Dietary L-Citrulline supplementation modulates nitric oxide synthesis and anti-oxidant status of laying hens during summer season

Abstract

Background L-Citrulline (L-Cit), a non-protein amino acid, has been implicated in several physiological functions including anti-inflammatory, anti-oxidative, and hypothermic roles, however, there is paucity of information with regards to its potential in poultry production. This study was designed to investigate the effects of dietary L-Cit supplementation on the production performance, nitric oxide production and anti-oxidant status of laying hens during summer periods. Hy-line laying hens (n = 288, 34 weeks old) were allotted to four treatment with 6 replicates of 12 chickens each. Dietary treatments of control (basal diets), 0.25%, 0.50% and 1.00% L-Cit supplementation were fed to chickens for eight (8) weeks. Production performance, egg quality characteristics, nitric oxide production and antioxidant properties were measured. Blood samples were collected at 4th and 8th weeks of experiment. ResultsAir temperature monitoring indicated average minimum and maximum recordings of 25.02 0 C and 31.01 0 C respectively. Dietary supplementation with L-Cit did not significantly (P > 0.05) influence the production performance, plasma biochemistry and rectal temperatures of laying hens. Egg shape index was increased with L-Cit diet, similarly, albumen heights and Haugh units also tended (P < 0.10) to improve with higher L-Cit supplementation. Plasma nitric oxide (NO x ) concentration was observed to increase with highest contents at 1% L-Cit supplementation. Likewise, nitric oxide synthase (NOS) enzyme activity for both total NOS (tNOS) and inducible NOS (iNOS) were upregulated with increasing L-Cit levels, although, tNOS was not affected at week 4. Anti-oxidant enzymes including catalase and superoxide dismutase (SOD) were increased with L-Cit supplementation, however, SOD activity was unchanged at week 4. Total anti-oxidant capacity increased with L-Cit groups at week 8. L-Cit supplementation attenuated the extent of lipid peroxidation measured by malondialdehyde levels, and also inhibited glutathione peroxidase activity. ConclusionDietary L-Cit supplementation enhanced nitric oxide synthesis, promoted antioxidant defense systems, and tended to improve internal egg quality traits of laying hens during summer season. 1% Production performanceEgg production and egg weights were recorded daily from different replicates, while body weights and feed intake were recorded on a weekly basis throughout the experimental period. Data computed were feed conversion ratio, laying rate, and egg mass based on the data recorded.Air and rectal temperature monitoring