Probing the genetics of parasite resistance

01-05-2010 | Contributor

AgResearch scientist Chris Morris is running a MAF Sustainable Farming Fund project looking at the genetics of resistance to internal parasites in cattle.

During the next few months he is keen to work with farmers on collecting samples from their newly weaned calves, as long as calf sire information is known. Faecal samples would be collected from all animals in a mob when monitor samples show that there is a parasite infection, and before the infection becomes serious.

The first objective of the trial is to collect faecal samples for faecal egg counts from 6000 weaned calves between 2009 and 2011, from the three calf crops born in 2008-2010.

The second objective is to collect DNA samples from each calf and each calf-sire.

Morris is in the second year of the project, and so far 2400 animals have been sampled. The faecal egg counts (FEC) are recorded in a commercial laboratory and the data will be used with the sire pedigrees to rank the calves for FEC and to derive breeding values for FEC for the calves and their sires.

Although drench resistance in New Zealand cattle may not seem to be above the radar, Morris says it is important to make a start at ranking sires within a breed, and to know which are the most desirable animals for resistance to parasites.

He says it is already possible with the type of data being collected to select bulls and make genetic progress for resistance, as shown in one overseas herd, and as also demonstrated in several New Zealand sheep experiments.

Research at Ruakura shows that resistance to parasites is a heritable trait in cattle, as it is in sheep.

In the future, DNA markers would be an easy way to select sires for resistance, or any other trait, but somebody has to calibrate the marker data in the first place.

Morris says it might be possible to piggy-back from the parallel work being done on resistance to parasites in sheep at Invermay, but it will still be necessary to validate the use of possible sheep DNA markers in cattle.

The resource being collected will provide that opportunity, he says.

A second project now being planned, but as yet unfunded, is to carry out molecular genetic work to identify the genes and a gene-test for FEC in cattle.

• Chris Morris can be contacted at AgResearch Ruakura (07) 838-5417 or chris.morris@agresearch.co.nz

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