11.01.2014

Pregnancy period of cow

Before a cow can produce milk she has to have a calf and on most farms these will be born in the spring. The dairy cows are brought into the milking parlour twice a day to be milked, usually very early in the morning and again in the afternoon. When the weather gets cold and wet in late autumn most farmers bring their cows into barns. The ability of a cow to successfully mate, conceive, give birth to and raise a healthy calf each year is essential to economical beef production. The body of the uterus of the cow is short and poorly developed, while the uterine horns are relatively long and well developed. Figure 2The ovarian changes during a typical 21-deay estrous cycle in which pregnancy does not occur. Any condition that prolongs the period of time that blood levels of progesterone remain high will have the same effect as pregnancy in stopping the regular 21-day cycle.
The reproductive cycle of the cow consists of a series of events that occur in a definite order over a period of days. Figures 2 and 3 show the ovarian changes and sequence of events in a typical 21-day cycle in which pregnancy does not occur. Days 0-1The cow is in for estrus (standing heat) on Day 0 for an average of 18 hours (range 12 to 24 hours). The discussion of events occurring during the previous cycle was based on a full cycle in which pregnancy does not occur. NB: The heat period lasts for about 36 hours starting when a cow will let another mount as per drawing below.
For more intensive management, cows must be identified by an ear tag, number brand or a neck chain. Essentially, successful heat detection begins with understanding one simple fact: there is only one sure sign of heat - a cow stands while other animals mount her.
Weather changes and temperature extremes can cause cows to exhibit estrus differently (or less noticeably). The average time a female is in standing heat is about 12 to 18 hours; cows usually ovulate (release the egg for fertilization) 25 to 30 hours after first standing. Traditionally, cows and heifers are inseminated about 12 hours after they are first observed standing. When a cow is in heat, she's likely to have mud on her rump and sides, as a result of the cows that have been riding her. A cow calendar as the above (sourced from CAIS Kenya - Central Artificial Insemination Station) is a very useful tool in estimating calving dates of cows. In summary, the reproductive tract of a cow is composed of the vulva, vestibule, vagina, cervix, uterus and ovaries. AI is not successful every time, so it is common to have to repeat the procedure at least once or twice before the cow becomes pregnant. The development of the foetus for the first 3 months of pregnancy is a slow process and no appreciable increase in the food requirement is needed.
Good feeding during pregnancy produces greater development of udder tissue and ensures a high milk i potential.


All does should, however, be exposed to a rising level of nutrition, a process referred to as flushing in preparation for pregnancy.
Imported semen is mainly used by cattle farmers who have pure bred cows and keep them for maximum milk yields or breeding of high quality stock for sale.
6.With the hand in the rectum, the inseminator may notice colon constrictions or "rings" attempting to force the left arm from the cow. 7.Because the reproductive tract is freely movable, cows that have strong rectal and abdominal contractions in response to being palpated may actually push their reproductive tract back into the pelvic cavity.
9.In most cows, the cervix will be located on the floor of the pelvic cavity near the anterior (front) end of the pelvis. This is because the grass in winter is not very nourishing and also cows don’t like very wet muddy conditions.
In the cow, the semen is deposited in the vagina near the cervix during natural mating with the bull. The dynamic development and regression of the corpus luteum and follicles are a continual process in the normal cycling cow until she becomes pregnant.
Occasionally the CL does not regress normally (persistent CL) even though the animal does not become pregnant. Heat without ovulation (anovulatory heat) will not result in pregnancy even though the female is bred. High levels of progesterone and low levels of estrogen prevent a cow from coming into heat. This cyclic process continues every 20 to 21 days in a normal-cycling cow, but changes if conception occurs. In the cow, this cycle averages 21 days in length (range is 17 to 24 days) and is concerned with preparing the reproductive system for estrus or heat (the period of sexual receptivity) and ovulation (the release of the egg). In AI, frozen semen from a sire (buck or bull) is defrosted and inserted into the cervix of a dam (doe or cow) in heat. Estrous is defined as the period of time when the female is receptive to the male and will stand for mating accurate heat detection is the key to a successful artificial insemination program.
Because mounting activity increases when more than one cow is in heat, it is not a bad idea to keep a cow in the herd that is standing until it's time for her to be inseminated. The cow calendar consist of two separate but connected discs, the lower disc displaying the days of the year and the upper disc the interval between service date, repeat heat cycles, and calving date. Towards the end of pregnancy, individual does can be confined to pens where the kids are born. Estrous is defined as the period of time when the female is receptive to the male and will stand for mating.
In older cows, the cervix may rest slightly over the pelvic bone and down into the abdominal cavity. The gestation period (the time that they are pregnant) is the same for cows as for humans at nine months and the cows will continue to be milked during the first six months. Female reproductive tracts of various farm animals are similar to the cow, but differ primarily in the shape of the uterus and cervix. During pregnancy, the cervix is filled with a thick mucus secretion known as the cervical plug, which protects the uterus from infections entering from the vagina.


The CL is fully functional from Day 5 to Day 15 of the cycle and then begins to regress if the female does not become pregnant.
In a pregnant female, CL regression does not occur and the cyclic activity stops until after calving.
Ovulation without behavioral estrus (silent heat) is not uncommon in cows, especially the first few weeks after calving. The cow is in a group that exhibits heat more than one time per year and is called polyestrus.
Progesterone is necessary for preparing the uterus to receive the fertilized egg and maintains the proper uterine environment for continuation of pregnancy.
Following pregnancy and a period of anestrus (no estrus cycles) the estrous cycle once again continues. During this period, the ovaries are relatively inactive except for the functional corpus luteum. If you can't catch the cow in heat, it doesn't matter how good the semen is, how careful your thawing procedure, or how skillful your insemination technique. Cows show more signs of heat when other activity is minimal - not at milking or feeding time. Nervousness, walking the fence, bawling, spooking, butting other cows and standing while others are lying down are other possible signs.
If you failed to observe heat and see a bloody discharge, write down the cow's number and the date in your notebook so you can pay special attention to her in about 15 days.
It also shows when a cow should be dried and steamed up (stop milking and start feeding to prepare for normal calving and highest possible milk production).
Thus the quantity and quality of the feed given over this period should be sufficient to meet the requirements of the foetus as well as those of the dam in preparation for parturition. Following calving, a cow generally remains anestrous (does not cycle) for an average of 60 days before estrous cycles are once again established. Even though cows will cycle at any time during the year, recent research has shown that day length may have an effect on cow fertility.
A gentle pat on the animal's rump or a soft spoken word as the inseminator approaches will help to avoid startling or surprising the cow. The key to mastering this step of the insemination process is knowing how to hold and manipulate the cervix and concentrating on doing the work with the hand inside the cow, not the one holding the gun. The length of the postpartum anestrous period can be affected by nutrition, lactation, environmental stress and numerous other factors.
Progesterone has a quieting effect on the uterus so that there are no contractions which might disturb pregnancy. This is because the rumen or stomach of the cow lays on the left side of the abdominal cavity, displacing the reproductive tract slightly to the right.



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