ADVICE FROM LLM ET VETS

Here are some tips and thoughts about maximising your success rates with embryo transfer. There's a lot we can do when it comes to managing, feeding and protecting recipient animals and their unborn valuable ET calves.

There is often great debate about diets of the animals during an embryo program. It is important to remember that the small undeveloped follicles in the ovaries, so called ‘pre-antral follicles’, are “earmarked” some two to three months before we even start a superovulation programme. So, in essence the future eggs have already begun their journey to become larger follicles containing fluid and an unfertile egg.

The fate of most of these follicles in normal cycling cows is to simply shrink away and be reabsorbed in the ovary. In superovulation, we are merely trying to encourage many more follicles to develop and become sufficiently large enough to induce multiple ovulation of unfertile eggs all capable of being fertilised. Embryo recovery of the early developing embryo occurs seven days later.

Donor selection

• Select cows which have returned to normal cyclic activity i.e. have had at least two heats after calving.
• A good reference heat followed by a scan of the uterus and ovaries a week or so later will help identify cows which are cystic or dirty prior to commencement of the superovulation programme.
• Avoid changes in diet from the time of the reference heat. Energy drenches (propylene glycol) can help on the days of FSH administration.
• Multivitamin drenches can be used at the reference heat and the start of the superovulation programme.
• Ultimately, many cows do very well provided they are on a good plane of nutrition and not losing excess body weight.
• Avoid stress or changes to housing group of the donor cow while she is on programme.

Recipients

• Maiden heifers make the best recipients: they have higher conception rates.Cows can be used providing they have a good body condition score, and they are clean and cycling.Embryos can be put in to heifers that were bulling 6, 7 or 8 days previously.A good reference heat is vital to the success of the transfer.
• Reference heats can be a natural observed heat or synchronised induced heats.
• Included heats (i.e. Following a CIDR and prostaglandin programme) work equally well providing good heat detection is undertaken.
• A wrong or inaccurate heat observation will mean no pregnancy as these recipients are not synchronised with the donor cow.
• Avoid feeding changes o the recipient group for four to six weeks either side of transfers. Try to keep the diet consistent.
• Mineral boluses such as Cosecure might help.
• Grass variation and grass silage variation can affect conception rates.

Disease

Despite the expense and effort involved in embryo transfer, many neglect the importance of selecting and protecting recipients and donors from common reproductive diseases. Consider the following when doing embryo transfer:

• Are the donors free of BVD?
• BVD and Lepto vaccination for all donors and recipients.
• Select recipients from herds where disease status is known. Of particular relevance in this respect are Johnes disease or Neospora.
• Consider screening recipients for Neospora infection. This disease is a very common cause of abortion.
• Where salmonella is known to have been a problem consider salmonella vaccination, another common cause of abortion.
• Monitor carefully mineral and trace element status of late gestation recipients to improve calf viability and survivial.
• Maximise calf survival against neonatal scour/septicaemia by vaccination against rotavirus, coronovirus and E.coli K99.
• Address any neonatal health issues and calf management on farm before recipients calve.

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