Slim ewes are the best kept

Not necessarily, according to Anthony Shepherd, principal of sheep industry consultancy Sheepmatters based at Cootamundra.

"I want a ewe which will cut a fair amount of wool and rear a lot of lambs and is not costly to run," Mr Shepherd said.

"From the work I am doing with my own flock and those of my clients, I have found that the biggest ewes are high energy cost ewes and the return is not commensurate with their energy needs."

Through his experience, Mr Shepherd has determined 75kg for a mature ewe, empty and off-shears is the limit for what he considers the most economical ewe.

"Bigger ewes don't cut any more wool and I cull all my ewes that weigh over 75kg," he said.

"By taking out the heavy fatty ewes, we are lifting net return per hectare from total progeny weaned on a carcase value (gross progeny carcase value minus ewe energy cost)."

Mr Shepherd said by removing those ewes from the system he is turning into a 'shearer's friend', but his ideals are not altruist.

"I am doing it so I can run more ewes per hectare," he said.

Taking out the ewes over 75kg and based on the carrying capacity of his property, Mr Shepherd is able to run and extra four and half ewes per hectare.

"I join for three weeks and based on an average 63kg bodyweight for my ewes and weaning 138 per cent lambs to ewes joined the extra return is another 6.2 lambs per ha," he said.

"By identifying those ewes which are pregnant in the first cycle, we are repeatedly rearing more lambs."

Figure one shows the amount of energy a ewe, during the different stages of pre-lambing, pregnancy and post lambing needs to maintain her condition and suckle her progeny.

He pointed out, sheep breeders were keeping older ewes in an attempt to quickly re-establish their flock after years of drought rather than buying in younger ewes.

"Those older ewes will get pregnant and there is going to be a lot of metabolic disorders this lambing because people are keeping these heavy fat ewes," he said.

"By understanding their energy requirements whether a single or twin mother, using that chart you are able to feed sufficiently to maintain her condition."

Running his ewes at about 60kg, Mr Shepherd pointed out their basic energy requirement is a lot less.

Mr Shepherd is breeding a Merino ewe based upon their maternal traits, with wool an important secondary consideration.

"We want a true dual-purpose ewe, with year in year out productivity," he said.

"With my Merino ewes weighing from 47 to 75kg, we are able to run more per ha and that is driving productivity.

"I don't want to waste my time on poor performers."

It might surprise sheep breeders to know the range of weights across their flock.

Further reading - How big should a Merino ewe be for best production?

Recently, Mr Shepherd has weighed 1280 first-cross ewes, mixed ages from maidens to five and half year and they averaged 91.8kg (68 to 138kg range).

"The industry is selecting on growth rate and early maturity," he said.

"As a consequence we are unknowingly selecting for a heavier adult body weight.

"But that is perceived productivity, it doesn't always turn into increased profit."

Mr Shepherd also highlighted current concerns with shearers having to drag the heavier weight ewes.

"It is a growing issue especially as many people are aware of the need for workplace safety," he said.

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