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Grass Tetany

Grass Tetany is one of a group of metabolic diseases of ruminant animals which is associated with low blood levels of magnesium.

By Department of Primary Industries - 17th August 2004 - Back to News

Blood serum magnesium levels in cattle normally range between 1.8 and 3mgm per 100ml. In grass tetany cases blood serum magnesium levels are often less than 0.9mgm per 100ml of blood.

The condition is most commonly seen 3 – 6 weeks post calving and in cows on their third calf or older. Annual incidence is highest during mid to late winter and early spring and is more common on grass rather than legume dominant pasture.

Paddocks that have been top dressed with nitrogenous and potash fertilizer to promote grass dominance rather than legume growth are the most dangerous. Grasses generally contain less magnesium than clovers and high soil and plant potassium levels inhibit the uptake of magnesium.

Grass tetany cases are connected to low magnesium soil levels or failure of plants to take up adequate amounts from the soil. Much of Gippsland has soils that are marginally deficient in magnesium.

Cold wet weather and the stresses of yarding cattle predispose to the development of grass tetany. Grass tetany may often occur with milk fever (hypocalcaemia) and acetonaemia (ketosis) which are the other common metabolic diseases of cattle. It may also affect calves.

The symptoms of grass tetany range from slight to very severe, leading to sudden death. These include staggering, stiffness in limbs, rapid heart rate, aggression, teeth grinding through to prostration, audible heart rate feet away from an affected animal, tetanic spasms, severe limb paddling, head thrown back, convulsions and death, often very quickly. There are usually no post mortem signs.

All affected cows should be treated as soon as possible after signs occur. Treatment is injection under the skin of "four in one" solutions that contain calcium, magnesium, phosphorous and dextrose. Also 350 ml of 20 % Epsom salts can be injected under the skin at the same time. Veterinary attention is needed once a cow is down and convulsing.

Prevention of grass tetany is achieved by providing magnesium supplementation before and during danger periods. This is generally done by feeding hay to which "Causmag" has been added. "Causmag" is crude magnesium oxide in powder form. It is added to the hay by opening the bales and spraying on a mixture of "Causmag" and water. The dose recommended is 500 grams "Causmag" in two litres of water per bale and fed every second day. This dose rate refers to small square bales.

Other preventatives are the administration of magnesium bullets which can release magnesium in the cows rumen for up to 90 days; magnesium blocks which contain molasses and salt; and "licker" drum rollers containing one part of Epsom salts, two parts of molasses and three parts of water are helpful. At all times provision of adequate hay, 4 - 6 kilos daily is necessary.

SETTING TARGETS - 1000 kg OF LAMB!

Luke North, DPI Hamilton.

Farming is becoming more intensive and one way of trying to get more out of the farm is to set production targets.

An aim of the Morelamb Quality Pastures (MQP) project being run by the Department of Primary Industries in conjunction with five-specialist prime lamb producers across South West Victoria is to produce 1000 kg of prime lamb per hectare.

Increasing the kilograms of lamb produced per hectare drives prime lamb profitability. The key drivers of producing 1000 kg of lamb are ewe-stocking rate, lambs sold per hectare and lamb turn off weights. Altering any of these will influence lamb production per hectare.

The MQP project is currently achieving 500 to 600 kg of live lamb per hectare that is 15% higher than the top 20% in the Farm Monitor Project. These above average lamb turn off weights per hectare are coming from producers who are selling their lambs at lighter weights in the 20 to 30 kg liveweight range.

Most traditional prime lamb producers in the district are lambing in spring and selling the lambs as suckers "off mum". With this system we are potentially making the best use of the mothers’ milk and also of a fresh spring flush.

To produce more lamb per hectare, producers are encouraged to review their production system keeping in mind the relationship between stocking rate and lamb turnoff weight.

Increasing the number of lambs at lower weights will increase lamb production but will require a greater number of ewes to be carried all year. This has implications for feed budgeting.

Aiming for higher stocking rates and possibly producing lighter lambs can challenge the production system. It does appear in the prime lamb industry that there is becoming a distinct difference between breeders and finishers.

Last year in particular, producers were making more money out of producing more lighter trade weight lambs that go onto finishers compared to those trying to breed and finish in the one system.

A successful prime lamb production system requires producers to know the critical points in their system to maximise production and profit. This most likely comes about by better pasture utilisation with a target of increasing stocking rates.

Increasing stocking rate is the biggest contributor to increased profit and with increasing stocking rate, various management techniques such as pasture production, grazing management, timing of lambing and increased lambing percentage are other important contributors.

Source: http://gippsland.com/

Published by: news@gippsland.com