Straggle Muster 145 - 4/3/2005
Inverdales - Lynden Prebble, Farm consultant
Both farmer experience and scientific research shows that using the Inverdale gene in a ewe flock will lift the scanning rate by 30 to 50 % in any breed of sheep. The Inverdale gene can be used in any breed change and so allows high fertility in a sheep that best suits the farm and farmer. It also means that the emphasis for genetic progress can be put onto other traits such as survival, growth rate and carcass characteristics because fertility is taken care of.
So high fertility can be combined with a sheep breed that has good attributes for meat, a hardy constitution, or whatever other characteristic is desirable. The gene is entirely natural having been selected from one particular ewe by George Davis of Agresearch Invermay.
How much the scanning rate increases, depends on how well the ewes are fed over mating (flushing). This means that considerable autumn feed can be saved (or not purchased in dry areas) while maintaining a high scanning rate. For example: unflushed ewes will scan around 190 to 200 % (counting triplets) while fully flushed ewes will scan 220 to 240 %. Most farmers are happy with 190 to 200 % and can then make money out of the saved feed. The feed required to flush 3 000 ewes for six weeks will feed 1 400 store lambs for eight weeks.
An independent analysis of the use of the Inverdale gene by Abacus Biotech Ltd for Ovita Ltd showed an increase in lamb sales of $ 96 283 on a 5 000 Inverdale ewe flock compared to a traditional ewe flock. Use of the Inverdale gene compared very favourably to other methods of increasing the lambing % in a ewe flock, such as crossbreeding or fertility injections.
The current drawback with using the Inverdale gene is that where an Inverdale is crossed over an Inverdale some of the ewe lambs are infertile. However the use of DNA testing will allow this issue to be handled quite simply.
Progress in DNA testing is going to allow commercial sheep farmers to select their ewe lamb replacements for various genes including the Inverdale gene, plus other meat, disease, survival and production genes as they are found. Current research work is closing in on genes for various meat characteristics and aspects of lamb survival and cold weather tolerance.
DNA testing is getting cheaper each year as technology allows greater automation and greater accuracy in handling large numbers of samples. Systems using electronic tags, auto drafters and combined tagging/sampling machines are being developed. Currently these can sample 300 animals per hour and are expected to get quicker as they are more refined.
With Inverdales the use of DNA typing will allow farmers to mate Inverdale to Inverdale and sort out the ewe lambs that are infertile along with those that don't possess other desirable genes.
Lynden Prebble
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