Have the welfare rights of sentient domesticated animals been compromised by high density housing so that their basic behavioural and social patterns, inherent and learned, can no longer be performed in a manner which provides them with relief and satisfaction? Everyone has an opinion on welfare, but an adequate definition is another matter. Ultimately, welfare, is more than the sum of all the effects of the system, it is a holistic outcome.
The great problem for farmers and legislators has been how to decide what is practically viable, yet welfare sustainable in housing systems. Studies in this thesis were conducted to test incremental changes to existing husbandry systems to try to quantify and compare the welfare outcomes achieved by those systems.
To understand how welfare improvements can be mandatorally implemented into commercial poultry management programs, it is first necessary to understand the ‘Code of Practice’ development process in Australia. This process has been documented, examined and recommendations made for incorporation in future ‘Code’ reviews.
The use of space by hens is a complex issue. In order to improve welfare, legislators have proscribed minimum stocking density and cage configurations. A series of experiments was conducted to evaluate welfare and production in modified conventional cages. Floor area per hen (density), and cage configurations were evaluated. It was found that there are likely to be negative welfare benefits (increased feather pecking and cannibalism, and more adverse interactions) if stocking density was changed from 450cm2/hen to 675cm2/hen or more for hens in Australian open sided high light intensity sheds The removal of alternate cage partitions had the positive welfare benefit of hens being able to feed over twice the original feed trough width, and access to three nipple watering points per cage rather than two.
Conventional cages are generally perceived by the public to deliver a poorer welfare outcome than alternative intensive systems. The Edinburgh Modified Cage (EMC) was designed to provide welfare positive resources whilst maintaining the advantages of cages. The welfare and performance of three Australian layer strains (small, medium, and large body size) in EMCs was evaluated, and in a subsequent trial, two strains at commercial stocking densities were assessed. The 1994 EMC design was not well suited to the larger Australian layer strains, (not enough height between the perch and the cage ceiling, insufficient space between the perch and both the front and back of the cage). Manure built up behind the perch creating a possible hygiene problem for the hens, and a significant increase in the number of dirty eggs. Rectangular perches caused a significant increase in the incidence of keel bone deformation. Nest laying decreased significantly when stocking density was increased, and feed consumption decreased significantly as stocking density increased.
Long claws of hens in intensive cages are a welfare problem. Abrasive tape on egg baffies in the EMC, Harrison and Salmet cages abraded and blunted the claws, and the welfare benefits were less breaking and painful tearing of claws, less damage to feet, less likelihood of skin tears to neighbouring hens due to scraping, and less chance of entrapment at cage joints. Feather loss was significantly worse on the breast and keel of hens in the EMC cages compared to similar size groups in conventional cages. Tibia and femur bone strength were not significantly better in EMCs with perches than in the conventional cages, however the breaking force of humeri from hens in the conventional cages had a tendency to be greater than the EMC five hen cages and was significantly greater than the EMC six hen cages.
Blood leucocyte profiles (total white cell count, heterophil, lymphocyte, monocyte, eosinophil, basophil and heterophil/lymphocyte (H/L) ratios) were found to vary significantly between strains of Australian layers. H/L ratio was greater for larger sized layers and when stocking density was increased.
A possible ranking system to compare alternative housing systems was proposed. Five housing systems (barn pens, Californian, Salmet, Harrison and EMCs). were compared across a range of production, physical and physiological parameters. A model has been developed to 'rank' housing systems based on quantifiable welfare outcomes they deliver, and a chart showing the complexity and inter-relationship of factors leading to welfare status across all poultry housing systems has been constructed.