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More fertile cattle worth millions to Australian producers

13 July, 2006

Research into finding the links between the genetic make-up of bulls and the fertility of their female progeny could be worth millions of dollars to Australian beef producers.

The potential to improve reproductive performance has been revealed in a major research project involving monthly ovarian scanning of 2000 heifers from weaning to first calving.

More than 36,000 pieces of data have been gathered by scientists from CSIRO, Queensland Department of Primary Industries and the Animal Genetics and Breeding Unit at Belmont Research Station and four other Queensland Department of Primary Industries research stations across the state.

CRC for Beef Genetic Technologies calculations show the northern Australian beef industry could generate an extra $35 million a year through improved female reproductive performance.

CSIRO Livestock Industries Technical Officer at Belmont, Nick Corbet, said regular scanning would continue over the next six breeding cycles to build a picture of lifetime calving performance.

Corbet said if the research led to an improvement in calving rates it would provide a significant boost to grazing profitability.

Fertility is a complex trait, but under conditions of good feed, no disease and no parasites, a cow could be expected to raise a calf every 12 months between the ages of three and 10 years.

Researchers decided to begin the fertility research with young cattle, looking for an early indicator of an animal’s lifetime reproductive performance.

Results of the ultrasound scanning have shown a huge variation in the age and weight of cattle at first ovulation. Extremes ranged from a 10-month old heifer weighing 214 kg to a 3.4 year old animal weighing 458 kg.

Through progeny testing and the use of Estimated Breeding Value data, bulls that consistently produce early ovulating heifers can be identified.

Early results have shown that age at first ovulation is moderately heritable with a moderate to strong genetic correlation between first ovulation age and calving success at first mating.

Heifers that ovulate younger are more likely to conceive and calve earlier following their first joining. Further data is being collected to determine whether the pattern of early calving persists over the female’s reproductive life.

”It will be particularly important to examine whether there are any negative impacts on lifetime fertility as a result of earlier calving following the first joining,” Corbet said.

The research showed the condition of heifers also affected breeding performance.

Heifers typically had a 3.3 to 4.6 mm rump fat measurement when they ovulated for the first time. Animals with less than 3 mm at time of mating had a lower rate of pregnancy with the optimum level being 5 to 7 mm.

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