There are two ways to manage breeding by AI in your herd – either breeding to observed heats or using hormones to synchronise cows ready for AI. Both options will give good results if performed correctly and the decision will be made based on labour availability, management facilities and potentially the timings of the breeding period.
AI to observed heats
- Beef cows that calve in target body condition score (BCS) around 2.5-3 should normally start cycling and show heats within 50-60 days of calving
- Cows in poor BCS may have extended anoestrus and show heats much later after calving
- 20-30 minute periods of heat detection 2-3 times daily can be an effective way of selecting cows for AI especially in autumn calving housed cows – early morning and evening are critical times to observe for heats
- Heat detection aids such as tail paint and activity meters/pedometers have also been used successfully in beef herds
- Cows should be inseminated within 12 hours of being seen standing to be mounted
Synchronisation for AI
Another method commonly used to reduce or eliminate the need for heat detection is to synchronise the oestrus cycle of the cows/heifers.
Synchronisation uses products such as prostaglandin (PG) injection, gonadotrophin releasing hormone injection (GnRH) and intravaginal progesterone devices to control the onset of oestrus which allows targeted heat detection or even fixed-time AI (TAI).
Your veterinary surgeon and insemination service provider can tailor a synchronisation programme that will suit your needs. In general, when synchronising beef cows, the use of progesterone implants and PG will be superior to programmes only using PG injections as progesterone implants are capable of inducing fertile heats in cows that are anoestrus, whereas PG injection will not.
Factors that are important to ensure success with synchronisation and AI include:
- How long calved are the cows?
- Are maiden heifers ready?
- Body condition score (BCS)/Nutrition/Trace elements
- Parasite control
- Infectious disease control
- Handling facilities
- Beef cows and heifers can be bred successfully by AI achieving conception rates to match bulls
- Synchronisation can eliminate or reduce the need for heat detection
- Economic benefit can be delivered by having batches of uniform, quality calves that are heavier at weaning
- The use of conventional or sexed semen is possible to breed replacement heifers with desirable maternal traits
For further information please contact your veterinary surgeon or Zoetis UK Ltd., Walton Oaks, Dorking Road, Walton on the Hill, Tadworth, Surrey KT20 7NS. Customer Support 0845 3008034. www.zoetis.co.uk Always seek the advice of your medicines provider. Use medicines responsibly (www.noah.co.uk/responsible)