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Cowra Local Livestock Health Update

Written by: The Cowra Phoenix


With stock going onto grazing crops this month it is timely to consider some of the ways we can avoid animal health issues on crops this autumn and winter. Gradual introduction to any new feed type gives the animals a chance to get used to eating the new feed and gives the rumen a chance to adapt. Moving stock on and off the crop for a few hours over a week or more is ideal but is not practical for most producers. If this isn’t possible, other strategies which may help with this adaption include: allowing access to a neighbouring pasture paddock and/or feeding good quality palatable hay for the first 1-2 weeks of grazing.

Hungry stock should never be given access to a crop – make sure they have a full belly before they go onto the crop. While grazing crops are high in energy and protein which is fantastic for production, they are low in fibre. This fibre needs to be provided in the form of hay. The type of hay you feed needs to be good enough quality that stock want to eat it.

Cereal crops like wheat and oats are low in calcium and magnesium. Pregnant, lactating and young animals, have a higher requirement for these minerals and it is essential that these are supplemented on cereal crops. Animals may go down and even die due to hypocalcaemia (milk fever) or hypomagnesaemia (grass tetany). A condition called rickets in lambs can also result in fragile bones which are prone to fractures.

The easiest way of supplementing calcium and magnesium is usually by feeding these minerals in a loose lick with salt. There are numerous pre-mixed loose licks available commercially, including several ‘weather-proof’ formulations which may be considered in very wet months.

Research has shown that both cattle and sheep experience a positive weight gain response to the supplementation of salt and magnesium on grazing wheat. Further research needs to be done, but this may be due to the buffering capacity that magnesium oxide (Causmag®) and/or calcium carbonate (lime) have on the rumen. For this reason, provision of a buffer should be considered on all grazing crops which have the potential to cause mild ruminal acidosis. Several pre-mixed loose licks also have ionophores, such as monensin and lasolacid added which have been shown to have positive effects on weight gain of cattle and sheep on lush forages due to their effect on the rumen bacteria.

It is important to remember that during periods of wet, cold, windy weather stock may graze less and consume less of the loose licks provided. This puts heavily pregnant animals or those with small lambs/calves at foot at a high risk of going down due to milk fever or grass tetany. Feeding good quality lucerne hay (which is high is calcium and magnesium) should be considered during these periods.
Both sheep and cattle experience a lag phase in liveweight gain for 1-2 weeks after introduction to dual purpose canola and forage brassica crops. This is in part due to avoidance of the crop and in part to rumen adjustment. This is an important consideration, as grazing for less than 2 weeks is unlikely to be productive.

Crop avoidance can also be potentially problematic when introducing pregnant and lactating cattle and sheep to brassica crops. The time off feed can be enough to cause pregnancy toxaemia and milk fever. Feeding a good quality legume based hay should be considered in this instance.

Bloat on lush crops, particularly brassica crops, is a big risk for cattle. Since the bloat capsules were taken off the market several years ago, the best bloat prevention currently available to producers is an ionophore, such as lasalocid or monensin, added to a commercially prepared loose lick. Many of these also contain salt, calcium and magnesium. It is important that producers are aware that ionophores are antibiotics and might not be an option if selling into certain ‘antibiotic-free’ markets.

If you would like further information or to chat about any animal health issues, please feel free to contact your local District Veterinarian Em Johnstone (0419 334 077) Or call 1300 795 299.

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