Technical information - Reproduction

Some considerations on optimisation of Bovine Reproduction techniques

BRAHMAN NEWS JUNE 2013 ISSUE #179 PAGE 42

by Luiz Porto Business Development Manager
Inventia Genetic Technologies Pty Ltd - IGT

The conception rate and the number of calves in the field are undoubtedly factors which impact on the financial returns and profitability of any rural property.

The quality of the calves and the genetic progress of the herd are also highly relevant to this. In fact the first step towards achieving a successful livestock enterprise is to obtain high quality calves in large numbers.

We know that nutrition and health go together when it comes to the productivity of a herd. Abortions and malformed calves can be avoided with a good vaccination and nutrition program. These two factors can also help increase in conception rates.

The responsible and effective management of a property requires the constant evaluation of the strategies that are being employed, such as breeding strategies. In times of crisis and reduced cash flow, the first tendency of most farmers is to stop any innovation and cut all investment. However this can have disastrous consequences in the medium to long term. "The cost of doing nothing in some enterprises can be much higher than the cost of doing something". For a farmer this instinct to reduce or abandon investment during a crisis can have serious negative results in the next generation, such as, in the case of breeding strategies, reduced calf numbers, lower genetic quality and fewer (if any) bulls for sale, all of which will result in reduced revenue and profit.

When I talk about breeding strategies, I mean artificial insemination, embryo transfer from superovulated cows and in vitro production of embryos (IFV). A lot of myth and misconception surround these concepts, giving rise to unrealistic expectations. A poor understanding of the dependency of these strategies on other related factors, such as vaccination, disease control, nutrition and recipient quality, also makes any analysis of breeding results difficult and complex.

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Cows that have been empty for a long time should not be used as recipients, nor should very old heifers because we know that they are more difficult to impregnate. If we know that excessively fat cows are known not to impregnate when with bull, why then use them as a recipient, in a program that involves a far greater financial investment?

In this article I would like to discuss these myths and false expectations about the results of the various breeding strategies and to provide ideas that can greatly improve the productivity of the mating season for those farmers who are willing to listen.

The artificial insemination technique of propagating genetic material from the male is widely used, especially in heifers, and a lot has changed in this area in recent times with the introduction of FTAI. This method is easy to perform and offers satisfactory results. In FTAI programs without oestrus detection one can expect a pregnancy rate of between 23-62%, with an average of 48% with one insemination (data are from 200,000 cows inseminated in Brazil in 2011). However this technique is not yet suitable for large projects using sexed semen, because the results that it produces are still too variable, and in instances very poor.

Embryo transfer from superovulated cow is a multiplication technique involving genetic material taken from bulls and cows in healthy condition. In this technique, hormones are used to generate more than one ovulation. One flushing from one donor can generate from 0 to more than 30 embryos, depending on the age, breed, nutritional status of the animal and capacity to respond to hormone treatment. The average number obtained per flushing is 7 embryos. Again, the use of sexed semen has not been successful with this technique. Not all donors will produce embryos and donors must be selected to improve results. The expected pregnancy rate is around 55-65%. The harvesting of embryos can be performed every 60 days. In most cases it is recommended to perform 3 super-ovulations after calving, and then to allow for a full term pregnancy by the donor, to regenerate the animal's physiology. After all, we all want our best cows to be pregnant every year!

In vitro fertilisation (IVF) is a technique that removes the eggs from the donor by ultrasound, usually without the use of hormones. The aspiration can be performed every 15-20 days. Even when the donor has become pregnant, ovum pick up (OPU) for IVF can still occur up to 90 days into the pregnancy. From 0 to more than 50 embryos can be produced from every donor. The average number is influenced by factors such as breed, age, nutritional status and the batch of semen used. Brahman and composite breeds with Bos Indicus respond very well to this technique. It can be started with aspirations at 40 days postpartum and on average 7 OPUs are undertaken before allowing the donor to become pregnant and rest. This technique is also economical in terms of semen usage. In some cases, eggs harvested from up to 10 cows can be fertilised with one single dose. This technique is very well suited for use with sexed semen, successfully enabling farmers to choose the sex they need. More males or more females!

The expected efficiency of this technique is 35-50%, with a 40% pregnancy rate being considered good for large-scale programs.

Both techniques (superovulation and IVF) require the use of recipients (cows or heifers) that have attained the appropriate size for the future calf birth and enough maternal capability to feed the calf. Those recipient animals will have their oestrus synchronized with or without detection to receive the embryos from either technique.

I believe that Fixed-Time Embryo Transfer (FTET) without the oestrous detection technique is the most suitable method for a large-scale IVF program. The expected efficiency in the treatment of synchronisation is 80 to 85%. However, not all ovulated animals will be suitable to receive embryos. For the vast majority the answer will undoubtedly be YES!

Recipients should be well managed in terms of sanitation, receive vaccines to prevent abortions and the most common diseases and parasites. They should be handled calmly, provided with good pasture, good water and any mineral supplements.

Cows that have been empty for a long time should not be used as recipients, nor should very old heifers because we know that they are more difficult to impregnate. We know that excessively fat cows are known not to impregnate when with a bull. Why then use them as a recipient, in a program that involves a far greater financial investment? Poor milk producing cows should be discarded, as should cows that have aborted or lost previous pregnancies or have a history of calving problems. The correct management of recipients involves the purchase of good cows and the disposal of the deficient ones.

On the subject of breeding efficiency, another important issue is the early diagnosis of pregnancy. Early pregnancy testing is a great management tool that should be considered when using IVF. Without it, farmers are not utilising the full potential and efficiency that is offered by the IVF technique.

It is important to emphasise that early pregnancy testing does not interfere negatively with the number of calves born using IVF or any other technique. I can say this on the basis of my 18 years of daily use of ultrasound in Brazil and the countless diagnoses I have made in my career. I am making this claim also on the basis of embryo physiology. The implantation or "attaching" of the placenta in utero in cattle occurs around day 33 of gestation (26 days after implantation of the embryo). Once attached, a competent professional can handle the animal without affecting the pregnancy. Therefore, YES! It is safe for an early pregnancy test to be performed
by a competent professional at the
appropriate time.

As a result of early pregnancy testing, the farmer will have information that he needs to know, such as early pregnancy losses. Early pregnancy loss is an indication of many other potential problems that need to be addressed sooner rather than later, especially diseases and nutrition.

Another benefit of early pregnancy testing is the savings on pasture that are made as a result of early disposal of empty
recipients. This can also increase efficiency in the use of recipients by recycling the good ones.

For example:

A farmer uses 100 recipients in an IVF program with 40% pregnancy rate:

If the pregnancy is tested at 90 days, the farmer will get only 40 calves in 90 days. However, if the pregnancy is tested earlier, say, after 30 days, then the farmer gets 40 pregnancies in the first program and another 24 pregnancies from the recycled recipients. Therefore, the farmer will have a total of 64, instead of 40 calves, from the 90 days program.

In this example the farmer would also need to take into account the cost of pasturing empty livestock and the cost of selling his bulls that were born with intervals greater than 90 days.

In conclusion, I would like to stress that the rational and judicious management of a herd is always necessary for a farmer, whatever the economic environment, and this includes attention at all times to breeding strategies. In the case of both superovulation and IVF, careful attention must be paid to the quality of the recipients. Neither of these techniques is able to achieve its full potential, in terms of pregnancy rate, if unsuitable animals are used. Early pregnancy testing is another valuable tool that is available to farmers as a means of detecting breeding problems early, avoiding wasted pasture resource
and increasing the productivity of good quality recipients.

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