Towards the chicken of the future: biomechanical compromises and constraints on locomotion and breathing in broiler chickens

Lead Research Organisation: Royal Veterinary College
Department Name: Comparative Biomedical Sciences CBS

Abstract

Each year over 30 billion broiler chickens are bred for human consumption; 800 million in the UK. Of these animals, almost 30% develop some form of obvious lameness as well as heart and lung problems, costing around £20million/year in the UK alone. These problems are linked to selective breeding for rapid growth rates- broilers take only 6 weeks to reach a slaughter mass of almost 3kg, which has changed from 15 weeks in the 1950s. As a result, the skeletons and other systems of broilers are immature, with compromised abilities to adapt to their environment as they grow to large sizes. Activity levels decline steeply as broilers age. Welfare problems related to inactivity increase with age and there is controversial but building evidence that slaughter-age broilers are in pain. However global food security depends on economical and environmentally-friendly chicken meat. We propose to develop a new scientific framework for understanding how the bodies of broilers change as they grow, focusing on the functions of the legs and their muscles during standing and walking, and the functions of the chest muscles during breathing when standing, sitting and walking. This framework would be founded on an extremely rigorous three-dimensional analysis (using x-rays) of how the skeleton actually is moved by the muscles during locomotion and breathing. It combines cutting-edge techniques for the experimental analysis of gait (including stability) and breathing (including metabolic energy cost for different activities) with anatomically-realistic 3D computer simulations of how the musculoskeletal system produces observed motions. Our novel synthesis of these approaches will allow us to tease apart how the body shape and posture of broilers changes as they grow and how these changes influence standing, moving and breathing. It will reveal tradeoffs between growth, health and behaviour, by filling a major gap in our understanding of broiler biology- studies are yet to peer insideliving broilers to see how their components work to achieve observed behaviours and how the interactions of these components influence the lives of broilers. Instead, most research has focused on external, qualitative observations of 'lameness' and 'leg weakness' during life or post-mortem diagnoses of numerous specific disorders. This study aims to redress this imbalance by spanning the gap between functioning organs, organisms and populations of broilers. We suspect that at 2 weeks of age broilers are quite adept at locomotion and breathing but these abilities tend to decline at 4 weeks and approach limits of viable performance at 6 weeks old. These declines could be driven by the rapid growth of edible breast muscles that make the body 'front heavy,' destabilizing the animal and causing the legs work harder for support, and concurrently incurring breathing difficulties. This vicious cycle would lead to fatigue, inactivity and poor health that has parallels with the human obesity crisis, but there is no simple solution to it. Understanding what selective breeding has done to the detailed anatomy of broilers and how this has affected their functional abilities is pivotal to any solution to the two related crises of leg and lung health in broilers. Furthermore, there may be an optimal body structure (such as larger legs, different breast muscle distribution) at some point early in chicken growth. This optimum could be promoted by selective breeding to reduce these problems if it were determined scientifically- as we intend. Our study would provide a new understanding of the linkages between anatomy, growth, standing and moving, breathing and metabolic energy costs in broiler chickens that would enable us to forge a new way of assessing which chickens move and breathe the best and why. This would help scientists, clinicians and industry to work together to promote better broiler health and welfare while still feeding the world.

Technical Summary

Two major health crises face broiler chicken breeding at the same time as the human population faces a food security crisis. The incidences of leg (varus valgus disease; femoral head necrosis) and heart/lung (pectoral myopathy; cardiac failure; pulmonary hypertension) pathologies increase during broiler ontogeny as activity declines. This incurs huge welfare and economic costs for the billions of broilers raised annually worldwide. Rapid growth rates seem to be a major cause of these problems but no easy solution has emerged. Three related obstacles are critical to any solution: (1) lack of fundamental understanding of how individual organs of the pelvic and pectoral apparatus interact in broilers to produce vital functions such as standing, moving and breathing, (2) how these interactions ultimately influence metabolic cost or stability and (3) how changes in morphology during growth influence those interactions. We propose to resolve these obstacles with an integrative study combining experimental analyses and anatomically-realistic computer simulations of standing, walking and breathing in broiler chickens from 2-6 weeks age, with an emphasis on the three-dimensional linkages between conformation and locomotor and ventilatory mechanics. This would create a new, mechanistically-based approach for quantifying how and why performance in locomotion or breathing differs among broilers of different age, health or conformation, and thus permit scientifically robust, evidence-based industrial and clinical decision-making for broiler breeding. It would thereby supplement and inform existing qualitative tools for evaluating broiler health. This study would build on a wealth of pilot data by the two teams and forge new interactions between them as well as with other researchers and clinicians, the industry and public understanding of this controversial and vital conundrum of poultry biology.

