There appear to be three major causes for out-of-feed events in grower-finisher facilities. Human errors are generally associated with empty bins. This occurs when feed is not ordered, prepared, or delivered in a timely manner. The second cause of out-of-feed events is bridging of ground feed in feed storage devices. In this case, issues associated with flowability prevent feed from flowing out of the storage device into the feed delivery system. The final cause of out-of-feed events is equipment malfunction, this generally increases as facilities age. The consequences to the pig are the same regardless of the cause of an out-of-feed event. Considerable anecdotal evidence suggests that when pigs are given access to feed following a period of deprivation, an increase in fighting and aggressive behaviors occurs, and it is likely that this will adversely affect the welfare of all pigs within that pen. Irregular availability of feed during two daily 2-hour periods has been used as a stressor in a study examining acute-phase protein levels as biomarkers for evaluation of distress in growing pigs. Short-term feed deprivation (24 hours) has been clearly shown to cause ulcers in growing pigs. Periodic feed interruptions would likely create a similar effect in pigs fed ad libitum. While most ulcers had been repaired within 28 days in pigs fed a diet with particle size 750 microns, stomach ulceration continued in pigs either remaining on a finely ground diet (550 microns) or continuing to experience weekly feed deprivations. Interruptions in feeding such as occur with out-of-feed events may be inciting factors for hemorrhagic bowel syndrome. Over-eating, especially after a period of feed deprivation, has been implicated as a cause of porcine intestinal hemorrhage syndrome. The following experiments were designed to examine the impact of repeated out-of-feed events on pig performance, carcass composition, and incidence of tail biting and skin lesions. In each of two experiments, out-of-feed events of 20-hour duration were created by closing the feeder delivery devices from noon until 8:00 am the following morning. In Experiment One, the treatments were never or weekly out-of-feed events for a 16-week period, and 1266-micron versus 1019-micron mash feed-particle size. In Experiment Two, the treatments were zero, one, two, or three out-of-feed events on random days every 2-week period in the 16-week study. In each experiment, there were four pens per treatment combination or treatment and 15 pigs per pen. Weekly events resulted in a 68-g per day lower daily gain for the first 8 weeks, and 35-g per day lower gain over the entire trial, compared to the never out-of-feed treatment, with no impact on feed conversion. Feed conversion was better when feed particle size was 1019 microns versus 1266 microns. In Experiment Two, there was a linear decrease in daily gain with increasing numbers of out-of-feed events during the first 8-week period, with no impact during the second 8-week period. There was no effect of treatments on feed conversion. It was concluded that repeated out-of-feed events had a bigger impact on growing pigs than on finishing pigs, with the impact expressed as lower weight gain with no effect on feed conversion.

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