Abstract
Simple SummaryMilk is considered a staple and complete food that contains several essential nutrients for humans. For instance, it is an excellent natural source of vitamin B12 (B12) due to the presence in the bovine rumen of a myriad of bacteria and archaea capable of producing the vitamin. This vitamin is only produced by prokaryotic microorganisms; vegetal products do not naturally contain it. A 250-mL glass of milk contains about 46% of the daily recommended dietary allowance of B12 for individuals over 13 years old. However, B12 concentration is variable in milk; therefore, identifying factors contributing to its variation is critical to ensure a stable B12 supply for consumers. The aims of these experiments are to gather more knowledge on possible sources of variation in B12 concentrations in milk in order to optimize and stabilize its levels and thereby improve the perception of milk in terms of its health benefits. We observed that B12 concentration increases when the conditions of the rumen are optimal, such as with elevated pH. We also studied if bedding type—e.g., recycled manure solid bedding or straw, which has been reported to impact milk microbiota—could have an impact on milk B12 concentration. In this study, no such correlation was detected. This paper is one of a series seeking to elucidate factors responsible for variations in milk B12 concentration.Milk is an excellent source of vitamin B12 (B12) for humans. Therefore, being able to guarantee a high and consistent concentration of this vitamin would enhance consumer perception of milk as a health food. The aim of the paper was to gather additional knowledge on factors that could explain B12 variation in cow milk through two observational studies: (1) to explore the relationship between milk B12 and ruminal conditions, such as pH and volatile fatty acid concentrations; and (2) to examine the impact of bedding on B12 concentrations in bulk tank milk. For study 1, a total of 72 milk and ruminal liquid samples were obtained from 45 Holstein cows fitted with ruminal cannula between 10 and 392 days of lactation. For study 2, bulk tank milk samples were obtained from 83 commercial herds; 26 herds used recycled manure solid bedding and 57 used straw bedding. Milk samples were analyzed for B12 using radioassay. Using principal component regression analysis, we observed that ruminal pH and the acetate:propionate ratio for cows receiving the early lactation ration were positively correlated with milk B12. Bedding did not influence milk B12 in bulk tanks, which averaged 4276 pg/mL. In conclusion, as B12 is synthesized by ruminal bacteria, optimizing ruminal conditions had a positive effect on milk B12, while bedding management had no influence.
Highlights
As early as the 1980s, Canadian and American reports indicated that overall fluid milk consumption per capita was decreasing [1,2]
There was a tendency for greater proportion of acetate and acetate: propionate ratio for group 2 cows compared with group 1 cows (p ≤ 0.08)
Using the actual nutrient composition of the diet, we showed that vitamin B12 in milk was positively correlated with dietary fiber concentration and negatively correlated with dietary starch and energy concentrations
Summary
As early as the 1980s, Canadian and American reports indicated that overall fluid milk consumption per capita was decreasing [1,2]. A survey conducted on consumers of plant-based beverages which sought to understand the decreasing consumption of dairy products indicated that drinkers of nondairy beverages believed that plant-based drinks helped to reduce the negative impacts of animal production on the environment [4]. Studies have shown differing effects of milk fat consumption on human health, even though no strong evidence of deleterious impact of moderate milk consumption has been shown [6]. Based on amino acid profile, the protein quality of cow milk is superior to that of plant-based beverages for human consumption [7]. Another example is the natural content of cow milk vitamin B12 , known as cyanocobalamin
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