Healthy bones for broiler chickens

Bahadır Can Güz

Research output: Thesisinternal PhD, WU

Abstract

Chicken meat is one of the main animal protein sources for humans and is nowadays the second most produced and con­sumed meat in the world. Since 1950s, broiler (meat-type) chickens have undergone radical phenotypic and genotypic changes as a result of an intense genetic selection for fast growth and better feed efficiency. Accompanied by better management conditions and better feed quality, this selection has provided several advan­tages, such as high amount of meat production in a short time, less environmental pollution and considerable financial benefits for pro­ducers. However, it has also caused downsides for broiler chickens, such as poor leg health, impaired locomotion and lameness. One of the main reasons for these downsides is an imbalance between high growth rate and immature bones, because the speed of bone development is unable to keep up with fast growth. Poor leg health causes serious welfare issues and considerable economic losses, since these chickens have difficulties accessing feed and water, suffer from pain, dehydration and starvation as results of high risk of leg bone fractures, developmental bone abnormalities and infec­tious and/or non-infectious leg disorders.

The main focus of this thesis is on leg bone development, specifically tibia, since it is the major weight carrying and the most loaded and affected leg bone during the growth period. The aim of this thesis was to investigate different approaches to improve leg health of fast and slower-growing broiler chickens by (1) dietary factors on the broiler chickens or indirectly via the broiler breeders, (2) incubation conditions and (3) environmental enrichment.

The General Introduction of this thesis first describes subop­timal leg health, bone abnormalities and leg disorders observed in broiler chickens and their welfare and economic consequenc­es. Then continues with leg bone quality measurements, such as bone morphological, biophysical and mechanical characteristics. Lastly, gives information on potential approaches, which are in­vestigated in this thesis to improve leg health in broiler chickens.

Chapter 1 of this thesis describes effects of a combina­tion of organic macro and trace minerals, fish oil and hydrolyzed collagen in the diet of fast-growing male broiler chickens on growth performance, tibia morphological, biophysical and mechanical characteristics (day 28, 35 and 42), leg disorders, locomotion and home pen behaviour. Results of this study showed that organic min­erals in the diet positively affected tibia morphological, biophysi­cal and mechanical characteristics and also growth performance, while hydrolyzed collagen in the diet did not affect tibia charac­teristics and fish oil in the diet negatively affected these charac­teristics. It can be concluded that bone development might need more available minerals in the diet of current fast-growing broiler chickens.

Chapter 2 of this thesis describes effects of green LED light during incubation, the separate effects of macro minerals source and trace minerals source during rearing on growth performance, tibia morphological, biophysical and mechanical characteristics (day 42), leg disorders, locomotion and home pen behaviour of fast-growing male broiler chickens. Results of this study showed that green LED light during incubation did not influence any of the tib­ia characteristics. Organic macro minerals positively affected tibia characteristics compared to inorganic minerals and trace mineral source did not affect these characteristics. It can be concluded that despite green light during incubation have been shown to pos­itively affect growth performance in this study, it did not affect tibia characteristics. The source of macro minerals in the diet of broiler chickens seems to play a major role in bone development, rather than the source of trace minerals.

Chapter 3 of this thesis describes effects of a combination of organic macro and trace minerals in the diet of fast and slow­er-growing broiler breeders on the amount of minerals in egg and hatchling, growth performance, tibia morphological, biophysi­cal and mechanical characteristics (at similar body weights), leg disorders and home pen behaviour of their male offspring broiler chickens. Results of this study showed that mineral concentration in eggs and hatchlings were hardly influenced, but almost all tib­ia morphological, biophysical and mechanical characteristics of slower-growing offspring broilers were positively affected, where­as this effect was hardly seen in fast-growing chickens. It can be concluded that trans-generational mineral availability in offspring appears to play a role via other mechanisms than via absolute min­eral concentrations in the egg and the source of minerals in slow­er-growing breeders’ diet appears to be more effective on bone development of their offspring than in fast-growing chickens, which might be related to time available for bone development.

