Effect of dietary energy and nutrient levels on performance and liver expression of respiratory chain genes in broiler chickens

This study aimed to evaluate the effects of energy and nutrient (lysine, calcium, and phosphorus) levels on animal performance and liver expression of genes related to lipid metabolism and electron transport in broilers from 22 to 42 days of age. A total of 432 male Cobb 500 broiler chickens were distributed in a completely randomized design with 3 treatments, 8 replications, and 18 birds per experimental unit. The first treatment (control) consisted of a diet based on corn and soybean meal with a metabolizable energy (ME) content of 12.70 MJ/kg. The second treatment was a high-energy (HE) diet (13.33 MJ/kg) formulated by increasing the ME value of the control diet by 0.63 MJ/kg and maintaining the same levels of digestible lysine, calcium (Ca), and available phosphorus (P). The third treatment was a high-energy and high-nutrient (HEHN) diet, providing 13.33 MJ/kg and a 5% increase in digestible lysine, Ca, and P levels in relation to the control diet. Animal performance and carcass yield were analyzed at 42 days of age. Expression levels of apolipoprotein B (APOB), NADH dehydrogenase subunit I (ND1), and cytochrome c oxidase (COX1) genes were also determined. Treatments exerted significant effects on performance but not on carcass yield. HE diets improved feed efficiency compared with the control. Furthermore, the HEHN diet enhanced weight gain compared with the control. COX1 and ND1 expression was influenced by dietary energy level. In conclusion, the results indicate that HEHN diets improve performance and alter the expression of genes related to lipid metabolism and electron transport in broiler chickens from 22 to 42 days of age but do not affect carcass yield.