美国养猪体系详解.ppt

* The goal if to have no more than 4-5 F temperature variation within 1 hr. Repeated variations of temperature of 4-5 F within short periods of time result in reduction in gain and increased opportunities for health challenges. However, gradual changes in temperature (such as cooling down 6-10 F at night and heating to recommended temperature beginning at 6-7 am) have been demonstrated to actually increase feed intake and daily gain if these begin 1 week after weaning. * * Typical dimensions of a tunnel room/barn. * An example of how tunnel barns are designed. Use the larger of the 2 values. * Example of why there is a minimum size to a tunnel barn. If there is an 8 ft ceiling, to get 300 fpm for a 41 ft wide barn, you need a minimum of 96,00 CFM regardless of the number of pigs. For a 1000 hd barn, you need 120,000 CFM to meet the 120 CFM design criteria for temperature removal. For a 1000 hd barn, the cross sectional velocity is 375 ft/min. If you had 1200 pigs in a 41 ft wide barn, the cross sectional velocity would go up to 450 ft/min at 120 cfm/pig. This illustrates why there is an upper limit to length (pig numbers per room) with tunnel ventilation. * Example of why there is a minimum size to a tunnel barn. If there is an 8 ft ceiling, to get 300 fpm for a 41 ft wide barn, you need a minimum of 96,00 CFM regardless of the number of pigs. For a 1000 hd barn, you need 120,000 CFM to meet the 120 CFM design criteria for temperature removal. For a 1000 hd barn, the cross sectional velocity is 375 ft/min. If you had 1200 pigs in a 41 ft wide barn, the cross sectional velocity would go up to 450 ft/min at 120 cfm/pig. This illustrates why there is an upper limit to length (pig numbers per room) with tunnel ventilation. * * * * * * * * * * * Fans tilted downward 15 degrees. Note that fans blow across the building (S to N). Idea is to force hot air out of building (N side) on calm days. Downward tilt increases air flow in pig zone. Note also the low stem wall – a