Alterations of dietary energy and amino acid densities during coccidiosis infections in broilers

Jespersen, Julianna Christine

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https://hdl.handle.net/2142/121997 Copy

Description

Title

Alterations of dietary energy and amino acid densities during coccidiosis infections in broilers

Author(s)

Jespersen, Julianna Christine

Issue Date

2023-11-22

Director of Research (if dissertation) or Advisor (if thesis)

Dilger, Ryan N

Doctoral Committee Chair(s)

Dilger, Ryan N

Committee Member(s)

• Parsons, Carl M
• Swanson, Kelly S
• Jarosinski, Keith W
• Harsh, Bailey N

Department of Study

Animal Sciences

Discipline

Animal Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• broiler
• coccidiosis
• performance
• amino acids
• methionine
• nutrition
• diet
• energy

Abstract

Coccidiosis is ubiquitous in the poultry industry, and, with the shift of consumer preference towards products derived from both antimicrobial- and cage-free poultry, will remain a pressing issue in the foreseeable future. Although immunity against Eimeria protozoa that cause coccidiosis infections can be generated through vaccination, which can replace the use of anticoccidial drugs, successful vaccination still inflicts a mild immune challenge on the chick. This immune challenge often results in losses of growth performance that may not be overcome by the time the chick reaches market age of approximately 35 to 42 days. Therefore, the need to ameliorate these losses due to both infection and the cost of vaccination presents itself. One such method of mitigating these losses is through nutritional intervention, where dietary nutrient levels and combinations are optimized for maximal performance of the bird. However, these ideal nutrient levels may be altered in birds experiencing immune challenges and ‘sickness’ behavior additionally influences how much the affected bird is willing to eat. As such, feed provided to birds during health challenges should consider these complications. Broiler feed majorly consists of 3 nutrient classes: carbohydrates, lipids, and protein (i.e., amino acids; AA). Each of these nutrients contribute to the energy content of the diet, referred to as apparent metabolizable energy (AME), and dietary AME is a key proponent of regulating feed intake in poultry. Carbohydrates, in the form of starch, are typically lesser-expensive ingredients that consist of the largest portion of the diet. Lipids, often as oil, are added to diets to increase energy density when cost-effective to producers. However, as muscle protein or meat is the main product of broiler chickens, it may be argued that AA content of the diet is the most important component to consider. Specifically, methionine is the first limiting AA for broilers fed standard corn/soybean meal-based rations, and it is involved in many metabolic processes that drive growth such as tricarboxylic acid cycle activity and methylation. Additionally, Met is involved in immune response pathways, including inflammation and B and T cell production. To determine if an ideal combination of starch, oil, and AA, specifically Met, existed to reduce growth performance loss during a coccidiosis infection in broilers, a total of 6 experiments were conducted. First, it was necessary to establish sufficient dosages of Eimeria oocysts to elicit a mild coccidiosis challenge with a desired reduction in growth performance of 10-15%, whether those oocysts were propagated within our own laboratory or acquired from a commercially-available coccidiosis vaccine. Two pilot trials were conducted using a total of 224 male Ross 308 broiler chicks randomly assigned to 1 of 8 experimental treatments. All treatments received the same common starter diet throughout the trials. Experimental treatments differed by challenge method (live-oocyst or over-vaccination) across the trials, and dosage of the respective challenge within each trial. Live-oocyst challenges in Pilot Trial 1 contained sporulated Eimeria oocysts of the species E. acervulina (range 50,000-150,000 oocysts) and E. tenella (range 10,000-30,000) according to treatment. Vaccine dosages in Pilot Trial 2 were calculated using average BW and the experimental treatments were designed to infect the birds with either 2×, 3×, or 4× the vaccination amount. Percent difference between each treatment and their respective control was