Breeding programmes for autumn calving cows are now into their sixth week for most dairy farmers. For those in spring calving it is the quietest time of year, with preparation for the calving season being the main priority.
It is now time to plan for the selection of sires for use in your spring AI breeding programme. One major difference between breeding programmes in the North and Republic of Ireland is the use of sexed semen.
A significant proportion of our clients in the North use sexed semen for the first round of AI in their maiden heifers. A stock bull is then used to catch the repeats. This approach is now used by many dairy farmers who normally use stock bulls to get heifers in calf. I would emphasise that sexed semen will only result in pregnancy rates greater than 50pc if the heifers are fit for breeding.
There are bulls available, Holstein (WMZ, EBI 169), British Friesian (CZS, EBI 131) and Jersey (PWI, EBI 114), with acceptable EBI figures using sexed semen.
There are many potential advantages from the use of sexed semen, but it can prove expensive if pregnancy rates fall below 45pc in maiden heifers. The maiden heifers need to be fit at the time of breeding. They need to have reached their target weights for age and breed. This is where the biggest mistakes are made. Take time to get your heifers weighed now to ensure they are on target to achieve the ideal breeding weight in May.
We scan heifers on many farms prior to breeding where sexed semen is used. We can identify heifers which have poorer reproductive potential and advise the use of unsexed semen. In addition, the scan is used to identify heifers coming into heat over the following two days -- those heifers which can either be heat synchronised immediately or one week later for the use of sexed semen.
The use of sexed semen has not been recommended in conjunction with oestrus synchronisation programmes. However, we have shown that by scanning in conjunction with oestrus synchronisation, pregnancy rates of 50pc-plus can be consistently achieved with sexed semen in maiden heifers. If an unacceptable proportion of the heifers scanned are unsuitable for the use of sexed semen, we will recommend that clients use conventional semen for breeding. The cost of sexed semen is greater than unsexed semen, which poses the question: why would one go to the trouble of using sexed semen in an AI breeding programme?
In one case in Derry, we found that the Friesian heifer calves born resulted in a faster repair of the reproductive tract compared with their counterparts that had Angus bull calves. A slower involution of the reproductive tract will increase the calving-to-pregnancy interval.
In conclusion, sexed semen has an important role to play in your AI breeding programme but requires greater attention to detail in the rearing of your maiden heifers.
Dr Dan Ryan is a breeding management consultant. www.cows365.com