In the final installment of Kiwi yarns (did Hannah really go to New Zealand I hear you ask?!) I’ll be talking all things minerals. Despite working predominantly with dairy cattle over in NZ, these principles apply to dairy cows, beef and sheep alike!
Given our recent tropical climate mineral supplementation is all the more important to bear in mind in the coming months, as we may see varying degrees of quality forage. Those feeding a TMR ration may also find dry matter intakes have dropped in the heat. When we combine all of these factors we may find that mineral intakes, from dietary sources, may have altered due to either the nature of what we are feeding or how we are feeding it.
So, what do we mean when we talk about minerals?
A mineral is a “solid, naturally occurring inorganic substance” that is required by the body to perform a variety of functions. These can be split into two groups: macrominerals – minerals that are required in larger amounts such as Calcium, Phosphorus and Magnesium, amongst others. We also have Trace Elements (or micro minerals), all essential elements for the body that are needed in tiny amounts, but are still essential for normal bodily functions, eg. Copper, Iodine and Selenium.
With dairy dry cow diet formulation a lot of the macrominerals are now heavily managed and diets are balanced to ensure issues with calcium and magnesium are greatly reduced or even totally avoided on some units! That said, we do still encounter the odd milk fever.
With a less obvious presentation occurring with trace element issues, they can often go unnoticed until there is a real issue.
So, what trace elements are important and why?
Selenium: selenium is essential for a wide range of functions relating to growth, immunity and fertility. This is because it is a component in a large number of proteins and enzymes responsible for physiological functions within the body. Selenium deficiencies can present in a wide range of ways such as ill thrift, poor immunity, poor fertility performance (including both cyclicity and issues post calving) or even white muscle disease (weak calves that fail to thrive).
Iodine: Iodine is essential for thyroid function and, similarly to selenium, is needed for a variety of bodily functions. Low levels can cause calves to be stillborn, along with fertility issues (including poor heat expression), poor growth and reduced milk production.
Cobalt: Also known as B12, cobalt is needed by micoroorganisms in the rumen to break down cellulose; ie. So that the rumen bacteria can fully utilise the diet they are presented with. Low levels can cause issues with growth.
Zinc: Similarly to most of the trace elements mentioned zinc is involved in a wide range of functions and low levels can be associated with poor growth and production, fertility, immunity and hoof growth.
Copper: In the UK we often find issues with over supplementation as opposed to under. Copper issues may be associated with poor fertility, ill thrift and can be identified by animals with pigmentation issues (spectacles).
Assessing mineral status
The easiest method of assessing mineral status is through blood samples, looking at circulating levels. However, minerals such as copper and cobalt are stored in the liver and so circulating levels can appear normal, whilst the actual levels in the body may not. In this case, liver biopsies can prove more useful and give a true assessment of an animal’s status.
So, how do we alter levels in the animal?
In the UK, we predominantly alter trace element levels through dietary/ oral supplementation. The key to supplementation is to assess all ways in which an animal is receiving minerals; which means looking at all aspects of a diet. Where animals may be competing for mineral access, such as top dressing or a mineral lick we cannot be sure how much they are receiving. Therefore, a mineral bolus is the ideal way of being fully confident in how much an animal is receiving.
So, what should I do about minerals?
Next time you have a vet on farm, discuss your herds mineral supplementation approach to identify if there are any weak points. If there are, the first step may be sampling a group to assess status and then choosing the most appropriate bolus to increase levels appropriately.
The bolus chosen should supply appropriate levels of the minerals required ie. You don’t want to be paying for something you don’t need and risking toxicity!
At LLM, we stock the Vetalis boluses which supply some of the highest amounts of daily iodine and selenium. These can be particularly useful for grazing cattle and dry cows. If you’re interested in hearing more, please don’t hesitate to call the practice.