15 ways to pro­tect your stock from worms

Worm bur­dens are a huge fac­tor in the health and wel­fare of live­stock on a block. You may not re­alise the big­gest con­trib­u­tors of par­a­sites are the young, or that drench­ing all your stock is one of the worst things you can do.

NZ Lifestyle Block - - Notebook - Source: Beef & Lamb NZ, www.beeflambnz.com * If an an­i­mal is gain­ing weight and do­ing well health-wise, even if it has a worm bur­den, it doesn’t re­quire drench­ing. Do fort­nightly checks on weight gain, con­di­tion score and health in­di­ca­tors, eg no scour­ing

The ob­jec­tive of good worm man­age­ment is to min­imise the im­pact of worms on an­i­mal per­for­mance while min­imis­ing the se­lec­tion for drench re­sis­tance.

Young stock are the ma­jor con­trib­u­tors to in­ter­nal par­a­site pop­u­la­tions in pas­ture. Sys­tems that are dom­i­nated by an­i­mals less than nine months of age are very sus­cep­ti­ble to high worm chal­lenges.

1. Re­duce the worm chal­lenge HOW: man­age the worm chal­lenge

Young stock are the ma­jor con­trib­u­tors to in­ter­nal par­a­site pop­u­la­tions. If your block is dom­i­nated by an­i­mals less than nine months of age, it will be very sus­cep­ti­ble to high worm chal­lenges.

The num­ber of lambs car­ried into au­tumn and where they graze sets the risk of fu­ture worm bur­dens. You want to avoid graz­ing lambs dur­ing the sum­mer and au­tumn in pas­ture where ewes will be lamb­ing the fol­low­ing spring.

3 ways to pre­vent the build-up of large worm pop­u­la­tions:

• put in new pas­ture • feed crops, hay or silage to slow down your pas­ture ro­ta­tion • cross-graze with other types of stock, eg cat­tle, horses

2. Im­prove the gene pool HOW: breed for par­a­site-re­sis­tance

Rams that have been se­lected for re­sis­tance or re­silience against worms and have high per­for­mance of­fer a real ge­netic ad­van­tage.

Im­por­tant progress has been made by some sheep breed­ers who have been se­lect­ing for ei­ther low fae­cal egg count lev­els (re­sis­tance), or time to first drench (re­silience), along with high an­i­mal per­for­mance.

It ap­pears that re­sis­tance or re­silience don’t nec­es­sar­ily have to come at the cost of an­i­mal pro­duc­tion. One good tool is the CARLA saliva test which helps you to se­lect sheep for these traits. It pro­vides an ac­cu­rate and sim­ple way to work out which an­i­mals suf­fer less from the ef­fects of par­a­sitic worms, and which pass fewer worm eggs onto pas­ture. www.car­lasali­vat­est.co.nz

3. Prac­tice good drench­ing

HOW: use fae­cal egg count test­ing, and drench strate­gi­cally Do a fae­cal egg count (FEC) test 10 days af­ter drench­ing to check that a drench is work­ing. The first drench af­ter wean­ing and the first au­tumn drench are good times to make the check. A full drench test should fol­low if the FEC test is not zero.

It’s de­sir­able to leave the health­i­est ewes or lambs in a mob un­drenched. This helps to main­tain a reser­voir of sus­cep­ti­ble worms in the pop­u­la­tion to di­lute down any re­sis­tant worms.

4 good drench­ing prac­tices

• Use a derquan­tel/abamectin or mon­epan­tel drench for quar­an­tine drench­ing sheep and a triple com­bi­na­tion for cat­tle. • Hold stock for 24 hours af­ter quar­an­tine drench­ing and then let them out onto a ‘wormy’ pad­dock so that any re­sis­tant sur­vivors are quickly di­luted down amongst the pop­u­la­tion in the pas­ture. • Where pos­si­ble, ex­tend the drench in­ter­val to help pre­serve drench ef­fec­tive­ness. This must be done with care af­ter con­sid­er­a­tion of the level of worm chal­lenge, FEC tests and/or liveweight gain mea­sure*. • Do not drench at less than 28 day in­ter­vals.

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