Browsing by Author "Ylinen, Vappu"

Micro algae are potential protein supplement for farm animals as micro algae are often rich in protein and contain nutritionally beneficial fatty acids. Micro algae grow rapidly and with low nutrient requirements, and can be cultivated in areas that are not suitable for cultivation of other food or feed. The aim of this study was to investigate whether micro algae can be used as an alternative protein supplement for rapeseed meal for dairy cows. We investigated how partial or total replacement of rapeseed meal with micro algae affects levels of dry matter intake, plasma concentrations of amino acids and metabolites, mammary gland metabolism, milk yield, and milk composition in dairy cows. Our hypothesis was that micro algae is less palatable than rapeseed meal, and therefore dry matter intake is lower in micro algae diets. Our second hypothesis was that micro algae contain less histidine than rapeseed meal, and therefore the milk and protein yields are lower in micro algae diets. The study was conducted at the research farm of University of Helsinki. Six multiparous Finnish Ayrshire cows participated in this experiment. The study design was a replicated 3 x 3 Latin square with 3-week periods. In the control diet, the protein supplement was rapeseed meal (2,3 kg air dry). The two other treatments were a diet where micro algae (Spirulina platensis and Chlorella vulgaris 1:1 mixture) replaced half of the rapeseed meal protein, and a diet where micro algae replaced all of the protein of rapeseed meal. In all diets, the cows were offered cereal-based concentrates, so that total concentrate portion was 11 kg /d and grass silage ad libitum. Replacing rapeseed meal partly or completely with micro algae had no effect on dry matter intake or digestibility of nutrients. In the micro algae diets, histidine intake was lower than in the control rapeseed diet. Lower histidine intake decreased the plasma histidine concentration linearly (56,5 – 50,5 µmol/l) but had no effect on milk, protein, or fat yields. Micro algae treatment had no effect on plasma metabolites or mammary gland metabolism. Plasma histidine concentration was high in all treatments, which may explain why the milk and protein yields did not decrease with micro algae diets. In addition, the cows were in late lactation, which may have attenuated the differences between treatments. The differences in fatty acid compositions between rapeseed and micro algae were reflected in the milk fatty acid compositions. However, the differences in milk fatty acid compositions were very small. This study suggests that micro algae can be used as a protein source for dairy cows. Micro algae can replace rapeseed meal partly or completely for dairy cows in late lactation without adverse effects in dry matter intake, or milk, protein, or fat yields.