Effects of dietary metabolizable energy density and inclusion of oxidized soybean oil on the growth performance, serum biochemical parameters, redox status, and wooden breast incidence of broilers.

Abstract

Dietary nutrients not only affect the growth and pectoral muscle production of broilers, but also are related to the occurrence of pectoral myopathies, such as wooden breast (WB) and white striping. We investigated whether dietary metabolizable energy (ME) densities and inclusion of oxidized soybean oil could affect growth performance, serum biochemical parameters, redox status, and incidence of WB in broilers. One hundred and forty-four 21-d-old Arbor Acres male broilers were assigned into four experimental diets using a 2×2 factorial arrangement, including two ME densities (3100 and 3220 kcal/kg) and two soybean oil types (Fresh oil with peroxide value = 10.23 mEq/kg or oxidized oil with peroxide value = 122.93 mEq/kg). The experiment was lasted for 21 days. The results demonstrated that high ME diets increased broiler body weight gain (BWG) by11.02%, feed intake by 4.98%, and abdominal fat percentage by 17.92%, while decreased feed to gain (F/G) ratio by 3.39% (P < 0.05). Oxidized soybean oil diet increased F/G ratio by 2.92% (P < 0.05) and had a tendency to decrease BWG (P = 0.08). Simultaneously, high ME diet increased concentrations of serum triglyceride, malondialdehyde and protein carbonyl (P < 0.05). Concurrently, oxidized soybean oil elevated activity of serum aspartate aminotransferase, and concentrations of glucose, high-density lipoprotein and total bile acid (P < 0.05). Meanwhile oxidized soybean oil increased protein carbonyl concentration and total antioxidant capacity activity (P < 0.05). Moreover, the high ME diet containing oxidized soybean oil decreased serum albumin and low-density lipoprotein levels (P < 0.05). Additionally, the incidence of WB in broilers increases with high ME diets (57.97% vs. 33.80%), and the incidence of WB in the oxidized soybean oil group was higher than that in the fresh soybean oil group (50.73% vs. 40.85%; P < 0.05). Meanwhile, the incidence of moderate and severe WB myopathy was highest in broilers fed high ME diet with oxidized soybean oil, which led to a substantial increase in cellular vacuolization, widespread inflammatory infiltration, and a marked thickening of the intercellular matrix, indicating more severe degradation of myofiber tissue. Thus, we concluded that the combination of high ME and oxidized soybean oil in the diet negatively affected broiler growth performance, serum biochemistry and redox homeostasis, and significantly elevated WB incidence and exacerbated pathological severity.