Bringing eggs and bones to light Affecting leg bone development in broiler chickens through ...

216 Pages·2017·27.61 MB·English

Bringing eggs and bones to light
Affecting leg bone development in broiler chickens
through perinatal lighting schedules
Carla W. van der Pol
Thesis committee
Promotor
Prof. Dr B. Kemp
Professor of Adaptation Physiology
Wageningen University & Research
Co-promotors
Dr H. van den Brand
Associate professor, Adaptation Physiology Group
Wageningen University & Research
Dr I. A. M. van Roovert-Reijrink
Manager Research
HatchTech B.V., Veenendaal
Other members
Prof. Dr P. W. G. Groot Koerkamp, Wageningen University & Research
Prof. Dr S. Özkan, Ege University, Turkey
Prof. Dr J. A. Stegeman, Utrecht University, the Netherlands
Dr I. C. de Jong, Wageningen University & Research
This research was conducted under the auspices of the Graduate School of Wageningen Institute of
Animal Sciences (WIAS)
Bringing eggs and bones to light
Affecting leg bone development in broiler chickens
through perinatal lighting schedules
Carla W. van der Pol
Thesis
submitted in fulfilment of the requirement of the degree of doctor
at Wageningen University
by the authority of the Rector Magnificus,
Prof. Dr A.P.J. Mol,
in the presence of the
Thesis Committee appointed by the Academic Board
to be defended in public
on Friday 12 May 2017
at 4 p.m. in the Aula.
Carla W. van der Pol
Bringing eggs and bones to light. Affecting leg bone development in broiler chickens through perinatal
lighting schedules
214 pages
PhD thesis, Wageningen University, Wageningen, the Netherlands (2017)
With references, with summary in English
ISBN: 978-94-6343-142-2
DOI: 10.18174/410024
Abstract
Leg bone pathologies are a common problem in broiler chickens, and they can lead to
decreased welfare and poor production performance. It can be speculated that the ae-
tiology of some leg bone pathologies lies, to some extent, in suboptimal early life bone
development. One factor that can be speculated to affect bone development, and conse-
quently leg health, in broiler chickens is application of light. Light has several properties,
such as light intensity, color, duration, and schedule. The present thesis focuses on ligh-
ting schedules. Aim was to investigate how lighting schedules applied during incubation
and in the early post hatch period (the brooding period) affected leg bone development
throughout a broiler’s life and leg health at slaughter age.
In 4 studies, effects of eggshell temperature (EST) and lighting schedule during incuba-
tion and in the brooding period on leg bone development, leg health, and production
parameters were explored. The first study found that an EST of 39.4°C led to lower bone
dimensions at hatch than an EST between 37.8 and 38.6°C. It was then decided that
incubation experiments on bone development would best be performed at a constant
EST of 37.8°C, as this is also an EST that leads to good hatchability and chick quality.
In two studies, the effects of circadian lighting schedules during incubation on leg bone
development and leg health were investigated. Staining of the embryonic leg bones sho-
wed that applying a circadian lighting schedule of 12 hours of light, followed by 12 hours
of darkness (12L:12D) resulted in an earlier onset of embryonic ossification of the tibia
than continuous light (24L). Compared to 24L, 12L:12D furthermore resulted in higher
tibia weight and length, and higher tibial cortical area, cortical thickness, and second
moment of area around the minor axis at hatch as revealed by MicroCT scanning. It was
furthermore found that 12L:12D resulted in a lower incidence of the leg pathology tibial
dyschondroplasia. Continuous darkness (24D) was mostly intermediate. On the other
hand, a circadian lighting schedule of 16 hours of light, followed by 8 hours of darkness
(16L:8D) did not show the same stimulatory effect on leg bone development, as no dif-
ferences in gene expression markers involved in embryonic ossification were found, leg
bone dimensions at hatch were not increased, and bone mineral content as determined
by DXA scanning was not higher for 16L:8D. It can therefore be speculated that the dark
period should exceed 8 hours per day during incubation for increased bone dimensions
and ossification. However, incidence and severity of the leg bone pathologies in the form
of bacterial chondronecrosis with osteomyelitis and epiphyseal plate abnormalities were
lowest for broilers exposed to 16L:8D during incubation, and tibial dyschondroplasia
tended to be lower for 16L:8D than for 24D. Interactions between incubation and mat-
ching or mismatching post hatch lighting schedules were not found. It was speculated
that the endocrine factors (pineal) melatonin, growth hormone, corticosterone, and IGF-
1 were a pathway through which light affected leg bone development, but no evidence
was found to support this hypothesis. Production performance was not greatly influen-
ced by incubation lighting schedule, but 24L was found to result in higher body weights
at slaughter age than 16L:8D and 24D. In the final experiment, lighting schedules were
applied during the brooding period from day 0 to 4 after hatching and leg bone develop-
ment was measured at day 4 post hatch. 24L led to increased leg bone dimensions, but
lower developmental stability of the leg bones than a lighting schedule with 1 or 6 hours
of darkness after every 2 hours of light.
The overall findings of this thesis suggest that continuous light during incubation and
in the brooding period had a detrimental effect on embryonic and early post hatch leg
bone development and health. The involvement of endocrine factors was not clarified
from the current results. Applying a light-dark rhythm during incubation may improve
embryonic leg bone development and leg health at slaughter age compared to continuous
light and continuous darkness, without affecting post hatch production performance,
but it appears that the dark period should last longer than 8 hours per day for optimal
leg bone development.
Table of contents
Chapter 1. General introduction 10
Chapter 2. Effect of eggshell temperature throughout incubation on broiler 36
hatchling leg bone development
Chapter 3. Circadian rhythms during incubation of broiler chicken embryos 52
and their effects on embryonic and post hatch leg bone develop-
ment
Chapter 4. Lighting schedule throughout incubation: effects on broiler deve- 78
lopment and post hatch performance
Chapter 5. Effects of lighting schedule during incubation of broiler chicken 98
embryos on leg bone development at hatch and related physiolo-
gical characteristics
Chapter 6. Incubation lighting schedules and their interaction with matching 120
or mismatching post hatch lighting schedules: effects on broiler
bone development and leg health at slaughter age
Chapter 7. Lighting schedule and dimming period in early life: consequences 144
for broiler chicken leg bone development
Chapter 8. General discussion 166
Summary 196
Dankwoord (Acknowledgements) 202
About the author 206
Training and Supervision Plan 212
Colophon 214

Chapter 1
General introduction
C. W. van der Pol
C. W. van der Pol