The weight of hatching eggs can influence broiler live performance regardless of hen age. Egg composition is altered with egg weight, but such alterations do not seem to have major effects on broiler growth and processing yields. The chick hatches with a yolk sac which provides nutrients for the transition to independent feeding. Alterations in egg weight and composition do not affect the proportion of yolk sac to body weight as much as its composition, particularly with eggs from very young hens. The contents of the yolk sac are high in fat and protein but very low in carbohydrate, which could lead to ketosis with prolonged fasting. Enhancing the first feed with either carbohydrate or gluconeogenics such as propionic acid may alleviate this ketosis and help early development. The digestive system of the chick is physically complete at hatching but is not fully competent at nutrient retrieval as many enterocytes are orientated to immunoglobulin uptake. Villi length and enzymatic activity increases with feeding, reaching maturity within a few weeks. Access to food and water after hatching varies, and long delays until placement are common. These delays cause losses in live performance. Loss in body weight due to late placement or undernutrition may also affect early muscle development. These adverse effects extend to marketing age and reduced meat yield. Factors that affect early chick development are gaining interest as the length of time to market progressively decreases and the chick's first days represent an increasing proportion of the total time for production.

Broiler lameness (syn. leg weakness) is a cause of commercial loss through mortality, culling and reduced performance and is a welfare concern both within and outside the broiler industry. Many of the cases of lameness are associated with infection in bone, joint or integument. Several groups of organisms have the potential to cause disease resulting in lameness, but the most common causes are restricted to a small group of infectious organisms. These bacterial, viral and fungal infections and their associated pathologies are systematically described.

This is a review of previously published data from experiments designed to measure the chicks' requirement for an essential amino acid in diets containing surplus protein (generally in the range 220–300 g crude protein (CP)/kg diet). The evidence shows that, within this range, the requirement for a first limiting amino acid increases nearly in direct proportion to the CP content of the diet. To explain this, the following possibilities are considered: (1) that energy supply was limiting the response to a critical amino acid, (2) that the experiments were conducted in environments which limited heat disposal by the chicks, (3) that results from the trials have been misinterpreted because growth rate rather than protein deposition was used as a response measure, (4) that the availability of amino acids in the diets was lower than had been assumed, (5) that nutrients other than the amino acid under study were limiting performance, and (6) that there was an imbalance of amino acids in the diet. It is concluded that only the last explanation fits the facts. The imbalances reported have led to a decline in the efficiency of the utilisation of the first limiting amino acid in some instances. The depressed growth observed with a high-protein diet limiting in one essential amino acid could not be attributed to lowered feed intake in most cases. The imbalance is, in these respects, different from classical imbalances which result from loading the diet with a mixture of essential amino acids. From the evidence reviewed, some doubt is cast on the validity of the dilution method for estimating amino acid requirements; nevertheless it its concluded that the dilution method remains the most trustworthy procedure for making estimates to be used in practical diet formulation. It is recommended that, in future, programmes for diet formulation should be modified to prevent surplus protein being permitted in the solution, unless a proportional adjustment is made to the minima prescribed for amino acids likely to be present in limiting proportions.

The concentrations of utilisable energy per unit of price is important information to allow choices to be made between feedstuffs for practical dietary formulations. There has been a long lasting debate as to whether net energy (NE) or metabolisable energy (ME) is preferable. Only one large data set of empirically determined net energy concentrations (NEp) of feedstuffs for poultry has been published. Although the ME system for describing the utilisable energy concentrations of feedstuffs is now widely used, different metabolised nutrients (protein, fat and carbohydrate) are utilised with different relative efficiencies for energy deposition. More recently, methods of predicting the NE of feeds from equations have been suggested. These include information on nutrient digestibility with or without determined ME values with corrections according to the efficiency by which the nutrients are utilised. The objectives of the present study were, firstly, to evaluate the relationship between determined apparent metabolisable energy (AME) and determined NEp concentrations for a range of poultry feedstuffs and, secondly, the relationship between four different NE prediction equations and determined NEp concentrations was evaluated using the same data set. There was a positive linear regression (p < 0.001) between the determined AME and NEp concentrations in a data set of 62 feedstuffs with a range of AME from 0.1 to 20.5 MJ/kg. This regression equation accounted for 92.8% of the variance in NEp. Each 1.0 MJ increase in AME gave a 0.69 MJ increase in NEp. However, this data set had a large proportion of low energy feedstuffs that are unlikely to be used in modern proprietary poultry diets. A subset of these data that included 40 feedstuffs with an AME range of 8.0–18.0 MJ/kg was also examined. The regression between determined AME and NEp concentrations in this smaller data set only accounted for 77.7% of the variance in NEp. There was evidence (p < 0.01) that AME overestimated the NEp concentrations of high protein feeds of animal origin compared with cereals, cereal byproducts and high protein vegetable feeds. Three NE prediction equations that require knowledge of the digestibility coefficients for protein, ether extract and carbohydrates all improved the precision of the NEp prediction. However, a fourth prediction equation that requires only AME and crude protein determinations gave an equally precise estimate of NEp.

