Milkoscan 133

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 ]:

Each goat was hand milked two times daily (07.00 A.M. and 05.00 P.M.) from 14 days postexperiment and reported as a one-day milk sample throughout the 90-day experimental period. Before milking, the nipple was washed and disinfected with 70% alcohol to prevent microbial contamination. Collected milk was carefully weighed using a digital balance and recorded to calculate the yields. For milk composition assessment, morning milk samples were collected weekly from 14 to 63 days postexperiment. Milk pH was immediately measured after milking. Milk samples (approximately, 150 mL) were conserved with bronopol (2-bromo-2-nitropropane-1,3-diol) and transported to the laboratory using a cooler at 4°C. These samples were analyzed for fat, protein, lactose, total solids, fat, and solids-not-fat using infrared spectroscopy (Milko Scan 133, Foss Electric, Denmark).

Milk samples were analyzed for fat, protein, lactose, and total solids-not-fat, using a Milkoscan 133 (Foss Electric, Hillerød, Denmark) calibrated for sheep milk according to the Mojonnier method for fat, the Kjeldahl method for protein, and the polarimetric method for lactose [26 ]. The milk oxidative stability was evaluated by measuring the levels of malondialdehyde (MDA), a secondary lipid oxidation product formed by hydrolysis of lipid hydroperoxides. MDA concentration was determined by applying a selective, third-order derivative spectrophotometric method previously developed by Botsoglou et al. [27 (link)].