The most widely used method of housing gestating sows in the United States is individual gestation stalls. However, the United States pork industry is undergoing pressure to eliminate the use of individual gestation stalls by animal welfare and (or) animal rights groups. The alternative to housing sows in individual gestation stalls is some type of group-housing. Although some people perceive that group-housing systems are more welfare friendly, the housing of sows in groups have the following welfare problems: (1) aggression during mixing of animals, (2) aggression at time of feeding when individual, non-locking feeding stalls are not used, (3) bullying by dominant animals, (4) feet, leg and back injuries due to excessive riding of each other during times of estrus, (5) excessively high feed intake by dominant animals when floor fed, (6) excessively low feed intake by subordinate animals when floor fed, (7) vulva biting, and (8) wounds and scars from fighting. A large number of variables are involved with the design and management of gestation facilities for group housing of sows. Although several European countries have specific regulations for designing and managing swine gestation facilities, the majority of variables involved with the design and management of a gestation facility for group-housed sows have not been investigated by scientists in the United States or foreign countries. The majority of the research has focused on the welfare of sows housed in individual stalls. A small amount of research has been conducted on the welfare of sows housed in groups. The effect of housing design on productivity of sows and gilts has not been extensively investigated.
Three spreadsheets (Microsoft Excel 2000) were developed to evaluate the production and financial implications between the following types of housing systems for gestating sows: (1) remodeling of an existing individual stalls gestation building into a facility that loosely house sows in pens, (2) a new gestation facility that loosely house sows in pens, and (3) a new hoop structure that loosely house sows in pens and feeds the sows either indoors or outdoors. The main input categories of the model include cost of building structure, cost of equipment, annual ownership cost, and annual variable cost of gestation facility. The following annual ownership cost can be easily changed: labor, feed, utilities, veterinary & health supplies, semen cost, loan payment, and depreciation on breeding stock. After the total annual ownership and variable costs are calculated, the user can change the reproductive performance values (farrowing rate and number of piglets weaned per litter) to estimate their effect on cost of the gestation phase per pig weaned.
