The Efficacy of Food‐Grade Substances to Protect Dietary Glutamine From Ruminal Degradation

This study was conducted to investigate the use of four, low cost, food‐grade substances to protect glutamine from microbial degradation in vitro, and subsequently validate their efficacy in vivo. Two in vitro trials were conducted using 250 mL bottles replicated in triplicate to test beeswax‐, paraffin wax‐, zein‐, and rice bran wax‐encapsulated glutamine (GlnFS1, GlnFS2, GlnFS3 and GlnFS4, respectively) compared to control (blank) and negative controls (GlnC, FS1, FS2, FS3 and FS4). Ammonium analysis was conducted to evaluate the degradation of glutamine at 30, 60, 90, 120, 180, 240, 300, 360, 420 and 480 min post inoculation. To further test the efficacy of the two most protective food‐grade substances in vivo, 16 Merino wethers (initial liveweight 53.75 ± 4.25 kg; 12 months old) were allocated to one of the treatments: control ( n = 3), GlnC ( n = 3), GlnFS1 ( n = 5), and GlnFS2 ( n = 5). Treatments were administered via oral syringe and bloods were taken via a jugular catheter every hour over 12 h post supplementation. Blood parameters including blood gases and plasma amino acid analyses were performed. The in vitro trial data were analysed using REML and area under the curve by R Software. Mixed models by SAS Software were used to analyse the in vivo data. All food‐grade substances protected glutamine from microbial degradation, with the highest protection observed for GlnFS1 and GlnFS2 (35.7% and 26.4%, respectively) compared to the GlnC in the in vitro trials. In the in vivo trial, an interaction between treatment and timepoint was observed for blood sodium ( p = 0.004). The blood pH of GlnFS1 and GlnFS2 were higher than control and GlnC ( p = 0.039). Alanine ( p = 0.049), glutamine ( p = 0.015), and histidine ( p < 0.001) were elevated in GlnC compared to other treatment groups (control, GlnFS1, and GlnFS2). A higher concentration of plasma glutamine was detected in the blood of GlnC wethers with no significant difference from the control group. Future studies must evaluate the bioavailability of GlnFS1 and GlnFS2 in vivo.