This review focuses on recent progress on the functions of choline and betaine and on the interactions between these two methyl donors and methionine chickens (mainly), pigs, fish (and crustaceans). When chickens receive a diet marginally deficient in methionine, supplementation with choline or betaine does not generally induce a return to the maximum growth rate. In this species betaine potentiates submaximal doses of some anticoccidial compounds, most probably through its osmolytic property. The ‘slimming’ effect which has been observed for betaine in a few assays with chickens and pigs has not been confirmed in several other species and therefore remains to be unequivocally demonstrated. In fish there is a need for phospholipids during the early stages of development. In salmonidae some studies suggest that betaine may facilitate the adaptation to sea water.

The activity of feeding and the metabolism caused by digestion and assimilation of food increase an animal's heat production. This increased heat production has been referred to as specific dynamic effect, specific dynamic action or heat increment (HI). HI is much larger when protein is a source of energy than when carbohydrate or fat are the sources of energy. HI for protein is much greater when the animal's ambient temperature is high than when it is low. Metabolisable energy is used more efficiently, thus having less HI, for maintenance than for production. A suggested explanation is that heat resulting from digestion and assimilation of food can substitute for the heat production in fasting when food provides energy equal to, or less than, maintenance requirements. When energy intake is large enough to support production, HI from anabolic processes becomes a waste product that cannot substitute for a fasting or maintenance function. The same rationale can be applied to the observation that dietary protein has a greater HI when an animal is at high temperatures. At low temperatures protein would be used for maintenance. At high temperatures the same amount of energy from protein would be enough to support production. As a result, HI of the protein would be increased at high temperatures. The high HI of protein or amino acids when at a high level in the diet can be at least partially explained. Protein synthesis requires a large amount of energy. Some energy is required to excrete nitrogenous waste. In addition, dietary protein stimulates protein turnover. Research findings have suggested that HI should be lowered by decreasing dietary protein. For non-ruminant animals this could be accomplished by discovering the essential amino acid requirements for an ideal protein. The ideal protein should result in a minimum HI. Research to date generally fails to document improved feed efficiency as a result of feeding an ideal protein.

Points that raise animal welfare concerns in the turkey broiler production chain are reviewed. Genetic selection of fast growing strains has increased locomotory problems and made natural mating impossible. A range of different photoperiods are used in practice (constant daylength, increased daylength with age, intermittent lighting) and have many consequences for welfare. High stocking densities have several drawbacks such as poor air quality, cannibalism and impairment of the gait of the birds. Methods of control against cannibalism, which include keeping birds at low light intensities or beak trimming, also raise welfare questions. Studies on the determination of optimal group size and on the possibility of enriching the pen environment are required. Depopulation procedures, transport and slaughter are further causes of poor animal welfare and would also benefit from further research.

A review is given on the effects of the inclusion of Jack beans (Canavalia ensifomis L. DC) in poultry diets. Their use is restricted by the presence of a number of antinutritional factors which affect performance when consumed by poultry. The principals of these are identified as concanavalin-A (a lectin), canavanine and canaline (so-called non-protein amino acids), urease and saponins. The mechanisms of their toxicity and the rationale behind the methods that have been used to detoxify Jack beans are described. These mainly involve heat processing, but other approaches such as ensiling, fermentation and addition of chemicals have been applied. It is concluded that, although substantial improvements in nutritional value can result from a number of such treatments, processed Jack beans still contain a residual toxic component which results in depressions in growth rate, food intake and food conversion efficiency when they are included in poultry diets.

The review presents information on non-starch polysaccharides (NSPs), the major antinutritive factors found in cereals and a variety of other feed ingredients. The unique characteristics of these compounds and their effects on the utilisation of other dietary components are highlighted. The effects of NSP on the gross weight of the gastrointestinal tract, mucosal structure and function are examined and some reference is made to other species on which more research has been conducted. More research is required into the effects of NSPs on the integrity of the intestinal mucosa in poultry. Such information may assist in the development of breeding and management strategies to reduce the effects of NSPs.

