ABSTRACT:In May 2003 differences in milk fat composition in two main dairy breeds in the Czech Republic, Czech Pied cattle and Holstein cattle, were studied in two uniform groups, each containing eight cows. The groups were housed together and received the same daily diet. Fatty acids were determined in mean milk samples from the individual cows as their methyl esters using a gas chromatography procedure. The groups of the fatty acids, namely saturated (SAFA), monounsaturated (MUFA) and polyunsaturated (PUFA) ones, were examined together with the individual acids. The milk fat of Czech Pied cattle was found to contain significantly less SAFAs than the fat of Holstein cows (60.78 and 63.62% of total acids; P < 0.05). Determined mean MUFA contents (27.64 and 25.76%) and total levels (34.31 and 32.11%) of all the unsaturated acids (MUFAs and PUFAs) were insignificantly elevated in the milk fat of Czech Pied cattle. The contents of the most of the individual fatty acids did not differ considerably between the breeds. In Holstein cows, significantly higher contents (P < 0.05) of capric acid (C 10:0 ) and stearic acid (C 18:0 ) 3.30 and 4.45%, respectively, as compared with 2.69 and 2.61% for Czech Pied cows, were observed. The milk fat of Czech Pied cows had significantly higher contents of oleic acid (C 18:1 ) 23.60% (P < 0.05) and of an isomer of octadecatrienic acid (C 18:3n4 ) 0.16% (P < 0.001) as compared with 21.68 and 0.10%, respectively, in the fat of Holstein cows.

ABSTRACT:The fatty acid (FA) composition of bulk milk fat was examined on three mountain dairy farms in the Czech Republic. Milk samples were collected in the period of indoor grass silage feeding (November-April) and in the grazing period (May-October). In total fifty FAs were identified in the milk fat. The two-way ANOVA with factors of the farm and of the period of milk sample collection was used for the evaluation of variation in FA concentrations. Significant differences between the farms (P < 0.01) were found in the concentration of five FAs, which accounted for 30.40 g/100 g total FAs. Significant differences between the indoor and the grazing period (P < 0.01) were found in the concentration of sixteen FAs, which accounted for 63.86 g/100 g total FAs. The content of long-chain (> C16), mono-and polyunsaturated FAs in the milk fat was higher in the grazing period (49.22, 31.69 and 4.69 g/100 g total FAs) than in the indoor period (42.25, 27.55 and 4.15 g/100 g total FAs, respectively; P < 0.01). The proportion of conjugated linoleic acid (CLA) was also higher in the grazing period (1.09 g/100 g total FAs) than in the indoor period (0.74 g/100 g total FAs; P < 0.01). The medium-chain (C12-C16) and the saturated FAs were more abundant in the milk fat in the indoor period (48.91 and 67.16 g/100 g total FAs) than in the grazing period (41.31 and 62.16 g/100 g total FAs; P < 0.001 and P < 0.01; respectively). These results indicated a positive influence of seasonal grazing on the FA profile of cow milk fat as regards its potential health effects in consumers.

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