Chapter 4 of this thesis describes effects of eggshell tempera­ture pattern in week 2 (37.8°C or 38.9°C) and week 3 (36.7°C and 37.8°C) of incubation of fast-growing male broiler chickens on tibia morphological, biophysical and mechanical characteristics (day 41 or 42), leg disorders and locomotion. Results of this study showed that a temperature of 38.9°C during the second week of incuba­tion improved tibia characteristics of fast-growing broiler chickens. Incubation temperature in the third week appears to interact with the incubation temperature in the second week, resulting in a most advanced tibia development after incubation at 38.9°C in week 2, followed by 37.8°C in week 3 of incubation. It can be concluded that a 1.1°C higher EST than normal in week 2 of incubation ap­pears to stimulate tibia morphological, biophysical and mechani­cal characteristics of broiler chickens. However, a 1.1°C lower EST in week 3 of incubation appears to have negative effects on tibia characteristics.

Chapter 5 of this thesis describes effects of pen enrichment consisting of ramps, platforms, perches, large distance between feed and water and live Black Soldier fly larvae in the moss-peat dust bathing area on growth performance, tibia morphologi­cal, biophysical and mechanical characteristics (at similar body weights), leg disorders, locomotion and home pen behaviour of fast and slower-growing male broiler chickens. Results of this study showed that pen enrichment positively affected tibia biophysical characteristics in both fast and slower-growing chickens, while no effect was found on tibia morphological and mechanical charac­teristics. It can be concluded that pen enrichment can stimulate pathways involved in ossification and mineralization, rather than anatomical and physical bone properties.

The General Discussion of this thesis summarizes the objectives and main findings from five experimental chapters and discusses how investigated approaches individually or together give insight in and improve our understanding of leg health of broiler chickens. This chapter ends with main conclusions and future research op­portunities.

The main conclusions of this thesis are:

(1) Replacement of a combination of inorganic macro and trace minerals by their organic varieties in the diet of fast-growing broiler chickens positively affected growth performance and tibia characteristics.

(2) Replacement of a combination of macro and trace min­erals by their organic varieties in the diet of fast and slower-grow­ing broiler breeders resulted in stimulated growth performance and tibia characteristics in slower-growing offspring broilers, while no ef­fect was observed in fast-growing offspring broilers.

(3) Trans-generational mineral availability in offspring broilers appears to play a role via other mechanisms than via absolute mineral concentrations in the egg, since mineral concentrations in eggs and hatchlings were not affected by mineral source.

(4) Replacement of inorganic macro minerals in the diet of fast-growing broiler chickens by their organic varieties seems to be more effective than organic trace minerals on tibia characteristics.

(5) Green LED light during incubation resulted in stimulated body weight gain, but no effect was found on bone development of broiler chickens.

(6) An eggshell temperature of 38.9°C during the second week of incubation was more effective on tibia characteristics of fast-growing broiler chickens compared to an eggshell tempera­ture of 37.8°C. An eggshell temperature of 38.9°C in second week, followed by 37.8°C in third week resulted in the most advanced tibia characteristics, while a 1.1°C lower EST in week 3 of incubation appears to have negative effects on tibia characteristics.

(7) Pen enrichment positively affected tibia biophysical characteristics of both slower and fast-growing chickens, while no effect was found on tibia morphological and mechanical characteristics. Pen enrichment also resulted in lower body weight gain in both fast and slower-growing chickens, potentially due to higher activity and use of metabolic energy or lower feed intake.

(8) It appears that tibia biophysical characteristics seem to give better response to source of the mineral both in broiler and broiler breeder diets, eggshell temperature during incubation and pen enrichment compared to morphological and mechanical characteristics,

(9) The relationship between tibia development and leg abnormalities and disorders remained unclear due to very low incidence of leg abnormalities and disorders.

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Kemp, Bas, Promotor
  • van den Brand, Henry, Co-promotor
Award date5 Jan 2022
Place of PublicationWageningen
Publisher
Print ISBNs9789463959841
DOIs
Publication statusPublished - 5 Jan 2022

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