Digestion system dt220

Chemical composition (fat, protein, lactose, total solids, and total solids no-fat) was analyzed using an IR spectrometer (MilkoScan 133; FOSS, Hillerød, Demark) after proper validation by Kjeldahl [22 ] and Gerber [23 ] methods. Casein content was analyzed according to the reference method, ISO 17997-1/IDF 29 [24 ] using a FOSS Kjeltec™ 8400 Analyzer Unit and a FOSS Digestion System DT220 (FOSS, Hillerød, Denmark). Fat corrected milk (FCM_6%) and energy corrected milk (ECM) yield were calculated using the following formulas:
Fat corrected milk (FCM) in 6% based on the Equation (1)

where F = fat content (%) and M = milk yield in kg [3 (link)].
Energy corrected milk (ECM) yield based on the Equation (2) [25 (link)].

FA profile was performed using an Agilent 6890 N gas chromatograph equipped with an HP-88 capillary column (60 m × 0.25 mm i.d. with 0.20 µm film thickness, Agilent). Information about the temperature program and standard used are available by Mavrommatis and Tsiplakou [26 (link)]. The groups of FA were defined as follow [24 ]:

Individual feed samples from alfalfa hay, wheat straw, Camelina seeds, and concentrates were collected and analyzed for organic matter (OM; Official Method 7.009), dry matter (DM; Official Method 7.007), and crude protein (CP; Official Method 7.016) according to AOAC [14 ]. Briefly, 0.5 g of 1 mm ground feedstuff was duplicate analyzed using a FOSS Kjeltec™ 8400 Analyzer Unit and a FOSS Digestion System DT220 (FOSS, Hillerød, Denmark) to estimate the nitrogen content, and then crude protein content was obtained by multiplying N × 6.25. Furthermore, ether extract was assayed based on Soxhlet [15 ] using 70 mL of petroleum ether (Sigma-Aldrich, St. Louis, MO, USA) per 1 g of 1 mm ground feedstuff for 50 min. Feed samples were also analyzed for neutral detergent fibre (NDF), assayed with a heat-stable amylase (Sigma-Aldrich, St. Louis, MO, USA) and acid detergent fibre (ADF), expressed exclusive of residual ash according to Van Soest et al. [16 (link)] using an ANKOM 2000 fiber analyzer and F57 filter bags (ANKOM Technology, Macedon, NY, USA) (Table 1). Feed samples were also analyzed for the determination of FA profile according to the method of O’ Fallon et al. [17 (link)] (Table 1).