Planned Impact

The major non-academic beneficiary of our study would be the poultry industry, exemplified by (but not limited to) our Industrial Project Partner Cobb-Vantress Inc. We already have established links with Cobb (and Aviagen), and the flexibility of our project allows us to build new links with other partners (e.g., Ross), which we shall pursue. Their greatest interest (see Cobb's Letter of Support) will be if we create or inspire/enable the future creation of tools that could directly or indirectly benefit their selection line tools, which would directly influence broiler breeding and thus potentially health. As that is one of our major aims, we expect excellent success in this benefit. Our research in turn would benefit from information from industry on their breeding programmes, extensive databases of morphological measurements and incidences of pathologies, results of different initiatives to improve health or alter growth, and other knowledge that is often confidential unless a formal industrial partnership such as ours with Cobb exists. The public would benefit from an improved understanding of the extremely controversial issue of broiler chicken health and growth, one of the most incendiary topics in animal welfare and food security. We already have experience working on delicate issues such as this from our previous collaborations with the poultry industry as well as on elephant gait and foot pathology in hoofed mammals (JH's past and current BBSRC grants). We see this as an excellent opportunity to engage the public with a study that is not only about a controversial issue of great global interest and importance, but also extremely attractive in terms of its technical aspects- we will generate compelling imagery of the 3D morphology and motions of the broiler musculoskeletal system. In our previous experience the media and public tremendously enjoy such visualizations, which can generate more positive engagement with the scientific process. Our Pathways to Impact outlines approaches (presentations, websites etc) to promote this outcome. In addition to its prominent Animal Health, Animal Welfare, and Economic/Social Impact components emphasised in our proposal, and its international and collaborative scope, this study fits key BBSRC priorities that emphasize its broad strategic relevance to UK, EU and global concerns, such as (also see Pathways to Impact): Ageing and health- the ontogenetic and functional transformations of the broiler musculoskeletal system that our study would focus upon have analogies with changes that occur during ageing in humans. In particular gait pathologies, obesity, and ontogenetic disorders of the musculoskeletal system in humans and other animals have basic principles (e.g. strength:weight ratios; imbalances of organ sizes) in common with problems seen in broiler chickens. Improving broiler health thus should have spin-off benefits to others. Crop/food security- Chicken meat is one of the most popular foods worldwide and is thought to generally be more environmentally friendly and economical than red meat. Food crises are already emerging, so demand for chicken meat is certain to grow, and broiler breeders/farmers are already planning to increase broiler growth rates to fuel this need. The obvious consequences are worsening broiler health crises, so our project is very timely. This issue is also tied to global security; there are growing concerns that the food crisis could (or already has) promote socio-political instability, particularly in these times of economic crisis. Our project also emphasizes the three R's by minimizing invasive research (our locomotor experiments are entirely non-invasive; our ventilatory experiments minimally so), promoting in silico approaches that could eventually help replace such techniques, and using rigorous methodology that will refine future analyses of locomotor and respiratory health. In this way, we lead by example for other researchers.

Publications

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Ellis RG (2018) Limb Kinematics, Kinetics and Muscle Dynamics During the Sit-to-Stand Transition in Greyhounds. in Frontiers in bioengineering and biotechnology

 
Description We have shown that common features of the gait of adult broiler chickens include extremely slow walking speeds, a wide base of support (large feet) and large lateral motions (waddling), which primarily reflect changes to cope with their apparent instability and large body mass. These features allow the chickens to keep the peak vertical forces on their limbs low (aiding in support against gravity), but result in high mediolateral (left-right) forces (due to waddling). Gait differences directly related to morphological characteristics also exist. Mechanical costs of locomotion were still similar across three lines of broilers (2 breeder "purelines" and 1 meat production line broiler) and were not exceptional when compared with more wild-type ground-running birds, implying surprisingly similar metabolic costs of gait although this needs further testing. Thus broiler chickens seem to have an awkward gait, but some aspects of their dynamics show rather surprising similarities to other avian bipeds.

We have shown how broiler chicken legs and bodies grow across the critical growth period from 2-6 weeks, revealing a huge increase in breast muscle mass but only modest increases in leg mass and leg muscle mass. Thus the ability of broilers to support their own weight likely declines during growth, helping to explain why activity levels decrease concurrently. This is reinforced by decreases in the sizes of visceral organs important for respiration, circulation and digestion. Incidence of limb pathologies such as bacterial chondronecrosis (infective death of joint cartilage) and tibial dyschondroplasia (deformation of the shank bones) increased during growth. Considered together with the relatively slow ossification (formation of bone) of elements of the respiratory skeleton, it seems that rapid growth of the breast muscles might compromise the efficacy of the respiratory apparatus, leading to breathing problems in older broiler chickens and subsequent declines in welfare.

