Milkoscan minor

Both yak and Holstein raw milk samples were analyzed for fat, protein, casein, and lactose, using a Foss milk analyzer (MilkoScan Minor, Foss Analytics, Hillerød, Denmark) calibrated before analysis. Concentrations of caseins (β-casein, α-casein, κ-casein, α-lactalbumin, and β-lactoglobulin) were measured via electrophoresis, as reported by Manderson et al. (1998) (link). Concentrations of Ca 2+ and Mg 2+ were measured using atomic absorption spectrophotometry, and concentrations of Na and K were determined via flame photometry.

The initial milk, the FO concentrate, and the FO concentrated milk reconstituted to single strength were analyzed for the following: concentration expressed as °Brix and measured with a Sper Scientific 300053 refractometer; water activity, measured with an AquaLab series 3 water activity meter (Meter); pH, measured at room temperature with a Thermo Scientific Orion Star A214 pH/ISE Benchtop pH meter; and color (L, a, b on the Hunter scale), measured with a Konica Minolta CR-400 chromameter. Additionally, TS content was determined by oven drying (AOAC International, 1996, methods 920.107 and 925.23 A) in a Blue M Stabil-Therm Pro-Tronix II electric oven, and milk composition was determined by near-infrared spectroscopy using a Milkoscan Minor (Foss). For quick estimation of TS content, a correlation curve between °Brix and TS (%) was developed (Figure 2).

Fresh raw bovine milk was obtained from a local dairy farm, stored overnight at 4°C, and then skimmed or standardized to 3.25% (wt/wt) fat content. One-liter portions underwent homogenization at 60°C (Universal Pilot Plant, Waukesha Cherry-Burrell, Philadelphia, PA) and (or) HTST pasteurization at 72°C for 15 s, and UHT processing at 135°C for 2 s in an Armfield model FT74P/T HTST/UHT (Armfield Inc., Denison, IA) plate-and-frame continuous pasteurizer (Tomasula and Kozempel, 2004) and were then stored at 4°C. Fresh sample was used within 1 d and processed samples were used in <3 d. The abbreviations used throughout the text to define the milk samples are as follows: R = raw unprocessed milk, RS = raw skim milk, RW = raw whole milk, H = homogenized milk, P = HTSTpasteurized milk, SP = HTST-pasteurized skim milk, HP = homogenized and HTST-pasteurized milk, SU = UHT-processed skim milk, and HU = homogenized and UHT-processed milk.
Fat, lactose, and protein were determined by a MilkoScan Minor (Foss, Eden Prairie, MN). Pepsin from porcine gastric mucosa (P7000; 250 U/mg of solid), porcine bile extract (B8631), and porcine pancreatin (P1750; 4 × USP) were purchased from Sigma-Aldrich Corp. (St. Louis, MO). All other chemicals were of analytical grade and were purchased from Sigma-Aldrich unless specified otherwise.

Samples of feed offered and orts were collected every day during the experimental period to determine the daily DMI. Samples of dietary ingredients were collected at the beginning of the experimental period and stored at -20°C until analyzed for the nutrient components of diets. The individual milk yield was recorded daily at morning and evening milkings throughout the experiment. Milk samples were collected on the last week of each experimental period, on d 19 to 21, and the samples were mixed thoroughly and divided into 2 portions. One aliquot was stored at 4°C with a preservative until analyzed for milk composition and SCC by infrared analysis (MilkoScan minor, Foss, Hillerod, Denmark) . The other aliquot was stored at -20°C until analyzed for FA composition by GC. Mammary blood flow (MBF) was measured by an indicator dilution technique that uses p-aminohippuric acid (PAH; Ten Have et al., 1995) . The PAH solution (15 mg/mL) was infused continuously (750 mg of PAH/h) for 6 h into the EPA catheters oriented to the mammary gland using a constant flow pump (longer pump, BT100-1L,