Oral Administration of a Medium Containing L-Citrulline-producing Live Bacteria Reduces Body Temperature in Chicks

Recently, we showed that oral administration of crystallized L-citrulline (L-Cit) caused hypothermia under a control thermoneutral temperature (CT) and provided thermotolerance under high ambient temperature (HT) in chicks. The aim of this study was to clarify whether oral administration of a medium containing L-Cit-producing live bacteria can reduce body temperature in chicks under CT. In Experiment 1, 7-day-old chicks were orally administered either a medium (containing mainly L-Cit-producing live bacteria and 277 mM L-Cit) or an equimolar amount of L-Cit to determine their effects on body temperature (acute treatment). In Experiment 2, chicks were subjected to the same treatment from 7 to 13 days of age (chronic treatment). Rectal and surface body temperatures were recorded daily after 1 h of treatment. Both acute and chronic oral administration of the medium, but not of the equimolar amount of L-Cit, significantly reduced the rectal and surface body temperatures of the chicks. Chronic administration of the medium resulted in consistently low rectal and surface body temperatures during the entire experimental period. In conclusion, acute or chronic administration of the medium containing L-Cit-producing live bacteria, but not of the equimolar amount of L-Cit, reduced the rectal and surface body temperatures of the chicks. Our results suggest that medium containing L-Cit-producing live bacteria can be used as a new feed supplement for lowering the body temperature of chicks.