Drying oven

Dry cinnamon bark was obtained from a neighborhood store in Riyadh, the capital of Saudi Arabia, and then shipped to the Department of Animal Production, King Saud University. Upon arrival, the bark was crushed and ground using a blender to a fine powder (particle size: 0.25–0.30 mm). The cinnamon bark powder was analyzed directly and mixed with dietary groups. The water content of the dried grounded cinnamon bark was evaluated using a drying oven (Binder, Bohemia, NY, USA). The crude protein level was determined by the Kjeldahl technique (N X 6.25) using a 2020 Digester and a Velp UDK 140 distillation unit. The raw fat content was evaluated using the Soxhlet apparatus. The raw fiber content was determined using a Dosi-Fiber. The ash content was analyzed by incinerating the dried samples at 600 °C for 6 h. The acid detergent fiber content was determined based on [29 ] methods nos. 930.15, 990.03, 920.39, 978.10, 942.05, and 973.18, respectively, as described by [30 (link)]. The neutral detergent fiber content was analyzed as described by [31 (link)]. Gross energy (kcal/kg) was calculated using a bomb calorimeter. All data were expressed on the basis of dry matter.

The onion peels (OPs) and passion fruit peels (PFPs) were washed, and the excess water was removed using a paper towel. Thenceforth, the peels were dried at 50 °C in a drying oven (BINDER GmbH, Tuttlingen, Germany), milled with a coffee grinder (Q.5321 Qilive, Auchan, Croix, France) to obtain particles below 18 mesh (1 mm) and stored in a desiccator at room temperature, protected from light. The bioactive compounds were extracted from both OP and PFP using a solid–liquid extraction with a Soxhlet apparatus. The extraction procedure was adapted from the literature [37 (link)]. Ethanol was used as a solvent, with a ratio of 1:20 m/V. The extractions were conducted for 1.5 h, in triplicate. Then, the solvent was evaporated using a rotary evaporator (Rotavapor R-200, BUCHI Laboratories, Flawil, Switzerland), followed by a gentle stream of nitrogen.