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Determining pregnancy in cattle has many benefits. You can get twice the meat then when the cow wasn't pregnant and a producer is able to know which cattle will be the keepers and which will need to be culled as soon as possible. All this because an open, unbred or non-pregnant cow is unable to produce returns in the form of a calf in exchange for the costs incurred and associated with keeping them on the farm , mainly in the form of feed, labour and upkeep on equipment and facilities, unlike a pregnant cow which can give birth to and raise a calf to weaning where it can be sold as either a food animal, or breeding stock; and by understanding the physical characteristics that shows how a cow or heifer could possibly be bred or pregnant, diagnoses of in determining the increased or decreased probability of pregnancy can be made without the often costly consultation by a veterinarian.
This article, then, is based on detecting pregnancy by determining whether a heifer or cow should be culled especially in a medium to large-sized cattle herd. "Open" (non-pregnant) cattle cost money to feed and care for because they are not carrying any potential--in the form of a calf--income to make any returns on the costs incurred with keeping them. Exceptions are if a producer has a special emotional bond with one or more heifers or cows as a pet , or if they just a small herd of only one to five animals. In these cases, most of the time second and third (or fourth and fifth and so on) chances can easily be given without much worry of any potential financial burden associated with keeping a female bovine that may not calve on time, if at all. (However, even if one cow comes up open for a farmer that has a tiny herd to rely on for income because [s]he is not even considered financially well off, such exceptions do not and cannot exist for that producer.) Dairy operations also are relatively more lenient on keeping poor-conceiving heifers and cows than beef operations because of the normally low conception rates associated with having a dairy herd. Usually cows and heifers have about two to three chances at successful conception-to-pregnancy before they too may risk being culled from the herd.
This article contains two sections. The first helps you understand the physical characteristics cows and heifers show when they are pregnant. The second explains the various methods available to perform manual checks to confirm if one or more cattle are pregnant.
Note: With the second section, the general descriptions of the mentioned commercially available tests are only offered in this article. If you have any further and/or more in-depth questions about any test or method mentioned here, please make sure that you first talk with your bovine or large-animal veterinarian about your options before making a final decision based on what you have read here.
Steps
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Observe the behaviour of cows and heifers. The behaviour of cows and heifers after they have conceived is one of the best non-invasive means of determining pregnancy in cattle. Simply put, pregnant cattle will not (or should not) come into estrus or "heat" for the entire duration of the 9.34-month (285 day) gestation period.
- The estrous cycle in cattle occurs, on average, every 21 days. If a cow or heifer has aborted or absorbed the embryo, she will soon come into estrus and continue regular cycling until she conceives again. Embryo absorption, early embryonic death, or fetal abortion can happen at any time during a cow's pregnancy and can be caused by anything, from extreme stress to a disease a cow acquired before or during her gestation. How to Tell when a Cow or Heifer Is in Estrus
fully explains the estrus activity shown by such cows. Thus if a cow unexpectedly starts to behave like she's in estrus during her pregnancy, particularly if she is several months along, chances are she aborted the fetus and is beginning to get back into regular cycling. Absorption of the embryo occurs within the first two to three weeks after breeding.
- False heats may be experienced by females during the first few weeks post-conception, and though they are rare, they can be easily misdiagnosed by the producer as an actual heat period. Such suspicions can only be confirmed or rejected if follow-up with a proper test (see below) is completed at least a month and a half after breeding.
- Observing behaviour also applies to cows' and heifers' male counterparts. Bulls will not show any interest to any cows that maintain pregnancy. They only show interest if a cow comes into heat and when she's ready to calve. This is because, during both periods, estrogen levels increase every time a cow is one to three days away from coming into heat, and when it's time for the calf to be born. (At birth, the fetus sends stress signals to the dam's nervous system which starts a cascade of hormonal events, such which largely includes progesterone levels decreasing and estrogen increasing.) A bull can sense this through performing what's known as the "flehmen response" where he "tests," via drinking, the urine of a female to check for pheromone activity. The bull tilts his head up high and back as far as he can to allow the fluid to drain into a sensory organ in his nasal passage called the Jacobson organ. Curling his upper lip up allows the urine to flow into this organ as deep as possible to better test for pheromone activity. High levels of progesterone in the cow's system, which would be present in the urine, will tell a bull that she is not available for his services. Besides getting a little bit of a head-butt to the ribs from the cow herself in displaying her disappointment in his flirtatious advances, it also tells him that it's probably best to find another female that would potentially be in more need of his amorous intentions.
