Effect Of L-carnitine On Performance And Antioxidant Capacity In Laying Hens

In modern poultry industry, there are many factors including immunization, heat or cold stress, and high levels of ammonia in the chickenhouse can cause the oxidative stress.. L-carnitine plays an important role in energy metabolism, and also has antioxidant and immunomodulatory roles, being used as free radicals scavenger and improving egg quality. A series of four trails were conduceted to determine the effect of L-carinitne on egg quality, immune function and antioxidant ability of laying hens.Trail 1: Effects of L-carnitine on performance, egg quality and lipid metabolism of laying hens. A total of five hundred and seventy-six Hyline Brown laying hens of 53 week-old were chosen and divided into 6 groups randomly, feeding diets with different inclusion levels of L-carnitine(0, 25, 50, 100, 200 or 400 mg/kg). 1)Dietary L-carnitine had no effect on performance(P>0.05). 2)Dietary supplemental L-carnitine significantly increased the albumen height and Haugh unit at the end of 3 week of feeding period(P<0.05), with the best effect at the diet supplemental level of 25 mg/kg. Meanwhile, dietary supplemental L-carnitine significantly increased the eggshell strength with a tendency to increase the yolk color at the end of 6 week(P<0.05). However, dietary supplemental L-carnitine had no effect on eggshell thickness and egg shape index(P>0.05). 3)The serum contents of TG, TC, HDLC and LDLC were significant decreased when the L-carnitine supplemented in the diets(P<0.05).Trail 2: Effect of L-carnitine on performance, antioxidant ability, and the immune function of laying hens. The experimental design was in line with trail 1. 1) Dietary supplementation of L-carnitine significantly increased total antioxidant capacity (P < 0.05), superoxide dismutase (P < 0.05), glutathione peroxidase (P < 0.05), while decreasing malondialdehyde level (P < 0.05). 2)The percentages of CD4+ (P < 0.05), CD8+ (P < 0.05) and CD3+ (P < 0.05) T lymphocytes and the ratio of CD4+/CD8+ lymphocytes (P < 0.05) were increased with dietary supplementation of L-carnitine, and the concentrations of lysozyme and IgG were also increased (P < 0.05). Trail 3: Effect of L-carnitine on egg quality and antioxidative ability of laying hens feeding sunflower oil-contained diet. A total of two hundred and eighty-eight Hyline laying hens of 27 week-old were divided into 4 dietary groups, including control group and the supplemental levels of L-carnitine 0, 200 or 400 mg L-carnitine/kg of feed with 3% sunflower oil. 1)Dietary sunflower oil and L-carnitine had no effect on layers'performance (P>0.05). 2)Dietary supplemental sunflower oil had a trend to decrease the albumen height (P=0.06) and significantly decrease Haugh unit (P<0.05) at the end of 6 week of feeding period, while dietary supplemental L-carnitine increased the albumen height and Haugh unit compared to non-L-carnitine supplemental group. Dietary sunflower oil had no effect on eggshell strength, but dietary supplemental L-carnitine significantly increased the eggshell strength (P<0.05). 3)The total antioxidative capacity decreased (P<0.05) and the MDA level increased significantly (P<0.05) when the sunflower oil was presented in the diet, but when L-carnitine was added, the total antioxidative capacity were increased and MDA level deeased compared to non-L-carnitine supplemental group. Sunflower oil didn't influence the activity of SOD compared to control group(P>0.05) , but significantly increased the activity of GSH-Px (P>0.05). Dietary L-carnitine significantly increased the SOD activity compared to control group (P<0.05), but didn't influence the GSH-Px (P>0.05). Trail 4: The effect of L-carnitine on egg quality and antioxidant status of laying hens feeding oxidized oil. Two hundred and eighty eight Hyline Brown laying hens of twenty seventy-week-old were randomly divided into four dietary treatments, which were supplemented with fresh oil (FO), oxidized oil (OO), oxidized oil plus 200 mg/kg L-carnitine (OO200) or oxidized oil plus 400mg/kg L-carnitine (OO400). 1)The performance were not influenced by the oxidized oil and L-carnitine (P>0.05). 2)At the end of 3 weeks, the eggshell strength decreased in OO group (P=0.09) compared to FO group, and in OO400 group the eggshell strength increased to the level of FO group . At the end of 6 weeks, the eggshell strength of OO group significantly decreased compared to FO group (P<0.01), however, in the OO400 group, the eggshell strength increased to the level of FO group, the Haugh unit was also increased significantly (P<0.01) and the albumen height had a trend to increase (P=0.06) in OO400 group. 3)The total antioxidative capacity and the activities of the SOD, GSH-PX and GST decreased and the level of MDA increased on d21 and d42 (P<0.05) in OO group compared to FO group, the adverse effect was eliminated when L-carnitine was presented in diet. 4)The mRNA levels of SOD, GST and Nrf2 in OO400 group were also higher than FO and OO group (P<0.05).In conclusion, dietary supplemental L-carnitine could improve the egg quality, lipid metabolism ,immune function and antioxidant ability of laying hens while there were no significant effects on most of egg performance parameters. Taking economic benefit and the result of trail 1 into consideration, 25 mg/kg L-carnitine was recommended at the current situation. The transcription factor Nrf2 passway might be involved in increasing antioxidant ability aspect.