Avian and Poultry Biology Reviews

Avian and Poultry Biology Reviews 13 (2), 2002

Electrolyte and Water Balance of the Early Avian Embryo: Effects of Egg Turning

G. K. Baggott 1*, D. C. Deeming 2 and G. V. Latter 1
1 School of Biological and Chemical Sciences, Birkbeck, University of London, Malet St., London WC1E 7HX, UK
2 Hatchery Consulting and Research, 9 Eagle Drive, Welton, Lincoln LN2 3LP, UK

ABSTRACT

Formation of sub-embryonic fluid (SEF) is a key aspect of the physiology of the early avian embryo.Herewe review the process of SEF formation and the factors which influence its composition and the rate of SEF production and depletion in the Japanese quail and domestic fowl.There is particular emphasis on the role of turning of the egg during incubation andwe briefly consider the broader role of egg turning during avian incubation. The bulk of the review deals with the growth of the area vasculosaof the yolk sac membrane, the cellular processes of SEF formation, and the water and electrolyte physiology of the avian embryo during the first half of incubation.We concludewith a brief discussion of the areas for future investigation.

Keywords: sub-embryonic fluid, albumen, yolk, egg turning, water and electrolyte physiology, Japanese quail, domestic fowl

A Review of the Aetiology and Pathology of Leg Weakness in Broilers in Relation to Welfare

R. H. Bradshaw*, R.D. Kirkden and D. M. Broom
Department of Clinical Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK

ABSTRACT

Leg disorders in broilers are a major economic and welfare problem. The aetiology of many disorders is complex but includes genetics, growth rate (due to feed restriction or lighting regime), feed conversion efficiency and body conformation, exercise, circadian rhythms, nutrition and stocking density. These categories are not mutually exclusive as one aetiological factor may affect another. Many studies of leg disorders fail to identify the specific pathological condition underlying the observed lameness. However, disorders may be classified according to underlying pathology as infectious, developmental and degenerative. This classification is difficult because these categories are also not mutually exclusive. Infectious conditions include bacterial chondronecrosis with osteomyelitis (BCO or femoral head necrosis, FHN), tenosynovitis and arthritis, infectious stunting syndrome (ISS) and viral induced neoplasia. Developmental conditions include varus valgus disease (VVD), rotated tibia, tibial dyschondroplasia (TD), rickets, chondrodystrophy and spondylolisthesis. Degenerative disorders include osteochondrosis (often TD), epiphyseolosis (often classified as FHN), degenerative joint disease (DJD), spontaneous rupture of the gastrocnemius tendon and contact dermatitis. BCO, TD, dermatitis and VVD are the most common disorders. Outbreaks of leg disorders are often site y context specific. The welfare of broilers with leg disorders may be impaired due to pain from the condition, an inability to walk leading to frustration and associated problems of being unable to feed and drink due to immobility (which may result in starvation). In assessing welfare, the individual broiler must be considered irrespective of the frequency of occurrence of the disorder. Most studies of welfare in relation to leg disorders have used a subjective gait scoring method (0 is normal walking and 5 is unable to walk). Gait scoring is a practical method for assessing broiler lameness in the field. The method provides a useful tool to employ in the field without recourse to pathological investigation and, while the method conflates conformity with pathology, it is a helpful and constructive additional method to assist in welfare studies. For birds with scores greater than 3, lameness may be viewed as severe enough to potentially impair welfare. It is difficult to assess all disorders in relation to frequency of occurrence and their impact on welfare due lack of evidence. BCO (or FHN and BCN) is the most common disorder and is often severe in form. TD (incl. epiphyseolysis) and rickets are common, often sub-clinical but when severe there is a considerable impact on welfare. Contact dermatitis may be common under certain conditions and causes poor welfare when severe. Gastrocnemius tendon slippage, tenosynovitis, DJD and spondylolisthesis are not so common but are likely to cause poor welfare when they occur (i.e. pain and prevention of certain behaviours). VVD and rotated tibia can be common but tend not to be directly painful unless another condition is present. However, they can cause poor welfare if the bird is not culled and lead to an inability to walk, feed, drink and perform other behaviours. ISS, viral induced neoplasia and chondrodystrophy have only a small impact on welfare in the UK flock, the last because it is no longer encountered. To decrease the prevalence of leg disorders, growth rate needs to be decelerated: meal feeding, feed restriction during the early period of rearing, lower stocking densities and increased activity can result in a considerable reduction in leg problems. Continuous lighting should be avoided; overall the light period should be reduced. There also needs to be careful management of litter to prevent dermatitis. Factors in the diet are also important, particularly Ca, P and D3 which can prevent certain disorders (e.g.TD). Further research is needed to establish the prevalence of disorders, underlying pathology in relation to subjective gait scores and analgesics in relation to pain mechanisms. A forum for discussion of these issues should be established and further control-trials conducted to investigate these factors.

Keywords: broiler, leg, disorders, welfare, aetiology, pathology, disease, lameness