A recent survey, by Spanish and Brazilian researchers, included results from flocks housed indoors in 16 countries.
A total of 176 million birds were included, kept in 6,040 flocks.
4,407 were cages (3,066 conventional and 1,341 furnished).
1,633 were in cage-free systems (412 in multi-tier and 290 in single tier) 931 flocks were not specified.
Details of beak trimming were given for 3,068 flocks, 84% of whom were trimmed. About half the flocks with intact beaks were in Norway, where the practice was banned in 1974.
Analysis of their data on mortality to 60 weeks indicated an average decline of approximately 0.35 – 0.65% per year in the cage-free aviaries.
Average figures from recent data showed:-
|
SYSTEM: |
AVERAGE MORTALITY |
RANGE |
|
Conventional Cage |
5% |
3 – 7% |
|
Furnished Cage |
3% |
0.5 – 5% |
|
Single Tier Aviary |
3% |
1 – 5% |
|
Multi Tier Aviary |
4% |
3.8 – 4.2% |
|
Non-Spec. Aviary |
3.5% |
2 – 4.5% |
Conventional cage mortality seemed to have reached a plateau over a 20 year period, but cage-free systems had dropped by 4-6% over 10 years.
The results seemed to confirm the results seen in Switzerland. Fifteen years after conventional cages were banned in Switzerland, infectious diseases often seen in other countries were mostly absent in Swiss flocks, due to the development of improved hygiene protocol and vaccination programmes.
Limited data was available from China, Mexico and Brazil.
The degree of experience managing cage-free systems seems to be a major reason for the lowering of mortality over time. Expect better results the longer flocks of cage-free layers are placed on units, and stockpersons get acquainted with the most beneficial management techniques.
