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group of pigs Scott Olson

Low-protein diets help slow finishing pig growth

Management strategy could be valuable during pandemic or other market disruptions.

Kansas State University swine researchers are reporting results of a study in which they were able to slow growth rates in pigs while waiting for packing plants to come back on line. They noted that the findings could be important any time markets are disrupted, whether for a global pandemic or other industry challenges.

Mike Tokach, a swine nutritionist with Kansas State Research & Extension and one of the lead investigators, said the study focused on reducing protein sources — namely, amino acids — from the animals’ diet. They focused on pigs weighing 200 lb., targeting the last 70-80 lb. those animals needed to reach market weight.

“We were able to buy three-and-a-half to four weeks of extra time to get those pigs to market,” Tokach said. “As many know, that was really crucial when we were going through some of the slowdowns (at packing plants, which caused a backlog of pigs on farms). Buying that extra (time) allowed some of our producers to keep their pigs on the farm longer while not getting them too heavy and still fitting into the packer’s window in terms of weight ranges.”

Amino acids are the building blocks for animal protein, or muscle, and are beneficial to pig growth. Lysine is an important amino acid often used in pigs’ diets.

“If we limit the intake of amino acids, that animal simply isn’t able to grow as fast,” Kansas State swine nutritionist Joel DeRouchey said. “Ultimately, that was our goal: to slow down growth while they’re still consuming a full amount of feed.”

DeRouchey said the researchers tested four diets to compare the effect of reduced lysine on pig growth:

  1. A diet with normal amounts of lysine for the entire late finishing period;
  2. A "slow" diet with normal amounts of lysine until the final two weeks of feeding, and then a corn-based diet that included only vitamins and minerals;
  3. A "slow" diet with reduced amounts (25%) of lysine for the entire late finishing period, and
  4. A "slow" diet with reduced lysine (25%) until the final two weeks of feeding, followed by a corn-based diet that included only vitamins and minerals.

“Ultimately, what we found through this research is when the pigs were on a slow diet, we reduced their growth performance fairly substantially,” DeRouchey said. “In fact, they were about 14 lb. lighter at the end of the 44-day finishing period by feeding reduced levels of amino acid.

“Interestingly, when we put them on a slow diet then moved them to a corn-based diet, they gave up another 12 lb., or were about 26 lb. lighter after a 44-day feeding period, which is very substantial. Those diets achieved the goal of holding those pigs while they’re still consuming a full amount of feed,” he said.

Tokach added that there were several positive outcomes of the study: “One that producers have, foremost in their minds, is the welfare of the animal,” he said. “You want to do something that’s not going to harm the pig while ... producing a safe and wholesome food product at the end.”

Tokach said another thing the team determined was “that you don’t want to start these low-protein diets too early. If we start them too early in the pig’s life, when they have very high levels of protein deposition, we can cause some vices (problems) to occur, and that’s when you have some difficulties on the animal welfare side, but if we start those diets after they are 200 lb. or heavier, we have not seen any adverse effects with the pigs.”

DeRouchey noted that one consequence of keeping the pigs on the farm longer is that feed efficiency is poor compared to normal times.

“When you’re in a situation that you can’t take those pigs to market and they’re already getting close to market weight, your goal is to minimize the cost of keeping those pigs around another day,” Tokach said. “So, even though feed efficiency is poor, the cost of that diet is so much lower when we aren’t including protein (amino acids). So, your actual cost per day is lower for the pig that is fed the corn-based holding diet.”

Tokach said Kansas State graduate student Zhong-xing (Johnson) Rao and veterinarian Jordan Gebhardt were instrumental in gathering the research data.

“Hopefully, we won’t have to use a strategy like this in the future, but if we have to, I think we have a pretty good idea of how we can prescribe the levels of performance that we want to achieve,” he said.

TAGS: Swine
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