**1. Introduction**

Phytogenic feed additives have been recognized as antimicrobials, antioxidants, antitoxigenic, anti-coccidiosis, and antiparasitic [1–3]. In addition, phyto-feed additives improve the palatability and digestibility of feed, enhance the absorption of nutrients, as well as manipulate the microbial habitat and gu<sup>t</sup> functions of domestic animals [4,5]. Moreover, they protect the feed lipids from oxidative damage and improve the antioxidant and immune status of the animal. Furthermore, phyto-feed supplementations are natural additives, less poisonous, residue-free, with more integrity and perfect as feed additives for poultry when compared to antibiotics [1]. Consequently, they can be considered as an important tool in poultry nutrition for enhancing growth performance, feed efficiency and reproductive performance, and reducing the incidence of diseases and the house emissions

**Citation:** Morshedy, S.A.;

Abdelmodather, A.M.; Basyony, M.M.; Zahran, S.A.; Hassan, M.A. Effects of Rocket Seed Oil, Wheat Germ Oil, and Their Mixture on Growth Performance, Feed Utilization, Digestibility, Redox Status, and Meat Fatty Acid Profile of Growing Rabbits. *Agriculture* **2021**, *11*, 662. https:// doi.org/10.3390/agriculture11070662

Academic Editors: Lubomira Gresakova, Emilio Sabia and Secundino <sup>L</sup>ópez

Received: 23 May 2021 Accepted: 12 July 2021 Published: 14 July 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

of poultry [1,4]. The inclusion of phytogenic feed additives in the diet can improve the nutritional value of meat and tissue composition [6].

As one of the phytogenic feed additives, vegetable oils, such as olive oil, rice bran oil, corn germ oil, and wheat germ oil are commonly used as food supplements in the human diet [7]. Vegetable oils are natural, healthy, and nutritious due to their high content of unsaturated fatty acids and functional molecules, and their high energy value [8].

Rocket (*Eruca sativa* Mill.) belongs to the large family of Brassicaceae (also called Cruciferae or the mustard family). The rocket is an annual or biannual herb that originated in the Mediterranean region and has spread through the world [9]. *E. sativa* species are widely used in folklore and traditional medicine for their therapeutic properties as digestive, astringent, laxative, emollient, depurative, diuretic, rubefacient, stimulant, and tonic [10]. The composition of rocket seeds has shown the presence of many active compounds, such as glucosinolates (glucoerucin and glucoraphanin), flavonoids (quercetin, kaempherol, and isohamnetin), carotenoids, and vitamin C, which are ascribed to antioxidant activity [10]. Rocket seeds contain up to 25–35% of oil [11] and rocket seed oil (RSO) has about 18% of the total saturated fatty acids and 82% of the total unsaturated fatty acids. Rocket seed oil prompts the regeneration of hepatic tissue, decreases hepatic lipid levels, and possesses potent free radical scavenging [12], as well as inhibits melanoma tumor growth in mice [13].

Additionally, rocket seed oil inhibits the growth of some Gram-positive and Gramnegative bacteria and has approximately the same efficiency as the broad-spectrum antibiotic Gentamicine [14]. Moreover, RSO ameliorated the harmful effect of aflatoxin on rabbit blood, semen, and pathological changes in the liver, kidney, and testes [15]. Furthermore, *E. sativa* improved significantly the final body weight, average daily gain, feed intake, and feed conversion ratio of rabbits [16]. The dietary supplementation of 1 g RSO/kg diet alone or with 1 g onion seed oil/kg diet in the growing rabbit's diet for 12 weeks under heat stress improved growth performance, carcass weight, and nutrient digestibility as well as enhanced immunity [17]. In this vein, Alagawany et al. [18] found that dietary supplementation with 0.5–2 g/kg diet of watercress oil alone or in combination with coconut oil for 8 weeks in intensive rabbit production improved growth performance, feed utilization, antioxidant status, and immunity, as well as reduced pathogenic cecal bacteria. On the other hand, the addition of high levels of RSO (1–3 mL/kg body weight) to the rabbits for 2 weeks resulted in a reduction of the body weight with an increasing RSO oil dose [19].

