Improvements in the health and productivity of livestock is key for the future sustainability of farming. The intake and utilisation of nutrients from the diet of the dairy cow plays an important role in maintaining the cow’s health, and the nutrients present within its milk also have important benefits for us as consumers.
This research was aimed at understanding how dairy cow breeding and management strategies can be optimised both for the benefit of the cow as well as for the dairy consumer. Specifically, we aimed to determine how levels of micronutrients (minerals and vitamins) within the cow and within its milk were related, and to establish the role played by diet and genetics.
Although dietary manipulation of micronutrient levels in livestock has been shown previously, there is still a lack of knowledge over the role of genetics and whether this could be exploited to improve nutrient levels to benefit the cow and the consumer through the milk produced.
Stage
Work CompletedDirectory of Expertise
Purpose
Our diet not only provides us with the energy needed to survive, but also other essential nutrients and micronutrients that help support health and wellbeing and stave off disease. Micronutrients, consisting of vitamins and minerals, cannot be synthesised within the body, and are required from the diet in small amounts throughout life as they are vital for maintaining normal function and good health.
Milk and dairy products provide us with a number of important micronutrients. For example, they are the principal dietary sources of calcium and iodine, making up to 40%-50% of our intakes. Calcium is required for healthy teeth and bones, whereas iodine is required for thyroid hormone production which is essential for optimum growth, function and physical development at all stages of life. In addition, ruminant products (dairy and beef) are currently the only dietary source of vitamin B12, and vegetarians and vegans can be prone to deficiency of vitamin B12 which can cause anaemia and impair the central nervous system.
In addition, dairy products can also contribute considerably to dietary intakes of a range of other micronutrients such as phosphorous, zinc, magnesium as well as other vitamins (A and B2).
As well as providing humans with a dietary source of micronutrients in their milk, dairy cattle themselves require an adequate supply of nutrients and micronutrients to maintain their own health. Suboptimal micronutrient intakes can affect cattle fitness, reducing animal performance as well as increasing the susceptibility to various diseases.
The aim of this study was to examine the relationship between the micronutrient status of the cow and the level of micronutrients in its milk. The research examined the effect of different feeding regimes and different seasons, in order to determine the role of the cow’s diet and genetics in controlling micronutrient levels. The results provide an insight into how diet and genetics can be best manipulated to simultaneously improve the health of both the cow and the consumer.
Results
This project involved colleagues working across SEFARI within the Rowett and Moredun Institutes and Scotland’s Rural College. In this study, around 1000 paired blood and milk samples from a research herd of UK dairy cows, taken across summer and winter seasons over a 5-year period, were analysed for concentrations of important micronutrients including calcium, iodine and vitamin B12.
The cows were fed either a diet based on a homegrown ration (including grazed grass, lucerne and grass silage) or a diet based on by-products from food and drinks manufacturing (including biscuit meal, breakfast cereal, wheat distillers dark grain, molasses).
Overall, we found mineral levels were influenced by the feeding system used. Cows fed on the homegrown diet had increased milk levels of calcium, iodine, phosphorous, potassium, copper, molybdenum and manganese and increased blood levels of iron, copper and molybdenum. While cows fed on the by-product diet had increased levels of selenium, sodium and magnesium in their milk and increased levels of selenium and phosphorous in their blood.
Furthermore, heritability estimates (the proportion of the variation in micronutrient levels controlled by genetics rather than environmental factors) were obtained for 16 of the 17 micronutrients in the milk samples, 6 of which were significant (calcium, selenium, zinc, magnesium, molybdenum, manganese). Whereas in blood samples, heritability estimates were obtained for 13 of the 15 micronutrients, 4 of which were significant (calcium, selenium, copper, potassium). These findings indicate that selection for beneficial mineral concentrations in both the cow and its milk is possible. Unfortunately, the heritability estimate for vitamin B12 within milk was not significant, but other studies have found that the genotype of the cow can affect the amount of vitamin B12 in milk indicating that these levels may also be increased by genetic selection.
In general, significant additive genetic correlations were also found between several of the milk and blood micronutrients, with most correlations being positive. For example, selection for milk calcium would likely boost phosphorous, zinc, and selenium concentrations, leading to multiple improvements in milk micronutrient levels for the benefit of the dairy consumer.
Overall, our results demonstrate a role for genetics (in addition to diet) in influencing micronutrient levels within the cow as well as its milk.
Benefits
This work provided strong evidence that micronutrient levels both within the milk and within the dairy cow themselves are significantly influenced by genetics, as well as diet. These findings are important as they demonstrate the potential to optimise dairy cow breeding strategies not only to improve the health of the cow but additionally, to maximise nutrient levels within the milk which can be passed on to the consumer.
Further research (and publications) will investigate how micronutrient levels within the cow relate to its immune function and (1) incidence of, for example, mastitis and lameness, and (2) fertility traits, including calving intervals and stillbirths, in order to gain greater understanding of how enhancing levels of micronutrients can be best exploited for the benefit of the animal overall.
Overall, these findings are improving our understanding of how to help support the livestock industry. We are identifying ways to improve the health and welfare of the dairy herd, while at the same time maximising the nutritional benefits in the milk, an insight which can also be used to improve public health.