Research progress of welfare-oriented breeding mode and technical equipments for laying hen

Abstract: Welfare-oriented housing system for laying hens has started to be explored in China in recent years, while it has been developed for 30 years in America and other countries in the world and achieved much research progress. After the European Union (EU) promulgated the ban of conventional cages, much progress has been made over the world in developing valid alternative housing systems to enrich hen's welfare. However, the ratio of welfare-oriented systems in laying hen housing system is still very low in the main egg-producing countries. Welfare-oriented systems not only enhance the welfare on laying hen, but also improve the health of hens, especially on aspect of the bone health. With more and more people paying attention to food quality and food safety, it is very crucial to develop new housing systems for laying hen in China, so as to enhance the health of the hens and their product quality and meanwhile reduce the use of veterinary drugs. Here, we reviewed the following aspects related to welfare-oriented poultry housing system. Firstly, we discussed the current classification and description of different laying hen housing systems. Furnished cage was a modified conventional cage. It also provided with litter materials, nests and perches for some foraging, dust bathing, nesting and perching. However, the space in the furnished cages was still limited for locomotion and comfortable behaviors such as wing flapping and flying. Non-cage system provided sufficient barn environment for hens, and a larger space for hens' behaviors in the horizontal and vertical plane than furnished cage. Free range housing system was supplied with some outdoor hours for hens. The novel style of free range systems named "the roundel" has been introduced. The different housing systems were compared on hen welfare, which included health, productivity and egg quality, and effects of social, economic, environment aspects on them. Hen welfare in non-cage system was better than that in cage system, such as the better egg quality. Mortality was generally lower in furnished cages if compared with conventional cages, but sometimes mortality could reach unacceptably high levels in non-cage systems. More comfortable behaviors have been observed in furnished cage system than in conventional cages. However EU market table eggs ordering system gave the same label for eggs laid in conventional or furnished cages. It also addressed the main problems of different housing systems. Systems with litter created a better environment for hen welfare, however damaged some aspect of hen health. A major reason was that hens contacted with manure which was mixed with litter. What was more, the concentrations of ammonia and particular matter in aviary systems were much higher than those in cage systems because of the use of litter. Small population scale was a nice choice for developing welfare-oriented housing systems based on the behavioral characteristics of hens. In the last part, we introduced a new type of free aviary laying hen housing system developed by our laboratory. It was a system which provided multi-tier feed and drinking floors. It also provided with multi-tier perches and 2 rows of nests, however without litter. One unit of the system raised 360 laying hens, so as to provide a considerably large space for hens' locomotion. In conclusion, no system currently under consideration was ideal now. Besides animal welfare, the advantages of conventional cages related to free from other hens, better health condition and lower cost should be in consideration in order to change the current design of housing systems. Even a housing system that was designed to be better to hen welfare could have a negative effect on welfare or even health if it was under poorly managed conditions. In the end, we looked into the future of welfare- oriented housing systems.