When lysine is too much of a good thing

Lysine hydrochloride is an essential amino acid used in poultry diets to help ensure balanced nutrition and flock performance. But as with anything else, it’s possible for birds to get too much of a good thing, said Jenny Fricke, DVM, a University of Saskatchewan poultry veterinarian.
calendar icon 12 January 2018
clock icon 3 minute read

Fricke learned this firsthand recently after some painstaking detective work. She and some other researchers had been asked to probe why some chickens were grossly underweight. The chickens were 7 days old when they were brought to her and clearly weren’t growing as expected.

“We weighed them and they were about half the weight they should be,” Fricke said.

At first she was stumped. She cut open the birds to look for clues — like lesions or signs of other common poultry diseases — but couldn’t find anything. She examined a sample of birds from other floors and found that many of them became lame when they were 12 days old, a phenomenon she also could not explain.

Their investigation also revealed that there had been some discrepancies in the amount of lysine combined with the feed during the last delivery — a situation that can make otherwise healthy birds eat less.

She and her colleagues opted to study 500 birds. The birds were put in cages and fed, and their lysine supplements increased by 2, 4, 6 and 8%.

The researchers noticed that in many of the birds that received increases in lysine supplements body weight declined, as did body weight gain. In addition, feed consumption went down and feed conversion was also reduced.

“We’ve got footage of birds trying to consume a higher-lysine diet,” she said, adding that the video suggested palatability of diet was an issue as well due to an excess of lysine in the diet.

“There have been reports that if you have an excess or deficiency (of lysine), birds will reduce their intake” of feed, she said.

She said there are several important lessons here for producers. One, always collect good feed samples when the birds are placed.

“You never know when you’re going to need it,” she said.

Two, be vigilant.

“We didn’t get these birds until they were 7 days of age,” she said.

In Canada, she said, broilers are typically on the floor for 35 days. She wonders if things could have been turned around if someone had noticed that the birds weren’t eating adequate amounts of feed days earlier.

“Reaction times are critical,” Fricke added. “At 7 days those birds were one-fifth of the way through their time on that farm. They were pretty far gone at that time.”

Third, too much of anything can be bad — even healthy amino acids.

“Making sure you have quality amino acids in the diet for the birds is important, but if you’ve got too much of a good thing the birds will respond appropriately and reduce their intake,” Fricke said.

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