calculated for growth performance for comparison. Through the results of these pilot trials, it was determined that a vaccine dosage of 3× the manufacturer’s recommendation (based on body weight) or a live-oocyst dosage of 100,000 E. acervulina and 20,000 E. tenella oocysts were sufficient in reducing overall body weight gain (BWG) by 13-17% compared to their respective control groups. Next, 2 trials were conducted to estimate ideal dietary combinations of starch, oil, and AA during a coccidiosis change in order to maximize performance according to the desired outcome of BWG or feed conversion ratio (FCR). These trials utilized 1,536 male Ross 308 broiler chicks in floor pens randomly assigned to 1 of 17 experimental treatments. All birds received common starter (d 0-10) and finisher (d 24-35) diets, and only differed based on their assigned experimental grower diet (d 10-24). Trial 1 experimental grower diets ranged from 2,700-3,300 kcal/kg AME. Trial 2 included 10 experimental grower diets following a simplex lattice design consisting of 3 basal lots formulated to have the highest starch (45.4%), oil (10.2%), or AA density (120%, 1.33% digestible Lys) and mixed in 4 equally spaced levels for each component (0, 0.33, 0.67, 1). These mixtures enabled varying densities of AA (80-120% of recommendation), starch:oil (4:1-20:1), and AME (2,940-3,450 kcal/kg). Bird and feeder weights were collected on d 0, 10, 24, and 35, and birds were exposed to an Eimeria challenge on d 11 or 12. In Trial 2, excreta samples were collected for AME determination and carcasses were processed on d 36. Data in both trials were analyzed separately using an analysis of variance (ANOVA), pooled t-test, or polynomial regression. In Trial 1, BWG and FCR were improved (P < 0.05) by increasing dietary AME. In Trial 2, birds receiving diets containing AA at 93-107% of recommendations and higher oil exhibited improved (P < 0.05) performance, but increased starch at the expense of oil reduced performance (P < 0.05). Relative breast and fat pad weights were not influenced by diet in Trial 2. We determined that broilers mildly-challenged with Eimeria would exhibit highest BWG when receiving diets containing 35.8% starch, 8.9% oil, and 101.3% of AA recommendations or optimal FCR when provided 36.9% starch, 9.2% supplemental oil, and 96.9% recommended AA. Last, we assessed if the Met requirement was altered during a coccidiosis infection based on results of growth performance, carcass traits, and health outcomes. Two trials were conducted using a total of 780 male Ross 308 broiler chicks in floor pens randomly assigned to 1 of 12 experimental treatments. All birds received common starter (d 0-10) and finisher (d 24-35, Trial 2) diets, and only differed based on their assigned experimental grower diet (d 10-24). All experimental grower diets were formulated to contain a combination of 35% starch, 5.4% supplemental oil, and 105% of AA recommendations, with the exception of Met. Trial 1 experimental grower diets ranged from 2.61 to 6.21 g/kg digestible Met. Trial 2 experimental grower diets were formulated to contain 15% below, at, or 15% above the Met requirement determined in Trial 1. Birds were exposed to an Eimeria challenge on d 11, with blood and tissue collection on d 18 and carcass processing on d 35 in Trial 2. Data were analyzed using a 1- or 2-way ANOVA. A non-linear regression analysis was conducted in Trial 1 to determine the Met requirement of 4.32 g/kg standardized ileal digestible Met using BWG. Coccidiosis infection reduced (P < 0.05) growth performance during the experimental grower and overall study periods in Trial 2. Increasing dietary Met from below requirement to meeting requirement during the grower period improved (P < 0.001) BWG and FCR, but this effect was only significant between treatments below and above the requirement for the overall study period. There was an interactive effect (P = 0.038) on FCR for the overall study period. Collectively, these results demonstrate that dietary nutrient density can be optimized and used as a method to reduce losses of growth performance during a coccidiosis challenge, and provide evidence that the Met requirement likely increased when optimizing FCR during a coccidiosis infection.

Graduation Semester

2023-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Julianna Jespersen

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