Problems with acidosis after missed feedings are greatly lowered when at least eight hours separate the first and second re-alimentation feedings.

There has been "zero published research" on makeup feeding strategies, so managers or producers usually follow anecdotal practices, said Richard Zinn, a professor at the University of California, Davis. The typical practice after a missed feeding is to give small portions of feed over frequent intervals until steers no longer act aggressively at the feed bunk.

Fluctuations in feed intake are thought to be the primary cause of ruminal acidosis, which can cause death. Zinn explained that when hungry cattle are allowed to rapidly consume their fill of a finishing diet, the rumen becomes "primed." Rumen pH becomes more acidic while ruminal glucose and lactic acid concentrations rise. When a steer eats again while in "primed" condition (feed is provided to hungry cattle shortly after a major feeding), glucose levels rise even higher, lactic acid levels increase, ruminal pH drops and the result can be acidosis.

Animal scientists from the Davis campus and Universidad Autonoma de Baja, Mexico, under took a study to identify the optimum time between makeup feedings. The evening feeding was skipped and re-alimentation strategies were evaluated beginning at the usual feeding time the next morning.

The following options were used: giving 100 percent of the total day's feed (17.6 lb.) at 8 a.m., 30 percent at 8 a.m. and 70 percent at 10 a.m., 30 percent at 8 a.m. and 70 percent at noon, 30 percent at 8 a.m. and 70 percent at 2 p.m., and 30 percent at 8 a.m. and 70 percent at 4 p.m.

When steers received their total daily feed at once -- "which is not a good idea" -- they ate it in less than 30 minutes. Researchers were surprised that pH did not go below 5.6, which is high enough to be considered safe from acidosis. "We found out if they were fed a lot at once, there was some ability to adapt to the challenge... It was the timing of the second feeding that can be critical," Zinn said.

Researchers found that pH dropped significantly to the acidic range when two and four-hour intervals were used. "To come back and feed again after two or four hours, when the rumen is already compromised, can result in acidosis, bloat and even digestive death."

He pointed out that just 10 animals were used in this study and steers could not eat more than their share. In a real-life feedlot, aggressive steers could easily eat much more than others. After a missed feeding, "They don't eat like normal. They inhale the feed... and often times it is the better doing more aggressive ones that die (from digestive problems)," Zinn said.

Steers were still in danger with the six-hour interval, although the risk was lower. The most successful strategy was an eight-hour interval since ruminal levels had adjusted enough to be in the safe range. "If you can wait about eight hours, you'll be OK," he said.

Zinn said producers should not attempt to replace much of the missed feed during the first day. That is hard to do, he acknowledged, because the tendency is to feed more when steers are still bellowing and crowding around feed bunks.

But, "If you miss a feeding, lose that feeding. Don't try to recover it the next day. You should not increase daily feed delivery by more than 5 percent of the previous average consumption," he said. Otherwise steers face even greater risk of acidosis, bloat and other ruminal problems.