Author ORCID Identifier

https://orcid.org/0000-0002-7824-2822

Date Available

11-4-2024

Year of Publication

2024

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Agriculture, Food and Environment

Department/School/Program

Animal and Food Sciences

First Advisor

Sunday A. Adedokun

Abstract

Three experiments were conducted to examine the effects of different feed additives in mitigating stress in broiler chickens. Experiment 1 used 504-day-old male by-product Cobb breeder chicks with 8 treatments replicated 9 times with 7 birds per replicate cage, structured as a 2x4 factorial arrangement of treatments. All birds were on the experimental diets for 20 days. There were 2 levels of lipopolysaccharide (LPS) challenge [no challenge vs. LPS challenge at 1 mg/kg BW) and 4 types of feed additives [no additive, 0.05% PostB, 0.1% PostB, and 0.1% TynagenTM]. In experiment 2, 672-day-old male by-product Cobb breeder chicks were randomly assigned to 8 treatments replicated 12 times with 7 birds per replicate, structured as a 2x4 factorial arrangement of treatments. Birds were on the experimental diets from day 0 to day 29. The treatments consisted of 2 HS levels [no HS (averaging 80oF from days 10-29) vs. HS (averaging 94oF for 6 hours per day from days 10-29)] and 4 feed additive types/levels [no additive, 0.04% ActigenTM, 0.08% ActigenTM, and Stepdown (0.08% ActigenTM in starter diet, 0.04% in grower diet)]. Each temperature group was replicated in two rooms (n=2) to check for the room effect. In experiment 3, 672-day-old male by-product Cobb breeder chicks were randomly assigned to 6 treatments replicated 16 times with 7 birds per replicate for 29 days. The treatments consisted of 2 HS levels [no HS (averaging 80oF from days 10-29) vs. HS (averaging 94oF for 6 hours per day from days 10-29)] and 3 supplemental feed additive types [no additive, 0.1% TynagenTM, and 0.1% PostB]. Each heat group was replicated in two rooms (n=2) to check for the room effect (8 replicates/room). In experiment 1, LPS challenge reduced (P < 0.05) bodyweight gain (BWG) and feed intake (FI) over days 0-20, while the supplemental feed additives improved (P < 0.05) feed efficiency (FE), especially in LPS-challenged birds. In addition, the LPS challenge reduced (P < 0.05) the levels of immunoglobulins A and M, but no significant effect of supplemental feed additives was observed. In experiment 2, HS reduced (P < 0.05) FI but increased (P < 0.05) FE between days 0-28. Across days 0-10, 0.08% ActigenTM improved the LBW and BWG compared to the basal diet. Furthermore, HS altered blood chemistry by decreasing (P < 0.05) the partial pressure of CO2, bicarbonate levels, base excess, total CO2, sodium, ionized calcium, hematocrit, and hemoglobin, but ActigenTM did not impact these response variables. In Experiment 3, HS reduced (P < 0.05 the LBW, BWG, and FI. However, birds that received 0.1% TynagenTM had higher (P < 0.05) FE than those placed on the basal diet across both d 11-28 and d 0-28. Furthermore, HS altered blood chemistry levels as it increased (P < 0.05) oxygen saturation and the partial pressure of oxygen while decreasing (P < 0.05) blood bicarbonate, total carbon dioxide, and ionized calcium levels. In addition, the HS-birds had a reduced (P < 0.05) jejunal villi width (VW) and crypt depth (CD), while 0.1% PostB improved the villi height (VH), VW and VH:CD in non-HS birds. In conclusion, both LPS challenge and heat stress had a detrimental impact on the performance, blood chemistry, and gut health of the birds, while the supplemented feed additives had a moderately ameliorative effect overall.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2024.410

Funding Information

This study was funded by Alltech Inc.

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