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Saline Dam Water Kills Lambs

The extremely dry seasonal conditions in North Central Victoria have caused high levels of salt in stock water supplies leading to high death rates in newborn lambs.

By Department of Primary Industries - 25th May 2005 - Back to News

Dr George Downing, District Veterinary Officer with the DPI at Bendigo, said lactating ewes decrease their water intake when it is very salty and consequently their milk tends to dry up.

"Newborn lambs effectively starve to death although it appears to be a mismothering problem," said Dr Downing.

"The maximum levels for salt in water for lactating ewes is 5,000 ppm. Recent investigations into levels in some dam water that had been replenished with bore water when it ran out, showed levels to be around 6,390 ppm," said Dr Downing.

While this is acceptable for dry sheep that can tolerate up to 10,000 ppm, it is too high for lambing ewes and young sheep.

Dr Downing said farmers should check the salinity of their stock water and if necessary consider carting water from an alternative source.

"Bore water may often have an acceptable salinity level initially, but if it is put into dams where evaporation rates can be quite high, these salinity levels may increase significantly. Bore water should be supplied through troughs and if necessary, troughs should be emptied periodically to counteract any increase in salt concentrations due to evaporation," said Dr Downing.

While high salinity levels in stock water may cause high mortalities in lambs, another major cause of mismothering and subsequent lamb deaths is inadequate feeding of lactating ewes. Lactating ewes need approximately 2.5 times as much feed as a dry sheep.

Dr Downing said that if they are not fed sufficient feed, their milk will dry up and they will walk away from the lamb.

As a rough guide, a dry sheep needs about 450 grams of grain per day for full maintenance. A lactating ewe therefore requires about 1.2kg grain.

Lactating ewes also require roughage in their diet, so oats is the best feed. However, hay can be supplied at about 20% of the overall ration. Ideally lactating ewes should be fed in the early afternoon to reduce losses from mismothering.

Gippsland farmers are advised to contact an Animal Health or Veterinary Officer at their local DPI office if they feel they are having similar problems.

CONTROLLING REDHEADED COCKCHAFERS

The red headed cockchafers have been having a field day in many parts of Gippsland this autumn. This is characterised by pasture "pulling" by grazing cattle and by flocks of birds that are chasing the grubs.

The problem has been made worse by the extended dry autumn following the much earlier than normal rains experienced in February. If substantial follow up rains had occurred, the plant roots would be recovering and/or surviving better to "hang on" to the soil. In this case, plant pulling may not have been so obvious and the cockchafer problem may not have appeared to be as bad, even though they would have still been present.

The only registered method of controlling the redheads is via an insect killing fungus, Metarhizium anisopliae, in a product called BiogreenTM. The fungi will attack all growth stages of the redheads, ie. the eggs, cockchafer grubs and the beetles. They will not attack the blackheaded cockchafer grubs at any growth stage.

Unfortunately the nature of this product requires that it be produced in batches and must then be used within a relatively short period of time after manufacture. This is a logistical nightmare for the company producing the fungi and for the distributors to handle. However since it is the only legal product available it is worth while that all concerned ensure the product is given a fair go to do the job by following all the recommended guidelines.

The product is in granular form and must be drilled into the soil. It should be active in the soil for 4-5 years, thereby spreading the upfront costs cost over this period. The product will have minimal effect the first season as the fungi must build up and spread but is effective after that. Therein lies the quandary for paddocks affected or decimated by the redheads to date.

If you re-sow the paddocks will the grubs just eat the new roots? Unfortunately the answer is not clear. If we get some decent rain the roots may survive the root eating grubs and remain active well into the winter. If dry conditions continue, chances of root survival may be slim. Sowing the seed with the fungi granules may help in this case. If re-sowing perhaps sow with a cheap seed such as an annual short rotation ryegrass. The grub will not affect oat roots so these could be sown, but nutritionally, are below that of the ryegrasses.

Cost. If you have lost say, 50% of your pasture this year and that may be conservatively 4 – 6 tonne dry matter per hectare, how much milk production have you lost? Way above the cost of the fungi treatment. Think of the next 2-5 years. Applying the fungi this year should minimise pasture damage by these guys in future years, well and truly covering your costs.

To achieve the maximum benefits the following guidelines need to be followed.

  • The granules must be drilled into the ground about 2 – 3 cm, and the soil closed over
    with harrows or roller.
  • The fungi should be placed in moist soil.
  • If spread over the surface, the granules must be covered with soil as soon as possible or the fungi will not survive. Even so, maybe not all of it will be buried if harrows are used, so don’t expect 100% effectiveness.
  • Don’t sow with high rates (>50 kg/ha) high analysis fertilisers, particularly those containing N and K.
  • There is no withholding period for this product.
  • Application rate is one bag (10 kg) per hectare.
  • Not suitable for alkaline soils ie. pH above 7.5

For further information contact Frank Mickan, Pasture and Fodder Conservation Specialist at DPI Ellinbank.


Source: http://gippsland.com/

Published by: news@gippsland.com



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