The nutritional antagonism of arginine (Arg) and lysine (Lys) was first identified and investigated in the 1950's and 1960's. The results of this early research suggest the optimum Arg:Lys ratio to fall between 0.8 and 1.7, depending upon dietary levels of electrolytes such as sodium, potassium, and chloride. Calculations from the more recent optimum amino acid balances included in widely referenced authoritative sources suggest the optimum Arg:Lys ratio to be in the range from 0.90 to 1.18. Changes from the ‘optimum’ value of the ratio can have adverse effects on the performance of growing poultry. The effect is more evident with an excess of lysine (low Arg:Lys ratio) than with an excess of arginine (high Arg:Lys ratio). Studies with heat-stressed broilers have shown that the optimum Arg:Lys ratio varies with ambient temperature. The Arg:Lys ratio for optimum broiler body weight gain and feed efficiency increases at high temperatures, probably because of a reduced uptake of arginine from the digestive tract. The improved response of broilers to increasing dietary Arg:Lys ratio is most clearly seen during heat stress with diets containing minimum concentrations of NaCI. This response diminishes with high dietary NaCl and with NaHCO3 supplementation, when the optimum dietary Arg:Lys ratio declines from the high ratio (~1.30) observed with low dietary NaCl. Furthermore, the nature of the methionine activity source influences the optimum dietary Arg:Lys ratio for heat-stressed broilers. The performance of broilers fed 2-hydroxy-4-(methylthio) butanoic acid (HMB) is optimised at high Arg:Lys ratios (1.35) whereas broilers fed equimolar supplements of DL-methionine (DLM) tend to optimise performance at lower Arg:Lys ratios (1.05). The selection of the correct methionine activity source as a dietary supplement is likely to become more important if the current trend to exclude animal protein feed ingredients with low Arg:Lys ratios from poultry diets continues.

Heritabilities for egg quality traits in Japanese quail are moderate to high, and there are strong genetic correlations between egg weight and its component parts. Egg quality is affected by selection on body weight, but these effects differ somewhat between experiments, maybe in relation to the origins of breeding lines. Selection on egg production could increase yolk content. Direct selection work on egg quality traits has shown that there was genetic variation for yolk-related characters. The ω6/ω3 PUFA ratio can be improved by selection.

The physical characteristics of the egg play an important role in the processes of embryo development and successful hatching. The most influential egg parameters are: weight, shell thickness and porosity, shape index, described as maximum breadth to length ratio, and the consistency of the contents. The average values of the physical characteristics mostly meet the requirements for the embryo's development. For those eggs, whose parameters do not fall in to the average range, the incubation process is more successful if the shell is thicker than average, the eggs are more pointed rather than round, and the contents firm. The results reported for investigations into incubating eggs, whose weights are not within the average values, are contradictory. Both thick shells and firm interiors, which are accepted as being higher than average, lead to an increase in egg weight, which probably results in the more successful hatching of embryos from heavier eggs.

This report is a standardized compendium of age-related reproductive response data of turkey hens from the use of dietary supplemental d-biotin, pyridoxine and folic acid; and of commercial and domestic egg injections of each of the crystalline vitamins to determine their limiting inherent essence in causing embryo failure. With reproductive response data reported in each of three grouped time periods of production (5–6 wk each), the system of analysis was not confounded with feed consumption with the progression of maternal age.

Maternal age had no effect on vitamin transport to the egg for any of the three vitamins; and no effect on hatchability or poult weight, with the exception of biotin and folic acid, respectively. With the progression of maternal age, higher dietary biotin and folic acid levels were required for hatchability and poult weight, respectively, after 5–6 wk of production.

There was a lack of/or minor effect of dietary pyridoxine on the transfer of vitamin B6, for hatchability of turkey eggs. Egg injections of pyridoxine were vital for increasing hatchability even though the hen's diet was amply supplemented with pyridoxine. Manual egg vitamin injections are considered valuable for diagnosing possible limiting vitamins for hatchability. The manual injection method utilized small egg numbers and was administered at selective intervals over the production cycle. Automated injections were utilized for commercial flocks where egg numbers were large. Automated egg injections performed in the commercial sector, had no detrimental influence on poult viability or growth after hatching. Statistical reliability existed between hatchability results of automated and manual egg injections of a single vitamin level, and between different flocks of the same strain, both commercial and experimental.

The report offers practical insight for versatile changes in meeting dietary and egg needs of the three vitamins for higher reproductive performance. The report also offers new insight for hatchability improvement with dietary biotin with the progression of age in the hen.

