Being born a twin does not reduce pregnancy rates in 15-month-old heifers

Leo and Liz Cummins presented a poster at the Proceedings of the 31st Biennial Conference of the Australian Society of Animal Production at Adelaide in July 2016. A PDF of the poster can be downloaded here, or you can read our information below.

Key Messages

  • Twin born calves grow out very satisfactorily.
  • At weaning time the output per cow with twins is 160%.
  • By mating time at 15 months of age, twin born heifers conceive and then calve at the same rate as their single born mates.

Detail

  • There is a widespread industry perception that “twin born calves never grow out and perform satisfactorily”.
  • Given the importance of weight and fat depth at mating for achieving satisfactory heifer pregnancy rates, the question is“does being born a twin reduce heifer fertility?
  • USMARC twinners are a composite twin selection line which reached a calving rate of 160%.
  • Our twinner group is a small commercial herd based on US Meat Animal Research Center (USMARC at Nebraska) twinner genetics which we have been importing and grading up to over the last 12 years.
  • In our herd, calves are tagged at birth. All calves are weighed at weaning in November (at approximately 8 months of age).
  • Steers and freemartins are sold soon after this and the breeding heifers retained.
  • Previous work at Hamilton and Grafton has shown that we can expect twins to show postweaning compensatory growth.
  • The results reported here only refer to heifers with 50 – 100% twinner blood and mated at 15 months of age.
  • Over the whole herd, we have a twinning rate of 35% per cow calving.
  • Our herd is mated for 8-9 weeks starting in June.
  • Early ultrasound pregnancy testing to count foetal numbers is carried out at an average of 11 weeks after the start of mating.
  • Being born a twin does not reduce pregnancy rates in 15-month-old heifers.
  • Twice daily calving inspections allow adequate supervision and good calving records.

Effect of birth type on calving results - poster 2016 copy Effect of birth type on preganacy status - poster 2016 copy Pregnancy rate - poster 2016 copy Weaning weights of 8m.o. heifers poster copy