Sea­son for zinc as fungi threat­ens


With warmer weather, grasses and weeds are flour­ish­ing. In a short time, fungi will be hav­ing a party as well.

The fun­gus Pithomyces char­tarum, which causes fa­cial eczema, pro­duces lots of spores. For cat­tle, ac­ci­den­tally eat­ing the spores leads to liver dam­age, sub­se­quent pho­to­sen­si­ti­sa­tion and of­ten hor­rific skin le­sions. By the time 5 per cent of a herd has ob­vi­ous skin dam­age, up to 70 per cent of the herd will be liver-dam­aged and at real risk of de­vel­op­ing skin signs.

Spore count­ing on your farm may help you man­age the disease. It will give you an in­di­ca­tion of the fa­cial eczema risk on your farm or in spe­cific pad­docks.

We ad­vise sup­ple­men­ta­tion with zinc from Jan­uary to May. It is im­por­tant to re­mem­ber that no zinc treat­ment regime will pro­vide full pro­tec­tion in sit­u­a­tions where spore chal­lenge is high. There­fore, care­ful ob­ser­va­tion of stock is needed to en­sure you in­ter­vene at the ear­li­est signs of disease.

Zinc ox­ide drench­ing is an op­tion in some dairy herds. It is prefer­able to drench an­i­mals daily, to pro­vide con­sis­tent lev­els of zinc. Over-dos­ing with zinc can pre­dis­pose cows to milk fever. Start drench­ing at half rates and in­crease slowly for a week or so to re­duce the risk of milk fever.

Zinc sul­phate added to the an­i­mals’ drink­ing water source is an­other op­tion. But water up­take of min­er­als is not guar­an­teed, even if us­ing an in-line dis­penser. Zinc sul­phate comes in two forms – monoz­inc and zinc hep­tahy­drate. The dosage re­quired for monoz­inc is lower than for zinc hep­tahy­drate; in fact it is al­most half. An­i­mals may take time to adapt to the taste of the zinc sul­phate in the water so grad­u­ally in­crease to a full dose.

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