MMN January 2025 – Outwintering Dairy Heifers

Remember, heifers will also require mineral supplementation and particularly for iodine if grazing rape, kale, turnips or swedes. Typically iodine requirements double when grazing brassicas. A trace element bolus may suffice but it is best to seek advice to ensure that requirements for major minerals and vitamins are also met.

Tips for grazing forage crops

Livestock should always be introduced to a forage crop slowly, with access for one to two hours a day initially and building up to full time access over a period of 7-10 days. Strip grazing with an electric fence is the best way in which to maximise utilisation of the crop, while minimising waste through trampling. Ensure that all animals can graze the strip at the same time, i.e. try to graze long narrow strips, again this will minimise trampling and wastage. If the field is on a slope, try to graze the cattle downhill. Always make sure there is access to fresh water. This will help maximise intakes and growth performance.

If adverse weather conditions persist and animals are underperforming have you got a plan to deal with this? i.e. can you split the group and provide additional feed to those struggling with growth/body condition? Also, can you provide straw bedding if conditions are very wet to provide a dry lie?

Potential health issues

Some health risks to be aware of include red water (or kale anaemia) when grazing kale, photosensitisation and sudden death. With red water, affected cattle will appear weak and pass red urine. This is due to excess levels of the amino acid compound S-methyl cysteine sulphoxide (SMCO). SMCO levels are higher when soil phosphate levels are low, and nitrogen and sulphur levels are high. Babesia infection, which is spread by ticks, would be another reason for “redwater”.

While sunshine is usually lacking at this time of year, there are compounds in brassicas that can cause skin sensitivity to sunlight. Affected animals will show peeling, red, sore skin, which can progress to ulceration and bleeding in extreme cases. The condition tends to occur when rape or kale is grazed when it is still growing. Therefore, it can be prevented by only putting stock onto mature plants. Note that skin lesions may also be seen with copper toxicity, other plant toxicities (e.g. bog asphodel), or malignant catarrhal fever in cattle. Bluetongue virus can also cause reddening of the skin and so it is worth getting affected animals examined by your vet to determine the cause.

There are many reasons for sudden death associated with forage crops, including clostridial disease, nitrate toxicity, staggers, acidosis and bloat. When grazing fodder beet, the high sugar content increases the risk of acidosis and clostridial enterotoxaemia (or pulpy kidney), and so all cattle should be given a full course of a multivalent clostridial vaccination and boosters to prevent deaths. Nitrate toxicity can be minimised by avoiding the use of high nitrate fertilisers. Forage crops are low in magnesium, therefore cattle may require supplementation to avoid issues with staggers. All sudden death cases should be fully investigated by your vet.

For more information on outwintering, have a look at SAC Consulting’s Outwintering Strategies for Livestock booklet available here:

https://www.sruc.ac.uk/media/ionjjj3r/outwintering-strategies-booklet-497866-sep-2022.pdf

 

lorna.macpherson@sac.co.uk; 07760990901

helen.carty@sruc.ac.uk; 01292 525438