Performing Department
(N/A)
Non Technical Summary
Up to 73% of egg laying hens experience catastrophic and sometimes even fatal changes to their keel bone. Besides the humanitarian aspect of animal suffering, it has direct financial consequences for farmers and consumers alike.This research aims to develop and deploy new sensors, as well as construct an animal computer model, to (finally) determine the root causes of the problem. As expressed by our industry partners, the results of our investigations will be used to re-design bird housing, including changes to perch, nest and litter area(s), to minimize or eliminate the keel bone damage.
Animal Health Component
100%
Research Effort Categories
Basic
80%
Applied
20%
Developmental
0%
Goals / Objectives
Throughout the life of laying hens, 52-73% can undergo catastrophic and sometimes even fatal changes to their keel bone (KB). At present, there is insufficient knowledge of the root causes of KB developmental calamity. Currently there are limited ways to monitor the biomechanical conditions experienced by egg-laying hens. We seek to transform the assessment of KB damage by employing quantitative assessment methods enabled by leveraging sensor developments, computer simulation and tissue characterization, and to demonstrate the methodology to a critical example.The following are specific objectives of this project:Objective 1: Measure external loading on hens: We will employ additively manufactured, custom force sensor technology to enable direct measurements of external forces on birds from external loading (impact and body weight measured from skin mounted sensors).Objective 2: Measure internal loading and strain on keel bones: We will extend our sensor technology to directly measure deformation conditions from internal loading (egg laying). We will implement direct bone mounted force and strain sensors for attachment to the keel bone, to measure external forces (impact) and bone deformation (egg laying).Objective 3: The Virtual Bird Model: We will build the Virtual Bird Model (VBM) as a finite element model based on 3D imaging of bird anatomy and tissue biomechanical properties. We will employ VBM to compute the skeletal stress state under loading external and internal to the bird.Objective 4: Measure and evaluate keel bone damage in extensive housing considering stocking density: We will integrate sensing and the Virtual Bird Model. We then apply the integrated approach in a setting to birds housed in an enriched colony setting and use stocking density as the housing design variable. We thereby will extend the sensing approach to monitor multiple birds over an extended time period and simultaneously sense forces at external and internal locations on birds together with bone strains. We will apply VBM to analyze the interaction between birds and of birds with enrichments to quantify the potential for keel bone damage.
Project Methods
MEASURE EXTERNAL LOADING ON HENSThis study aims to collect force data from sensors on birds' skin to investigate keel bone fractures, particularly from high-force events like collisions. Custom-made PVdF force sensors, created via 3D printing, will be placed on the birds' skin over the keel bone. These sensors will be attached using medical adhesive tape or surgical glue. The collected force data will be processed by a compact development board equipped with customizable electronics for charge-to-voltage conversion, data storage, and wireless transmission. This board can be housed in a backpack between the bird's wings, and thin film wires will connect it to sensor sheet.To validate the data from previous experiment, external PVdF force sensors will be positioned around the keel bone area and subjected to known forces, ensuring the accuracy of force measurements. The collected force sensory data will undergo pre-processing and be stored locally on a specialized commercial board equipped with custom electronics, memory, and a wireless transmitter. This board will also incorporate additional sensors like an accelerometer and thermometer. All data will be timestamped, enabling insights such as correlations between measured forces and bird movements, including interactions with caretakers. Validation of timestamped data will involve room-mounted cameras capturing the bird's activities from various angles, similar to previous studies. The entire setup will be housed in a previously developed "backpack".MEASURE AND EVALUATE LOADING AND STRAIN ON KEEL BONESThe study's objective is to measure bone strains on the keel bone, complementing existing knowledge about applied forces. To achieve this, two strain sensors will be surgically attached to the keel bone, allowing for the measurement of strains resulting from external impacts (e.g., collisions) and internal forces (e.g., bird's weight or egg laying). Calibration of the strain sensor data will be conducted using 3D printed bone models and excised keel bones with known forces applied for validation.The study will use 3D printed keel bone models or keel bones from euthanized birds. Two strain sensors will be attached to the bone surface to measure strain in two directions. Controlled mechanical forces will be applied to the bone, and strain data will be collected from the sensors. Finite element models will analyze the bone, considering appropriate material