Effects of Dietary Supplementation of a Resin-Purified Aqueous-Isopropanol Olive Leaf Extract on Meat and Liver Antioxidant Parameters in Broilers

Abstract

Olive leaves are byproducts οf the agro-industrial sector and are rich in bioactive compounds with antioxidant properties. They could be supplemented in poultry diets powdered or less frequently as extracts to improve performance, health and product quality. The objective of this study was to investigate the possible beneficial effects of an aqueous isopropanol olive leaf extract—purified through filtration (250–25 µm) and a resin (XAD-4)—when supplemented in broiler chickens’ diets, on meat quality parameters, focusing mainly on antioxidant parameters as there is limited published information. For this purpose, four-hundred-and-eighty-day-old broilers were randomly assigned to four dietary treatments: T1 (control: basal diet); T2 (1% olive leaf extract); T3 (2.5% olive leaf extract); T4 (positive control: 0.1% encapsulated oregano oil commercially used as feed additive). At the end of the experimental period (day 42), the birds were slaughtered, and samples from breast, thigh meat and liver were collected for antioxidant parameters evaluation. On day 1, after slaughter, in thigh meat, Malondialdehyde (MDA) was lower in T2 compared to T3, and total phenolic content (TPC) was higher in T2 compared to T3 and T4. Total antioxidant capacity (TAC) was increased in T2 and T4 breast meat compared to the control. In liver, T4 treatment resulted in higher TPC. The lack of dose-dependent effect for olive leaf extract may be attributed to the pro-oxidant effects of some bioactive compounds found in olive leaves, such as oleuropein, when supplemented at higher levels. In summary, it can be inferred that the inclusion of 1% olive leaf extract in the feed of broilers has the potential to mitigate oxidation in broiler meat and maybe enhance its quality.

Effects of Enriched-in-Oleuropein Olive Leaf Extract Dietary Supplementation on Egg Quality and Antioxidant Parameters in Laying Hens

“…The extraction and the HPLC-DAD analyses were carried out at the Department of Pharmacognosy and Natural Products Chemistry, Faculty of Pharmacy, University of Athens, Greece. The extraction of olive leaves was performed according to our previous work [5], and the extract obtained was condensed and dried prior to HPLC-DAD analyses, following COI/T.20/Doc. No 29/Rev.1 2017 elution protocol [28].…”

“…The extracts obtained were further processed. The antioxidant parameters measured were the following: Total phenol content (TPC), Total flavonoid content (TFC), DPPH • scavenging, and Cupric ion Reducing Antioxidant Capacity (CUPRAC), as in previously published methodology [5,34].…”

“…The methanolic extracts obtained were analyzed chromatographically using a Shimadzu Nexera X2 UHPLC System (Shimadzu Corporation, Kyoto, Japan). More details about the UHPLC system are described in our previous published work [5]. For UHPLC data acquisition and analysis, the exact methods are further described in Tsimidou et al (2019) [35].…”

“…It is generally acknowledged that eggs are the primary animal protein source for humans and are highly nutritious, exhibit a multitude of valuable biochemical properties, and are known worldwide for their substantial antioxidant capabilities [2]. Waste materials and byproducts are used to extract beneficial nutrients to meet customer and societal needs for high-quality, safe, and environmentally friendly processed foods [3][4][5]. Laying hens may also be exposed to stimuli that increase oxidative stress at different phases of production.…”

“…Elsewhere, olive leaf powder added to the diet of Japanese quails increased egg production while decreasing metabolic parameters such as serum lipids and cholesterol [27]. Recently, our research group reported that the supplementation of olive leaf extract at the level of 1% in broilers alleviated oxidation in broiler meat [5]. Therefore, it can be deduced that any oxidative challenge experienced by laying hens will have an impact on both their metabolism and the parameters associated with egg quality.…”