Three Steps Closer To Drench-Free Sheep

They say you can’t have your cake and eat it too. But farmer-funded research shows that farmers may soon be reducing their reliance on chemical drenches, while increasing their profits.

“We can’t rely on drenches to solve our parasite problems forever,” says WoolPro production research manager Dr Ken Geenty.

“Consumers want their food to be produced as naturally as possible. Also, there are very real farm management issues associated with drenching including resistance, cost and the fact that, until now, we’ve been selecting animals for breeding purposes that need drenches to survive.”

At Riverside Farm, near Masterton, researchers are studying the benefits of feeding sheep the so-called ‘goldie’ variety of the condensed tannin-containing Lotus corniculatus (birdsfoot trefoil).

The project, which is funded by WoolPro, is a joint venture between Massey University and AgResearch.

While still in its early stages, the study has already shown that undrenched lambs grazing lotus until weaning grew at 260 g/day, while their pasture-grazed counterparts grew at a more sluggish 190 g/day. They also grew an average 19 per cent more wool.

Faecal egg counts, which indicate presence of internal parasites, are also much lower for sheep grazing lotus, and lotus-fed ewes and lambs have fewer dags.

Prof Tom Barry and Colombian Masters student Carlos Ramirez are measuring sheep production, forage nutritive value and forage dry matter production. They’ll then calculate how much farmers should sow in lotus to give the best results. The complete study will take two years.

Previous trials have shown that lotus-fed sheep have up to 34 per cent higher ovulation rates and higher lambing percentages than sheep fed on a ryegrass/white clover mix.

Meanwhile, WoolPro/Meat New Zealand subsidiary Sheep Improvement Limited (SIL) is being used by progressive breeders aiming to create drench-free sheep.

“All rams are not created equal,” says John McEwan, manager of WormFEC – a service based at Invermay which helps breeders test their animals’ resistance to internal parasites.

SIL collects performance data from around 40 New Zealand ram breeders, who are selecting for resistance to internal parasites.

When buying rams, commercial sheep farmers can use SIL breeding values (BVs) for parasite resistance to select their rams.

“Choosing rams with greater natural resistance to internal parasites is an insurance policy against relying too much on chemicals for parasite control,” Mr McEwan says.

“By reducing pasture contamination with parasite larvae, farmers can improve animal health, boosting productivity and economic returns.”

Reduced faecal egg counts are most beneficial for dual purpose or dam breeds, such as Romney, Coopworth and Perendale, because of the positive effect a reduced egg count can have on lamb health, says Mr McEwan.

And, at Lincoln, AgResearch scientist David Scobie is gazing into a crystal ball to see if it is possible to create the perfect sheep.

“There is the potential for an organic, low-chemical niche-marketed sheep which will gain a premium from discerning consumers,” says Dr Scobie. He believes such an animal will be bred in numbers within a decade.

“Our modelling suggests expenditure would be halved, while niche-marketed wool would gain twice as much per kilo, giving the producer a gross margin of $14.75 rather than the current return of around $6.”

He says the best option all-round – for the animal, the farmer and the shearer – would be for sheep to have less wool around the head, legs, belly and backside. These are the ‘fiddly bits’ when it comes to shearing, and only yield about a kilo of oddment wool worth a couple of dollars.

Dr Scobie believes the reduced wool pattern would be the biggest hurdle in creating the improved sheep, and suggests the Finnish Landrace or Gotland Pelt breeds could be used early in a cross-breeding programme for their short tails, along with East Friesians for their bare tail and backside.

He says there is great flexibility with breeding, as many of the desired characteristics are already found in existing breeds. Bare bellies are found in breeds like the Wiltshire Horn, and bare breeches are present in the Border Leicester, Poll Dorset, Texel, Perendale and Cheviot.

To demonstrate the practicalities of the ideal sheep, crossbred hoggets were trimmed to resemble the breeding goal of a wool-free head, legs, belly and breech. The AgResearch study, funded by WoolPro, found the trimmed sheep required only half the blows and half the time to shear compared with untrimmed sheep.

Although total fleece weight was reduced by 1 kg (to 3.0 kg), half of this was comprised of oddments.

Another part of the study concluded that the perfect sheep would have a genetically short tail, bare of wool, so crutching and docking wouldn’t be required.

It would also be born ‘mulesed’ and would remain cleaner throughout its life. Time-consuming and costly tail-docking, crutching, and flystrike treatment would be a thing of the past. The low-input sheep would produce more lambs and require less chemical treatment.

AgResearch, with funding from FRST, is continuing with the development of a welfare-friendly sheep incorporating a short tail from the Finn and a wool-free tail and backside from the East Friesian.

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