In Northern Ireland, the average age at which suckler cows produce their first calf is 31 months with subsequent calving intervals of 399 days thereafter.
Both measures are substantially longer than the industry target of 24 months and 365 days, respectively, but they can be compared to those in the Republic of Ireland.
With the average herd size counting less than 20 cows and many part time producers in Northern Ireland, synchronised AI can provide a good alternative to either natural service using bulls or the need for heat detection.
Synchronisation and artificial insemination (AI) have many advantages in the suckler herd including:
Access to quality terminal sires with accurate Estimated Breeding Value (EBV) data allowing selection of easy calving, fast growing, uniform quality calves for beef production.
Access to sires with maternal traits suitable for producing homebred beef heifer replacements.
Increasing the percentage of cows calved in the first 21 days of the calving period by having groups of cows/heifers all bred on day one of the mating period. Having a more compact calving period has a direct advantage in terms of calf management and can result in heavier calves at weaning.
However, the use of artificial insemination is still uncommon in the UK commercial beef suckler herd. Many beef farmers do not consider AI due to the problems of heat detection and handling for AI and some are concerned about poor conception rates when using AI after natural heat detection or in conjunction with synchronisation. Others worry about the cost of synchronisation programmes and AI.
The cost of synchronisation and AI is substantial, but we must not underestimate the cost of natural service. The true cost of keeping a reasonable quality stock bull on farm may be up to £1600 per year, based on bull purchase price of £4,000 and average longevity of four working years.
In the UK many beef stock bulls sire only around 30-40 calves per year and therefore the estimated cost of each calf produced by natural service is around £45. In Northern Ireland with beef suckler herds averaging 18 cows this cost could be considerably higher (£88/calf based on bull purchase price and longevity as above). Substituting a bull with AI could therefore deliver a cost-benefit.
There is often a misconception that all bulls are super-fertile. However, when routine bull breeding soundness examinations are carried out many studies have shown that one in five bulls on farm could be subfertile.
In order to increase their chances of success with AI farmers should aim to calve their replacement heifers at two years of age therefore first mating must be commenced by 15 months of age. Heifers should be around 65% of mature bodyweight at first service or around 420 kg for a mature cow weight of 650 kg.
Cows should be at least 45 days calved before entering a synchronisation programme to ensure best results. Cows calved less than 45 days are more likely to be in anoestrus (non-cyclic) and resulting pregnancy rates from the first post-calving heat may be poor.
Energy deficiency leading to poor body condition scores and prolonged anoestrus is by far the most common cause of poor fertility in many herds. Therefore forward planning is essential to ensure cows are calved at target body condition scores (2.5-3) to ensure most are cycling prior to synchronisation.
A pilot study led by AFBI involving 140 beef heifers on five farms located throughout Northern Ireland in the spring of 2013 using either a synchronisation programme with heat detection or a programme with fixed time AI resulted in 58% conception to first service for both programmes despite the horrific summer of 2012 and the heavy snowfall in late spring 2013.
Synchronisation uses products such as prostaglandin injection (for example Prellim®), GnRH injection (such as Acegon®) and intravaginal progesterone devices (e.g.CIDR®) to control the onset of heat which allows targeted heat detection or fixed time AI.
Your Veterinary Surgeon can tailor a synchronisation programme that will suit your needs. In general, when synchronising beef cows the use of progesterone implants (CIDR®) and prostaglandin injection (Prellim®) are mostly superior to programmes using prostaglandin injections alone as progesterone implants are capable of producing fertile heats in cows that are in anoestrus (non-cyclic) whereas prostaglandin injection will not.