Table of Contents
Chair:Mark Measures (IOTA)
Science is reporting that our milk is rather deficient, other evidence suggests the reverse. This session is to get a better handle on what the state of knowledge really is and try to draw some guidance on ensuring that our animals have the minerals for their own health and for the health of humans.
The discussion that followed the presentations brought out the following points:
- Most minerals supplemented well in excess of requirements.
- Forage source affects status.
- Blood not always good indicator of mineral status.
Forage analysis is a good starting point.One person needs to be responsible for the mineral nutrition and include supply from all sources.
Individual speaker presentations and abstracts
Minerals have traditionally been supplemented to cattle to rectify deficiencies that may be present in forages and supplementary feeds to ensure optimal performance and health. In a recent survey of winter mineral feeding levels to dairy cows in the UK, Sinclair and Atkins (2015) reported that most minerals were being fed at levels well above requirements, with organic herds supplementing at a similar level to non-organic herds. In support of this, Kendall et al., (2015) reported that approximately 40% of cull dairy cattle and 17% of cull beef cattle had liver copper concentrations above the recommended maximum limit. Over-supplementing minerals not only increases diet cost, but can have a negative environmental impact (e.g. phosphorus), interfere with the absorption and metabolism of other minerals, and for copper in particular, be toxic. Reasons for over-supplementation are varied, but undoubtedly many farmers wish to avoid signs of deficiency, which are widely reported, particularly in high forage or extensive grazing systems. To reduce these issues, mineral feeding levels should be based on national recommended feeding levels, include a forage analysis, take account of all sources (e.g. water, free access minerals, boluses), and have one person on the farm who has overall responsibility.
Milk is a significant source of iodine in our diet but it appears that organic milk contains less iodine than that produced under more conventional management. Since organic milk is superior in many other nutritional components and considered to offer health benefit, its lower supply of iodine (and other trace elements?) is disappointing and could discourage consumption, especially by pregnant and nursing mothers or young children – the very people to potentially benefit most from higher omega-3 fatty acid consumption. As well as producing milk with sub-optimum levels of trace elements for consumers, could organic management also be detrimental for our cows, possibly reducing fertility and/or calf viability. This talk plans to explores the trace element content of organic milk, how it might be enhanced and can we have too much of these good things.
In organic animal husbandry, many uncertainties and inconsistencies exist regarding provision with minerals and trace elements. The organic principles of health can be viewed as unique and call for a focus on resilience which can be useful in the way in which diets and mineral compositions are planned for ruminants. The organic principles stress that animals should be given a framework and conditions within which they can meet their natural needs in different life situation, such as growth, yielding and pregnancy. When it comes to mineral supply, the question is, however, what their ‘natural needs’ are, and to which extent they can meet them through access e.g. to natural pastures and different types of feed. The presentation will focus on these aspects and how this can guide the organic dairy farmer regarding mineral and trace element supply. Studies on the use of herbs in grass fields have mostly dealt with the milk quality, and less with animal health, although there might be interesting observations and perspectives regarding animal health. Different strategies exist, using high nutrient feed stuffs, diverse diets, and different types of supplement minerals. According to the organic principles, it is also important to combine the supplement of minerals with priorities such as using local feed stuffs and high proportion of forage to ruminants have to be combined as part the feeding strategies.