Performing Department
(N/A)
Non Technical Summary
The global population has been rising and is expected to reach over 9 billion people by the year 2050. To help feed this growing global population, current agricultural practices must be evaluated for efficiency and production capacity. In addition to a growing population size concomitant challenges regarding freshwater availability and rising average global temperatures have arisen. Many countries including the United States are now experiencing unprecedented bouts of freshwater scarcity and sustained periods of heat stress. Heat stress creates an additional challenge in agricultural production through decreases in yields and efficiencies, increases in water consumption and increased rates of mortality. Finding methods of decreasing water usage in agriculture, particularly under potential periods of heat stress is imperative for creating a water and food sustainable future.As water is regarded as the most important nutrient, further understanding of mechanisms regarding the relationship of water utilization, growth and meat quality are of high importance. It is also important to understand how the environment, particularly periods of heat stress can impact these relationships. The successful completion of this research will serve as the first step in understanding water efficiency mechanisms in commercial broilers and how selection for improved water efficiency can be utilized in selection indices to create a more water sustainable future. As each subobjective is independent of the next, this project is poised to identify relationships between water efficiency, growth, meat quality and heat stress adaptation and will provide insight on numerous new directions for future research projects.Selection for water efficiency in broilers has been a thought for many years, however having the ability and the technology to accurately select has been limited. With growing concerns about water usage and the tie to litter moisture, footpad health and broiler welfare, the industry has shown significant enthusiasm for selection for water efficiency. At the University of Arkansas, a divergent selection program for water conversion ratio in broilers has been established. Broiler lines have been created from a randombred control population that are divergently selected for both high (HWCR) and low (LWCR) water conversion ratio. These lines have been selected for 4 generations and show clear divergence as well as a moderate heritability for water efficiency related traits. These are the first documented models for water efficiency in commercial broilers and are the backbone of the proposed research.With established models for water efficiency, utilizing the HWCR, LWCR and randombred control the first objective will aim to establish relationships between water efficiency, yield, and meat quality. Because selection for water efficiency has not been extensively studied, it is unclear what impact selection for improved water efficiency may have on yield and meat quality. Our hope is that selection has not had a negative impact on meat quality. Based on preliminary data collected from the lines, body weight has not yet been affected and it appears that the LWCR, a line selected to be more water efficient, may have been water utilization capabilities through improved water homeostasis. Water homeostasis mechanisms is the main focus for the second objective. This objective will utilize the LWCR and HWCR lines under periods of either a thermoneutral environment (TN) or a period of chronic, daily heat stress (HS). Live performance and efficiency related measurements such as body weight, feed and water intake, and feed and water conversion will be measured. At the end of the study, samples will be collected from multiple tissues and subjected to a multi-omics approach. This multi-omics approach will help to identify how water efficiency selection and heat stress affect water homeostasis in the commercial broiler. Understanding these pathways will help us to better under selection for water efficiency and determine a path forward for creating a more water efficient broiler. Information determined from these studies have the potential to be applied to other species for improved water efficiency, heat stress tolerance and overall sustainable of the agricultural community. While freshwater availability may currently be taken for granted, it is unclear what may happen in the future with regards to our resources. To feed the growing population, we must ensure a water efficient and sustainable future in agricultural production.
Animal Health Component
10%
Research Effort Categories
Basic
50%
Applied
10%
Developmental
40%
Goals / Objectives
Genetic selection of the commercial broiler has created a fast growing, high yielding and efficient protein source capable of feeding the growing global population. Unfortunately, selection indices have neglected to include traits associated with water efficiency in their programs due to lack of knowledge surrounding feasibility of selection and potential impact on other economically important traits. As more regions experience fresh water scarcity, it is important to understand if selection for water efficiency can be utilized in selection programs. Therefore, the goal of this project is to further identify how selection for water efficiency has impacted economically important traits of the commercial broiler such as growth and meat quality under potentially adverse conditions such as periods of heat stress and to fully understand the mechanisms behind water efficiency and water utilization in broilers.Working with genetic lines that have been divergently selected for water conversion ratio/water efficiency for 4 generations, this project is divided into 2 main objectives.Objective 1. Identify the impact of divergent selection for water efficiency on muscle growth and meat quality. This can be accomplished through a traditional grow-out study using the low water conversion ratio (LWCR), high water conversion ratio (HWCR) and randombred control (MRB) broiler lines. At processing ages, meat quality can be evaluated through myopathy scoring, color, and pH.Objective 2. Determine the impact of chronic heat stress on broiler lines divergently selected for water efficiency. This objective can be further subdivided into 2 sub-aims. The first sub-aim will be to determine the effect of chronic heat stress on live performance and efficiency related characteristics. Using the LWCR, HWCR and MRB lines, birds will either be subjected to a thermal neutral environment of to a period of chronic heat stress, During this time, feed intake, water intake and body weight gain will be recorded as well as mortality. Following the period of heat stress, samples will be collecting for molecular analysis. These samples will be use for the second sub-aim in which tissues including the brain, tongue, small intestine, kidney and muscle will be subjected to real-time q-PCR and Western blotting. These samples will help build a better understanding of water efficiency and homeostasis within the research populations under two environmental conditions.
