LOOKNG at sheep worming options for 2015, an overriding priority is to use a minimal number of treatments with maximum efficacy when they are given, according to Zoetis vet, Andrew Montgomery.

He points out that the number roundworm eggs passed by ewes in faeces rises significantly at lambing. To counteract this, research has found that treating ewes at lambing with long acting injectable 2% moxidectin - trade name, Cydectin 2% LA for sheep - significantly reduced faecal egg outputs over more than 60-days post-treatment, compared with a 0.1% oral drench of the same active ingredient."

In lambs from treated ewes, the study found those grazing with injection-treated mothers had significantly lower faecal egg counts (FECs) than lambs grazing with drenched ones.

"This regime appears to lessen the worm challenge to lambs and may offer potential for higher growth rates and reduced anthelmintic use," says Mr Montgomery. "In turn, fewer lamb treatments would thereby also reduce costs and selection pressure for anthelmintic resistance."

In a farm demonstration of this strategy, two ewe groups received a dose of injectable 2% moxidectin and a flukicide on exit from the lambing shed, while another two matched groups had flukicide only.

All ewes grazed the same pasture divided into four blocks. At four, eight and 13 weeks post-lambing, fresh dung samples from several lambs were collected from each group and sent off for FEC.

The first sampling showed no difference between lambs from treated or untreated ewes. However, four weeks later saw a marked differential), with lambs from untreated ewes showing a count of 1850 eggs per gram, comprising a combination of nematodirus and strongyle eggs. Even so, these lambs were reported to be showing no outward signs of worm infestation.

Prompted by the FECs, lambs from the two untreated ewe groups were dosed with an ivermectin drench.

Five weeks later, these lambs showed a reduced but still significant FEC of 700. Even just before this treatment, no clear outward signs of worm burdens had been observed.

Meanwhile, lambs from the Cydectin-treated ewe groups continued to show an FEC of 50 and so still did not need anthelmintic treatment.

Judging from lamb growth rates, both regimes were similarly effective and, by early July, lambs were fit for slaughter. In the adults, however, a marked difference was reported at shearing, with moxidectin treated ewes showing better body condition and wool quality.