USDA Research Supports Glutamine as Antibiotic Alternative

ARS scientists are studying a natural supplement as a possible alternative to antibiotics for promoting pig health and growth. ( USDA/ARS )

Research in pigs suggests the natural amino acid glutamine, used as a feed additive, could provide a viable alternative to antibiotics fed for growth promotion and gut health. The research findings, from scientists with the USDA’s Agricultural Research Service (ARS), were recently published in the Journal of Animal Science.

Beginning in 2017, the FDA’s Guidance for Industry 213 resulted in removal of label indications for production or performance uses of medically important antibiotics in livestock feed. At the same time, new veterinary feed directive (VFD) rules placed the use of medically important feed antibiotics for prevention, control or treatment of disease under the oversight of veterinarians. Consequently, producers are looking for non-antibiotic alternatives for enhancing performance and protecting gut health.

The researchers note that L-glutamine is a conditionally essential amino acid that is a major energy source for rapidly dividing cells including enterocytes and lymphocytes. It serves as an immunomodulator that inhibits pro-inflammatory cytokines. Previous research has indicated that including dietary L-glutamine as a growth promoter can improve productivity in healthy and unstressed pigs. Little is known though, about its effects on the health of piglets following typical production stressors. So, the researchers set out to compare L-glutamine supplementation with dietary chlortetracycline and no supplement, in post-weaning pigs during a period of simulated transport and heat stress.

They hypothesized that withholding dietary antibiotics would negatively impact the overall well-being of piglets, and that diet supplementation with L-glutamine would have a similar effect on piglet health and welfare as dietary antibiotics.

The researchers found that withholding dietary antibiotics during this period did negatively affect animal health and welfare, with increased intestinal damage, reduced feed intake and growth, and increased behaviors associated with illness. In this trial, however, pigs fed L-glutamine, at 0.20% as-fed performed similarly to those fed the dietary antibiotic. Throughout the 14-day dietary treatment phase, feed intake was greater overall in pigs fed glutamine compared to either of the other groups, while pigs fed antibiotics performed better than those given neither supplement. Body weights for the glutamine and antibiotic groups were similar, with both being heavier than those in the non-supplement groups.

The researchers conclude that L-glutamine could be a viable alternative to dietary antibiotics. “However, because piglets were weaned and transported under simulated conditions, any implications toward the use of L-glutamine as an antibiotic alternative would need to be confirmed under commercial production conditions.”

Read the abstract or full report from the Journal of Animal Science.