Intensive genetic selection of broiler breeders and layer hens for economically important production traits, which has been carried out for almost a century, resulted in considerable differences in the mechanisms of growth and development and, thus, in avian metabolism, both during embryogenesis and after hatching. Selection for meat production (broiler breeders) and eggs (layer hens) led to increased productivity but also brought about metabolic disorders. That intensive genetic selection of broiler breeders and layer hens is effective is seen, for example, in the differences in growth and development, metabolism of the yolk sac, hormones and lipids, gas exchange, and thermogenesis. Due to genetic proximity and different developmental mechanisms in broiler breeders and layer hens, avian embryos and chicks serve as excellent models for fundamental scientific research. This review paper discusses the consequences of different growth rates as a result of long-term genetic selection on embryonic development and metabolic rate of broilers and layers. The evidence presented herein indicates that it would be worth comparing these issues in a meta-analysis.

Because the production of oat geese in Poland, destined mostly for markets of Western Europe, has increased, there is a need for a review on the performance traits of these geese and on the quality of their meat and fat. Goose production is based on a genotype of Italian geese brought to Poland in 1962 and selected for improving their reproduction and meat traits. Currently the population of geese, their reproduction and the commercial birds derived from them, are referred to as White Kołudzka® geese. Selection of these birds is based on a programme based on genetic improvement of strains W11 (reproduction traits) and W33 (meat traits). The programme's aim is not only to enhance breeding and the performance value of these strains, but to produce, as a result of cross breeding, good quality of meat and fat in the form of the crossbred W31, and thus to produce oat geese that meet today's market requirements. Poland is one of the largest goose producers in Europe. Goose meat and fat show high nutritional quality due to the specific nutrition and conditions in which the geese are kept, i.e. in open-air runs and at pasture. Recently, goose meat has become increasingly popular and has attracted much consumer interest. This increase in demand requires more knowledge about the meat's nutritional value. Polish oat geese are reared up to 14 weeks of age, then fattened freely with oats up to the 17 th week of age. Fattening with oats results in good quality meat and fat, with excellent sensory properties. The following paper reviews the rearing systems, slaughter value and quality of meat and fat of White Kołudzka® geese kept under semi-intensive systems.

Genetic selection that has been carried out for several dozen years has led to significant progress in poultry production by improving productive traits and increasing the profitability of broiler breeder and layer hen production. After hatching, broilers and layers differ mainly in feed intake, growth rate, efficiency of nutrient utilization, and development of muscles and adipose tissue. A key role can be played by hormonal mechanisms of appetite control in broilers and layers. The paper discusses the consequences of different growth rates resulting from long-term genetic selection on feed intake, efficiency of nutrient utilization, and development of muscles and adipose tissue, with particular consideration of the hormonal mechanisms of appetite control in broilers and layers. The information presented in this review paper shows that it would be worth comparing these issues in a meta-analysis.

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