SHEEP BREEDING » Arnie & Fiona Gray
Business Rural
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Research probes embryo survival Karen Phelps Involvement in studies by the AgResearch animal reproduction experts examining embryo survival and the ability to increase the number of twins born without increasing triplets could lead to the development of a DNA test for the specific genes involved. A romney flock owned by Arnie and Fiona Gray – who, with their son, Robert, farm two units in western Southland – has been involved in the trials, which were initiated by retired AgResearch scientist George Davis. A family-tree search traced the genetic trait back to a common grand-sire from the Davisdale line of romneys, which was initially established by Davis. The Grays’ flock follows this Davisdale line and they have been involved in the research, including work around embryo survival rate, with AgResearch since 2006. Laproscopic work is done on the Grays’ flock to measure the number of fertile eggs each ewe produces. The same sheep are then pregnancyscanned to determine the embryo-survival rate. Patterns have been observed which suggest that a single gene affects ovulation rate. Scientists have also uncovered genetics that affect embryo survival. Arnie Gray says it has been discovered that a percentage of ewes will absorb one of the embryos before day 35. “The ewes will go on to give birth to a single lamb and the farmer will never know that eggs were lost,” he says. “Increasing embryo survival therefore provides farmers with an opportunity to maximise the number of twins produced.” Two genes appear to be involved In the strain of Davisdale sheep, and AgResearch is currently working to develop a DNA test for these genes, he says. The Grays’ mixed-age ewes that carry the genes are pregnancy-scanning at 75 per cent carrying twins, 10% carrying singles, and 13% carrying triplets Their 545-hectare (520ha effective) home Braecroft Farm, at Feldwick, runs 7300 stock units and operates as a commercial romney and romtex breeding and fattening unit. There are 5500 ewes all together – 600 recorded, 2200 romney and 1700 romtex or crossbred ewes.
LaproscopIC work is undertaken on Arnie and Fiona Gray’s Western Southland romney flock to measure the number of fertile eggs a sheep produces. The sheep are then pregnancy-tested to determine embryo survival rate.
The ewes will go on to give birth and the farmer will never know that eggs were lost.
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