Trials of sheep breeds

Professor Hugh Blair of Massey University told delegates to the International Sheep Veterinarian Conference in Rotorua that the turnaround time from making selection decisions in ram breeding flocks to realising gains from those decisions on commercial farms is about seven years. The problem is, no one really knows what consumers of meat and wool will want seven years out.

While that’s the challenge facing ram breeders, he says no farmer should be suffering from a lack of lambs from their flock. He says if they are they should change their breed or their breeder.

In his paper to the conference, Blair talked about the history of sheep breeding in New Zealand and the progress and research made by scientists over the past 100 or more years. He says the objective all along has been to improve farm profitability, but that’s not always happened. 

“If we take the Romney sheep from what was delivered to New Zealand in the 1880’s to what we had by the 1940s, it was quite a different beast. Wool was king and so wool was on every part of the animal - it was almost on its nose and its hooves. The price of wool was a pound a pound so it was thought that by making these changes to the sheep that the farmer would be producing a whole lot more wool. In fact they weren’t,” he explains.

The amount of extra wool from the ‘wooled up Romney’ compared with open faced lines was negligible and the extra wool created problems.

“The big sticking point was that by putting wool everywhere we actually affected the temperature control of the ewes, which meant their reproductive rate was not as good as those animals that were open faced. Research by AL Rae, T S Chang, Morrie McDonald George Wickham and others at Massey in the late 1950s and ‘60s showed that those animals with wool on the face and points had poorer control over blood vessel constriction and dilation so when an animal had to lose body heat it couldn’t do so efficiently. So what Morrie in particular showed was that if there was a small increase in ewe body temperature, you decreased the proportion of fertilised eggs that would implant.”

It’s a nice example of an unintended outcome of selective breeding, says Blair. In that case, the advent of weighing wool clips in the 1950s turned things around, scientists advocating that to increase fleece weights farmers must measure and record the performance of their flocks.

“Then came such things as breeding values and away we went – the rest is history. We didn’t start that well, but where we are now is that New Zealand makes very effective use of the principles of genetics in our production systems.”

While New Zealand has developed new breeds of sheep such as the Coopworth and Perendale, it’s also applied genetics to develop ‘strains of breeds’, for example with facial eczema tolerance.

Changes to the research structures in the 1980s and 1990s created some issues in the breeding field as the consolidation of MAF and DSIR into AgResearch coincided with the introduction of breeds such as the Finnish Landrace, Texel and Oxford Down. A change to research funding channels also made it difficult for scientists to get backing for the long-term work needed for breed comparisons. The result was farmers started their own on-farm experiments.

“Farmers would take two Texels, or three Finnish Landrace rams and they would cross them over groups of animals on their property and measure them, against in their terms, the other purebreds they had on their property. And they would say – wow - the introduction of a half Texel was great, or that it wasn’t. The problem was we didn’t have controlled experiments… Farmers were left doing it on their own and we had a very mixed up phase though the ‘90s.”

But by 2000, things were starting to settle down.

“You had some major breeders through Hawkes Bay, Wairarapa, Manawatu and quite a number down in the South Island who had all infused a portion of genes from a variety of those exotics into their lines of sheep. 

“They’re now marketing them under their particular brands. They are not being marketed [as] Romneys or Merinos or any other breed.”