properties. This analysis will provide theoretical strain data, and comparison between measured and computed strain data will serve as the basis for calibrating the sensor output.To measure the keel bone's actual strain under in-vivo conditions, surgical placement of strain sensors will be carried out. The collected data will be compared to calibration data to determine in-vivo strain levels. Similar to PVdF force sensors, a commercial board will be utilized to collect, store, and transmit this data, mounted on the birds' backs. Communication between the strain sensors and the board will be facilitated through thin film interconnects, minimizing bird discomfort and simplifying the surgery.Initially, thicker commercial strain sensors will be used for quicker data collection, but custom-designed, thinner sensors tailored to the keel bone's shape will be produced in-house. These custom sensors will offer greater flexibility and comfort for the birds, ultimately improving the quality of data collection and the birds' comfort during the experiment.The main goal is to accurately measure forces affecting birds' keel bones. Current 3D PVdF force sensors, while easy to use on the skin, do not directly measure bone forces, have uncertain lifespans, and their thickness can dampen impact measurements. To overcome these challenges, the study will develop nanomesh PVdF sensors that are surgically attached to the keel bone's surface, providing more precise and durable measurements. These nanomesh sensors, combined with ultra-thin strain sensors, are flexible and biocompatible, enabling long-term monitoring of both impact and egg-laying forces. The development of these sensors will be expedited by previous research efforts. Surgical placement of these sensors will be guided by an experienced poultry surgeon and overseen by a PACUC veterinarian, with data transmitted to a storage board located in a backpack on the bird's shoulder via thin film interconnects, minimizing bird discomfort during the experiment.VIRTUAL BIRD MODELThe study involves conducting 3D CT scans of 6 birds housed in conventional cages to analyze the biomechanics of their keel bones and pectoralis muscles. This imaging process follows established procedures and results in 3D representations of the birds' skeletal structures and muscle anatomy. Image segmentation techniques will be used to isolate the keel bone by analyzing image greyscales, allowing for the distinction between cartilage and bone domains, which are crucial for subsequent biomechanical analysis.The primary focus of the biomechanical characterization is on the keel bone, and this will be achieved using the in-vivo reference indentation method (RPI). Multiple RPI measurements will be conducted at various locations along the keel bone to understand its spatial variation in biomechanical properties. To validate this approach, reference samples from the keel bone will undergo both RPI and standard 3-point bend experiments. To characterize the pectoralis muscle, excised muscle tissue will be utilized due to limitations in current in-vivo methods. This will involve performing specialized biaxial tensile tests to measure hyperelastic passive tissue properties, with the resulting data being translated into elastic constitutive parameters following established protocols.The Virtual Bird Model (VBM) will be developed as a finite element model, utilizing reconstructed animal anatomy and specialized software to create a finite element mesh. It will incorporate tissue biomechanical properties and simulate deformations, strains, and stresses during quasi-static loading conditions resembling palpation exercises. Computational analysis will be performed using a finite element code, and the computed stress data for the keel bone will be compared to its strength data. A keel bone damage risk criterion will be calculated by assessing the ratio of computed principal stress / strain to measured bone strength. The VBM will undergo validation steps, including experiments on excised keel bones and extension to dynamic loading conditions, to assess its accuracy and effectiveness.EVALUATE KEEL BONE DAMAGE IN EXTENSIVE HOUSING CONSIDERING STOCKING DENSITYEgg-laying hens will be housed at varying stocking densities in enriched colony cage systems to demonstrate the proposed approach. Different cohorts of birds will be observed for varying durations, and data on body weight, egg production, and keel bone damage will be collected. All birds will wear acceleration sensors, and some focal hens will have custom-made PVdF sensors to monitor impact forces. The study aims to analyze acceleration data and video recordings to identify critical events, especially collisions with perches, and correlate them with stocking density. Researchers will also examine the relationship between impact forces, acceleration, and behavior, hypothesizing that significant accelerations correspond to high impact forces. Additionally, the study will calculate a new parameter, skeletal deformation distance, to describe a hen's ability to absorb energy during impacts, and measure bone strains to predict keel bone fracture likelihood. VBM will be used to analyze impact events, and its validity will be assessed by comparing computed contact forces and bone strain data to measured values in the enriched cage environment.