For the next series of letters we are going to examine ways to improve breeding efficiency. Most of our livestock enterprises require that the females be on a regular reproductive cycle and if there is not a planned program to maintain breeding efficiency the calving interval tends to lengthen and this changes the profit picture. Unless we know why there are reasons why the female does not conceive the enterprise can get into deep trouble very quickly.
There are sexually transmitted diseases that can totally disrupt any breeding program and they will be covered in subsequent letters. Brucellosis, Vibrio, Chalamidia, BVD, IBR, Trichosomasis, and a host of other problems can become a giant problem if they are allowed to get started but fortunately there are vaccinations for most of these problems and that tends to be in a category where the local veterinarian is much more qualified to answer your questions than I am because the geographic factor becomes a very real part of this equation. In the US, for example, there are certain areas where blackleg is a great problem and other areas where it simply is not a problem.
The local vet is a valuable reference resource for any livestock enterprise and I am very eager to have the consultant become acquainted with him or her because very often the two businesses can be mutually supportive and it is an error to get off on the wrong foot with the local vet.
I have found that some vets are interested in working with consultants. May I suggest that you try this on a few of them and see if we can a invite a vet with an open mind to our seminars. If we could find an ally it will be a treasure for him or her and us both.
There is a very interesting thing I have discovered about vets, if he is a good vet, he will take time explain what he is doing and why he is doing it. The vet, who is too busy to explain or coach or encourage his livestock owner, simply will not be successful. Many of them wind up in small animal practice and cannot or will not be bothered with livestock. My advice is finding the vet who wants help you make money with your livestock and cultivate a mutually rewarding friendship. Sometimes the money you pay the vet for the time he spent just analyzing your problem may be the best money the farmer will ever spend with the vet.
Actually when the consultant and vet develop a good working relationship it is very possible that they can each refer business to each other. This is an area where the consultant has the option to take the lead and I can assure you that you will never have too many friends.
The single organ that produces the eggs is called the ovary. This letter will examine some of the facts we know about this remarkable organ.
First of all the ovary has a boss. The Pituitary gland sends hormones to many of the organs and other glands in the body and the pituitary can be compared to the conductor of the orchestra. The pituitary gland is an endocrine gland, which means it has no ducts but sends out its messages or hormones through the blood stream.
The place to begin with hormones is to have a clear and simple definition. Hormones are nothing more or less than a chemical message. Some of them are nothing more than a simple on / off switch. In order for the body function like a factory there has to be an internal communications system. The hormones carried by the blood are such a system. Hormones could be compared to letters that are sent by mail. There is a marker on the hormone very similar to the address on your letter. There is a receptor or "hook’ on the gland that receives the hormone so that when the hormone passes by the gland or organ that is to get the message the address and hook action stops the hormone at the proper destination. The Psalmist says that we are fearfully and wonderfully made. The creator used a good plan.
Now that we know the ovary has a boss and a way to integrate her actions in harmony with the rest of the factory, it is time to look at the work the ovary must do.
There are three main jobs the ovary must perform:
When the female is born as a part of the maturation process when the ovary is being developed she develops the eggs she will use for the rest of her life. The female before she reaches sexual maturity has all the eggs she will ever have in the storage department.
Big difference from the male who produces new sperm cells every day for most of his life.
The female waits for a signal or a hormonal message before she selects the egg that will be submitted to the ripening process. Remember the "boss" sends the chemical message or the hormone that suggests to the ovary it is time to choose another egg.
This is probably the time to remind you that in today’s high-tech method of getting more than one calf at a time from the dam for embryo transplant we give the cow a shot to superovulate her and make her drop more than one egg. The hormone shot has given us the ability to get many eggs available for fertilization at one breeding. This same hormone is the reason why some women who are patients of a fertility clinic may have abnormally large multiple births. We had a woman in the US who delivered 7 live babies with one pregnancy.
2. Ripen the egg When the ovary gets the chemical message of the instructions to select and egg and then ripen it or prepare it for fertilization the message is from the "boss" pituitary gland and the specific hormone is called FSH or Follicle Stimulating Hormone. I have included a drawing of the ovary with this letter and the different stages of ovarian activity are marked on the one drawing. The follicle is a fluid filled cavity that surrounds the egg and nurtures it into the form necessary to prepare it for fertilization.
The egg is going to receive a covering that acts as a special protective layer and a layer that has a special effect to allow only one sperm into the egg at the time of fertilization.
