Variation in Fat Globule Size in Bovine Milk

摘要: The objectives of this study were to investigate the sources of variation in milk fat globule (MFG) size in bovine milk and its prediction using mid-infrared spectroscopy. Mean MFG size was measured in 2,076 milk samples from 399 Ayrshire, Brown Swiss, Holstein, and Jersey cows, and expressed as volume moment mean (D [4, 3]) and surface moment mean (D [3, 2]). The mid-infrared (MIR) spectra of the samples, and milk performance data were also recorded during routine milk recording and testing. The effects of herd, breed, days in milk, season, milking period, age at calving, parity, and individual animal on the variation observed MFG size were investigated. Herd, breed, days in milk, season, and milking period had significant effects (p< 0.05) on mean MFG size. MFG size was the largest at the beginning stage of lactation and subsequently decreased. Milk samples with the smallest MFG on average came from Holstein cows, and the largest from Jersey and Brown Swiss cows. Partial least squares regression was used to predict MFG size from MIR spectra of samples with a calibration dataset containing 2,034 and 2,032 samples for D [4, 3] and D [3, 2], respectively. Coefficients of determination of cross validation for D [4, 3] and D [3, 2] prediction models were 0.51 and 0.54, respectively. The associated ratio of performance deviation values (RPD) were 1.43 and 1.48 for D [4, 3] and D [3, 2], respectively. With these models, mean MFG size cannot be accurately quantified, but results may be sufficient to screen samples for having either small or large MFG on average. A significant correlation (p< 0.001) between D [4, 3] and D [3, 2] with milk fat …