The present study was undertaken to investigate whether dietary lycopene (LP) could prevent the copper-mediated oxidation of low density lipoprotein (LDL), and affect growth performance, relative organ weights, plasma and meat lipid profiles, and LP contents in plasma and tissues in broiler chickens. A total of 160 day-old male broiler chicks were randomly allotted into 16 pens with rice husk as a bedding material. Each experiment had 4 replicates, 10 chicks per replicate (n = 4 per treatment). A corn-soybean meal base diet was used as a control diet (CONT). To formulate the experimental diets, the base diet was added with LP at the levels of 10 (LP10) or 20 mg/kg (LP20), or 17 g/kg of tomato paste (TP17) which was equivalent to 5 ppm of LP. The experiment lasted 4 weeks. Growth performance and relative organ weights were not affected (p > 0.05) by any of dietary treatments. Dietary LP significantly lowered (p < 0.05) triglyceride and LDL cholesterol at 2 weeks of age, but did not affect them at 4 weeks of age. Total cholesterol in thigh meats was not altered by dietary treatments. LP was not detected in leg meats in all chicks, nor in liver or plasma of the CONT group. LP was found in liver and plasma, being the former greater in the concentration, of the chicks fed diets containing LP10, LP20, or TP17. At 2 and 4 weeks, the copper-mediated oxidation of LDL was delayed (p < 0.05) in either LP- or TP-fed chickens compared with the CONT group. In conclusion, LP lowers triglyceride and LDL cholesterol, is deposited into serum and liver, and prevents the LDL oxidation in broiler chickens, confirming the role of LP in the lipid-lowering and antioxidant properties in broiler chickens.
Antioxidant Broiler chickens Growth performance Lycopene
Lycopene (LP) is an aliphatic hydrocarbon, a bright red pigment, which is a naturally present carotenoid in fruits and vegetables. Tomatoes are known to be the major source of LP with the content of 3100–8600 µg per 100 g of tomatoes or their products (Stahl and Sies 1996). The most well-known biological effects of LP intake are to act as the antioxidant or hypocholesterolemic agent (Di Mascio et al. 1989). It has been known that the hypocholesterolemic or triglyceride-lowering effect of LP is attributed to inhibition of de novo cholesterol synthesis and lipogenesis (Chung et al. 2012; Palozza et al. 2012). Indeed, Fuhrman et al. (1997) proved that LP suppressed the cholesterol synthesis from acetate by 73 % using the macrophage cell line, and confirmed in vitro observation in healthy males in vivo that the concentration of plasma low-density lipoprotein (LDL) cholesterol was reduced by 14 % by LP intake for 3 months. In studies with chickens, dietary LP has been known to improve meat quality via inhibiting lipid peroxidation and also to lower serum lipids. For example, Sun et al. (2015) observed that dietary LP lowered malondialdehyde (MDA) content in liver with enhanced antioxidant enzyme system. In line with the well-established role as natural antioxidant, dietary LP significantly lowered MDA concentration in cooked or raw breast meats stored at refrigeration or 4 °C and retarded the iron-induced lipid oxidation in raw breast meat samples (Botsoglou et al. 2004). Of interest, when chickens were exposed to various stressors such as heat or challenge with T-2 toxin or lipopolysaccharide, dietary LP has been known to enhance hosts’ antioxidant systems and improve the oxidative stability of meats (Leal et al. 1999; Sahin et al. 2006, 2008; Sun et al. 2014a). In clinical trial with human, LP has been known to inhibit the LDL oxidation with decreasing risk of atherosclerosis and coronary heart disease in human (Agarwal and Rao 1998; Fuhrman et al. 2000; Basu and Imrhan 2007). It is reported that LP absorbed is transported mainly by LDL, which primarily accumulate in liver, seminal vesicles and prostate tissue (Palozza et al. 2012). It is however that LP effect on LDL oxidation which had been reported in human has not been tested in chickens, which prompted us to test whether dietary LP could play a role in inhibiting LDL oxidation in broiler chickens. In addition, production traits, lipid profile in blood and meat, and presence of LP in blood, liver and thigh meats were monitored. Previously, it was reported that dietary LP increased in villus height and villus height:crypt depth ratio and enhanced growth performance in broiler chickens (Sevcikova et al. 2008; Sun et al. 2015).