Munster Cattle Breeding Group

Maximizing Conception Rates with Sexed Semen

04/21/2021 20:03:44

Sexed semen trials in Ireland have demonstrated a relative conception rate of 80% - if you are achieving 60% conception in cows with conventional, you will on average get 48% with sexed semen. Sexed semen has a lower number of sperm than conventional semen, it has undergone a sorting process and also bulls vary in their conception rates following the sexing process. The variability in sexed semen conception rates is more than double that of conventional semen.

Cow Selection:

  • Select cows that are retaining for 2022 and want replacement heifers from and that have the highest chance of conception.
  • Cows calved 60 to 90 days – the higher your 6-week calving rate the greater your choice.
  • Parity 1 to 4 – Younger cows have higher conception - Careful with some 1st calvers if BCS is low and they have not coated off yet.
  • BCS 3.0 or greater is ideal.
  • Cows with no issues at calving or since calving – Difficult Calving, Milk fever, RFM, Endometritis, Lameness etc.
  • Keep intakes maximized during the breeding season – watch the bulk tank - % protein & volume are excellent indicators of energy.

Heifer Selection:

  • Heifers – Ensure at Target Weight and BCS greater than 3.
  • Heifers cycling regularly – Avoid its use on heifers on their 1st or 2nd cycle.
  • Maximize intakes during breeding and for the following month.

 Heat Detection and Timing of AI:

  • Sexed semen should ideally be used in the 1st 10 days of breeding and no later than the 1st 3 weeks. This is important due to the variability of the product.
  • Synchronization has a major role to play in the success of sexed semen – As it allows precise timing of AI, animals can be bred in the 1st week of the breeding season and any repeats can be bred in the 1st month. Use the fixed timed AI synchronisation protocols for cows and heifers.
  • Accurate heat detection is crucial – only use sexed semen when you are sure of the heats. Use two methods in heifers – scratch cards and crayons. Use conventional semen when unsure of the heats.
  • Ideal time for inseminating with sexed semen is 10 to 20 hours after the start of standing heat.

Sexed Semen Selection and Handling:

  1. Use a panel of Sexed Semen Sires avoid the dependence on one or two sires- Spread the risk.
  2. Sires with superior proven field fertility in conventional semen are better candidates for sexed semen, however it cannot be predicted how bulls perform after the sexing process.
  3. Thaw the sexed semen in a clean descaled water flask with fresh boiled cooled water changed daily, topped up as required to ensure the straw is fully submerged.
  4. Thawing temperature 35 to 37 deg C for 45 seconds. Thaw a max of two straws at a time.
  5. Inseminate animals within 5 minutes of thawing. Help the technician as much as you can to achieve this.

Flexibility Required To Maintain Fertility of the Herd:

  • Ideal time for inseminating with sexed semen is 10 to 20 hours after the start of standing heat, animals presented for AI that are at the beginning of heat should get conventional semen.
  • If you get a poor response to synchronisation and your experienced AI technician informs you that they do not feel right use conventional semen.
  • Spray mark those heifers and cows that have lost their CIDR/PRID prior to removal at the synchronisation protocol for sexed semen and use conventional semen on these animals.
  • If we get very severe weather, or the bulk tank is dropping in volume or protein % or if the animals are experiencing a setback switch to conventional semen.

 

Posted on  Wednesday, 21 April 2021
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