The follicle itself has the function to prepare the individual to exhibit signs of heat when the egg is ripe.
3. The next step in this process is that the Ovary must release the ripe egg. The ovary is surrounded by a funnel shaped enlargement of the fallopian tube. When the follicle ruptures the egg is going to fall into the fallopian tube where it begins a journey into the uterus.
If the female is exposed to a bull or is inseminated, the sperm and the egg will meet in the fallopian tube.
The egg has a protective coating that was generated during it’s brief stay in the follicle. One sperm will find a place where it may enter the egg. The sperm has a sort of a cap like structure on the very tip of the body of the sperm. When the opening into the egg is found the cap like structure disappears and the egg accepts the body of the sperm and the tail of the sperm drops off. These actions happen in very rapid succession. When they do, there is a locking type action on the covering of the egg that repels all other sperm. No more may enter the egg. At that moment a new individual is conceived. We call that new being a zygote. The zygote has the chromosomes contributed by both parents. A new individual has just been conceived and will grow into a new member of the species.
One other really interesting thing occurs in the body of the mother at that moment. Go to the picture of the ovary so you can visualize that when the follicle which nurtured the egg ruptures it is broken exactly like the skin is broken when you rupture a pimple. This break in the follicle wall begins to bleed and the cavity where the egg was matured is now filled with a blood clot. We call that blood clot a corpus rubrum, or red body. When the body of the mother gets the message that conception has occurred, the corpus rubrum undergoes a change and becomes organized and turns into the corpus luteum or yellow body.
In the midst of all this activity and hormonal messaging throughout all the female reproductive organs, an interesting change is happening on the wall of the uterus. After the conception occurs, a signal of some sort is sent to the uterus to begin to produce a product we call uterine milk which will nourish the egg before the placental tissue can nourish the new individual.
Think of the case of the cow who has been superovulated and may at this point have as many as 25 embryos in her uterus. Obviously that would kill the cow so these embryos need to be flushed from her. At this point they may be implanted in foster mothers or frozen to be implanted at a later time. They must be removed from the cow before they begin to nidate or establish placentas. When they have started to establish placentas and are flushed out of the cow at that time they will all be killed.
The knowledge we have learned in the last 15 years about the intricate mechanisms associated with early pregnancy have been a great benefit to the saving of lives in human medicine.
The statement, "knowledge is power" is certainly applicable in the business of getting multiple offspring from a super cow. The things we know from this research and new business can be useful in helping us get better conception and care for our cows in the average dairy.
When the new individual is beginning to establish a placenta there is another change taking place in the ovary. The follicle that has turned into a corpus rubrum will undergo a change and the structure will become organized and will change color form a red color to a yellow color. This new structure, the corpus luteum prevents new heat periods until after the calf is born. This is because the yellow body will now begin to act as an endocrine gland and produce lutenizing hormone.
Pregnancy stops the ovarian cycle and the yellow body will prevent the cow from coming into heat.
This set of spectacular changes in the cow’s metabolism helps me realize why we get such great benefit from thinking about cow comfort in the heavy springer or the cow close to parturition..
A smooth and normal calving, with no retained placenta and easy entry into the new lactation sets the stage for normal heat cycles. The normal heat cycle is a flushing action helps get the uterus in condition to receive another calf when it happens after about 60 days from the birth.
Good animal husbandry demands that we approach all aspects of management with a view that plans for changes in animal behavior at least 3 to 6 months ahead.
Good management throughout the critical dry period is one of the most important set of maneuvers. The housing, ration balancing, exercise, and cow comfort all become factors that improve our chances of an excellent lactation. The cow can only achieve her top potential if we give her the benefit of every opportunity.
This is certainly the time we need to be sure that the forage we are using is tested so we know what level of protein is in the pregnant cow’s diet. When she begins to milk we increase her protein but not before.
If we know what levels of minerals are in the forges we use, we can wisely compound supplements.
The consultant will be the one who must provide the leadership, advice and encouragement to provide the moves at the right time. When we started to talk about the ovary and wind up this session talking about the dry cow I hope this shines a light on ways you can do a better job with your consulting and in turn make your clients more profits.
Our next issue will talk about the care of the cow at calving time and then later we need a session on good breeding techniques. Believe in yourself with all your might.
Doc Bob the cow doc.
This is the picture
All the stages of the ovarian cycle are on the same
ovary. Begin at the upper left and circle the
drawing in a clockwise fashion to get the proper sequence
