CHICKEN EGG PRODUCTION BY BREED TRIAL

Regarding this last aspect, it is important to stress that the laying period begins at pubertal age that is reached by the animals at different ages and body weights according to the genotype. In fact the hen genotype mainly affects the oviposition performance and the egg weight and component proportions behavioural responses of the birds are also important as well as changes in the quality of the eggs throughout the productive cycle. In outdoor conditions the hen strain and the management of the birds constitute important steps of the productive cycle. According to the animalsвЂ™ welfare goals, outdoor rearing conditions allow the hens to better perform their behavioural traits in comparison to intensive production and the farms involved in tourism and animal welfare usually rear chickens and hens under outdoor and pasture conditions. The importance of purebreds is now increasing in industrialized countries as people and rural tourism become more interested in typical food products, with particular characteristics that allow them to distinguish a farm product from an industrial product. Purebred hens are currently a small part of the worldwide population of reared hens since they are still widely reared in less developed countries. Eggs of hybrid hens differ in eggshell colour, weight and percentages of yolk and albumen according to the strain, but the highest differences exist between hybrid and purebred genotypes. Throughout the last fifty years many traits of poultry eggs have been modified and improved by genetic selection to satisfy the requirements of consumers and a food industry which uses egg albumen and yolk for many purposes. Under outdoor conditions the laying behaviour of the purebred hens and the nest management are important factors for the saleable egg rate. The RM hens showed the highest% of defective eggs, especially for overcrowding at nest, HB showed the lowest. In conclusion, according to an egg scoring evaluation (egg weight = medium-large size, yolk to albumen ratio = 0.5, total inclusions = none), HW showed a higher quality than HB and RM, and ER was intermediate. The purebreds showed meat spots% higher than blood spots HW showed the lowest total inclusion%. With aging, the yolk to albumen ratio linearly increased in all groups, eggshell% changed in ER, HW, RM (cubic) and in HB (linear). The eggshell colour varied among brown eggshell ER, RM, and HB. Double-yolk egg% was higher in hybrids than in purebreds. Broken and out-of-nest egg% were higher in RM and HW than ER and HB, respectively. The hybrids showed a higher laying rate and hen-day edible egg mass, and a lower body weight than the purebreds. Significant ( p < 0.01) differences among genotypes were found. Italian dual-purpose purebred (Ermellinata di Rovigo-ER and Robusta maculata-RM) and hybrid (Hy-Line Brown-HB and Hy-Line White 36-HW) hens (flock size: 70 birds/genotype) were allowed outdoors (4 m 2/bird, good pasture during the growing period and poor pasture throughout the laying period, according to the season) and indoors (0.20 m 2/bird, five birds/individual nest) and fed commercial feed.

CHICKEN EGG PRODUCTION BY BREED TRIAL

The four genotypes were reared on the same trial station, on four areas (one genotype/area), and under the same environmental conditions from hatching until the end of the trial. This study compared the yield performance, laying behavioural traits and egg quality of purebred and hybrid hens (from 28 until 44 weeks of age, considering four periods) reared under outdoor conditions. The local breeds showed differences from hybrid hens both for yield performance and laying behaviour and for both egg size and external and internal quality. The knowledge of the variation of these traits is useful for managing the breeding of these genotypes and the offer to the consumers. A comparison between purebred and hybrid hens throughout the laying period was carried out in order to study yield performance, laying behavioural traits and egg quality. At present, the Veneto region shows an important poultry biodiversity with many breeds, whose egg production traits are not well known. In Northern Italy, in the Po river plain, a relevant part of the maize production was used also for poultry feeding and many breeds existed in the last centuries. Many countries have a historic poultry tradition, with breeds used for domestic egg production. Nowadays, the consumer has a choice of table eggs depending on rearing system, egg size, eggshell and yolk colour, produced by a few worldwide hybrid strains.

Chicken egg production by breed