Academic poultry science in the United States had its origins in the early part of the 20th century. It reached its peak with 45 active departments in the 1940's, but then started to decline significantly in the 1960's. Today, there are only 7 active departments. There have been a number of published theories as to why as the industry grew the academic programs disappeared. Declining student numbers and failure to address industry concerns are the primary theories. This paper addresses all of the available published work together to present the situation as it evolved and point to the potential outcome.

Apart from elimination of errors in obtaining exact measurements of feed intake and total faeces output in the traditional total collection method, the use of markers to determine nutrient digestibility of feeds in animal species would fit into animal welfare considerations. The external marker chromic oxide has been the prominent marker in the 1960s to evaluate metabolizable energy content of feeds for poultry. A preliminary feeding period of 5 days and collection of a sample representing day and night excreta over a 24 hour period have been suggested as protocol to get reliable results with the use of chromic oxide as marker. However, difficulty in obtaining repeatability between laboratories because of the analytical assay for chromic oxide, variability in results, incomplete and inconsistent recovery in excreta, and hazardous possibilities, resulted in replacement of the chromic oxide marker technique with the method of total excreta collection. Although titanium dioxide, which can be analysed by an accurate and simple colourimetrical assay, has been used in several studies in poultry, only one study has evaluated this marker for recovery (98%) in excreta. The internal marker, acid-insoluble ash, which also could present an external marker when the internal content is aided with the use of siliceous substances, is gaining popularity in recent times, although most studies presented higher digestibility values with this marker in avian species than those derived through the total excreta collection method. Lack of standardisation of analytical assays could partly explain the latter phenomenon. Although crude fibre has presented recovery rates of near 100% in excreta of laying hens and turkeys, fear of possible digestion of this substance by cecal microflora has prevented the further utilisation of this substance as marker. Lignin, determined by digestion in 72% sulphuric acid, presented recovery rates of 99 and 98% in chickens and ostriches, respectively, and similar (P>0.05) results than the total collection method in partridges. The elimination of the use of markers to determine energy metabolizability and nutrient digestibility with avian species have been based on a small number of studies conducted mainly before 1965, and extrapolation of results obtained with other animal species.

Genetic variations for feed utilization efficiency widely exist in meat-type chickens, even in populations that have undergone selection for the trait. The trait has moderate heritability and is moderately correlated with growth rate. The genetic basis for the trait was thought to be different from that for growth even though they may be related. As a result, the improvement in feed efficient through selection for body weight should be limiting. Fast growing birds require more nutrients and energy for maintenance. When age-fixed measure is used, part of the genetic variation of feed efficiency for growth may be masked. For this reason, adjusted age-fixed feed efficiency should be used in commercial breeding. The combination of restricted maximum likelihood (REML) method with an animal model can greatly account for the effect of selection of breeding population, leading to more accurate estimates of genetic parameters. The identification of quantitative trait loci (QTL) for feed efficiency in chickens has begun. The incorporation QTL in the prediction of breeding value will further improve selection efficiency for feed efficiency. While it was generally assumed that there is little variation in digestibility and metabolizability of feed within and between different strains or breeds, selection for growth rate has resulted in increased digestive enzyme activity. This suggests that the improvement in digestive ability could not be ignored in investigating new approach for increasing feed efficiency in meat-type chickens. Selection for improved FCR makes birds deposit less of the retained energy as fat and convert more energy and nitrogen into body protein. A negative effect of selection for feed efficiency is that, the combination of fast growth and improved FCR is related to increased occurrence of ascites. Index selection based on weight gain and feed intake could be better for improving FCR.

Broilers are reared in an intensive production system starting with a small initial live weight that increases dramatically by the end of the production cycle. Within the broiler house there are consequent changes in heat, moisture and carbon dioxide production. Microbial decomposition of faeces and litter produces a number of aerial contaminants, particularly ammonia and dust as well as a complex of compounds responsible for the characteristic odour associated with these enterprises. The concentrationof most aerosol particles increases during the production period. Ammonia emissions from livestock buildings have considerable localised environmental effects when deposited on the adjacent land. High levels of inspirable dust can cause respiratory problems in broilers and the particles carry a proportion of the odorous volatile compounds that often attracts adverse comment by neighbouring residents.

The weight of poultry manure produced per day approximately equals the weight of feed eatenby poultry each day. Diet reformulation may reduce valuable nutrient waste but feed waste in manure can be used economically as a source of fertilizer, fuel and ruminant feed. Its value as apoultry feed is uncertain and needs further investigation.

Development of chicken embryo culture techniques provides precise methods for the manipulation of early chicken embryos and has made it possible to analyse the results of themanipulation in hatched chickens. Various attempts have been made to introduce exogenous DNA into the chicken germline, but an efficient method for producing transgenic chickensby non-viral methods has not yet been devised. Since the system for producing germline cimaeric chickens has been established by the transfer of primordial germ cells isolated from early stage embryos, manipulation of primordial germ cells seems to be one of the mostpromising methods for genetic manipulation in chickens.

The high cost of rearing pathogen-free poultry, coupled with increases in importation from non-European countries where hygienic measures may be less stringent indicates that biological approaches to control of infection with food-borne pathogens will continue to be important. The major measures are dealt with in this review, together with the positive and negative aspects of each of these approaches. They include antibiotic therapy and prophylaxis, competitive exclusion using intestinal flora preparations, live and killed vaccines and the increasing interest in exploiting natural genetic resistance to infection and disease.