Effects of Glutamine on Rumen Digestive Enzymes and the Barrier Function of the Ruminal Epithelium in Hu Lambs Fed a High-Concentrate Finishing Diet

Abstract

The present experiment aimed to research the effects of glutamine (Gln) on the digestive and barrier function of the ruminal epithelium in Hu lambs fed a high-concentrate finishing diet containing some soybean meal and cottonseed meal. Thirty healthy 3-month-old male Hu lambs were randomly divided into three treatments. Lambs were fed a high-concentrate diet and supplemented with 0, 0.5, and 1% Gln on diet for 60 days. The experimental results show that the Gln treatment group had lower pepsin and cellulase enzyme activity, propionate acid concentration, and IL-6, TNF-α, claudin-1, and ZO-1 mRNA expression in the ruminal epithelium (p < 0.05); as well as increases in lipase enzyme activity, the ratio of propionic acid to acetic acid, the IL-10 content in the plasma, and the mRNA expression of IL-2 and IL-10 in the ruminal epithelium, in contrast to the CON (control group) treatment (p < 0.05). Taken together, the findings of this present study support the addition of Gln to improve digestive enzyme activity, the ruminal epithelium’s barrier, and fermentation and immune function by supplying energy to the mononuclear cells, improving the ruminal epithelium’s morphology and integrity, and mediating the mRNA expression of tight junction proteins (TJs) and cytokines.

Metabolism and Nutrition of L-Glutamate and L-Glutamine in Ruminants

“…At present, the National Research Council (NRC) has not established dietary requirements for preruminants or ruminants (e.g., calves, beef cattle, dairy cows, lambs, and ewes) for Glu or Gln [ 75 , 121 ]. However, there is evidence that preruminants, as well as adult sheep, goats, dairy cows, and cattle, require dietary Glu ( Table 5 ) and Gln ( Table 6 ) supplementation for maximal growth and production performance, as well as for optimal (particularly intestinal) health and function, as detailed in the following sections [ 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 , 151 , 152 , 153 , 154 , 155 , 156 , 157 , 158 , 159 , 160 , 161 , 162 , 163 , 164 , 165 , 166 ]. This represents a paradigm shift in ruminant nutrition.…”

“…Based on the finding that dietary supplementation with Gln improved gastrointestinal integrity and function in young pigs [ 85 ], studies were conducted with lambs to determine the role of Gln in their ruminal functions. Specifically, Wu et al [ 141 ] reported that supplementing 0.5% or 1% Gln to a concentrate diet for 60 days enhanced the expression of claudin-1 and interleukin-10 (an anti-inflammatory cytokine) in ruminal epithelial cells by about 105% and 50%, respectively, in healthy 3-month-old male Hu lambs with an initial mean BW of 26.75 kg, compared with the control group. Furthermore, supplementation with 0.5% or 1% Gln increased pH, the ratio of acetate/propionate, and lipase activity in the ruminal fluid by about 4%, 25%, and 30% respectively, as well as the concentrations of interleukin-10 in serum by about 40% [ 141 ].…”

“…Specifically, Wu et al [ 141 ] reported that supplementing 0.5% or 1% Gln to a concentrate diet for 60 days enhanced the expression of claudin-1 and interleukin-10 (an anti-inflammatory cytokine) in ruminal epithelial cells by about 105% and 50%, respectively, in healthy 3-month-old male Hu lambs with an initial mean BW of 26.75 kg, compared with the control group. Furthermore, supplementation with 0.5% or 1% Gln increased pH, the ratio of acetate/propionate, and lipase activity in the ruminal fluid by about 4%, 25%, and 30% respectively, as well as the concentrations of interleukin-10 in serum by about 40% [ 141 ]. Collectively, Gln may play an important role in the development of ruminal fermentative activity, as well as the integrity, antioxidative capacity, and anti-inflammatory function of ruminal epithelial cells.…”

“…Pregnant sheep receiving the intravenous administration of 300 mg Gln/kg BW/day for 23 days exhibited normal rates of feed intake and fetal growth [ 167 ]. Postweaning lambs receiving dietary supplementation with 1% Gln (equivalent to approximately 0.5 g Gln/kg BW/day) for 60 days did not show any adverse responses [ 141 ]. Ocheja et al [ 68 ] reported that goats can tolerate the oral administration of 0.2 g Gln/kg BW/day for 21 days.…”