Back to school: Improving the pigs environment
It is important that personnel attending to pigs are trained on the fundamentals of maintaining their environment and know how to operate modern equipment and controllers.
Pigs have been reared in confinement for millennia, but controlled environments and consideration of the ecologic needs of the pig are still new ideas. The pig's environment must provide feed, water, fresh air, space, shelter and waste disposal.
Pigs will not eat if water is unavailable. Weaned and growing pigs drink about 10 to 15 percent of their body weight per day. Gestating sows and boars need 8 to 12 liters per day. Lactating sows consume 25 liters or more. Water flow rates are 250 to 400 milliliters per minute for nursery-age pigs, and 500 to 700 milliliters per minute for grow-finish pigs. Waterers for sows and boars should provide 750 to 1,000 milliliters per minute. Pressure controllers reduce wastage and ensure good consumption.
Nipple waterers should be adjustable to shoulder height; this is particularly important for weaned pigs. It's important that gestating sows have a constant water supply to prevent urine concentration, bladder stones and urinary tract infection. Prolonged water deprivation due to failure of the water system, or when no water is provided to pigs during long distance transport, causes an accumulation of sodium in the brain. Upon rehydration, sodium ions caught in the extracellular matrix osmotically draw water suddenly into the brain, resulting in edema, central nervous system signs, incoordination, convulsions and death. Also called “salt poisoning” (a misnomer), water deprivation can resemble pseudorabies or strep meningitis, and is diagnosed in the lab by the finding of eosinophils in the meninges and cuffing blood vessels in the brain.
Access to feed
Nutrition is a fundamental ecologic need. Out-of-feed events might seem to spare feed but can also result in tail biting, gastric disease and sudden deaths from intestinal torsion and “haemorrhagic bowel syndrome.” There are many pig operations where all of the feed is moved by hand labor, but in the future, properly designed feeders that are adjustable, that provide good access to feed and that don't waste feed will eventually become essential.
The main thing in environmental control is control. Metal, brick, glass and concrete provide shelter, but such materials conduct heat about one hundred times as fast as insulation materials. Insulating the roof and walls and minimizing use of glass windows helps control temperature in summer and winter.
The healthy pig is hot at 39.2C. In hot weather, heat from the sun and pig body heat must be removed, or pigs get too hot and won't eat. Heat loss becomes an economic problem when the environment is so cold that feed energy intended for growth is diverted to maintaining basic warmth. When pigs are too hot or too cold, feed efficiency suffers.
Thermoneutral zone (TNZ) is the temperature range at which the pig is comfortable, about 15-24C for breeding and growing pigs, and 34-38C for newborns. Piglets in farrowing and nursery may have subnormal body temperature (hypothermia) if the environment is cold and their energy intake is too low to support a normal body temperature. The body allows its temperature to drop to conserve energy, but body growth is halted and negative immune system consequences follow. When piglet body temperature is below normal, sow milk adequacy and piglet diet quality should be examined as well as environmental temperature. It is too common that neonatal piglets and weaned piglets are allowed to be too cold while grow-finish pigs are kept so warm that feed intake and growth rates are reduced.
Pigs need fresh air. An old rule of thumb for a full pig house is to exchange air 6 to 60 times each hour by continuous minimum ventilation. Moisture, pathogens and potentially toxic gases go out and fresh air with oxygen comes in. A common error is to shut off all ventilation to conserve heat. When this is done, moisture, ammonia and pathogen levels will reach intolerable levels, which damages the building, harms both the pigs' health and the workers' health, and also wastes feed in the long run by slower growth and more days to market.
Adjusting temperature and ventilation rates
Ventilation rate and temperature tables size the fans for pig houses and give start points for setting up controllers. Animal husbandry staff should be trained to observe pigs and adjust controllers to meet the ever-changing situation. Relative humidity control is the key to providing adequate minimum ventilation rates. If relative humidity is maintained at 60-70 percent or below, pathogens and toxic gases are controlled and oxygen levels will be adequate. High relative humidity quickly leads to pathogen buildup and disease issues. Proper ventilation does not waste heat, but does utilize heat to remove moisture. In a well-insulated building, much of the heat comes from the pigs themselves and supplemental heat requirements are not high.
The quality of the space is as important as the area per pig.
Pigs require space, and the quality of the space is as important as the area per pig. Unventilated buildings have a low carrying capacity and must be stocked at a much lower density than high quality ventilated space.
Air inlet control
Most modern pig buildings ventilate by negative pressure employing machine-controlled or weighted “automatic” inlets to bring air in with velocity for air mixing and draft avoidance. Inlet air flow speed range is 500 to 1,000 feet per minute or 3 to 6 meters per second, equivalent to -0.05 to -0.10 water-inches of “static pressure” (vacuum).
Inlet openings are maintained at approximately constant ratio to air exhaust rates. Loss of static pressure due to spurious inlets and failure to provide inlets that open and close with changing ventilation rates are common faults. Even some new construction has poor inlet control and fails predictably. Leaky fan housings, open doors, open manure ports, manure channels connecting rooms and cracks in the walls are all unwanted air inlets that must be managed. Avoid short-circuiting air from inlets or open windows that are nearby to fans. The routing of manure flows to storage and removal are important considerations in ventilation design that are often overlooked such that the manure ports become unwanted uncontrolled air inlets.
Pigs have strong sanitation-driven behavior. If given the opportunity, pigs develop a niche that separates their sleeping area from the latrine. Variance from natural sanitation behavior (poor dunging patterns) indicates something is wrong in the environment. Aberrant behavior such as tail biting in pigs is generally a sign of a provision fault — the pig cannot get something that he needs.
E. Wayne Johnson, DVM, is senior technical consultant at Enable Ag-Tech Consulting, Beijing
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