This study was conducted to determine the effects of two production systems (organic vs conventional cages) on egg quality parameters during the late laying period. The effects of a production system were investigated on external and internal quality and on the sensory attributes. The eggs produced in organic system had paler yolks (P0.001) and thinner egg shells (P0.05) than the eggs produced in the cages. Overall sensory quality was improved in eggs deriving from hens allocated in cages. Differences between organic and cage eggs indicated lower redness and higher yellowness (P0.001) in organic eggs than in cage eggs. The organic eggs were characterised by a higher content of -linolenic and docosapentaenoic acid (P0.05) and lower content of linoleic acid (P0.05) than the eggs from cages. The ratio of omega fatty acids, n-6/n-3, was most favourable in the organic eggs (5.93:1). In the cage eggs, the ratio n-6/n-3 was significantly (P005) higher (955:1).

The objective of this study was to evaluate effects of two commercially available probiotic additives, containing Bacillus spores, on carcass and meat characteristics, serum lipids and concentration of cecal volatile fatty acids of meat type chickens. Birds were fed regular corn-soy meal based feed (control), supplemented with additive A, containing 1.6 × 10(6) spores per gram of feed of Bacillus subtilis and Bacillus licheniformis (group A) or additive B, containing the same concentration of Bacillus cereus var. toyoi spores (group B). One hundred and twenty birds (20 per replicate) were slaughtered at the age of 55 days. Results showed that birds in group B had higher (p < 0.05) final body weight compared to birds from group A and higher carcass weights and yield percentages compared with control. Breasts and whole legs were also heavier in group B, compared to control, but not the yield. Group A had higher yield of wings and lower abdominal fat weight compared to group B (p< 0.05), but not compared with control. Total cholesterol was not affected by the dietary treatment, on contrary both probiotics elevated the LDL (p < 0.05) and lowered HDL cholesterol, thus unfavourably changed animal's blood serum cholesterol profile. Both probiotics influenced the cecal fermentation, which was observed as decrease in cecal concentrations of propionic, butyric, n-butyric and n-valeric acids, but the differences compared to control group were statistically significant for group A only. It was established that probiotic additive B was more effective regarding carcass and meat part weights than additive A, however the animals from group B also had more abdominal fat and their meat had significantly higher conductivity than control group, which is not considered as beneficial.

An F(3) resource population originating from a cross between two divergently selected lines for high (D+ line) or low (D- line) body weight at 8-weeks of age (BW55) was generated and used for Quantitative Trait Locus (QTL) mapping. From an initial cross of two founder F(0) animals from D(+) and D(-) lines, progeny were randomly intercrossed over two generations following a full sib intercross line (FSIL) design. One hundred and seventy-five genome-wide polymorphic markers were employed in the DNA pooling and selective genotyping of F(3) to identify markers with significant effects on BW55. Fifty-three markers on GGA2, 5 and 11 were then genotyped in the whole F(3) population of 503 birds, where interval mapping with GridQTL software was employed. Eighteen QTL for body weight, carcass traits and some internal organ weights were identified. On GGA2, a comparison between 2-QTL vs. 1-QTL analysis revealed two separate QTL regions for body, feet, breast muscle and carcass weight. Given co-localization of QTL for some highly correlated traits, we concluded that there were 11 distinct QTL mapped. Four QTL localized to already mapped QTL from other studies, but seven QTL have not been previously reported and are hence novel and unique to our selection line. This study provides a low resolution QTL map for various traits and establishes a genetic resource for future fine-mapping and positional cloning in the advanced FSIL generations.

No abstract

Chickens of the Slovenian commercial Prelux-bro line were divergently selected over 34 generations for high and low BW at 8 wk of age. The aim of the study was to estimate responses to selection with a nonlinear model. Estimates of BW for each generation were provided by the mixed model. For fitting generation means against generation or cumulative selection differential, an exponential model was used. Estimates of realized heritability over generations were derived from regression of the response on cumulative selection differential. After 34 generations, the lines differed by approximately 2,220 g for males and 1,860 g for females. Estimates for a selection limit in the high line were 2,598.4 and 2,144.1 g, for males and females, respectively. A selection limit was not reached in the low line. Half of the selection response was obtained after approximately 6 to 8 generations in the high line and 20 to 28 generations in the low line. Estimated realized heritability decreased over generations. Heritability was larger for females than males and reduction of heritability was more rapid in the high line than in the low line. Genetic SD decreased over generations. Phenotypic SD increased over generations in the high line, but was constant in the low line in the initial 22 generations and decreased thereafter. According to the good fit of the nonlinear model and informative parameter estimates, the results confirmed the usefulness of the nonlinear model for analyzing responses to long-term selection.