1. Computed tomography was used for the in vivo determination of yolk ratio in 7000 domestic hen eggs, originated from two markedly different genotypes, in order to examine the effect of egg yolk ratio, gender and genotype on the development of hatched chicks. 2. Eggs with extremely low, average and extremely high yolk ratio were chosen for further investigation (n = 350 in each group in both genotypes). After incubating the selected eggs, hatched birds were reared and slaughtered at 11 weeks of age. 3. The yolk ratio of eggs significantly affected the body composition of the chickens at hatching and during rearing to 8-9 weeks of age. 4. Chickens of a genotype selected partly for weight gain had significantly higher live weight from hatching to the end of the rearing period and had better slaughter characteristics than those of the dual purpose TETRA-H genotype. 5. At hatching, only the dry matter content of the body was affected by the gender of the birds. The effect of gender on the live weight and body composition of chickens was evident from the 5th week of age to the time of slaughter. 6. It was concluded that eggs with a low yolk ratio were most beneficial for broiler production, because chickens hatched from these eggs had the highest slaughter weight and muscle index and the lowest fat index for their body mass.
The experiment was carried out with altogether 1740 non-beak-trimmed laying hens, which originated from Bábolna TETRA Ltd., representing two different types (Rhode Island Red (RIR) and Rhode Island White (RIW)) and four different lines (Lines 1–2: RIR, Lines 3–4: RIW). The plumage and body condition of randomly selected 120 hens (30 hens/line) was examined at 20, 46, and 62 weeks of age. The egg production and the mortality of the sampled hens were recorded daily. Based on the results, it was established that the lines differ clearly in most of the examined traits. It was also pointed out that injurious pecking of the hens resulted not only in damages in the plumage but also in the body condition. The results obviously demonstrated that the highest egg production and the lowest mortality rate were reached by those hens, which had the best plumage and body condition. Because the occurrence of injurious pecking seems to depend on the genetic background, selection of the hens (lines, families, individuals) for calm temperament will be very important in the future in order to maintain the high production level in non-beak-trimmed layer flocks.
1. Using the so-called TOBEC (Total Body Electrical Conductivity) method, which allows the determination of egg composition in vivo, correlations between egg composition, hatchability and hatched chicks' development were studied. 2. A total of 1500 hen eggs (Ross-308) were measured by TOBEC, and eggs with extremely high (10%, n = 150), extremely low (10%, n = 150) and average (10%, n = 150) electrical conductivity values were chosen for further investigation. 3. During the incubation period, it was observed that eggs with high electrical conductivity had a significantly higher mortality than eggs with low electrical conductivity. 4. It was observed that both the increase in electrical conductivity at the same egg weight, and the increase in egg weight at the same electrical conductivity resulted in an increase in the hatching weight. 5. It was found that the dry matter, protein and fat content of the chicks hatched from eggs with low electrical conductivity was higher at hatching than that of the chicks hatched from eggs with high electrical conductivity. 6. At 42 d of age the liveweight of cocks and pullets hatched from eggs with low electrical conductivity was 3.2 and 8.2% higher than the liveweight of cocks and pullets hatched from eggs with high electrical conductivity. 7. Because of the higher liveweight at slaughter, there was a significant superiority of the chicks hatched from eggs with low electrical conductivity in the case of the examined carcase traits at slaughter. 8. Similar tendencies were found also in the ratios of carcase variables to liveweight, but the between group differences were not statistically significant in this case. 9. Based on the results it was concluded that TOBEC seems to be a useful method for separating eggs with different composition. 10. This could be a good starting point for further in vivo investigations in order to clarify the effect of egg composition on hatchability and further development.
The experiment was started with 1,508 Rhode Island Red (RIR) and 1,820 Rhode Island White (RIW) type non-beak-trimmed day-old pullets, which were originated from 58 RIR and 70 RIW different pedigree cocks, respectively. From all of the 128 cocks 26 half sibling offspring were tested. The pure line pullets were raised up to 18 weeks of age in a closed building, in deep litter pens and moved to the laying house and placed into three types of keeping systems [furnished cage, alternative pen (litter and floor) and conventional cage] thereafter. The number of dead birds and the cause of mortality were recorded daily during the whole rearing and egg-laying period, up to 72 weeks of age. During the rearing period the most frequent cause of mortality was wasting, which accounted for nearly 36% of the total mortality. Aggression was responsible for 28.3% of the total mortality. Depending on the type of the pullets (RIR or RIW), differences were observed in the frequency of occurrence of mortality causes. For example, oedema and beak deformation occurred only in the RIR, whereas technological injury and aggression only in the RIW pullets during the rearing period. During the egg-laying period aggression was the most common cause of mortality. Its lowest occurrence was observed in the alternative pens. In both of the examined types there were found cocks, whose offspring died exclusively by aggression, and cocks, whose offspring did not show any loss due to aggression. The ratio of these cocks differed significantly (P<0.05) between the two types examined. Based on the results it was established that the genetic background has significant effect on the mortality caused by aggression in non-beak-trimmed laying hens.
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