Abstract
Intake of milk fat in human nutrition is important because of unsaturated and especially essential fatty acids (FAs), linoleic and α-linolenic acid, and conjugated linoleic acid (CLA), which is found only in meat and milk of ruminants. The objective of our study was to investigate the effect of paternal bulls on fatty acids composition in milk fat of dairy cows of different breeds. The milk samples were taken in total from 299 dairy cows from 11 dairy farms. In experiment Holstein (H, n = 105), Red Holstein (R, n = 120) and Pinzgau (P, n = 74) breeds originated from different bulls were used. Individual milk samples were analyzed for fatty acids in milk fat using gas chromatography (apparatus GC Varian 3800, Techtron, USA), using FID detector in capillary column Omegawax 530; 30 m. In the chromatography records there were identified 54 fatty acids inclusive of particular isomers. Their relative proportions were expressed in percent's (%). Among the studied breeds, the highest content of conjugated linoleic acid (CLA) - 0.67%, essential FAs (EFA) - 2.98%, monounsaturated FAs (MUFA) - 25.84% and the lowest atherogenic index (AI) - 3.10 was at breed P. Within this breed there was high variability and daughters of bull COS1 achieved significant above-average values of CLA content 1.07%, EFA 3.71%, MUFA 29.93% and under breed average AI = 2.40. The group of daughters of NOB3 was significant lower in CLA, 0.50% as compared with an average of P breed. . From the breed H bull MTY2 showed significantly higher value of 0.62% CLA, EFA 3.42%, 34.29% MUFA and lower value of AI, 1.9 as compared to H breed average. Statistically significantly lower levels of CLA 0.29% and 21.46% MUFA and higher AI 3.72 in milk fat of his daughters, bull STY3 may be considered as potential worser of these properties. At the breed R bull MOR506 showed in compar to the breed average significantly higher value of the EFA 3.80% and also the higher content of CLA 0.50% and MUFA 25.09%, resulting in statistically significant lower AI = 2.91. Bull MOR506 could be considered as potential improver of milk fat composition. The above described variability in the composition of milk fat of dairy cows and the subsequent relationships between these values suggest that the selection of the bull according to the fatty acid composition of milk fat may be considered.
Highlights
In recent decades, the intake of milk fat in human nutrition considered a negative factor in relation to cardiovascular disease
In order to assess the possibility of genetic influence on the composition of fatty acids in milk fat of dairy cows we evaluated groups of cows according to their bull in comparison with the results of the whole group of cows of the some breed
We evaluated the content of positive conjugated linoleic acid (CLA), essential fatty acids (EFA), monounsaturated FAs (MUFA) and on the opposite, the atherogenic index (AI), which relatively high value is undesirable
Summary
The intake of milk fat in human nutrition considered a negative factor in relation to cardiovascular disease. The intake of milk fat in human nutrition is important because of unsaturated and especially essential fatty acids (EFA), linoleic and α-linolenic acid, and especially conjugated linoleic acid (CLA), which is found only in meat and milk of ruminants. Health effects of EFA are gaining prominence within the latest medical research, recognizing the importance of milk fat in the human diet. The latest research confirms, besides of nutrition of dairy cows, the importance of genetic effects on the composition of fatty acids in milk fat, and consider it necessary to evaluate this regard at breeds reared in Slovakia. Capps et al (1999) described the Jersey breed cows that produce lower levels of conjugated linoleic acid (CLA) than Holstein when they were fed complete feed mixture with the addition of hay. An interesting difference (close to statistical significance) was found for the representation of health desirable CLA (0.42 > 0.38%)
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