Professor Hugh Blair says the five-year trial, which is funded by B+LNZ, began in 2017 and is following the lifetime performance of single and twin ewe lambs retained from a hogget lambing. These animals are being compared with a control group of twin ewe lambs retained from mixed-age ewes.
In the first year of the trial, drought conditions meant it was a struggle to get the twin lambs born from the hoggets to a 40kg mating weight, but for those that were mated, there was no difference in the number of lambs born/ewe pregnant to the other two cohorts (single lambs from one-year-old ewes and twin lambs from mixed-age ewes).
These animals are now lambing as three-year-olds and the big difference the researchers are now seeing is in mature ewe weight.
The ewes, born as singles or twins from hoggets, are about 5kgs lighter than the ewes born as twins from mixed-age ewes, but their reproductive performance is the same.
“While they are lighter, they are still getting pregnant at the same rate and have the same fecundity.”
On an efficiency basis, comparing kilograms of lambs weaned per kilogram of mature liveweight, these animals are showing an advantage.
Professor Blair stresses that while significant, these are just preliminary results and the researchers will be particularly interested in the lifetime performance of these sheep. Whether early reproductive performance will be penalized with reduced longevity.
While there is a genetic benefit to retaining lambs born as hoggets as replacements, Professor Blair says this benefit is small compared to the possibility of greater ewe efficiency.
“The biggest seller is efficiency in terms of kilograms of lambs weaned per kilogram of maternal bodyweight.”
The trial is set to run until 2022 and having the ability to follow these sheep through their lifetime is critical to understand whether there are economic benefits to retaining lambs from hoggets as replacement ewes.
Professor Blair says he is very grateful for B+LNZ’s willingness to invest in a long-term trial which will ultimately provide farmers with sound information.