Broilers in colony systems — performance and welfare
Use of colony cage systems for broilers can raise productivity, and help to solve bird welfare concerns
Poultry meat consumption around the globe is steadily rising and, consequently, the poultry industry worldwide is registering a growing demand for housing systems.
Any poultry producer's decision on a management system, i.e. floor management or a colony with broilers kept in large groups, will depend on several factors, including statutory, local, climatic and other requirements, as well as on the availability of specific resources.
In the member states of the European Union, for example, poultry farmers are required by law to provide their broilers with access to litter. Other countries may allow broilers to be kept in systems without litter.
Working with local conditions
An example of the latter approach is Russia, where broilers have been grown in multi-tier colony systems since the 1970s. In Russia, this approach is a particularly practical one, considering that winters there are very cold and temperatures fall far below 0C in many places. In comparison with floor management, use of colony systems can save significant amounts of energy.
Since they were first used in Russia, demand for broiler colony systems has grown significantly and not only to address the circumstances in that market.
It also makes sense to increase the stocking density in countries where space is an extremely limited resource or where there are few agricultural areas, for example in densely populated countries such as Japan or South Korea.
Another example of where they can be particularly beneficial is in desert regions, where the lack of availability of functional litter can act as a limiting factor to production.
Apart from being a management type without litter, colony systems draw interest due to the following factors: The large group sizes compared with the number of feeding and drinking places (106 birds per section at a final fattening weight of 1.8 kg, 8.9 birds per nipple, 53 birds per feed pan) and ready access to feed and water. This allows poultry keepers to ensure that modern broilers express their full genetic potential.
Additionally, in colony cages, birds stand on flexible plastic flooring, which prevents constant contact with droppings. Instead, the excrement drops onto manure belts and is transported out of the house.
Despite the popularity of these systems, there is a lack of scientifically reliable data with regard to the economic parameters.
For this reason, the University of Göttingen was asked to carry out an empirical study to examine the performance, including feed conversion, weight gain, and duration of grow-out of broilers kept in a colony system, and to also look at animal health and welfare indicators, most notably the state of foot health.
The data analyzed by the University of Göttingen Livestock Production Systems research group were collected from a single batch of birds - 76,320 Ross 308 broilers - on a poultry farm in Turkey.
The poultry house measured 18 meters wide and 110 meters long and was equipped with six rows of a colony system. Each row consisted of 42 colony system cages (1.6 m x 2.4 m) with four tiers. In total, there were 1,008 colony system units with 76 birds kept in each cage. The house was further equipped with a multi-step cross-ventilation system.
One of the key measures of the data collection was the daily weighing of the control groups. Three control points per row were selected, from which 10 birds from each of the four tiers per colony unit were weighed. The control points were situated at the beginning, middle and end of each row. Between Days 19 and 34 of the grow-out, the feet of the birds were also examined.
At the end of the grow-out period, on Day 37, the birds had reached an average weight of 2,379 grams. The daily weight gain amounted to an average of 64.3 grams. Due to this high gain, the weight of the broilers on Day 32 was two days ahead of the live weight development standardized by breeder Aviagen (at a mortality of 1.33 percent). It seems likely that the daily weight gains can be attributed to the favorable bird-to-feeding place ratio, as well as to the good lighting of the colony systems at the beginning of the batch, that form part of the colony system in which the birds were reared.
The feed conversion ratio was at a good 1:1.57. As feed losses are easy to recognize by staff as a result of the system's plastic flooring, corresponding measures can be taken immediately where necessary, so contributing to efficient resource use.
By way of comparison, it is worth looking at studies conducted by the Lower Saxony Chamber of Agriculture's production branch in Germany in 2010. These found an average weight of 1,927 grams for broilers exclusively kept on the floor as required by European Union law after day 34.9 of the batch. The daily weight gains amounted to 55.1 grams at a feed conversion of 1:1.72.
Problems with broiler feet have been long recognized, and have become a focal point of debate on animal protection, food safety and reduced carcass quality. Some European countries have adopted foot pad dermatitis (FPD) as an indicator for bird welfare in broiler production.
The condition causes suffering, so negatively impacting health and performance. Should birds become lame, they will no longer be able to stand, and this increases strain on the chest. While pododermatis can be due to various factors, moist litter is among the most important causes. Pododermatitis was therefore a central parameter for the evaluation of the colony system in this study:
Starting with day 19 of the grow-out, 360 birds from the control groups were checked for any changes to their foot pads every three days during weighing. The changes were divided into three different classes in accordance with Berk's three-step scoring system. A score of 0 means no change to the feet, while a score of 1 indicates hyperkeratosis, i.e. excessive thickening of the skin and superficial lesions (wounds). Severe and deep lesions are a characteristic for score 2.
The study showed that for 98.0 percent of the birds examined, no changes to the feet pads were detected by day 34 of the grow-out. Only 2.0 percent of the birds exhibited changes, of which 1.4 percent were slight changes (score 1), and only 0.6 percent displayed severe lesions (score 2).
These results are due to the fact that the birds only had very little contact with their droppings, i.e. the ground was dry. The plastic flooring aids this, as air can constantly reach the chickens and, consequently, their feet dried very quickly.
Similar studies have shown that only 35.5 percent of birds kept in floor management systems do not show signs of pododermatitis. 26.1 percent exhibited mild hyperkeratosis and superficial lesions (score 1), while 38.4 percent had strong lesions (score 2).
The performance of broilers kept in this colony system is considered clearly above average. Important factors such as daily weight gains of 64 grams and a feed conversion of 1:1.57 underline the economic advantages of management systems without litter.
In addition, mortality as well as foot pad infections were at a very low level. This leads to reduced doses of medicines and affords higher levels of animal welfare, despite the limited space for movement.