We have collected a huge dataset on the 3D gait biomechanics and energetics of broiler chickens from 2-6 weeks of age, including 3D x-ray motion analysis of skeletal motions as well as group activity patterns and metabolic costs, to test how the mechanics of locomotion relate to metabolism across growth, and whether these contribute to a decline in welfare and general health across growth. Results of these final analyses, including groundbreaking computer simulations of muscle function and metabolic cost during locomotion, are shortly forthcoming. A paper on our metabolic cost measurements of groups of broiler chickens was published in Scientific Reports: Using a novel 'group-respirometry' approach whereby 5 birds were monitored simultaneously, metabolic rates associated with resting and activity were calculated. The proportion of overall metabolic rate accounted for by locomotor behaviour decreased over development, corresponding to declining activity levels, mean and peak walking speeds. Consequently, resting metabolism accounted for a greater proportion of overall metabolic rate in the older, heavier birds. These data are consistent with the inference that broilers allocate energy to activity within a constrained metabolic budget and that there is a reducing metabolic scope for exercise throughout their development. Comparison with similarly sized galliform species reveals that in broilers selected for meat production, locomotion is relatively energetically expensive.
Exploitation Route Refinement of management of poultry- better breeding and welfare, leading to better public relations and economic benefits.
Sectors Agriculture, Food and Drink,Environment,Culture, Heritage, Museums and Collections,Pharmaceuticals and Medical Biotechnology,Other

URL http://thechickenofthefuture.com/
 
Description Development of new management regimes for chickens, in broiler industry. Follow-on RVC/Cobb-Vantress Inc. funding to apply this to industrial setting, devising selection criteria for breeding better-walking chickens. This has just completed in October 2016 and final results and applications are being evaluated and discussed with the industrial sponsor. The impact is still uncertain- a large amount of data were collected and largely processed but the postdoc involved left a research career and did not complete the analyses or publications, so we are seeking additional new funding for staff to finish this work and deliver on the final impacts. It is clear that there will be economic impacts to the industry from this and they are very keen to obtain them, so we are optimistic that this will happen in the near future.
First Year Of Impact 2018
Sector Agriculture, Food and Drink,Environment,Culture, Heritage, Museums and Collections
Impact Types Economic

 
Description Biomechanical simulations of chicken gait to inspire and inform artificial selection on measurable anatomical traits in chicken breeding
Amount £61,164 (GBP)
Organisation Cobb Europe 
Sector Private
Country United Kingdom
Start 10/2014 
End 10/2016
 
Title Dynamic simulation code for OpenSim software 
Description New simulation algorithms for estimating maximal speed, energetic cost, and gait dynamics in legged land animals, for open source OpenSim software. 
Type Of Material Computer model/algorithm 
Provided To Others? No  
Impact Still in development, but operational. 
URL https://simtk.org/home/opensim
 
Description Chicken postdoc from Brazil 
Organisation State University of Campinas
Country Brazil 
Sector Academic/University 
PI Contribution Collaboration on chicken behaviour, feeding and welfare- hosting postdoctoral researcher Dr. Diego Pereira Neves (CV included as URL here) for 1 year as visiting researcher.
Collaborator Contribution Collaboration on chicken behaviour, feeding and welfare- 1 year of Brazilian funding to visit UK and work in our lab. Funded by the Brazilian Scientific Council.
Impact outcomes not yet possible; postdoc just arrived
Start Year 2014
 
Description New collaboration with Brown University 
Organisation Brown University
Country United States 
Sector Academic/University 
PI Contribution New collaboration with fellow (now at RVC ) on dinosaur foot pressures/mechanics, as per EU Marie Curie fellowship.
Start Year 2011
 
Description Agriculture industry story on research project 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Report on our ongoing research was published by a major industry interest group representing farmers and related agricultural representatives.
Year(s) Of Engagement Activity 2011
URL http://www.thepoultrysite.com/articles/2216/biomechanical-compromises-and-constraints-on-locomotion-...
 