Project Methods
This project will utilize three, distinct broiler research lines selected and maintained at the University of Arkansas. The first line serves as the base/control population and is a random bred broiler population developed in 2015 (MRB). From the MRB line, two divergent populations have been derived including the low water conversion line (LWCR), selected for a low WCR and improved water efficiency and the high water conversion ratio line (HWCR) selected for a high water conversion ratio and decreased water efficiency. These populations are in their 5th generation of selection and are established models for high and low water efficiency, exhibiting differences in their WCR since generation 2 of selection.For objective 1, eggs from the MRB, LWCR and HWCR lines will be collected, incubated, and hatched. Day of hatch chicks will be individually wing-banded for line identification, weighed and placed by line into floor pens (5ft x 10ft) equipped with two commercial hanging feeders, a nipple water line attached to a low flow water monitoring system and fresh pine shavings at a density of 25 chicks per pen. Feed and water intake will be recorded daily with body weights recorded weekly for calculation of weekly WCR, FCR and water:feed intake ratio. At d 55, 10 males and 10 females per line will be randomly selected for histology. A breast tissue sample measuring 1cm x 1cm will be taken from the left pectoralis major muscle and stored in formalin for histological analysis after a 24 hour chill. Histology samples will be processed and stained using Hematoxylin and Eosin Y. Once stained, samples will be evaluated for fiber number, fiber diameter, endomysium, and perimysium spacing using ImagePro software. On d 56, all remaining birds will be processed at the University of Arkansas pilot processing plant. Back dock live, carcass and fat pad weights will be recorded. Following a 4 h ice bath chill, chilled carcass weights will be recorded, and birds will be manual deboned for parts weights. Breast fillets will be scored by a trained professional for woody breast, white striping and spaghetti breast. Breast fillet color will be recorded using a Minolta CR-400 colorimeter at 4 and 24 h post mortem on the ventral side of the left breast fillet with breast pH being recorded using a Testo 205 pH probe. Breast fillets will be wrapped and placed in a 4?C cooler overnight and weighed at 24 h post mortem for calculation of drip loss. The results of this study will be used to evaluate efficiencies, yields and an overall assessment of meat quality. Following the data collection, results will be disseminated to the audience through oral presentations at scientific conferences as well as through a peer-reviewed publication. Information gathered from this experiment will be of key interest to primary breeding companies as it is currently unclear how selection for water efficiency related traits may impact traits currently considered as economically important such as yield and meat quality. A short communication regarding the relationship between water efficiency and meat quality will be produced and provided to members of the poultry industry, specifically those involved in the selection of broiler lines.For objective 2, Eggs from the LWCR and HWCR line will be collected, incubated, hatched and wing-banded by line for identification (n=144/line). Twelve individually controlled, environmental chambers will be split into 2 pens so each chamber can accommodate both research lines. Chicks will be placed by line into 24 floor pens (5ft x 10ft) equipped with 1 hanging feed can, a commercial nipple water line attached to a low flow water monitoring system and fresh pine shavings at a density of 12 chicks per pen (n=12 pens/line). Daily feed and water intake, daily mortality and weekly individual body weights will be recorded from hatch to 49 days. This will allow for the calculation of feed conversion ratio (FCR), water conversion ratio (WCR) and water intake:feed intake ratio. At the start of each trial, iButton sensors will be placed in each chamber as well as at several locations around the facilities exterior and interior for monitoring ambient temperatures. In addition, on d22, iButtons will be orally gavages on 2 birds per pen to record internal body temperature throughout each experiment as previously described. All birds will be reared under standard industry conditions from placement until d 28. Temperatures will gradually decrease from 32?C on day of placement to 24?C by d 28. Temperatures will be adjusted according to bird comfort and welfare. On d 28, 6 of the 12 chambers will begin a period of daily chronic cyclic heat stress (8h/day from 9 am to 5 pm) to mimic Arkansas summer hot season. This cyclic heat stress will occur daily until processing. The remaining 6 chambers will stay at a thermal neutral temperature (24?C) for the remainder of the testing period. All live performance measurements including body weight, and feed and water intake will occur prior to the initiation of heat stress on a daily (feed and water) or weekly basis (body weight). As water homeostasis is regulated by gut, gut health and integrity, will be assessed using FITC-D. To define the cellular mechanisms and identify molecular signatures involved in the regulation of water homeostasis, omics approaches will be used. On d 46, 2 birds per pen will be humanely euthanized and samples collected from the brain, tongue, small intestine (3 sections-illeum, jejunem, duodenum), salt gland, kidney and muscle. Each sample will be placed into a snap cap tube and flash frozen in liquid nitrogen and stored in a -80?C until use. Samples will be processed and subject to transcriptomic analysis. An additional subset of samples will be evaluated for proteomic and metabolomic analyses. Key differentially expressed genes and proteins will be confirmed by real-time quantitative PCR and Western blotting. Multi-Omics data will be subjected to bioinformatic tool (Ingenuity Pathway Analysis) for pathway and network analysis as well as prediction of upstream regulators and down-stream effectors. Combining and integrating transcriptomics, proteomics and metabolomics can be novel and essential procedures to build a solid mechanistic understanding of water homeostasis and efficiency, and to define how these complex metabolic networks are altered in the heat stress conditions. Concepts derived from this objective will be disseminated to the audience through oral presentations and peer reviewed publications.