About two thirds of the suckler herds in Northern Ireland have less than 20 cows. Many of these farms cannot afford to purchase a top quality recorded stock bull. Use of artificial insemination (AI) is difficult as many farmers keep cows in remote locations or have off farm employment. Synchronisation enables groups of cows to be prepared for breeding at a time selected in advance. It gets around the problems of accurate heat detection, which can limit the use of AI in suckler herds. AI allows beef producers to gain access to superior genetics, through the use of bulls with high Estimated Breeding Values. Several bulls may be selected for use in the herd, allowing flexibility. The mating policy includes bulling heifers to easy calving bulls and the selection of milkier cows mated to beef bulls with good 200 day milk EBVs for the production of heifer replacements.

Guidelines to synchronisation

The following are general guidelines. For detailed instruction on the different methods of synchronisation contact your local vet.

DO

DON’T

AI following synchronisation

In cows single fixed time AI can be carried out 56 hours after the implants have been removed, with heifers the AI should be carried out 48 hours after implant removal. Double fixed time Ai can be carried out at 48 and 72 hours after the implant has been removed. All animals should be AI’d whether or not they are seen in heat.

Improving conception rates

PMSG may be given by intramuscular injection at the time of implant removal. It should be used in beef cows where their condition (body score <3) and plane of nutrition are poor and in adult cattle, which have calved less than 60 days previously. Approximate cost £2/cow.

Many trials have found positive benefits from injecting cows with GnRH or GnRH agonist (for example fertirelin acetate). Cows can be treated at the time of insemination or between days 11 to13 after insemination. When treated at insemination conception rates have been shown to improve by about four - six percent. But it was found to be more successful when cows were treated between days 11 to 13 after insemination, with conception rates improving by about 11 percent (54 to 65 percent conception to first service. Approximate cost £5/cow.

Unlike heifers, cows have a much greater range in their length of oestrus. When a more precise synchronisation is required e.g. for embryo transfer or large-scale synchronisation, the additional treatment with a prostaglandin injection a minimum of 24 hours before the implant is removed, will give a tighter oestrus period. In this case one insemination 54-56 hours after implant removal is required.

In recent years work has been carried out by SAC scientists to develop a Triple Synchronisation programme. It has been shown using CIDR implants, GNRH and prostaglandin injections that conception rates of 90 percent can be achieved. This programme costs around £50/pregnancy.

Before considering any of the above seek advice from your local Veterinary Surgeon.

Planning Chart for Synchronisation and Ai

Although the program can be started on any day of the week the following option avoids weekend operations.

Preferred regime

Day of implant removal											AI
0	1	2	3	4	5	6	7	8	9	10	11
Mon	Tue	Wed	Thur	Fri	Sat	Sun	Mon	Tue	Wed	Thur	Fri

Timing is crucial

Using the preferred regime aim to insert and remove implants in the morning and AI cows 56 hours after removal.

For example, if you want to inseminate on a Friday, implant/inject on the Monday morning of the previous week (day 0). Remove the implant and inject with PMSG on Wednesday morning of the following week (day 9). Heifers can then be inseminated on Friday morning [48 hours after implant removal] (day 11) and cows on Friday afternoon [56 hours after implant removal] (day 11).

What to do if cows are still standing following AI

Occasionally cows will show standing heat after they have been inseminated. If an individual cow is still showing standing heat on the day following AI it is worth having her served again.

What to do with repeat breeders.

Synchronisation may have a beneficial effect on repeat breeders. If the problem with these cows is a short or silent heat, their continual repeating may be due to wrong time AI. In such cases synchronisation may eliminate this problem.

Proven benefit of synchronisation and AI

In a series of projects, Beef Technologists at Greenmount College examined the use of crestar implants and CIDR devices as methods of synchronisation. In the first project a total of 12 spring calving suckled calf producers used the crestar implant during a two year period. In the first year, 91 cows were synchronised and double AI’d at 48 and 72 hours after withdrawal of the implant. In the second year, 43 cows were single AI’d at 56 hours after the implants were removed.

In the first year of the 91 cows exposed to synchronisation and double insemination, 55 AI calves were produced. This resulted in a conception rate to Ai of 60.4 percent. In Year 2, of 43 cows exposed to synchronisation and single AI, 20 produced calves. A conception rate to Ai of 46.5 percent.

Table 1. The 200 day weight, conformation* and growth potential^ scores of calves born to cows synchronised and Ai’d or natural service

 

	MALE			FEMALE
	AI	Home bred	Difference	AI	Home bred	Defference
200 day weight	294	258	36	279	228	51
Conformation score	2.2	2.6	0.4	2.6	2.7	0.1
Growth potentail score	2.4	2.9	0.5	2.6	2.9	0.3

* Based on a conformation score where E=1, U=2, R=3, O=4, P=5
^ Based on a growth potential score where 1= excellent, 2 = very good, 3=good, 4= fair and 5 = poor

Table 1 shows the performance of the calves born to Ai sires and those born to natural service. The male and female calves produced by AI bulls were 36 and 51 kg heavier at 200 days of age than the calves bred by natural service. This extra weight was reflected in the higher growth potential scores for AI calves. Also the calves born to Ai sires were better shaped as indicated by higher conformation scores.

Economics

Assuming the following costs/cow, crestar and insertion by vet £8.13, crestar removal by vet £1.20 and single AI costing £8.95, the cost of the synchronisation and double AI is £46.73/calf born (60 percent conception rate and £28/cow synchronised and double AI’d). The cost of the synchronisation and single AI is £41.50/calf born (46 percent conception rate and £19.10/cow synchronised and single AI’d). Assuming natural service costs of £18/calf for a bull producing 40 calves per annum, though the cost on the average sized N.Ireland farm is likely to be double this at £36/calf, where a bull can be substituted by synchronisation and Ai the increased weight and calf quality must cover the additional cost. In the project outlined above the additional weight at 200 days averaged 43kg/calf. This in itself should cover the synchronisation and Ai costs even before considering possible premiums for improvements in the quality of the calves as denoted by improved conformation and growth potential scores. It is much more difficult to justify synchronisation and AI where it is not substituting for a bull. From the project it is calculated that the extra weight gain would have to be worth £109/100kg to cover the costs of synchronisation and double Ai or £97/100kg to cover the costs of synchronisation and single AI

Using Crestar or CIDR synchronisation techniques

In a subsequent three year project based on 12 farms, cows were selected for synchronisation using the crestar technique or the CIDR technique. Initially in year one the cows were randomly selected but in years two and three cows were physically assessed as to their suitability for using the CIDR. Only cows assessed to firmly retain the CIDR implant were synchronised using this technique. In total 195 cows were synchronised using the crestar technique and 58.5 percent held in calf to first service. A similar conception rate was observed when using the CIDR technique. Of 134 cows synchronised, 55.2 percent held in calf to first service.

Summary of Synchronisation and AI

Advantages

Disadvantages

Conclusions

Don’t keep a bull to mate less than 15 cows/year, it is more economical to use synchronisation and AI.

At store and finished beef prices above 75p/kg liveweight it is more economical to use synchronisation and AI rather than mate cows to a poor quality bull.