Browsing by Author "Kankfelt, Sampo"

Vitamin B12 is crucial for human well-being, and its intake from diet primarily comes from animal-derived products. Cow's milk is a good source of B12 for humans due to its high B12 content, and it is essential to investigate whether the vitamin concentration can be influenced, for example, by the animal's diet. The aim of the thesis was to determine the nutritional and metabolic factors influencing the B12 concentration in cow's milk. The meta-analysis dataset consisted of three experiments conducted in the Viikki Research Farm from 2019 to 2022. The study subjects were primiparous and multiparous Ayrshire cows. The average days in milk was 149 days. Proportion of concentrate in the cows' diets varied from 40 to 45 %. The dataset consisted of individual observations and contained 166 different variables, with number of observations ranging from 64 to 97. Variables included dry matter intake, nutrient intakes and digestibilities, concentrations of plasma metabolites and insulin, milk yield, and composition of milk, including fatty acids. The average vitamin B12 content of milk was 3.34 ng/g (1.33–6.77 ng/g). Relationships between the studied variables were analyzed using SAS software, employing correlation and regression analysis. The results indicated that the factors with highest correlation coefficient with milk B12 concentration were the stage of lactation, plasma insulin concentration, and milk protein, fat, and dry matter concentration. The best explanatory power (R2=0.597) was achieved with a regression model where milk B12 concentration was explained by milk fat content, plasma insulin concentration, and the stage of lactation. Contrary to the hypothesis, no significant relationships were observed between dietary fiber and starch contents and milk B12 vitamin concentration. Results might have been influenced by the small size of the dataset and relatively small variation in the compositions of the diets. Due to the limited variation in diet compositions, the dataset might not have been ideally suited for the study of nutritional factors. The meta-analysis did not reveal clear nutritional strategies to increase the B12 vitamin concentration in milk. However, the study highlighted the plasma insulin concentration, which positively correlated with the milk B12 vitamin concentration. The relationship between plasma insulin and milk B12 vitamin concentration presents an interesting subject for further research.