Laying hens have physiological responses that affect their productive performance when given different ambient temperatures. The objectives of this study were, first, to quantitatively describe the relationship between different constant environmental temperatures and egg production characteristics of laying hens by a statistical analysis and assessment of the published literature. Second, to compare the effect of different cycling environmental temperatures on the egg production characteristics of laying hens. Twenty-nine experiments were selected that had compared different constant temperatures and that included 21°C within their range. Differences in egg production were expressed as a proportion of the treatment group given 21°C within that experiment. An exponential curve with the addition of a linear trend gave the best (P<0.001) description of egg numbers, weight and mass, feed intakes and egg composition variables. There was a linear decrease (P<0.001) in measures of shell strength with increasing temperature. A second statistical analysis compared eight published experiments that had described the egg laying responses of laying hens kept in daily fluctuating temperatures and had been compared to a treatment group kept at 21°C within the same experiment. The results indicated that the egg laying responses of the hens were best predicted by computing the mean of the predicted responses to each of the temperatures that occurred during the day. However, information on the low temperature, the proportion of the day at the low temperature and the amplitude of the temperature cycle were required to give a precise prediction of the egg laying responses.

Selenium (Se) has a special place among the feed-derived natural antioxidants, being an integral part of selenoproteins participating in the regulation of various physiological processes in the body. As a part of glutathione peroxidase (GSH-Px) Se belongs to the first and second major levels of antioxidant defence in the cell. There are two major sources of Se for poultry organic selenium, mainly in the form of selenomethionine (SeMet), which can be found in any feed ingredient in varying concentrations and inorganic selenium, mainly selenite or selenate, which are widely used for dietary supplementation. There is a principal difference in metabolism and efficiency of these two forms of selenium, with SeMet being more effective. In fact SeMet possesses antioxidant properties, however, in some conditions selenite can be a pro-oxidant. Se deficiency and excess in modern poultry production are very rare. In general, adequate Se supplementation is considered to be a crucial factor in maintaining the high productive and reproductive characteristics of commercial poultry.

The main aim of nutrition is to optimise productive efficiency, but this is usually only achieved when health is also optimised. Thus health and consequent welfare are major priorities in modern nutritional practices. The dietary contents of energy, protein and amino acids can be varied to alter specific production outputs, for example, growth rate, body composition, egg weight, usually without any adverse welfare impact. Genetic predispositions to specific disorders affecting the skeletal or cardiopulmonary systems associated with selection of broilers for fast growth can be partially overcome by changes to diet composition or feed supply aimed at suppressing growth rate. Vitamin and mineral deficiencies or imbalances can lead more directly to specific lesions and welfare problems. Metabolic disorders affecting poultry may not always be caused by nutrition, but good nutrition can often alleviate their impacts. Nutritional modifications can also help poultry to cope with stresses. The ban on the use of antibacterial feed additives is putting increasing pressure on the correct formulation of diets and the introduction of novel additives to optimise bird performance and health.

The work comments on the results of four experiments on biological responses of growing turkeys to fresh or oxidized fat applied in a concentrate mixture in amounts from 2% at the beginning (1–4 weeks) to 5% in the end period of fattening (13–16 weeks). The content of fat with a high peroxide value (50–150 meq O2/kg), which contained simultaneously a higher content of selenium (0.3 mg/kg), vitamin E (30–40 mg/kg) and vitamin A (1200–15000 IU/kg) caused reduction in body weight gain of turkeys, mainly as a result of lowered feed intake. Enriching diets with fat of a very high degree of oxidation (100–150 meq O2/kg) did not result in worsening of the turkeys' health condition, but considerably lowered their vitamin E reserves. Symptoms of muscular dystrophy and changes in biochemical and enzymatic indices in serum and liver were not observed. However, a decrease in the activity of lactic dehydrogenase in liver lesion of hepatocytes was noted, that was partially confirmed in microscopic assay and ultrastructural characteristics of liver. The rise in temperature (from 23°C to 30°C) in the rearing pens reduced the effect of the turkey feeding, while not, at the same time increasing a negative effect of oxidized fat on the fattening results. Products of fat oxidation increased the birds' susceptibility to virus infections causing haemorrhagic intestinal inflammation.

Resulting from EU-wide initiatives of animal welfare organizations, the Council of the European Union has approved stricter legal standards for keeping laying hens in battery cages (Council Directive 1999/74/EC). The economic impacts of this legislative review can be summarized as follows:

1. The current trade protection in favour of EU-producers versus imports from non-member countries amounts to approximately 0,01 Euro/egg. Hence, there is little scope for passing increased costs on to consumers.

2. Competitive disadvantages for the EU-producers, caused by increasing legal standards for keeping laying hens will become even more critical if future WTO-agreements cause further reduction in tariffs. As a whole, this will lead to a drastic cut in EU egg production.

3. Due to their cost advantages, countries with less stringent standards for keeping laying hens will extend their share of the EU- egg market. Thus, looking at the global picture, stricter legal standards within the EU will not lead to an improvement of animal welfare, but to a regional shift of the problems.

4. The fall in egg production in the EU will result in heavy losses to net value-added and employment. Given a decline in production of 10 billion eggs, it can be estimated that

- net value-added will decrease by approximately 270 million Euros.

- employment will lower by approximately 12,000 jobs.