Browsing by Subject "tyydyttyneet rasvahapot"

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  • Tapola, Tuire (Helsingin yliopisto, 2020)
    Milk fat contains a lot of (70–75 %) saturated fat, which is connected to Finnish public heart and coronary diseases. However, it is possible to alter the fatty acid composition of milk fat by giving cows lipid supplements such as crushed rapeseeds. The aim of this pilot study was to investigate how the lipids of crushed rapeseeds affect dairy cow’s milk fatty acid composition. The effects of rapeseed lipids on saturated and unsaturated fatty acid concentrations in milk fat were studied in particular. Additionally, it was investigated how dietary lipids affect cows’ dry matter (DM) intake and milk production as it is known that high amounts of lipids can reduce DM intake and fiber digestion in the rumen. The study consisted of two successive three week long periods of which the first one was control period and the second one test period. There were six ayrshire cows which had been on average 181 days in milk at the beginning of the study. The cows were given partial total mixed ratio (pTMR) containing grass silage as forage (60 % of diet DM) during the whole study. Concentrates comprised cereals, rapeseed meal, molassed sugar beet pulp and mineral supplements. Control diet’s barley was replaced by oats and most of the rapeseed meal was replaced by crushed rapeseed in the test diet. Crushed rapeseed was added 160 g/kg pTMR DM. Cows were also given complete feed 3kg/day at milkings. Lipids of crushed rapeseeds reduced the concentration of saturated fatty acids by 20 % in milk fat. Of all the saturated fatty acids, palmitic acid (C16:0) was decreased by 38 % and stearic acid (C18:0) was increased by 94 %. Of these two saturated fatty acids, C16:0 is linked to higher total plasma cholesterol levels whereas C18:0 is considered to have a neutral effect in humans. The concentration of monounsaturated oleic acid (cis-9 C18:1), which is known to be hypocholesteremic, increased by 78 % in milk fat. Test diet caused decline in DM intake and milk production. It is likely that the milk production decreased partly because the cows were in declining milk production phase. Test feed decreased the apparent digestibility of neutral detergent fiber (NDF), because the amount of rapeseed lipids in the diet was high (48 g/kg diet DM). Crushed rapeseeds suit excellently to alter dairy cow’s milk fatty acid composition. The amount of lipid supplementation should not be too high in order to avoid decreases in DM intake and NDF digestibility as occurred in this study.