Compost-bedded pack barns (CBP) are receiving increasing attention as a housing system for dairy cows that has potential to improve animal welfare. This article reviews current scientific knowledge about CBP with the aim of providing a comprehensive tool for producers and researchers using this housing system. In CBP, cows are provided with an open bedded pack area rather than the individual stalls and concrete alleys found in freestall systems. The bedded pack, a mixture of organic bedding and cattle excreta, is cultivated frequently (1-3 times per day) to incorporate fresh manure and air into the pack, thus promoting an aerobic composting process. To function well, CBP generally require a large area per cow. Optimal animal densities over the bedded area range from 7.4 to more than 15 m 2 /cow depending on several factors, including climate, bedding, pack management, and cow characteristics. Studies have indicated that CBP, compared with conventional systems such as freestall barns, have the potential to improve the welfare of dairy cows. In particular, the main reported benefits include improved comfort during resting, better foot and leg health, and more natural animal behavior. Research has also indicated that adequate udder health can be achieved in CBP. However, because the bedded pack has been shown to contain high bacterial concentrations, proper management is essential to maintain adequate cow cleanliness and reduce the risk of mastitis. Controlling pack moisture is consistently indicated as the most important issue with CBP. Especially under cold and humid weather conditions, large amounts of bedding may be necessary to keep the pack adequately dry and comfortable for the cows. Nevertheless, the improvements in cow health may offset the higher costs of bedding.

The objective of this review was to describe recent changes and expected developments in housing systems for dairy cows. These new developments should create an appropriate production environment for modern high-producing dairy cows and stimulate dairy farmingrelated developments in management, agro-technology, and equipment. Increased labor efficiency has been an important driver of the change from tie-stall barns to cubicle barns (also known as freestall barns). In future housing systems, the natural behavior of cows, climate control, emissions of ammonia and greenhouse gases, reuse of waste, manure quality, the aesthetics of buildings in the landscape, and capital efficiency are becoming increasingly important elements. To address future requirements, new concepts beyond cubicle barns must be developed. Freewalk housing systems; that is, loose housing systems without cubicles, would meet some of these future demands. These systems operate with composting bedding material or artificial permeable floors as lying and walking areas. However, these barns are still in development. Combinations of cubicle and freewalk housing systems, together with other techniques being developed, might become a major future housing system. Other techniques and systems that are being explored according to sustainability criteria include the multi-climate shed, the CowToilet (Hanskamp Agro-Tech, Doetinchem, the Netherlands) to separate feces and urine, and multifunctional buildings. These buildings and techniques can be part of land-based or, less commonly, city-based farming systems, such as floating farms.

In the Netherlands there is a remarkable difference in environmental performance between the average commercial dairy farm and some experimental dairy farms. Despite 15 years of policies and measures to decrease nutrient losses, experimental dairy farms based on careful nutrient management, like 'De Marke', realize much higher resource use efficiencies and much lower nutrient surpluses than the average commercial dairy farm.This paper discusses the transitions that are needed to bridge the gap between experimental dairy farms and commercial pilot farms. In the project 'Cows & Opportunities', 17 farms were selected representing the full range of conditions for dairy farming, with emphasis on dry sandy soils because of their environmental constraints. There are intensive discussions and communications between farmers, extension services, advisers from the industry, researchers and policy makers. Firstly, all farms were thoroughly analysed in terms of agronomic and environmental performance in the original situation. Secondly, opportunities for improving their performance were analysed using sustainability criteria like nutrient losses, energy and water use, emission of greenhouse gases, crop protection, accumulation of heavy metals, and nature development. Thirdly, an outline for a farm development plan was formulated to meet the nitrogen and phosphorus surplus targets set by the Dutch government. These first outlines (designs) were thoroughly discussed between farmers and researchers. After modelling the farm design to calculate the environmental and economic effects, the farm development plan was adjusted wherever needed, approved and implemented. The performance of the farm will be monitored and evaluated over the next few years. In the original situation, the MINAS nitrogen surplus on the farms ranged from 47 to 349 kg ha-1 , with an average of 207 kg. The modelling results indicated an average N surplus of 131 kg ha-I after implementation of the farm development plans, Le., 19 kg ha-1 less than the target surplus. The project 'Cows & Opportunities' demonstrates that it is-po&sible to meet the nitrogen and phosphorus surplus targets by taking simple measures. The project yields useful information on the relations between management measures, constraints, nutrient balances and environmental performance.

By-products like sawdust and straw are applied in compost bedded-pack barns (CBP) for cattle. These materials, which are gradually mixed with excreta and undergo a composting process, serve as a lying bed for the cattle. This study aims to assess the perception of consumers and farmers regarding the use of CBP during the grazing season of cattle for raising other animals or for growing food crops. This was examined by combining surveys with consumers from eight European countries and cattle farmers, focus groups with consumers, and in-depth interviews with individual farmers who implemented alternative uses of compost. The results showed that farmers preferred the compost bedded-pack system to the cubicle system in terms of sustainability and market aspects, although the cost of the bedding material required for CBP was seen as a significant negative aspect. Around half of all consumers indicated that the compost can be used for non-edible products and 26% indicated the compost can be used for raising other animals. Furthermore, 5% of consumers felt that compost should not be used for any other purpose. There were statistically significant differences between countries; therefore, regional specificities should be taken into account when marketing products from compost in CBP barns.

Summary UK Gaseous emissions of four bedded pack dairy farms were measured using the flux chamber method.One used wood chips as bedding material, the other three used compost of green waste. Emissions of ammonia per m 2 bedding area were considerably lower compared to the concrete slatted floor housing system that acted as a reference system. Due to large area per cow the emissions per cow were however 175%-475% higher compared to the reference system. Emissions of nitrous oxide (N2O)were 3.5 to 25 times higher than typical emission from the reference system. Methane emission however ranged from 6% to 25% of the reference system.