Midnight Feeding Of Hens Improves Eggshell Quality, UF Research Finds

May 22, 1996

GAINESVILLE—Give a hen a midnight snack and she’ll lay eggs with stronger shells, University of Florida researchers have found.

The classic nocturnal raid on the refrigerator it’s not. The hens who drew research duty were conditioned to dine at midnight on a calcium-rich feed to increase the amount of that mineral in their digestive tract when they are producing the shell of the egg.

Adding the late-night snack to the hens’ regular diet helped them lay eggs with stronger shells, said UF Graduate Research Professor Robert Harms.

The finding could mean millions to the poultry industry. About 4.8 percent of eggs never make it to market, mostly because of cracked and broken shells. With 10 million hens in Florida laying about 8 million eggs a day, the loss adds up. Nationally, the industry loses about $100 million a year because of poor shell quality.

“Cracked eggs represent a tremendous loss to the poultry industry,” Harms said. “Loss of productivity on poultry farms due to cracked eggs is a big, big situation. Many of the eggs a hen lays never reach the consumer.”

The poultry industry, including both broilers and laying hens, will contribute approximately $350 million to Florida’s economy this year, said poultry science Associate Professor Don Sloan, who collaborated with Harms on the research. About two-thirds of that income is in egg production, he said.

“Eggs are mechanically handled, so the better the shell the fewer cracked eggs we’ll have,” Harms said.

Egg producers who have tested Harms’ theory swear by it.

Tampa Farm Service complex manager Siegfried von Bargen said he is using midnight feedings on two flocks of about 58,000 hens each.

“Now, when I see a problem with eggshell quality, I try midnight feeding and it works,” von Bargen said. “In a week to 10 days, I started seeing better shell quality.”

Studies have long shown that hens have less calcium in their digestive system after midnight, when most of the eggshell — made up of pure calcium carbonite — is being formed. In fact, Harms tested his theory that midnight feedings would improve eggshells more than two decades ago, rousting henhouse after henhouse.

“They would wake up, walk around a little and then go back to sleep,” Harms said. “Getting the birds to eat at midnight just didn’t work back then.”

But henhouses today are more high-tech. In a modern henhouse, light and dark can be controlled and feeders are timed to run only when the lights are on. With such control, the chickens can be conditioned to eat when a farmer wants them to eat.

This time Harms’ experiment worked.

“It didn’t work 20 years ago, but it works now. Hens now are conditioned to eat when the lights are on. So we turn the lights on at midnight,” Harms said. “We know more about nutrition for laying hens these days than we do about human nutrition. It’s very exact.”