Consequences of different growth rates in broiler breeder and layer hens on embryogenesis, metabolism and metabolic rate: A review

Abstract

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.

Bioimpedance as a Non-Invasive Method to Evaluate Eggs and Poultry

“…These differences may be attributed to body size, because layer chicks are smaller than broiler chicks (Wilson, 1991). Chicks body size is influenced by egg weight, weight loss during incubation, genetic strain (Wilson, 1991;Tůmová & Gous, 2012), and embryo body mass (Buzala et al, 2015), which is greater in broilers than in layers. No significant differences between sexes were found for the evaluated parameters (Table 4).…”

Effects of the inclusion of sunflower hulls in the diet on growth performance and digestive tract traits of broilers and pullets fed a broiler diet from zero to 21 d of age. A comparative study

“…Similar data have been reported by Mahagna and Nir (1996) and Zavarize et al (2012) comparing broilers and pullets at young ages. The data suggest that when comparing chicken lines with marked differences in rate of growth, the interest of comparing in relative terms the weight and length of the GIT organs should be taken cautiously (Buzala et al, 2015).…”

Ovarian Morphology and Egg Quality Traits of Egyptian Selected Strain for Egg Production Compared with Commercial Laying Strains

“…Intensive genetic selection of layer hens for economically important production traits results in considerable differences in the mechanisms of growth and development (Buzała et al, 2015). Sexual maturity, defined as age at production of the first egg, is influenced by chronological age, body weight, and body composition (Oruwari & Brody, 1988).…”

“…Also, different genetic selection programs that were used in poultry breeding for almost a hundred years, led to positive effects in improving production performance in poultry (Buzała et al, 2015). Selection index, in layers breeding programs, that includes more than 30 closely related traits made it possible for balanced genetic improvements in different traits even when the traits are negatively correlated (Blanco et al, 2014).…”