L-theanine, a natural nonprotein amino acid with a high biological activity, is reported to exert anti-stress properties. An experiment with a 3 ? 2 factorial arrangement was conducted to investigate the effects of dietary L-theanine on growth performance and immune function in lipopolysaccharide(LPS)-challenged broilers. A total of 432 one-day-old male yellow-feathered broilers were randomly assigned to 3 dietary treatments(control, antibiotic and L-theanine diets) with 2 subgroups of each(6 replicate cages;12 birds/cage). Birds from each subgroup of the 3 dietary treatments were intra-abdominally injected with the same amount of LPS or saline at 24, 25, 26 d of age. Both dietary L-theanine and antibiotic improved(P < 0.05) the growth performance of birds before LPS injection(d 1 to 21). The effect of dietary L-theanine was better(P < 0.05) than that of antibiotic. Lipopolysaccharide decreased feed intake(FI) and body weight gain(BWG) from d 22 to 28(P < 0.05), BWG and feed to gain ratio(F:G) from d 29 to 56(P < 0.05), increased mortality in different growth periods(P < 0.05), elevated the levels of serum cortisol, a1-acid glycoprotein(a1-AGP), interleukin-6(IL-6) on d 24 and 25(P < 0.05), reduced immune organ indexes and contents of jejunal mucosal secretory immunoglobulin A(s Ig A) on d 28(P < 0.05). The decreased FI and BWG, as well as increased F:G and mortality in LPS-challenged birds, were alleviated by dietary L-theanine or antibiotic from d 29 to 56 and from d 1 to 56. Dietary L-theanine mitigated the elevated serum a1-AGP level on d 25, serum IL-6 concentration on d 24 and 26, and the decreased jejunal mucosal s Ig A content on d 28 of the LPS-challenged birds. The results indicated that L-theanine had potential to alleviate LPS-induced immune stress in broilers.
Rui LiZehe SongJianfei ZhaoDongxiao HuoZhiyong FanDe-Xing HouXi He
