October 07, 2021

Interpretive Summary: Effects of supplemental d-methionine in comparison to l-methionine on nitrogen retention...

Interpretive Summary: Effects of supplemental d-methionine in comparison to l-methionine on nitrogen retention, gut morphology, antioxidant status, and mRNA abundance of amino acid transporters in weanling pigs

By Anne Zinn

A study recently published in the Journal of Animal Science compared the bioavailability and efficiency of d-Methionine and l-Methionine when fed to weaning pigs. Methionine is a limiting amino acid in swine diets, but because of its high requirement by pigs and its low concentration in many feed ingredients, supplementation with synthetic sources of methionine is common in diets fed to pigs. One of the main synthetic methionine sources is dl-methionine, which is considered 100% bioavailable to pigs, but l-methionine has recently become available to the feed industry. While there have been recent studies demonstrating that the relative bioavailability for l-methionine is not different from that of d-methionine when fed to growing pigs, there is little information demonstrating the relative bioavailability of pure d-methionine against  l-methionine for pigs.

The present study tested the hypothesis that the relative bioavailability by weaning pigs of methionine in d-methionine would not be different from that in l-methionine pigs if nitrogen retention is used as the response criterion and that there would not be any differences between d-methionine and l-methionine in their ability to maintain intestinal morphology, antioxidant capacity, and expression of genes related to methionine metabolism.

Overall, results indicated that supplementing d-methionine or l-methionine improved nitrogen retention and decreased urinary nitrogen excretion of weanling pigs; it was concluded that the relative bioavailability for d-methionine was 101% with l-methionine used as the standard. The addition of d-methionine to diets resulted in indicators for morphology in the duodenum and jejunum that were not different from those of pigs fed diets containing l-methionine. Antioxidant-related parameters in liver, muscle, and plasma, as well as abundance of mRNA needed to express amino acid transporters involved in methionine metabolism in duodenum and jejunum, were also not impacted by the source of Methionine that was added to the diet.

The full paper can be found on the Journal of Animal Science webpage.