The success of any embryo transfer programme is based on good stockmanship and attention to detail with respect to general management and the treatment programme. Our experience highlights the following areas which need special attention when preparing recipients:
Maiden heifers are generally preferred as recipients as they average 5-10% better pregnancy rate when compared to cows. However in some situations this can be countered by the improved calving ease of cows. Indeed, when transferring embryos from larger beef breeds or embryos sired by a bull with a poor index for calving ease, cows are preferable.
Maiden heifers (depending on their breed) should be at least 15 months old, cycling regularly and weigh a minimum of 350kg at the time of transfer, but should only be selected when there is a reasonable expectation of a natural calving. This is very important when considering recipients for beef breed embryo transfer.
When using cows as recipients, young animals (4th calvers or less), which have no history of reproductive or health problems, should be selected. Lactation stresses will reduce pregnancy rates and cows should therefore be allowed to pass peak yield before being synchronized.
For heat detection and recording, all recipients should be clearly identifiable from a distance by a freeze brand or large ear tag.
If possible the chosen recipients should be segregated as a group and managed as such. Major changes in routine management e.g. spring turn-out, autumn housing or other changes in diet should be avoided in the period 6 weeks before and 6 weeks after transfer. Routine treatments such as vaccinations, worming, fly repellent etc should be completed prior to an ET programme.
Purchased recipients should have at least 6 weeks to settle on a new farm. They will often have an unknown nutritional and reproductive history and may bring a disease problem to an otherwise healthy herd. It is wise in this situation to discuss an isolation and vaccination programme with your Vet, not least because diseases such as leptospirosis or BVD and deficiencies of copper and selenium can have a devastating effect on an ET programme.
Diet and Body Condition
Recipients should be in general good health and moderate condition score at transfer (condition score 2.5). Results are depressed when recipients are either too fat or too thin. A long fibre based diet should be used if possible. Hay, big bale silage or straw are probably best. A low protein coarse mix as a concentrate supplement is preferable (barley isn't ideal). Sugar beet pulp is also useful if an energy or fibre source is needed. Both can also be used as mineral carriers. The aim of the diet is to achieve a moderate rising plane of nutrition.
If recipients are at grass - lush wet pasture should be avoided and they should be buffer fed if possible.
In our experience recipients managed indoors give 5-10% better pregnancy rates than those managed at grass.
Mineral and Trace Elements
As with the donor cow, adequate supplementation of trace elements and minerals is important for fertility. On farms where there is a known deficiency your Vet should be consulted, but in general some form of supplementation should be instigated for ET programmes.
Several trace elements have a major role in reproductive processes including copper, selenium, manganese, phosphorus and zinc and these in particular should be supplemented in ET programmes. Recipients should be fed 100g per day of a good quality powdered mineral for at least 6 weeks before the planned transfer date.
In management situations where feeding powdered mineral at a set rate is difficult i.e. at grass or with large housed groups, recipients can be bolused (e.g. Cosecure or Agrimin Alltrace), and then supplemented with free access mineral (e.g. molassed mineral buckets).
Heat detection and recording is important to the success of any embryo transfer programme. Recipients should be clearly identifiable with a large ear tag or freeze brand. The time of onset of each standing heat should be recorded.
To observe heats accurately, at least 3 observation periods of 20-30 minutes are advisable. Cattle showing riding behaviour, marked flanks, sliming or other signs of heat should be watched carefully until they are seen to stand.
- Maiden heifers should be 15 months or older, cycling and at least 350kg in weight
- Cows should be 4th calvers or less, past peak yield and have no history of health or reproductive problems
- Manage recipients as a group and avoid stress for 6 weeks before and after transfer
- Discuss control of diseases affecting fertility with your Vet.
- Diet should be long fibre based and have moderate protein content. Avoid lush, wet grass
- Ensure that recipients are well supplemented with minerals and trace elements
- Heat detect carefully and record onset of heat accurately