- The estrous cycle in cattle occurs, on average, every 21 days. If a cow or heifer has aborted or absorbed the embryo, she will soon come into estrus and continue regular cycling until she conceives again. Embryo absorption, early embryonic death, or fetal abortion can happen at any time during a cow's pregnancy and can be caused by anything, from extreme stress to a disease a cow acquired before or during her gestation. How to Tell when a Cow or Heifer Is in Estrus
fully explains the estrus activity shown by such cows. Thus if a cow unexpectedly starts to behave like she's in estrus during her pregnancy, particularly if she is several months along, chances are she aborted the fetus and is beginning to get back into regular cycling. Absorption of the embryo occurs within the first two to three weeks after breeding.
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Pay attention to physical changes of cows and heifers. Changes to size and shape of body parts can be noticed in both cows and heifers, primarily with the abdomen (or "barrel"), and the udder.
- Unlike humans, cows do not typically show their "baby bump" until they're about half-way through gestation. Only after then do you begin to see how the cow or heifer is getting larger in the abdominal region. By mid- to late-third trimester when a cow or heifer is considered "heavily pregnant," she synonymously looks quite like a large, round barrel with a head, a tail, and four legs.
- In heifers, the udder begins to fill out more and reach maturity. Heifers that are "virgin" or not yet conceived will have an under-developed udder that is only resembled by the presence of four small teats tucked up under their belly between their hind legs. As they progress into their gestation period, the udder gradually becomes more prominent until she gives birth. A heifer will not have as defined an udder as a mature cow will (nor even a mature dairy cow), but it will be as big an udder as a heifer will need to feed her newborn calf.
- Mature cows already have a fully developed udder so there will be no change in the physical structure of the mammary organ as in the bred heifers. Cows also will not begin to fill up with milk until they are showing signs that calving is imminent. However, a cow that is pregnant and still has a calf to suckle will continue to produce milk until that calf is weaned. With dairy cows, when they successfully conceive and become pregnant they will continue to lactate until they are "dried off" or, essentially, forced to stop producing milk by not taking any more milk from them for the next two months until they calve.
- The belief that a cow must become pregnant in order to produce milk is purely myth . Cows only become pregnant to produce a calf, and only produce milk with the intent to feed that calf. That a cow becomes pregnant and is producing milk is purely coincidental due to the overlap of the length of lactation period (6 to 8 months for beef cattle , 10 months for dairy) and the gestation period (approximately 9.5 months in all female bovines).
- Mature cows already have a fully developed udder so there will be no change in the physical structure of the mammary organ as in the bred heifers. Cows also will not begin to fill up with milk until they are showing signs that calving is imminent. However, a cow that is pregnant and still has a calf to suckle will continue to produce milk until that calf is weaned. With dairy cows, when they successfully conceive and become pregnant they will continue to lactate until they are "dried off" or, essentially, forced to stop producing milk by not taking any more milk from them for the next two months until they calve.
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Fetal responsiveness to physical or observational pregnancy testing. The below pregnancy tests, if they can be called that, are inaccurate as best and should only performed on females that are in late pregnancy, i.e., from months 5 to 9. They should not be counted as reliable tests for determining pregnancy especially with inability to perform such tests at early gestation, and because results confirming pregnancy are less of a guarantee than other more reliable methods mentioned in the next section. However, they can be done purely out of curiosity and interest in seeing the physical responses of the fetus when one or more of such tests are performed.
- Abdominal ballottement (bumping).
This can only be used in females that are five to seven months into their pregnancy. To feel for the fetus, use the following technique:
- 1. Place your hand or fist against the lower right flank region of the abdomen, then
- 2. Make a short, vigorous inward-upward thrust and keep your hand in place. You will feel the hard fetus come back against your hand. The amniotic fluid will allow the fetus to recede against your bump but fall back in place almost immediately.
- The size of the fetus determines the effectiveness of this technique, which means that it can only be done when the cow is over halfway through her gestation period and not one and a half to three months (45 to 90 days) post-breeding. Because of that it's not an effective technique for early-detection pregnancy nor for large herds that need to be "preg-checked" in a short matter of time. It's best for small herds and for producers that would want to feel for a fetal calf that is only a few months away from birthing for curiosity's sake.
