With the breeding season having commenced on many dairy farms, the use of synchronisation programmes for replacement heifers may be one avenue by which the workload involved with breeding is reduced.
On many farms, replacement heifers are located on out-blocks away from the yard, which poses challenges when it comes to observing heats and using artificial insemination (AI). To overcome this challenge, synchronisation protocols have been developed to maximise submission rates. However, care is needed to ensure that the protocol is followed correctly to maximise success rates. There are two categories of synchronisation available:
Protocol 1: Heifers are bred as normal for the first week and a prostaglandin (PG) injection is administered to heifers that have not yet been inseminated on day seven after mating start date. The PG protocol requires heat detection, is effective only in heifers that are cycling and 90–100% of heifers can be submitted within 10 days of mating start date.
Protocol 2: A timed AI (TAI) protocol is implemented over an eight-day period, facilitating AI of all heifers on a single day. The TAI protocol does not require heat detection, is effective in heifers that are cycling or not cycling and submitting 100% of heifers on mating start date allows the breeding of the main dairy herd to be prioritised thereafter.
Protocol 1: Heifer synchronisation with prostaglandin
When using this protocol, heifers are observed and mated during the first seven days of the breeding season. Any heifer which is not served after the first seven days then receives an injection of prostaglandin (PG). Over the following two to five days, heifers are again observed and any heifer on heat is served.
However, some heifers (<10%) may not show signs of heat after the first shot of PG and a second shot will be required 11 days after the initial injection. Again, observation following this shot is key and any heifer which fails to show signs of heat may be artificially inseminated 72 and 96 hours post injection.
This protocol will only work when heifers are cycling and works best when heifers are at target weight. With this protocol ~33% of heifers receive no PG, ~66% receive one shot and <10% receive a second injection. AI occurs over a period of 21 days and most of the heifers are bred by day 10. With this synchronisation programme, observation is key and the use of heat detection aids may make it easier to identify any heifers on heat.
Figure 1: Heifer synchronisation with prostaglandin
Prostaglandin protocol for synchronisation
Protocol 2: Heifer Timed AI (TAI)
This protocol is eight days from start to finish and allows for 100% submission rates to be achieved to first service, as fixed time AI is used regardless of signs of heat. It also promotes cyclicity in heifers that are not yet cycling, but these animals should be close to their target weights.
Day 0 (figure 2) is the day on which fixed time AI is carried out. Progesterone devices (CIRD or PRIDs) and an injection of GnRH is administered eight days before the mating start date. The progesterone device stays in-situ for six days and is removed two days before AI occurs.
Two injections of prostaglandin are involved. The first shot is administered three days before AI and the second injection two days before insemination. This two-shot programme is required as 10-20% of heifers don’t respond to the initial injection of PG and conception rates are increased 5-10% by administering the second dose.
On the day of AI, heifers are inseminated at a fixed time and also receive another shot of GnRH. When this protocol is used, the first round of breeding is completed over eight days and heifers are brought into the handling facilities on four occasions.
Source: EMM/ The Agriculture and Food Development Authority