Egg production systems

Summary
In each of the three year, a trial was started with up to 700 hens in the ”Eco cottage” build by DIAS at the beginning of 1997. The first trial was commenced by rearing four lines/line crosses in the conventional rearing system in Foulum and at the age of 16 weeks the pullets were transferred to the ”Eco cottage”. The pur-pose was to compare 3 extensively bred lines/line crosses from the small hatchery Hellevad in Vendsyssel with IsaBrown. The basic comparison was concluded at the time the hens had been in lay for 7 month, and the major results was that IsaBrown had laid considerable more eggs than the three Hellevad lines, but also that the IsaBrown during the 7 months had a mortality caused by cannibalism on 16% whereas the Hellevad lines did not show cannibalistic activity at all. Addition of the amino acid Methionine to the diet resulted in heavier eggs, otherwise no effect was observed. After concluding the basic test 40 hens from each of the lines were inoculated with eggs from Ascaridia galli; there was a considerable difference between lines in development and fecundity of the parasites, though the establishment of the roundworm was unaffected. It looks like that a choice of less susceptible lines could reduce the excretion of the parasite eggs and thus reduce the infection pressure in organic flocks of hens.

The two following trial in the ”Eco cottage” were concentrated on the matter of rearing condition. In the second trial all chickens were placed as day-old in the ”Eco cottage” and the treatment was as follows: Low versus high light intensity (3 lux versus 30 lux) in a cross factorial trial with early or late access to outdoor areas (6 weeks versus 16 weeks. No influence of these treatments was observed on laying intensity or feed consumption, while the frequency of floor laid eggs was higher at law light intensity during rearing. – At the third trial the factors investigated was: a) Rearing in conventional houses versus Eco cottage, b) rearing with or without mowing before placing in the laying house at 16 weeks, and c) high or low density of birds during laying (3.5 hens or 7 hens per m² indoor, and 7 or 3.5 m² per hen outdoor). As to the a) hens reared in conventional systems had a poorer feather cover at 39 weeks and a lower egg size otherwise no effect was found. Higher density during the laying period resulted in poorer laying intensity, more eggs laid on floor and a bit surprising also a better feather cover. In this trial was also carried out a comprehensive investigation of the effect of density on infection level with the roundworm Ascaridia galli.

Breeding and selection for tendency to feather pecking has been a success in the sense that significant difference was established between lines regarding tendency to perform feather pecking, but also the condition of the feather cover measured as areas with a lack of feather cover was different. The results obtained over the three generations corresponds to a realised heritability of feather pecking tendency of 0.2, which is the level of heritability that exists for laying performance. Observations indicate that an antagonistic co-variation exist between laying performance and tendency to feather pecking.

The results of the Tåstrup experiment, in which animal welfare and weight gain were compared in chickens exposed to 3 levels of continuous Ascaridia infection showed that significantly fewer worms developed into the adult stage at high infection levels. This was also reflected in lower egg excretion in the heavily infected chickens. Furthermore, significantly fewer worms established in the most heavily infected Group 3 after reinfection. Thus, the results indicate that the chickens acquire an effective resistance against Ascaridia infections.

he examinations of persistence of infective Ascaridia eggs in contaminated outdoor runs showed that the nematode eggs survived for at least 4 years. Further analyses of the results are needed, but the results indicate that the soil infectivity becomes reduced with time, and that the parasite load in the individual chickens became more variable.