Wheat (*Triticum aestivum* L.) germ is produced during wheat milling and is used worldwide as a diet supplement in the feed formulation of farm animals [20]. Wheat germ oil (WGO) represents about 10–15% of the whole wheat germ [21]. In addition, it contains tocopherol derivatives and tocotrienols [22], n − 3 fatty acids, especially alphalinolenic acid [23], fat-soluble carotenoids [24], phytosterols, especially D5-avenasterol [25] and phenolic compounds [26]. Moreover, wheat germ oil has an anti-inflammatory effect and strong antioxidant effects [21,26]. Whereas, it reduces O2-production and NADPH oxidase activity, and thereby, decreases oxidative stress [23]. WGO manages the serum lipid profile and prevents hypercholesterolemia and atherosclerosis in male albino rabbits fed high cholesterol diet [27]. Other benefits of wheat germ and its derivatives are lowering cholesterol absorption, retarding platelet aggregation, delaying ageing, improving physical endurance, enhancing fertility [25], as well as preventing and curing carcinogenesis [28]. Furthermore, dietary WGO supplementation increased the body weight of male broilers [29].

Taking previous knowledge into account, the present study aimed to investigate the effects of RSO, WGO, and their mixture on growth performance, feed utilization, nutrient digestibility, carcass characteristics, meat fatty acid profile, and redox and immune status of growing rabbits.

#### **2. Materials and Methods**

#### *2.1. Animal Management and Feeding*

Eighty-four V-line rabbits at 5 weeks of age (after weaning) with an initial BW of 535.60 ± 13.48 g were assigned randomly into four experimental groups (seven replicates in each group, three rabbits in each replicate). The first group served as the control and received 0.3 mL/kg BW of distilled water (CON), the second group received 0.3 mL/kg BW of rocket seed oil (RSO), the third group received 0.3 mL/kg BW of wheat germ oil (WGO), and the fourth group received a mixture of oils consisting of 0.15 mL of RSO and 0.15 mL of WGO/kg BW (MOs). The oils of wheat germ and rocket seeds were obtained from El Madina Factory for natural seed extract in Borg El Arab, Alexandria, Egypt.

Rabbits were given oils once daily via gavage (oral administration) for 7 weeks from 28 May to 15 July. The basal ration was formulated and pelleted to meet the nutrient requirements of rabbits, according to the NRC [30]. The rations were offered to rabbits *ad libitum*. The ingredients and chemical composition of the pelleted rations are shown in Table 1. The rabbits were offered free access to freshwater.


**Table 1.** The ingredients and chemical analysis of the experimental ration.

1 It provides the following nutrients (unit/kg diet): Vitamin A, 12,000 IU; vitamin D3, 2000 IU; vitamin E, 11 IU; vitamin K, 2 mg; pantothenic acid (d-Ca pantothenate), 10 mg; folic acid, 1 mg; choline (choline chloride), 250 mg; Mn (manganous oxide), 60 mg; Fe (ferrous sulfate), 30 mg; Zn (zinc oxide), 50; Cu (copper sulfate), 10 mg; iodine (ethylenediamine dihydroiodide), 1 mg; cobalt (cobalt sulphate heptahydrated), 0.1 mg; and Se (sodium selenite), 0.1 mg.

All the rabbits were kept under similar management, as well as hygienic and environmental conditions. Freshwater was automatically available all the time through stainless steel nipples that were fixed in each cage. The rabbits were housed in galvanized wire cages (dimensions: 40 × 50 × 65 cm) located in a well-ventilated building. The daily photoperiod is a 16:8 h light-dark cycle. This study was conducted at the Rabbit Research Laboratory, Department of Animal and Fish Production, Faculty of Agriculture (Saba Basha), Alexandria University. All the protocols applied in the present experiment have been approved by the Alexandria University, Animal Care and Use Committee with approval no. AU: 19/21/03/25/3/16.

#### *2.2. Body Weight and Feed Intake*

The rations were removed at night before the days of rabbit weight. The growing rabbits were weighed weekly in the morning before being given a feed. The average daily gain (ADG) and weight gain percentage were calculated. The feed intake was recorded biweekly, then daily feed consumption was calculated by dividing the weekly feed intake by 14 days. The feed conversion ratio (FCR) was calculated by dividing the daily feed intake by the average daily gain.
