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Artificial insemination strategies for the beef suckler herd

Chris Gregory BVSc MRCVS, Molecare Veterinary Services

Artificial insemination (AI) has become an integral tool in the dairy industry; reaping the rewards of rapid genetic improvement, easy calving, reduced reliance on bulls and increasing the value of crossbred calves.

The intention of this article is certainly not to suggest a blanket adoption of AI across all suckler herds, as it will not suit everyone but rather highlight its potential to improve herd characteristics.

Likewise, I will not dwell on the logistics of implementing an AI programme. A successful AI programme will rely on a solid plan including the prudent selection of healthy animals, committed heat detection and the means for efficient handling.

Potential benefits of AI:

1. Reduce (potentially eliminate) the bull power required across the herd and the costs/ hazards associated with keeping bulls.
2. Insurance against bull failure, particularly when relying on a single or limited team of bulls.
3. Access to genetics that may be unavailable locally, or too expensive to buy, especially if TB is causing restrictions!
4. An increased choice for rapid introduction of improved genetics and hybrid vigour; selection of maternal traits for replacement animals (e.g. age at first service, milk yield,
calf growth rates, easy calving) vs. strong terminal traits (e.g. carcass quality and growth rates).
5. Improved biosecurity versus hiring/buying a bull from an unknown source.

One of the major considerations in a commercial herd is the continuous production of quality replacement animals. A closed herd breeding programme will inevitably result in a limited number of cows contributing to the gene pool, stagnating the improvement of successive generations. On the other hand, buying in un-related replacements comes with the uncertainties of unknown disease status and genetic potential.

AI could be used to target just a proportion of the herd, or a specific time period, (e.g. maiden heifers, or the first two-three weeks of the breeding season) specifically to generate improved replacement animals; selecting for maternal traits complementary to known weaknesses in the herd. A terminal sire could then finish the job and sweep any returns.

Heat detection (natural observation) or ‘fixed-time AI’ (synchronised)?

This is the crunch decision for use of AI. Reliable heat detection and timing of service are vital for a successful AI programme. Routine heat detection should be practiced a minimum of twice daily for 20-30 minutes. Animals bulling in the morning should be served the same afternoon. Animals bulling in the afternoon should be served the following morning.

The alternative is to utilise (hormonal) synchronization and fixed time AI, manipulating the reproductive cycle to time insemination without heat detection (‘serve blind’).

Advantages:

1. Heat detection not required.
2. Some synchronisation protocols can be used to bring non-cycling or more recently calved cows back into a calving block, i.e. tighten a calving block.
3. Multiple animals can be served on the same day, saving cost on technician visit fees.
4. Control over timing of calving period(s), e.g. plan batches of replacement/high value calves to optimise early husbandry.

Disadvantages:

1. Multiple handlings and strict timings to administer hormones.
2. Conception rates can vary (30-70%).
3. Relatively expensive.

Selecting the right animals for AI:

The reproductive cycle and expression of heat, is prone to interference by many factors (e.g. diet, environment, handling, stage of production), therefore consistency is vital.

Rough criteria for selection of eligible cows:

1. >60 days post calving – allow for uterine involution and return to cyclicity (NB: Some synchronization protocols can expedite this).
2. Maiden heifers – less stress vs lactating cows therefore higher submission and conception rates. Targeting these animals for AI will likely yield the best results.
3. Feed – Consistent, quality nutrition six weeks prior to and following AI. Target Body Condition Scores (BCS) of 2.5-3.
4. Housing – Avoid periods of heat stress and group changes. Overstocking can lead to crowding and false bulling behaviors; cows are less likely to demonstrate heat when housed on slippery surfaces.
5. Handling – Avoid any unnecessary ‘stress’ (abnormal routine); especially during a synchronisation protocol. We should also avoid vaccinations and other routine herd treatments during the programme.