were processed and analyzed differently. Briefly, 16s rDNA sequencing was conducted on the NovaSeq platform using paired-end reads. Microbiome data underwent quality control and chimera filtering using DADA2. Clean data was then used to construct operational taxonomic units (OTU), and proceed with diversity analysis, species classification annotation, and differential analysis. Taxonomic classification was performed using SILVA (release 138) and NT-16s databases with confidence level set at >0.07. Differential abundance analysis was conducted based on the relative abundance table. Fisher's exact test, Mann-Whitney U, and Kruskal-Wallis tests were used for statistical differences testing.
Results showed that prebiotic supplementation negatively affected both body weight (p0.05) on these metrics. Prebiotic-fed hens also exhibited reduced egg production (p = 0.002) compared to control and EO diets. Although egg weight, yolk color, yolk weight, and albumen height remained consistent across treatments (p>0.05), external egg quality assessments revealed significant differences in eggshell thickness and breaking strength between the low and high EO diets (p = 0.01; p = 0.0003, respectively), though these treatments were not significantly different when compared to the control diet.
Microbial analysis showed higher microbial diversity in the ceca when compared to the ileum (p < 0.001), with a highly dominant presence of the Lactobacillalesgenus in the ileum. Notably, high EO diets significantly increased Lactobacillus coryniformis (p = 0.009) and Lactobacillus capillatus (p = 0.04) compared to the control diet. Clostridium sensu stricto (mean 0.011) and Salmonella bongori (mean 0.001) were witnessed in control diet birds, while these microorganisms were absent from the high EO and prebiotic diet fed birds. Lastly, this feeding trial observed that the vast majority of potentially pathogenic, anaerobic, biofilm former, and gram-negative microorganisms are found in the ceca. In contrast, aerobic, facultative anaerobic, and mobile microorganisms are found in the ileum.
These findings suggest that while EO supplementation alone does not enhance production parameters or egg quality compared to standard diets, it could support beneficial microbiota, offering a promising route to reduce AGP reliance and mitigate antibiotic resistance in livestock production.