Warn­ing -- choose your bull with care

The Northland Age - - Local News -

Dairy farm­ers are us­ing a range of tac­tics, in­clud­ing “due dili­gence”, quar­an­tine and opt­ing for vir­gin bulls to pro­tect their cows from My­coplasma bo­vis, ac­cord­ing to DairyNZ.

The dis­ease, which was mainly spread via close phys­i­cal con­tact with in­fected an­i­mals, made us­ing bulls that had been ex­posed to other stock an added risk, DairyNZ re­sponse man­ager Hamish Hodg­son said.

Some farm­ers were think­ing twice about con­tin­u­ing to use a com­bi­na­tion of ar­ti­fi­cial insem­i­na­tion and bulls, and con­sid­er­ing ex­tend­ing AI to re­move bulls from the equa­tion al­to­gether, or re­duce the num­ber re­quired.

DairyNZ had re­ceived a num­ber of in­quiries from farm­ers over re­cent weeks want­ing more in­for­ma­tion to weigh up the risks and ben­e­fits as­so­ci­ated with each ap­proach.

Mr Hodg­son said the best thing farm­ers could do to pro­tect their herds and farms was to “do their home­work”, but there was no sil­ver bul­let. Both AI and bulls had pros and cons.

While a lot of farm­ers had been con­sid­er­ing adapt­ing their usual ap­proach, most weren’t mak­ing dras­tic changes, how­ever. The ma­jor­ity ap­peared to be stick­ing with a com­bi­na­tion of AI and bulls, despite re­ports that some farm­ers were shy­ing away from us­ing bulls.

“There have been some mur­murs that farm­ers were go­ing to avoid us­ing bulls and just use ar­ti­fi­cial breed­ing, how­ever, af­ter con­sid­er­ing the risk and the cost to their busi­nesses, few have elected to pro­ceed with a full AI sys­tem due to the likely low­er­ing of over­all fer­til­ity stats, per­ceived costs, and in­creased labour for ac­cu­rate heat de­tec­tion,” Mr Hodg­son said.

“Those us­ing bulls should still do their due dili­gence, check where they’ve come from and if they’ve been in herds with a his­tory of dis­ease. This is ex­tremely im­por­tant, es­pe­cially if they’re older bulls that have done a few mat­ing sea­sons on other farms.”

He un­der­stood there had been a spike in de­mand for vir­gin bulls that had had min­i­mal ex­po­sure to other an­i­mals, while farm­ers had also been ask­ing about M. bo­vis tests for bulls.

“There is a poly­merase chain re­ac­tion (PCR) test that is highly sen­si­tive and will de­tect if M. bo­vis is present in a sam­ple, but the com­plex na­ture of the dis­ease can make this chal­leng­ing,” he added.

“Be­cause in­fected an­i­mals only shed the bac­te­ria in­ter­mit­tently, it is de­pen­dent on M. bo­vis be­ing present where the sam­ple is taken, and on the day the an­i­mal is tested.

“This means a re­sult of ‘not de­tected’ doesn’t nec­es­sar­ily mean it’s dis­ease-free. That’s why we’re rec­om­mend­ing farm­ers gather as much in­for­ma­tion as pos­si­ble about the source of any bulls and don’t rely on PCR re­sults.”

DairyNZ rec­om­mended that farm­ers keep bulls apart from their main herds for at least seven days to al­low time for the dis­ease to present it­self if they’re in­fected.

Any farmer con­cerned about the health of bulls should con­tact their vet­eri­nar­ian be­fore in­tro­duc­ing them to their herd.

■ For more in­for­ma­tion on mit­i­gat­ing the risks of M. bo­vis this mat­ing sea­son, go to dairynz.co.nz/mbo­vis

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