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Health Issues To Look Out For When Grazing Forage Crops

29 October 2021

When it comes to utilisation, the main health concerns for forage crops are as follows:

ProblemRisk FactorsAssessSolution
NitratesBrassicas following:
• high level of nitrate fertiliser use
• a short growing season
• a drought period
Test plant if concerned, over 2% Nitrate concentration is unsafeRemove stock and reassess after some time
Photosensitive substancesRape and rape-kale hybrids during sunny weather. Lighter breeds more susceptibleStock will show signs – bald patches, scabby skinRemove affected, reduce duration on crop, offer grass run back
Anaemia (aka Red Water)Brassicas in soils low in phosphate, high in nitrogen and sulphur and flowering foragesMonitor growth rates/condition and look for anaemia signsProvide hay/silage/grass
Goitrogens and Iodine deficiencyBrassicas, especially root brassicas and those floweringThyroid enlargement, weak young, high still born rates, poor growth rates. Brassicas will often need to be fed with additional IodineProvide supplementary Iodine
Copper deficiencySoils with high levels of sulphur and molybdenum. Sheep more susceptible than cattle, particularly in breeds such as Scottish BlackfaceBlood/liver test, forage test: copper, sulphur, molybdenumProvide supplementary Copper if required * unlikely to be applicable for continental breeds
BloatRapid ingestion of lush leafy forage, post nitrogen fertiliser applications, frosted or wet forage, young or fasted animalsLivestock behaviour (look for laboured breathing and signs of discomfort) and rumen distensionProvide hay/silage/grass. Transition on to crop carefully
ChokingBulb cropsLivestock behaviourAllow plant to mature. Transition on to crop carefully

In other words, the key measures to reduce risk involve careful transitioning, targeted mineral supplementation and supply of additional conserved forage. Minerals can be oversupplied and lead to toxicity so be careful and do not provide from multiple sources (e.g., boluses and feed minerals) particularly close to lambing. Monitor livestock regularly, especially during the transition period.

Poppy Frater, 

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