ABSTRACT:In an experiment with three strains of Dominant genotype the effect of oviposition on egg quality characteristics was investigated. Laying hens of the Blue strain (group 1), Plymouth Rock (group 2) and their F1 cross (group 3) from 20 to 64 weeks of age were housed on litter (9 birds per m 2 ). The collection time was at 6.00, 10.00 and 14.00 h. Eggs were gathered in a 28-day interval, every two days all produced eggs (720 eggs in total). The time of oviposition was influenced by genotype. The highest number of eggs was collected in the Plymouth Rock strain at 6.00 (53.5%) and the lowest in the Blue strain at 14.00 (11.1%). There were interactions between the time of oviposition and genotype in egg weight. Eggs laid in the morning at 6.00 were significantly heavier (60.5 g, 64.9 g and 62.1 g) in comparison with eggs laid in the afternoon (59.3 g, 62.4 g and 62.7 g). The heaviest eggs were produced by the Plymouth Rock strain. Significant interactions were observed in eggshell weight when the heaviest eggshell was in afternoon eggs (5.6 g, 5.8 and 5.9 g) and F1 genotype. The egg shape index was also affected by the genotype and time of oviposition. Among the albumen quality characteristics only Haugh Units were influenced by genotype and significantly higher numbers were determined in the Plymouth Rock strain (85.0, 85.3 and 84.7). The genotype significantly affected also the yolk index which was the highest in F1 genotype (45.4%, 45.4% and 44.5%).

The study examined the effect of dietary supplements of sodium selenite (SS), selenium-enriched yeast (Sel-Plex®, SP) and selenium-enriched alga Chlorella (SCH) on growth traits, carcass analysis, selenium content in breast meat, glutathione peroxidase (GSH-Px) activity in breast and thigh meat and liver of chickens. The experiment was realized with seven hundred thirty-five cockerels Ross 308 randomly divided into 7 dietary treatments with 3 replications in each treatment. Chickens were fed a diet supplemented with 0 (control), 0.15 or 0.30 mg of selenium/kg in the form of sodium selenite (SS), Sel-Plex® (SP) and selenium-enriched alga Chlorella (SCH). Selenium addition influenced body weight at 21 (P ≤ 0.001) and 35 (P ≤ 0.05) days of age. Significantly higher body weight at 35 days of age was determined in chickens receiving 0.15 mg of selenium from SP (2 122 g) and 0.3 mg of selenium from SCH (2 116 g) contrary to dietary treatment with a lower level of selenium from SCH (2 010 g) per kg of feed. The selenium content in breast muscle was increased (P ≤ 0.001) by both the lower and higher selenium concentration in the form of SP (0.6 and 0.85 mg/kg dry matter) and SCH (0.6 and 0.82 mg/kg dry matter) in comparison with the control (0.31 mg/kg dry matter). A significant increase (P ≤ 0.001) was ascertained even in SS treatments, but no significant differences were found between both levels. The selenium source and level, including SS, significantly (P ≤ 0.001) influenced the GSH-Px activity in breast and thigh meat.  

-This investigation was carried out to evaluate certain egg quality characteristics of ISA Brown laying hens and Japanese quails (Coturnix coturnix japonica) in relation to their age. One hundred forty-four brown-egg ISA Brown laying hens and one hundred female quails were used in the study. A total of 1,678 eggs of laying hens and 2,060 eggs of Japanese quails were used during the experiment. The eggs for technological values were collected during two consecutive days in a 4-week period when the laying hens were from 20 to 60 weeks of age and the quails were from nine to 49 weeks of age. The results show that egg weight was affected by the age of the hens and quails (overall means 61.13 g and 12.52 g, respectively). Despite frequens fluctuations, as the age of the laying hens and quails increased, the yolk index and yolk proportion increased as well, while the albumen index, eggshell strength and shell thickness decreased. The increasing age of the hens also led to a decrease in egg shape index and eggshell proportion, but these parameters increased in the quails. A significantly higher proportion of albumen was found in the hens than in the quails, but of worse quality than in the quails as expressed by Haugh units score. The egg from ISA Brown hens had a darker yolk color than those from Japanese quails (5.90 vs. 4.87 in the La Roche scale).

ABSTRACT:The effect of three housing systems (conventional cages, enriched cages and litter) on egg quality parameters was evaluated in two experiments with four brown laying strains ISA Brown, Hisex Brown, Bovans Brown and Moravia BSL. During 40 weeks of lay the total number of 7200 eggs was produced and analysed for egg weight, egg component weight and eggshell quality indicators. In 60 eggs, pore density in the small-end, large-end and equatorial areas was determined. Significant interactions between genotype and housing were found out in egg weight (P ≤ 0.001), yolk and albumen weight (P ≤ 0.001) and yolk colour (P ≤ 0.001). Haugh units were the highest in eggs laid in cages and the lowest in the ISA Brown strain. Eggshell quality indicators were affected more by genotype than by housing. The interaction between genotype and housing was not significant for eggshell thickness but it was significant for eggshell weight and strength. Although eggshell thickness was lower in eggs produced in cages, eggshell strength was higher. A significant negative correlation was found out between pore density and housing system. Results of the study suggest that the ability of a strain to produce eggs of high quality in a particular housing system should be considered, even within brown strains.

AbstrAct:The effect of weaning age on growth, feed consumption, digestibility of nutrients, carcass yield, mortality and parasite incidence was studied in a balance experiment. Forty Hyplus ® rabbits proceeding from a commercial rabbitry were assigned to four groups of 10 rabbits according to weaning age at 25, 28, 31 and 35 days. The experimental diet had 17.03% crude protein, 4.66% fat and 18.30% crude fibre. Feed and water were available ad libitum. At the end of the experiment, at 84 days of age, six rabbits per group were slaughtered. In the experiment, most results of performance were not significantly (P ≤ 0.05) affected by weaning age. Only the rabbits weaned at 25 days of age had higher live weight (P ≤ 0.05) at the age of 35 days (996, 986, 971 and 910 g, respectively), but at the end of the experiment we did not find any differences between groups. Higher digestibility of nutrients was recorded in the second collection period. In the first collection period the digestibility of nutrients was higher in rabbits weaned at 25 days of age in comparison with the other groups. No differences between groups in the digestibility of nutrients were observed in the second period. The age of weaning did not influence carcass characteristics. Dressing percentage was insignificantly higher in rabbits weaned at 25 and 35 days of age (53.11 and 53.07%, respectively) in comparison with rabbits weaned at 28 and 31 days of age (50.89 and 52.67%, respectively). There was no significant effect of weaning age on mortality. The incidence of Eimeria ssp. was the highest after weaning in rabbits at the age of 35 days.