Four consistent stock brand names of white egg shell laying fowl were compared with four such stocks laying brown shelled eggs. Data were derived from the Combined Summaries of European Random Sample Egg Production Tests (ERSEPT) 1979-1992 and from the North Carolina Layer Performance and Management Test (NCLPMT) 1984-1992. In the former, laying performance was recorded from 141 to 500 days of age and the data were based on annual means derived from about six testing stations, while the latter involved one testing station with recording over two cycles of production from 140 to 434 days and from 435 to 728 days (which included a moult). Although identical stocks were not available in both continents, results for egg mass show a similar initial superiority for the white egg shell stocks. This advantage decreased over the years and changed to an advantage for the brown egg stocks of about 0.5 kg in the ERSEPT and 1.1 and 0.7 kg, respectively, in the first and second cycles of the NCLPMT. In the ERSEPT the white egg stock advantage in terms of feed to egg mass ratio decreased. This can be attributed to greater genetic gains by the brown egg stocks whose final body weight declined (from 510 g to 270 g above that of the white egg stocks); increased mean egg weight (with the gap between the stock types widening from 2.3 to 3.3 g); and to some extent, earlier sexual maturity, as indicated by decreased age at 50% production. Results of the NCLPMT also show that the improved egg mass for the brown egg stocks was achieved by closing the gap in hen-housed production (20 eggs per bird) while maintaining an egg weight superiority of 3.4 g. The improvement in performance was particularly evident in the first production cycle. In the second cycle the brown egg stocks showed higher mortality rates, together with increased food consumption and a smaller egg size advantage. In both production cycles the brown egg stocks were characterized by much higher levels of meat spots.

The paper reviews the literature on vaccines against infectious coryza of chickens. Our knowledge of natural immunity, antigens involved in protection and the degree of cross-serovar protection provided by vaccines is summarized. The effect of variables such as antigen dose, inactivating agent and adjuvant type on vaccine efficacy is reviewed. The protective ability of a new generation infectious coryza vaccine based on a live attenuated strain of Haemophilus paragallinarum is discussed.

At the Central Industries' laboratory in Mississippi, USA a total of 15 689 cases were diagnosed as positive for poultry diseases between 1970 and 1990. The average number of cases diagnosed per year was 784, ranging from 319 in 1974 to 1319 in 1989. A total of 52 diseases or conditions is included in the results of this survey. Each case was categorized into one of seven aetiological groups. The principal diagnosis over the 20-year period was bacterial diseases (6979 cases), followed by diseases of unknown aetiology (3660 cases), parasitic diseases (2515 cases), viral diseases (1121 cases), management errors (771 cases), nutritional deficiencies (339 cases) and fungal diseases (304 cases). Although the total incidence of disease did not appear to vary from one season to another, hot weather resulted in more skeletal diseases being diagnosed while fowl pox and ‘brooder pneumonia’ were most prevalent in cold weather. Tapeworm infestations were highest in the autumn.

Beak trimming remains a controversial subject. It has undoubted economic advantages for the producer, in particular by reducing the incidence of cannibalism and feather pecking, but the procedure is traumatic for the bird and deprives it of important sensory feedback from its beak. It can have harmful neuroanatomical consequences: although the tissue damage is repaired the sensory receptors are not replaced, neuromas may form and become a source of chronic pain. The danger of neuroma formation is reduced and may be absent if the procedure is performed only in young birds. Beak trimming results in both immediate and more persistent effects on behaviour, food intake and body weight. Trimmed birds are generally less active, show less behaviour involving pecking, eat less and grow more slowly than controls. These changes are primarily a consequence of the sensory deprivation. In caged medium hybrid layers and growing broilers beak trimming is difficult to justify, whereas the incidence of pecking damage is so high in light hybrids in multi-bird cages at high stocking densities that beak trimming is universal. A case can also be made for its continuation, on welfare as well as on production grounds, in floor-housed flocks of laying fowl and breeding turkeys. In these contexts it reduces mortality by inhibiting feather pecking, cannibalism and, possibly, aggressive pecking. In the long term beak trimming should be phased out and undesirable behaviour controlled by environmental means and by increased effort being devoted to the genetic selection of commercial stocks which do not engage in damaging pecking, either in cages or when floor-housed in large flocks.

Although it is generally assumed that stress is detrimental to the well-being of poultry, there are positive aspects which are often overlooked. In the context of evolution, stressors such as infectious agents, climatic extremes, and domestication processes play important roles in inter-population and intra-population genetic variability. Pathological, immunological and behavioural studies in both avian and mammalian species indicate that too much or too little stress is undesirable, and that a certain degree of stress is essential for maintaining normal biological functions. Prior stressful experiences, particularly during the neonatal stage, may have long-term benefits in helping an individual to cope with subsequent stressors. Reliability of stress indicators and their variability at both population and individual levels is a major factor in attempting to quantify ‘optimum stress’.

The problems of predicting the growth, body conformation and feed intake of a flock of growing chickens are analysed in order to identify the key components needed to produce an effective model. Distinctions are made between the problems of a bird at one time, a bird over time, and a group of birds at a time. When considering a bird at a time a series of sub-problems is identified, including the prediction of the potential for growth and the way in which body composition should be taken into account. Given solutions to these problems, those of predicting the requirement of the bird for the resources of energy and nutrients for maintenance, growth and fattening then arise. For a bird fed ad libitum the rate of feed intake needs to be accurately predicted by the model if it is to be successful in predicting growth rate and efficiency. An approach to this problem is outlined, together with an initial approach to the problems raised when attempting to model populations of birds.