As part of a series on reminders for farm animal health plans, Canterbury veterinarian Ben Allott looks at trace element supplementation.

The Autumn period often brings a focus to discussions around trace element supplementation. There are several points to highlight.

The genuine need to supplement different trace elements is highly variable across the country. Stock classes carried, soil types, fertiliser history, forage types used and feeding levels are just some of the many factors that will influence the trace element status of stock on a farm. The need to supplement should be based on farm specific monitoring.

Strong NZ-based animal trials generated the reference ranges advocated by Neville Grace, Scott Knowles, and Andrew Sykes are robust for livestock. Beef + Lamb NZ have two excellent factsheets covering this material.  Trace element nutrition of sheep and Trace element nutrition of cattle are both freely available on the its knowledge hub. Double check that your advisor is making recommendations based on these NZ reference ranges rather than from material derived from overseas data.

Monitor trace element status.  Every test you do should contribute important information to your understanding of the farm. Different sampling methods, e.g. blood testing versus liver testing, give contrasting bits of information. It takes a well-planned approach with a thorough understanding of your farm system to execute a testing regime well. Sit down with an animal health advisor before spending money on testing. Develop a well-planned approach to ensure your spend delivers genuine value for money.

What testing/monitoring options do you have?

Liver biopsy – while more time-consuming to collect, biopsies provide the most reliable assessment of the trace element status of a group of animals, particularly in the case of assessing copper and vitamin B12 status.

Blood samples – useful for confirming the current (adequate vs. deficient) status of a mob but less useful in making longer term projections.

The analogy I like to use for copper is:
‘A liver biopsy is like measuring how much water is in the tank at the top of  the hill. I know if there is enough for my immediate need. But I can also make an estimate as to how long the water (copper) will last me. A blood test is like turning on the tap at the bottom of the hill – there is enough water coming out for right now but this test doesn’t give any information about how long the water will last.”

Herbage testing – if you are testing the feed quality of herbage on a block/crop or doing dry matter assessment for yield calculations you can extend your feed test to include a number of trace elements.  We have a good understanding of the nutritional requirements for copper, selenium, cobalt and this feed test information can be very useful.

We are several steps away from our animals here and the relationship between soil status and animal status is less reliable.  However, an understanding of the soil type and fertility, the measurement of some key trace elements, and the assessment of levels of interfering elements can provide useful insights into likely animal status. This may trigger targeted animal testing to provide more robust measurement of the true need to supplement.

Doing your own visual/measured assessment, observing and measuring the response to supplementation is a valid and very valuable process to undertake.  It is important to get good advice on designing these trials to ensure the data collected is valid, and able to be interpreted in a useful way.

General reminders for sheep late autumn

  • Scanning: In the March article I briefly discussed how different approaches to scanning can provide numerous benefits to managing tight feed supply.  Remember, for the sheep scanner to age fetuses reliably, or to pick out triplets, the scanning date will need to be earlier.
  • Shearing: Late-pregnancy/pre-lamb shearing brings with it a number of risks i.e. milk fever, sleepy sickness, and reduced lamb vigour. These risks are significantly increased in years where more ewes are in low body condition and when winter/spring feed levels are tight. If you shear ewes in late pregnancy seriously explore autumn shearing in early/mid pregnancy.
  • Body condition scoring: Feed levels are very tight through many areas of the country and there’s a lot of discussion around feed supplements for sheep, grain versus pellets etc. Drafting low body condition ewes allows you to target higher cost supplements to the sheep that need it, reducing the amount of imported feed used. Sheep in adequate body condition can go on to tighter maintenance-only allocations.
  • Iodine deficiency: It is a common cause of higher lamb loss, particularly in farm systems with brassica wintering.  Scanning is a common time-point for iodine supplementation to occur if necessary. If you have not looked at whether iodine deficiency could be affecting lamb wastage on your farm now is the time to ask the question.
  • Nitrates: Be conscious of the risk of nitrate toxicity on autumn-sown grasses, fodder cereal crops, N-fertilised pasture, and brassica crops. The Hill Laboratories NZ website has an excellent free technical note that I refer to constantly called ‘Nitrate-nitrogen in pasture & stock feeds.’
    With high nitrate feeds the highest risk is during the introduction of new feed types. A slow transition period with increased allocations over a 7-10 day period will significantly lower the risk. Hungry sheep that gorge on feed are at higher risk – gut fill before the crop/green feed allocation to slow down intake is useful.

Reminders for beef cattle:

  • Drenching young cattle: most weaners will have had their first drench and will be lining up for their next pre-winter drench sometime in later May.  My standard recommendation is that this drench should be an oral, triple combination drench and if pre-winter lice control is needed,  use a separate lice specific product.
  • Copper and Selenium supplementation of young cattle: If a genuine need to supplement is confirmed the treatment options are numerous, each with their pro’s and con’s. There is no one right answer but there are a few points to discuss with your advisor. In general terms, oral bolus products provide a larger amount of trace element, supplement the animal for a longer period, and are safer than many injection products. E.g. a 2mL dose of copper injection provides 100mg of copper.  A 20g copper wire bolus (once efficiency of absorption is factored in) is likely to provide at least 9-10 times more available copper.
  • Toxicity risk: Many injectable products should not be used alongside other animal health treatments due to the risk of toxicity. This can make them more difficult to safely use in mobs, particularly young stock, where you want to minimise yarding events.
  • Transitioning young cattle on to winter crop: Yes, it is recommended to reduce the risk of stock dying from rumen acidosis, bloat, and nitrate toxicity but a well-managed transition can significantly increase average daily gain through the rest of winter. Many young cattle that develop bloating and diarrhoea when introduced to crop are suffering from sub-clinical acidosis which goes on to reduce their feed intake, feed conversion efficiency and growth rates for the rest of winter.  The time taken transitioning onto crop is well worth the effort.