Description Cambridge University Biological Society lecture 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Undergraduate students
Results and Impact Public seminar entitled "The evolutionary struggles of giant land animals against gravity" to local zoological society, which stimulated discussion of my team's BBSRC- and NERC-funded research projects afterwards, and subsequent emails thanking me for my stimulating presentation as well as an invitation to do future events.
Year(s) Of Engagement Activity 2015
 
Description Careers Day at local school 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Presentation to 5th year at Greneway School, Royston, Herts, UK: 30 minutes providing information about what it is like to be a scientist and study extinct and living (especially large) animals and be a university professor, and then 30 minutes of discussion answering questions about animals, careers and related topics. Teachers reported that students had rave reviews of the event and it increased their interest in STEM subjects and careers. Featured BBSRC funded work on chickens and NERC funded work on tetrapod fossils.
Year(s) Of Engagement Activity 2016
 
Description Chicken research blog 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Project blog dedicated to BBSRC "Towards the chicken of the future" grant research and subsequent work. Run by the entire collaborative group at RVC and Univ. Manchester.

7,939 views to date, thus the goal of disseminating the research is being achieved.
Year(s) Of Engagement Activity 2012,2013,2014,2015,2016
URL http://thechickenofthefuture.com/
 
Description International chicken workshop 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Type Of Presentation keynote/invited speaker
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Broad audience of scientists, clinicians, poultry industry, media and government/policymakers attended (~100 attendees) to watch 26 presentations across 2 days of talks by top world experts on all aspects of chicken biology, with a strong emphasis on the broiler chicken industry. Discussion sections between/after talks and social events to continue discussions.

Well attended and received- very positive media coverage:
http://www.wattagnet.com/Lessons_learned_at_the_Vet_College.html
http://www.nature.com/news/chicken-project-gets-off-the-ground-1.15300
Year(s) Of Engagement Activity 2014
URL http://thechickenofthefuture.com/symposium2014
 
Description Palaeocast podcast interview 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact 48-minute online podcast interview with PI Hutchinson about his research in palaeontology, anatomy and biomechanics, including NERC and BBSRC funded research, which led to numerous online discussions and interactions about careers in science especially my general subject area.
Year(s) Of Engagement Activity 2016
URL http://www.palaeocast.com/episode-58-animal-biomechanics/
 
Description RVC Open Day bones demonstration 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact RVC Hawkshead campus open day event, where our research team presented a publically accessible stand showing different kinds of animal bones and how these relate to biomechanics, behaviour, welfare, evolution and other topics of general interest as well as direct connection to our BBSRC- and NERC-funded research. Visitors were streaming through the stand (hosted by 5 postgrad researchers) for >6 hours and had many interactions with those hosting the stands to answer their questions about relevant topics and about our research.
Year(s) Of Engagement Activity 2015
 
Description RVC Public Engagement Event 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact "Chicken, egg, what next?" Chicken of the Future public engagement event at RVC's Camden Campus:
http://www.rvc.ac.uk/study/rvc-for-all/night-at-the-vet-college#panel-april-2014-event-chicken-egg-what-next

Visitors rated Night at the Vet College 4.5 out of 5 for enjoyment. Approximately half the attendees had never been to RVC before. There were comments showing that people will consider study options in future. There was evidence that some visitors will approach food choices with new information. 35% of visitors found out about careers. Education visits have been booked as a result of the event.
Facebook photo album:
https://www.facebook.com/media/set/?set=a.758459984184483.1073741864.135224739841347&type=3
Year(s) Of Engagement Activity 2014
URL http://issuu.com/g.kimble/docs/night_at_the_vet_college_final
 
Description Science Blog 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Anatomy blog: sharing the latest scientific research and insights from Prof. Hutchinson's team, with a strong focus on RCUK-funded research. Highly visual and stimulating discussion. As of submission in 2016, total 354,000 views, 3239 followers, 1855 comments, 161 posts.

255,944 all-time views (average 250/day) as of 14/10/2014; 1,529 comments, 750 Subscribers, 642 shares; with additional viewers (53,412) and subscribers (92) at associated Youtube Channel: https://www.youtube.com/user/Whatsinjohnsfreezer
Year(s) Of Engagement Activity 2012,2013,2014,2015,2016
URL http://whatsinjohnsfreezer.com/
 
Description Twitter: Science Communication 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Persistent, daily public engagement by Prof. Hutchinson on his personal account, which regularly addresses scientific research that his team is conducting, including RCUK-funded research. Averages ~250,000 impressions/month; as of submission in 2016 is 27,500 tweets total, 4778 followers, 1652 photos and videos.

>19,000 tweets, >3,000 followers, Klout score ~63 as of 14 October 2014-- indicates strong engagement in science communication. Twitter Analytics indicate 224.9K impressions (views) and thousands of engagements (clicks, favourites, retweets, replies etc.) during a representative month.
Year(s) Of Engagement Activity 2012,2013,2014,2015,2016
URL https://twitter.com/JohnRHutchinson