- Formation of uterine seal or mucosal plug in the cervix. Typically a pregnant cow will form a seal in the cervix to protect the fetus from foreign bodies (bacteria and soil, mostly) entering the uterus. The plug can only be seen with a speculum and light that is inserted in the vaginal canal. The mucosal plug can also be felt via rectal palpation. This method is not always reliable because the plug is not always readily observed because it may form deeper in the cervix than throughout the entire organ.
- Fetal heart beat. This is best performed after the sixth month of gestation, though detection can be unreliable as it is not as certain as with other classes or species of farm animals as in cows. Use of a stethoscope is recommended even though pressing an ear against the right lower abdominal region and listening will also yield good results. The fetal heart beat can be distinguished from the dam with its greater frequency and higher and lighter pitch. This method is not recommended if the cow is not cooperative nor accustomed to human touch. Do this only on cows or heifers that are accustomed to your touch and you trust each other enough to be able to do this without a stethoscope and without getting kicked. Like with bumping cows, this can only be done on those cows in the last two-thirds of their pregnancy, and is not ideal if early detection of pregnancy takes higher precedence than mere curiosity and a willingness to wait for a long period of time before being able to determine pregnancy of a cow or heifer.
- Fetal movement. Patience is much needed to observe voluntary fetal movements on the right side of the cow through the abdominal wall because you just need to wait see such movements. This can only be done when the cow or heifer is in the latter half of pregnancy, and is certainly not ideal for either early detection or if you wish to have results without waiting for either the right time to detect nor to see any results.
- Abdominal ballottement (bumping).
This can only be used in females that are five to seven months into their pregnancy. To feel for the fetus, use the following technique:
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Perform an accurate scientific pregnancy diagnosis to confirm observations. Four primary pregnancy tests are available for producers to choose from in order of cost to use: Rectal palpation, PAG ELISA with blood and milk samples, and ultrasound. Such pregnancy tests can be utilized based on the type of cattle (dairy or beef, and even purebred versus commercial), and level of record keeping done. Some tests are better to use than others based on expense and ease of use, and how well breeding records are kept. For example, PAG ELISA via either milk or blood testing is not recommended if inadequate and imprecise records are habitually kept for either beef or dairy operations. The second section below describes the methods to use, what is involved with carrying out such methods and whether it may be right for your herd or not.
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Catch and restrain the cow or heifer. Pregnancy testing often cannot be done while an animal is loose for several reasons, including the cow or heifer is not accustomed to being in close proximity to humans, and safety to both the human handler and the animal in question. A squeeze chute is ideal, though a 6' by 3' box with a head-gate is also preferable. A "medina" gate or a gate that confines a cow so that she has no choice but to back out to escape is also good for a small number of animals that need checking.
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Choose your method of pregnancy detection. There are several methods available to check pregnancy, each with their strengths and weaknesses.
- Rectal palpation.
More commonly referred to as "preg-checking." Please see the article How to Perform Rectal Palpation in Cows and Heifers
for more comprehensive information.
- This is the most popular and common method used by large animal veterinarians, artificial insemination technicians and cattlemen for both beef and dairy herds, primarily because of its timeliness--it guarantees early diagnosis at 45 to 90 days post-breeding, and it allows results to be determined within seconds compared with other methods mentioned here. An experienced technician or large-animal veterinarian can perform this method and determine pregnancy with 98 percent accuracy in about 5 to 10 seconds, however technicians with less experience typically take longer to make a diagnosis, and accuracy may be lower. It's also the cheapest form of pregnancy checking compared with the other main methods like milk pregnancy testing, blood testing, and ultrasound.
- Hazard of abortion is quite minimal especially when performed by experienced operators, however it is a risk with this form of pregnancy checking. Other risks associated are spread of disease from cow to cow particularly if shoulder-length gloves are not changed after preg-checking each female. If there are many females to check (well over 100 cattle, for example), that means a lot of dirty gloves to throw away. Thus, as far as risk of disease transfer is concerned, it's a risk to consider if you don't want to have to switch to a new glove after checking every cow.
- The operator applies this method to recognize any changes in uterine arteries and the tone, size, and location of the uterine horns through the rectal wall. Often only one of the uterine horns (out of only two) will be either more swollen or lowered deeper into the body cavity of the female, and the uterine arteries may be more distended with extra blood pumping to the newly formed placenta connecting the fetus to the dam.
