Replacement of soybean oil by Hermetia illucens larvae fat in broiler diets alters the breast muscle lipidome and reduces lipid oxidation of the breast muscle during heat-processing.

Replacement of soybean oil by insect fat from Hermetia illucens (HI) has been reported to increase the proportions of saturated fatty acids (SFA) and decrease those of polyunsaturated fatty acids (PUFA) in total lipids of breast and thigh meat in broilers. Since the susceptibility of meat to oxidation is strongly dependent on its PUFA content, the present study hypothesised that replacement of soybean oil by HI larvae fat in broiler diets reduces the formation of lipid oxidation products, including oxidation products of cholesterol and phytosterols, in heat-processed breast muscle of broilers. To test this hypothesis, 100 male, 1-day-old Cobb 500 broilers were assigned to three groups and fed three different nutrient adequate diets, which varied only in the fat source (group HI-0: 0% HI larvae fat and 5% soybean oil; group HI-2.5: 2.5% HI larvae fat and 2.5% soybean oil; group HI-5.0: 5.0% HI larvae fat and 0% soybean oil), in a three-phase feeding system for 35 days. While the growth performance of the broilers was not different, the absolute and relative breast muscle weights were higher in group HI-5.0 than in group HI-0 (p < 0.05). The proportions of C12:0, C14:0, C14:1, C16:0, C16:1 and total SFA were higher and those of C18:1, C18:2 n-6, C18:3 n-3 and total PUFA were lower in breast muscle total lipids of group HI-5.0 than in groups HI-2.5 and HI-0 (p < 0.05). Lipidomic analysis of breast muscle revealed that the concentration of triacylglycerols was 46% and 53% lower in groups HI-2.5 and HI-5.0, respectively, than in group HI-0 (p < 0.05), whereas all other lipid classes detected did not differ among groups. Concentrations of thiobarbituric acid-reactive substances, 7α-hydroxycholesterol, 7ß-hydroxycholesterol and total cholesterol oxidation products in heat-processed breast muscle were lower in group HI-5.0 than in group HI-0 (p < 0.05). Concentrations of oxidation products of phytosterols in heat-processed breast muscle were generally much lower than those of cholesterol oxidation products and did not differ between the three groups of broilers. In conclusion, complete replacement of soybean oil with HI larvae fat in broiler diets strongly alters the fatty acid composition of breast muscle total lipids and reduce lipid oxidation of the breast muscle during heat-processing.

Effects of supplementation of DL-methionine on tissue and plasma antioxidant status during heat-induced oxidative stress in broilers.

Exposure to high ambient temperature has been shown to impair growth performance and to cause oxidative stress in broilers. This study investigated the hypothesis that supplementation with methionine (Met) as DL-Met (DLM) more than the National Research Council recommendations improves growth performance and alleviates oxidative stress in broilers exposed to high ambient temperature. One-day-old male Cobb-500 broilers (n = 68) were allotted to 4 groups and phase-fed 3 basal diets during days 1 to 10, 11 to 21, and 22 to 35. One group was kept under thermoneutral temperature conditions and received the basal diets with Met + cysteine (Cys) concentrations according to recommendations of NRC. The other 3 groups were kept in a room with an increased ambient temperature from week 3 to 5 and were fed either the basal diet or the basal diets supplemented with 2 levels of DLM in which Met + Cys concentrations exceeded NRC recommendations by around 20% (group DLM1) and 40% (group DLM2), respectively. As expected, the broilers exposed to high ambient temperature showed a lower feed intake, lower body weight gains, a higher feed:gain ratio, and biochemical indications of oxidative stress in comparison to broilers kept under thermoneutral temperature conditions. Supplementation of DLM did not improve the growth performance in broilers exposed to high ambient temperature. However, the broilers supplemented with DLM had increased concentrations of glutathione in liver and breast muscle (groups DLM1 and DLM2), increased concentrations of tocopherols in the liver (group DLM2), and reduced concentrations of 7α-hydroxycholesterol and 7-ketocholesterol in heat-processed thigh muscle (groups DLM1 and DLM2) in comparison to the control group exposed to high ambient temperature. Concentrations of thiobarbituric acid-reactive substances and vitamin C in plasma, liver, and muscle were not different between the 3 groups exposed to heat stress. Nevertheless, the study shows that supplementation of DLM in slight excess of the Met concentration required for maximum growth performance improved the antioxidant status in tissues and reduced the susceptibility of muscle toward oxidation in heat-stressed broilers.

Thermal stability of plant sterols and formation of their oxidation products in vegetable oils and margarines upon controlled heating.

Fat-based products like vegetable oils and margarines are commonly used for cooking, which may enhance oxidation of plant sterols (PS) present therein, leading to the formation of PS oxidation products (POP). The present study aims to assess the kinetics of POP formation in six different fat-based products. Vegetable oils and margarines without and with added PS (7.5-7.6% w/w) in esterified form were heated in a Petri-dish at temperatures of 150, 180 and 210°C for 8, 12 and 16min. PS and POP were analysed using GC-FID and GC-MS-SIM, respectively. Increasing PS content, temperature and heating time led to higher POP formation in all tested fat-based products. PS (either naturally occurring or added) in margarines were less susceptible to oxidation as compared to PS in vegetable oils. The susceptibility of sitosterol to oxidation was about 20% lower than that of campesterol under all the applied experimental conditions. During heating, the relative abundance of 7-keto-PS (expressed as% of total POP) decreased in all the fat-based products regardless of their PS contents, which was accompanied by an increase in the relative abundance of 7-OH-PS and 5,6-epoxy-PS, while PS-triols were fairly unchanged. In conclusion, heating time, temperature, initial PS content and the matrix of the fat-based products (vegetable oil vs. margarine) showed distinct effects on POP formation and composition of individual POP formed.