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    Egg storage conditions and manipulations during storage: effect on egg quality traits, embryonic development, hatchability and chick quality of broiler hatching eggs
    (Taylor & Francis Ltd, 2024) Tainika, Brian; Abdallah, Nasir; Damaziak, Krzysztof; Nganga, Zacharia Waithaka; Shah, Tahir; Wojcik, Wojciech
    The egg storage conditions including the duration, temperature and egg turning and positioning and manipulations, especially prewarming and preincubation during egg storage, are consistently important components for poultry breeders and hatcheries. This review paper provides a comprehensive analysis of the effects of egg storage conditions and manipulations during egg storage on egg quality characteristics and embryonic development and subsequent effect on hatchability and chick quality. The egg storage duration and temperature have been deeply studied compared with the egg turning and positioning and manipulations during storage. Storing hatching eggs above 21 degrees C for > 7 d increases embryonic mortality and reduces hatchability. Concurrent with insufficient turning or cessation of turning and longer storage durations, these lead to increased embryonic mortality, reduced hatchability and compromised chick quality. Furthermore, it was identified that the potential mechanisms underlying the observed effects of egg storage conditions include variations in yolk and albumen characteristics, gas exchange and blastoderm development, which should equally remain in optimal ranges during storage. Meanwhile, during egg storage period, manipulations comprising prewarming and preincubation are recommended due to their role in increasing embryonic development, hatchability and chick quality. Generally, the effects of the storage conditions are highly associated with the breeder age and timing in case of manipulations during storage. Furthermore, it is essential that studies fully explore the genetic variability and the changes in integrity of external egg characteristics, such as changes in eggshell thickness and conductivity in relation to storage conditions, and their impacts on embryonic development, hatchability and chick quality. Conclusively, understanding the effects of egg storage conditions can help poultry producers implement appropriate strategies to improve overall production efficiency and profitability.
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    Welfare issues in broiler chickens: overview
    (Taylor & Francis Ltd, 2023) Tainika, Brian; Sekeroglu, Ahmet; Akyol, Ahmet; Nganga, Zacharia Waithaka
    Development of quality welfare assessment protocols is a necessary step towards achieving high broiler welfare standards. Rapid growth rate and highly intensive commercial production systems have been highly associated with poor welfare indicated by mainly leg deformities, high stress levels and increased fear responses. Stress response in broilers is characterised by increased corticosterone and heterophil-to-lymphocyte ratio especially under heat stress, high light intensity, high stocking density, and an unenriched environment. Rearing environment, genotypes, high light intensity and human handling highly influence fear responses as proved during tonic immobility, open field, novel enrichment, and avoidance distance tests. Lameness which is usually visually assessed by a gait score scale remains an undisputable indicator of poor welfare in broiler production due to its effects on mobility and association with pain. Other leg problems including footpad dermatitis and hock burn also remain significant and they are highly associated with fast growth, high stocking density, poor litter quality, and poor or non-enriched production systems. Litter management and good ventilation are necessary to ensure good plumage conditions, reduction in ammonia emissions thereby promoting the well-being of broilers. Generally, broilers should be motivated and able to exhibit natural behaviours without straining including feeding, drinking, walking, and stretching thereby enhancing bird health, performance, production, and consumer satisfaction. Using a systematic approach, the important welfare parameters including stress, fear response, leg problems, plumage condition, environment, and behaviour are intensively discussed to explore the latest insights of broiler chickens' welfare.