engleski

Effects of milking interval on milk constituents from various fractions of ewe milk

The aim of this study was to evaluate the effects of milking interval (8 and 16 h) on milk constituents (fat, protein, lactose and dry matter percentage, and somatic cell count) in different milk fractions in Istrian x Awassi x East Friesian crossbreed ewes. Milk fraction samples of 20 ewes were collected during morning and evening milking in early lactation after 25% (M25), 50% (M50), 75% (M75) and 100% (M100) of main milk yield, and machine stripping fraction (MS) when milk flow decreased below 100 g/min from the whole udder. For the statistical analysis, a repeated measures model was used with ewe as a random effect and milking time, peak flow rate, total milk yield, milking interval and milk fraction nested within milking interval defined as fixed effects. The relationships between milk fractions and constituents within milking interval were tested by using linear, quadratic and cubic contrasts. The fat content during main milking ranged from 5.81 to 6.30 % and from 3.00 to 5.70 % after the 8 and 16 h from previous milking, respectively. Compared to the main milk fractions, the MS fraction fat content was higher (P < 0.05) after both milking intervals. Protein, lactose and dry matter did not change (P > 0.05) through the main milking fractions in both milking intervals. In contrast, MS fraction was lowest (P < 0.05) for protein and lactose, while highest for dry matter. Higher somatic cell count were observed in the M25 and MS fractions compared to all other milk fractions (P<0.05). Milk fat, protein, dry matter and somatic cell count were best described by a quadratic function, while lactose was described by a linear after 16 h and a cubic function after 8 h milking interval. Milking interval strongly influenced all the milk constituents in various milk fractions during ewe milking. Changes in milk constituents between and during ewe milking should be taken into account when analytical milk samples are taken.

milk fractions; milking interval; dairy ewes

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