Evidence from published trials is reviewed to investigate whether there is any need to change the recommended optimal light intensity for laying fowls from 5 lux. Although some recent trials have recorded excellent performances from birds exposed to light intensities of less than 5 lux, it is concluded that this has more to do with the ability of modern pullets to lay well even without photostimulation than with any change in the threshold of light sensitivity. There is good recent evidence that the stimulation of early sexual maturity a large increment in the photoperiod during the growing stage requires minimal intensity of 2lux, and that 41ux is probably required for maximal response. By combining the results from all available trials, it is possible demonstrate small but significant effects of light intensity on egg size, food intake and mortality. An economic analysis, which takes into account all these responses, indicates that the optimal profit occurs at about .5 lux. Although the prices used in that analysis are both local and ephemeral, the optimum will vary very little within other cost structures, because it is determined almost entirely by the lower outputs predicted at intensities below 51ux and the greater electricity cost in providing very much higher intensities. It recognised that, because maximising profit is not always the sole objective enterprises involving animal production, considerations for the welfare of both the livestock and workers may make it prudent to recommend a slightly higher value such as 1O lux.

Sunflower meal (SFM) has the potential to be a major feed ingredient for poultry in many countries not suitable for extensive soyabean cultivation. SFM is a good source of protein with amino acid availabilities similar to those of soyabean meal (SBM), and much higher than those in cottonseed or rapeseed meals. Its lysine content is relatively low but this can be resolved with supplemental lysine. Fibre content should be decreased to a minimum by dehulling during processing of the sunflower seed for oil extraction. Fibre < 12%) can still cause bulky feed at higher inclusion rates (< 30%), and as a result dietary nutrient dilution (particularly in broiler diets) may occur. Nevertheless, pelleting the diet can help overcome the bulkiness and thereby lead to improved growth and feed efficiency. Another characteristic of SFM is that it does not have anti-nutritional factors such as those found in soyabean, cottonseed and rapeseed meals. Enzyme supplementation to SFM-based diets in different types of poultry species need further study. The ingredient can successfully be included in layer, broiler and waterfowl diets to replace 50–100% of soyabean meal, depending on the type of diet and the nature of the other ingredients.

Ostrich meat may be consumed as a healthy alternative to beef. The establishment of ostrich farming systems is not sufficient to satisfy consumer demand without the use of a successful production and marketing strategy. Given the current export driven nature of the industry in Southern Africa and the need for the development of a domestic market, a good understanding of the position of ostrich meat in the marketing mix and the key elements in meat processing is necessary.

Mycoplasma synoviae belongs to the class Mollicutes which includes the mycoplasmas, the ureaplasmas, the acholeplasmas and the spiroplasmas. These organisms, most of which are parasites or commensals of plants, insects and animals, are among the smallest prokaryotes capable of independent life. Numerous factors have been associated with the pathogenicity of Mycoplasma infection, including cytadhesion to host target cells, evasion of host immune defences, stimulation of host immune-related self injury, toxin production and harmful effects on host cell metabolism. In animals, mycoplasmas usually colonise mucosal epithelial surfaces of the upper respiratory and urogenital tracts and the mammary gland; however, some mycoplasmas have the potential to invade systemically. Strains of M. synoviae differ in the severity with which they cause disease in poultry, from subclinical infection to upper respiratory disease and, occasionally, septicaemia and synovitis. Current findings indicate that the pathogenicity of M. synoviae in poultry involves attachment and colonisation of the organisms in target tissues; however, one or more as yet unidentified factors seem also to be necessary.

Post-mortem assessment of poultry health requires both identification and classification of the severity and chronicity of lesions. Such assessments are essential for deciding the necessity for treatment or its withdrawal. Poultry meat inspection and routine necropsies are also complicated by subclinical as well as hidden inflammatory processes which result in decreased production. Measurement of changes in the plasma levels of hepatic acute phase proteins in mammalian species is known to give an indication of the stage and severity of inflammatory processes as well as identifying inaccessible lesions. For poultry, several papers have been published on the plasma changes of some acute phase proteins in association with some common poultry diseases and general inflammatory processes. Some have corresponded well with the severity and stages of lesions. It is suggested that measurement of such proteins could be used to complement routine necropsy findings. Understanding the chicken acute phase response, major acute phase proteins present, and their advantages and shortfalls as markers of inflammation, is paramount to the achievement of these goals.

Birds live longer than mammals of comparable sizes, contrary to what their metabolic rates, plasma gulcose concentrations and body tempratures, all of which are higher than mammalian norms, would suggest. Although these factors should predispose them to accelerated tissue degeneration, this has been shown not to happen. In this paper the possible mechanism whereby birds limit the accelerated tissue damage that should be associated with the above characteristics are explored. Specifically, this review will focus on the relationship in chickens between the raised concentrations of plasma glucose and the lack of associated tissue complications. We propose that the role of uric acid in birds should be re-examined. Until now uric acid has been considered to be little more than an excretory by-product where its role as an antioxidant can be directly linked to the resistance of birds to glucose-mediated tissue damage. It is suggested that, compared with mammals, the lower rate of generation of reactive oxygen species in birds in association with their stronger antioxidant-defence system contributes to their longevity.