Kjeltec system 1002

The dry matter content was determined [32 ] by drying samples in an oven at 105 °C until a constant weight was obtained (method no 925.09B; AOAC, 1990). The crude protein content was determined by the Kjeldahl method using the Kjeltec system 1002 apparatus (Foss-Tecator AB, Höganäs, Sweden), and a conversion factor of 6.25 was used to convert total nitrogen to crude protein (method no. 984.13; AOAC, 1990). Crude fat was determined by the Soxhlet extraction method (method no. 920.39C; AOAC, 1990). Ash was determined by incineration in a muffle furnace at 550 °C for 24 h (method no. 920.153; AOAC, 1990). Crude fiber content was determined using the FiberCap 2022 system (Fos-Tecator AB, Höganäs, Sweden) according to method no. 962.09E (AOAC, 1990). The content of sugar was determined by Bertrand’s method [33 ,34 ].

The dry matter content was determined [25 ] by drying samples in an oven at 105 °C until a constant weight was obtained (method No. 950.46B; AOAC, 1990). The crude protein content was determined by the Kjeldahl method using the Kjeltec system 1002 apparatus (Foss-Tecator AB, Höganäs, Sweden), and a conversion factor of 6.25 was used to convert total nitrogen to crude protein (method No. 981.10; AOAC, 1990). Crude fat was determined by the Soxhlet extraction method (method No. 960.39; AOAC, 1990). Ash was determined by incineration in a muffle furnace at 550 °C for 24 h (method No. 920.153; AOAC, 1990). The content of protein, fat and ash were expressed as the weight percentage of dry matter from muscle tissues.
The cholesterol content in meat was determined according to the extraction method described by Polak et al. [26 (link)] and followed by HPLC separation and analysis on Shimadzu 10 A HPLC system (Shimadzu Corp., Kyoto, Japan). The data collection and evaluation were performed by using LC Solution (Shimadzu Corp., Kyoto, Japan) operating system. The analytical column was LiChrospher 100 RP-18e, 150 × 4.6 mm, 5 μm (Alltech Associates Inc., Columbia, MD, USA) with a guard column (LiChrospher 100 RP-18, 7.5 × 4.6 mm). The cholesterol content was expressed as mg/100 g fresh meat.

Oat, winter wheat grain, and straw yields (kg ha⁻¹) were determined. The grain yield was converted to standard moisture content (14%), and straw was converted to dry matter (DM). Plant samples were dried and ground using a ZM200 ultra-centrifugal mill (Retch, Haan, Germany) with 1 mm mesh sieves. Grain and straw N content (kg ha⁻¹) was determined in the sulphuric acid digestates using the Kjeldahl method with a Kjeltec system 1002 (Foss Tecator, Hoganas, Sweden). To determine nitrate (N-NO₃, kg ha⁻¹) nitrogen content, soil samples were collected four times: in autumn after winter wheat sowing, 21 November 2018 (Assessment 1); in spring before winter wheat growth resumed, 25 March 2019 (Assessment 2); in autumn, when all experimental plots were ploughed, 16 October 2019 (Assessment 3); and before spring wheat sowing, 23 April 2020 (Assessment 4); all were at 0–30 cm and 30–60 cm depths. One soil sample consisted of five drills from each plot. Nitrate nitrogen (N-NO₃) was determined by the ionometric method. The samples were placed in 1 mol L⁻¹ KCl extract, w/v ratio 1:5.