Friday, 05 June 2020 10:24

Monitoring trace elements key to sheep health

Written by  Staff Reporters
About 30% of the pastures in New Zealand will not provide an adequate selenium intake for grazing livestock. About 30% of the pastures in New Zealand will not provide an adequate selenium intake for grazing livestock.

Assessing the trace element status of a flock should be part of your animal health programme. 

There are four important trace elements to consider in New Zealand sheep flocks. These are selenium (Se), copper (Cu), iodine (I), and cobalt (Co). 

A trace element deficiency will impact on ewe (and ram) fertility, as well as the health and growth of lambs. 

In some situations, a trace element deficiency may be subclinical or marginal and, therefore, can only be detected by collecting the appropriate blood and liver samples for trace element and/or enzyme determinations. 

As most trace element deficiencies occur in lambs, prevention is the best approach. To prevent white muscle disease (Se), swayback (Cu) and goitre (I), treat the ewe in early gestation with Se, Cu and I. Preventing Co deficiency is the exception – lambs are best treated with vitamin B12 at docking. 

In this article we will look at Selenium – Se.

Selenium

About 30% of the pastures in New Zealand will not provide an adequate selenium (Se) intake for grazing livestock. The main role of Se is as an antioxidant to protect the integrity of the cell membranes. It also maintains the integrity of the immune system. 

Clinical signs of selenium deficiency 

• Poor lamb growth rates.

• Infertility in ewes as a result of embryonic mortality, which occurs three to four weeks after conception. This results in a higher percent of barren ewes and a low lambing percentage. 

• Poorer motility and increased morphological defects in ram sperm. 

• White muscle disease in lambs, characterised by a non-inflammatory degeneration or necrosis of the skeletal and cardiac muscles. Lambs are born dead or die suddenly within few days of birth. 

Selenium deficiency diagnosis 

Sheep grazing pastures with 100 nmol/L reflect deficient, marginal and adequate selenium status, respectively. Some vets use blood glutathione peroxidase activity, and the respective values for deficiency and adequacy are 3.0kU/L @25 degrees C. Liver selenium concentrations of 450 nmol/kg fresh tissue reflect deficient, marginal and adequate Se status, respectively.

Preventing SE deficiency

[Warning: Use only one of the following approaches to prevent selenium deficiency, otherwise selenium toxicity could become a serious problem.] 

Inject ewes and rams subcutaneously in the neck region with a long-acting product containing barium selenate four weeks before mating. 

The dose is 50mg Se (1mg Se/kg LW). This will increase the selenium status of the ewe during gestation and lactation; the effect being the selenium status of their lambs will be increased from birth to weaning or time of slaughter. 

Lambs do not have to be supplemented with selenium, since treating the ewe protects the lamb from white muscle disease and ensures good growth rates until at least weaning. 

If ewes have not been treated and their lambs are selenium deficient, then they can be treated at three to four weeks of age at docking time. The dose is 12mg Se (1mg Se/kg LW) and its efficacy is for at least 10 months. 

Oral dosing of 5mg of selenium (0.1mg Se/ kg LW) as sodium selenate to ewes and rams at four weeks before mating. The ewes again at four weeks before lambing, and a further 2mg Se to their lambs at docking. Lambs will require further drenching at 6-8-week intervals to maintain selenium status. 

Top-dress in the autumn with 0.5 or 1kg of selenium prills to provide 10g Se/ha annually. 

The ewes (and rams) must graze a selenium-treated pasture for a minimum of eight weeks; namely four weeks pre-mating and the following four weeks during mating. 

Their lambs are likely to need a further 2mg selenium at docking. Preferably, ewes should be grazed on selenium-treated pasture for at least 16 weeks. 

From a management point of view, after applying the selenium-amended fertiliser, the pastures must not grazed for at least four weeks, to allow the Se to be ‘washed’ into the soil and taken up by the pasture.

Dose ewes with one 10g Se bolus (iron) pellet, four weeks before mating.

• Information from Beef+Lamb NZ factsheet: ‘Trace element nutrition of sheep’. Next issue Copper, Iron and Cobalt

More like this

National feed scheme launched for farmers

The Ministry for Primary Industries (MPI) and Federated Farmers have restarted the national Feed Coordination Service to help farmers recovering from Cyclone Gabrielle.

The worst is still to come

Driving from home base in the Horowhenua through Hawke’s Bay and up the East Coast, it’s pretty evident that feed for cows is in short supply and that ground is still wet.

Maximising triplet survival

High quality feed, reduced stocking rates and shelter will all help enhance triplet lamb survival and ultimately benefit the bottom line.

Controlling feed costs

Everywhere I go, whether it be in town or on farm, I hear a similar topic being discussed. It’s the fact prices have risen and as a result farmers and growers have become very focused on controlling on-farm costs.

Featured

Dairy sheep and goat turmoil

Dairy sheep and goat farmers are being told to reduce milk supply as processors face a slump in global demand for their products.

Hurry up and slow down!

OPINION: We have good friends from way back who had lived in one of our major cities for many years.

Editorial: Passage to India

OPINION: Even before the National-led coalition came into power, India was very much at the fore of its trade agenda.

National

Knowing bugs means fewer drugs

A mastitis management company claims to deliver the fastest and most accurate mastitis testing available at scale for New Zealand…

Machinery & Products

100 years of Farmall Tractors

Returning after an enforced break, the Wheat and Wheels Rally will take place on the Lauriston -Barhill Road, North-East of…

JD unveils its latest beast

John Deere has unveiled its most powerful tractor ever, with the launch of the all new 9RX Series Tractor line-up…

Biggest Quadtrac coming to NZ!

In the biggest announcement that Case IH Australia/New Zealand has made around its tractor range, its biggest tractor is about…

A different shade of blue for Norwood

Norwood and ARGO Tractors, the Italian manufacturer of Landini and McCormick tractors, have announced an agreement that gives Norwood exclusive…

Kubota tests diesel engines

Kubota last month used the UK LAMMA Show to test the water with its new 200hp, four-cylinder 09-series diesel engines.

» Latest Print Issues Online

The Hound

Why?

OPINION: A mate of yours truly wants to know why the beef schedule differential is now more than 45-50 cents…

Fat to cut

OPINION: Your canine crusader understands that MPI were recently in front of the Parliamentary Primary Sector Select Committee for an…

» Connect with Rural News

» eNewsletter

Subscribe to our weekly newsletter