Prior to being part of trace element trial, Hawarden farmers Mark and Sam Zino hadn’t been entirely happy with the performance of their ewe flock.
While their lambing percentages were consistently sitting around 146%, Mark felt their ewes could be doing better.
A series of blood tests showed that the ewes were lacking selenium and once this was addressed, lambing percentages lifted to 151–153%.
“Last year we had no feed and a storm at lambing and they still delivered a really good result,” says Mark.
On the advice of North Canterbury sheep and beef vet Erin Riley, the Zinos treated their ewes with selenium and long-acting iodine and LSD (Lamb Survival Drench) pre-lambing. Subsequent blood tests have shown that selenium levels have consistently been in the optimum range.
While there are costs associated with testing for trace elements, for the Zinos, a five-percentage point lift in lambing percentage resulting from addressing deficiencies generated a return on investment of between 200-300%.
Speaking at a Beef + Lamb New Zealand Farming for Profit field day on the Zino’s 1060ha property, Erin outlined the work she has been doing with 40 North Canterbury farm businesses, monitoring their trace element status.
She said most of the research done on trace elements in sheep and beef had been carried out in the 1980s and 90s, yet sheep systems today were completely different.
Sheep were different genetically, ewe performance has lifted significantly, farmers were cutting back on drenches which often included selenium. Commonly used novel drenches such as Zolvix and Startect don’t contain minerals.
Erin encouraged sheep and beef farmers to find out what the trace element status is on their farm as a starting point.
“It may have been a few years since you last tested, but with droughts and seasonal changes animal reserves get used up.”
“Monitoring and testing can help you make informed decisions. Is your treatment working or can you change what you are doing to get the right results at the right price.?”
She says there is no point in treating stock with trace elements if they don’t need it.
Erin stressed that every farm will be different with their trace element status, hence the need for regular monitoring and measuring.
“The best time to be testing sheep is just after weaning and before mating and between scanning and pre-lambing because then you have time to do treatments if required. It also gives you an idea of how things are tracking along.”
How and when trace elements are tested
Selenium levels are tested through a blood test, vitamin B12 and copper levels are tested through liver samples while the thyroid glands of dead lambs give the best indication of iodine levels in a sheep flock.
For selenium, blood tests from a sample of five sheep taken at weaning or premating or scanning will cost around $300 (including the lab fee). Liver biopsies, to test for Copper and B12, are taken at the processing plant and will cost around $340 for 10 samples.
Liver biopsies taken from live animals cost $250–$300 for five samples with lab fees of around $170 on top of that.
Lamb post-mortems to measure the thyroid gland cost around $300–$350 for 10–15 lambs.
Why trace elements are important
Selenium
Selenium is important for various functions within the immune system as well as for sperm development and embryonic survival, particularly in the first 30 days of pregnancy.
Deficiencies can be associated with low scanning percentages or late lambing.
Selenium is also linked to increased milk production and is associated with lamb growth. White muscle disease is a result of selenium deficiency.
Erin said every farm is different and even neighbouring farms where the sheep had been given similar treatments can have a completely different selenium status.
This means that a treatment that might be effective for one farm might be inadequate for the other.
Short-acting selenium treatments will only last two to four weeks before dropping back down to their original levels.
Erin said selenium is stored in the liver, so if stored selenium levels are low, a short-acting treatment may be insufficient to restore selenium to optimal levels.
“Even long-acting injections can have different effects of different farms. On some farms, a long-acting injection of selenium will maintain selenium at optimal levels, on others it won’t and will need to be repeated.”
B12/ Cobalt
Cobalt is turned into B12 by microbes in the rumen. Sheep use B12 for energy/glucose production as well as protein production and red blood cells. Younger lambs need more B12 than older lambs or ewes.
Cobalt availability is highly seasonal and low cobalt levels can occur in dry conditions or when grass is growing quickly.
Erin found cobalt levels to be particularly low during the dry 2023/24 season.
Iodine
Iodine is taken up by the thyroid gland to produce thyroid hormones which are involved in energy metabolism, heat production and protein production. Iodine is used in the development of the foetal brain, lungs, heart and wool follicles.
Iodine deficiency is linked to poor lamb survival.
An adult ewe’s thyroid gland can hold 80% of her body’s iodine reserves but a lamb’s thyroid gland develops independently from the ewe. This means lambs solely derive iodine from their mother’s daily intake and cannot use their mother’s reserves.
Blood tests will only show what iodine has been eaten that day, so if a ewe is not being supplemented with iodine, her iodine levels will be low.
Ewes wintered on brassica crops will need iodine and oral treatment may not be enough, they may need a long-acting injection or bolus treatment.
Copper
Copper is essential for a number of activities within the body. Signs of deficiency include sway back, ill thrift, abnormal wool growth, anaemia and bone disorders.
Fine wool breeds in particular can be affected by copper deficiency, possibly due to them having a higher demand for copper for their fleece growth.