Worm resilience is the ability of the sheep to grow in spite of worm burden. Worm resistance is the sheep using natural antibodies to fight worms.
Positives for resilience, the sheep are not using any energy to produce antibodies putting all energy into growth. Negatives are larger worm residuals on the pasture.
Positives for resistance are less worm contamination on pasture. Negatives are sheep transferring energy from growth to producing antibodies.
Our aim is to have a ewe that never needs drenching and their lambs minimal drenching with weight gains that are industry acceptable in conjunction with other physical traits.
In the year 2000 the ARDG and WRIG with advice from AgResearch scientists set out to find a protocol for breeding worm resilient sheep. After six years with funding from MAF the protocol was set.
Ram and or ewe lambs are weaned, weighed and drenched, depending on FEC counts somewhere about 6-8 weeks the lambs are weighed again and a faecal egg sample is taken. Any lamb that hasn’t put on the same weight gain as the control group (which is drenched every four weeks) is drenched. This procedure is repeated every 10-14 days until the mob is down to about 10% of the original. At this point all lambs are drenched; the last 10% sometimes go up to 16 weeks without a drench, whilst achieving substantial weight gains.
In 2007 we did saliva testing hoping this would be an easier way of getting results but we still had to do the other test. In the meantime we have been supplying Ovita with blood samples from every ram that has been single sire mated in the ARDG. DNA breeding values are now available from Pfizer on FEC.
The ARDG is also supplying rams to Poukawa Research Station which evaluate rams nationwide for industry traits including FEC and FE.