Mechanically ventilated swine confinement facilities should have alarms or backup ventilation systems in the event of an electrical outage, which could stress or even kill pigs in a matter of hours.

A University of Illinois agricultural engineering group, led by Matt Robert, conducted three trials looking at the effects of temperature and carbon dioxide in a 2,000-head, 45 × 125-ft., totally slotted nursery barn. Shallow manure pits were flushed 12 times a day using recycled lagoon water.

In the first trial, the impact of temperature was evaluated for 50-lb. pigs. Three, 24-in. mixing fans located near the ceiling were left on while the ventilation system was shut off. With just the mixing fans on, the increase in temperature in the building was slow. It took about 60 minutes for the pigs to become stressed by temperature. Outside temperature was 57° F. Carbon dioxide levels increased to levels of concern of 4% in about 80 minutes. Stress from lack of oxygen was documented at about 95 minutes.

In this same trial, by 115 minutes, carbon dioxide levels approached 5% and temperatures reached 95° F. Results revealed that carbon dioxide affects pigs before they are affected by temperature. After 15 minutes at each of these temperature and carbon dioxide levels, pigs become stressed enough to seriously harm productivity.

In the second trial, also with 50-lb. pigs, the mixing fans were turned off along with the ventilation fans. Critical stress levels from temperature and carbon dioxide remained the same as in the first trial. Circulating air in the barn with the mixing fans could increase the time before pigs become severely stressed to 75 minutes for temperature and 95 minutes for carbon dioxide, the researchers suggested. Again, outside temperature was 57° F.

The third test was performed in a building with 15-lb. pigs. The critical temperature for this group was 100° F, but the temperature never reached a point where the pigs were stressed because the outside air temperature averaged 54° F. Carbon dioxide levels resulting in oxygen deficiency occurred at about 150 minutes into the test.

Overall, it took almost three times as much time for the 15-lb. pigs to be stressed by the environmental changes as it did for the 50-lb. pigs.

The three trials confirmed the need for backup electrical generation for mechanically ventilated swine units.

Researchers: M.J. Robert, C.S. Shaffer, T.L. Funk and Y. Zhang, University of Illinois. Contact Robert at (217) 898-8168; fax (217) 355-3775 or e-mail