- This is the most popular and common method used by large animal veterinarians, artificial insemination technicians and cattlemen for both beef and dairy herds, primarily because of its timeliness--it guarantees early diagnosis at 45 to 90 days post-breeding, and it allows results to be determined within seconds compared with other methods mentioned here. An experienced technician or large-animal veterinarian can perform this method and determine pregnancy with 98 percent accuracy in about 5 to 10 seconds, however technicians with less experience typically take longer to make a diagnosis, and accuracy may be lower. It's also the cheapest form of pregnancy checking compared with the other main methods like milk pregnancy testing, blood testing, and ultrasound.
- Blood test.
Blood tests are used to test for pregnancy-specific proteins found in the serum of blood. Pregnancy-associated glycoproteins (PAGs) are placenta-expressed inactive aspartic proteinases often referred to as pregnancy-recognition markers [1]
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Research source
. Unlike the hormone progesterone which is commonly known to be associated with pregnancy, PAGs are present only during pregnancy (and around 60 to 90 days after calving), thus are the best means to determine pregnancy status in cows. An ELISA (enzyme-linked immunosorbant assay) or RIA (radioimmunoassay) test singles out these proteinases and shows their concentration levels in both milk (see below) and blood samples. ELISA testing is more popular to use because results can be obtained faster than RIA, generally. You will not get the time frame of how far along in gestation a cow or heifer is, but you will get a yes-or-no answer on whether the female is pregnant or not, or if the female needs to be rechecked (another sample of blood is drawn from the animal in question and sent back to the lab).
- Ideal for both beef and dairy herds. Blood testing is gaining popularity over palpation per rectum because of less stress and trauma on cattle, significantly reduced disease risk, and more accurate diagnosis. Blood samples are also relatively easy to get, provided a veterinarian can show you how to properly take them so that you do not need to call out a vet every time. The lab you are planning on sending your blood samples too will supply you with the tubes, the box those tubes are in and the bubble wrap they are contained in. The companies that offer these tests include BioPRYN - Biotracking LLC (Moscow, ID), PAG-IDEXX Labs (Westbrook, ME), and DG29 - Genex, CRI (Shawano, WI).
- Timing is important. Cattle should not be blood tested until they are both 90 days after calving and around 30 to 50 days into gestation for optimum results.
- Blood samples can be taken from either the neck or the tail. The neck offers the large jugular vein, and the tail the coccygeal vein, which is a main vessel that runs underneath the tail. Basically a sample is taken by inserting a needle straight into the vein and drawing back on the plunger until you get around 2 to 5 mL of blood. A vacuum-sealed tube with a rubber top is used to collect the blood from the syringe, simply by poking the needle into the rubber top and allowing the sample to vacate into the tube. The vacuum in the tube should be enough that you don't need to apply any pressure to the syringe to put the blood into the tube. When all samples are taken enough to fill the box supplied by the lab where you are to send them, wrap them in bubble wrap and mail your samples the very day you've taken the samples. If you cannot mail them immediately, like on a Friday or on the weekend, put them on ice or in the refrigerator until you can mail them Monday morning.
- Samples must be properly labelled and accurate and precise records must also be kept in order to avoid any potential and inadvertent culling of cows that may actually be pregnant. Tag numbers (also other identification names or numbers) can be used, as long as all cows and heifers are re-tagged if they have missing tags. Remember to label the sample with which farm, which sample, and which cow it came from.
- The ELISA test is generally performed as follows: PAGs are detected with anti-PAG antibody-coated plates, a detector substrate, a conjugate, and a dye with wash and incubation periods in between before results are analyzed [2]
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. The dye allows the technician to judge the amount of PAG in the blood sample, since the deeper coloured the sample, the higher the concentration of PAG. Accuracy of such results are high, most samples have an accuracy of at least 90 to 99%. Sensitivity can much higher, from 97 to 100%.
- Results from blood tests generally won't be sent back to the producer immediately. At the earliest, results can be expected two to three business days after the samples are sent in.
- Milk Pregnancy Test.
As with the blood test above, milk pregnancy test uses a PAG ELISA (Pregnancy Associated Glycoproteins Enzyme-Linked Immunosorbent Assay) test to affirm pregnancy in cows and heifers.
- Recommended for herds with accurate breeding and artificial insemination (AI)
records. I's a test primarily for dairy herds, however research has found equally accurate results can be had with beef breeding herds as well. Samples must be sent to a laboratory that will do this test for you. Cost per sample depends on where you are sending samples to, and through whom (i.e., for dairy producers in the US, through DHIA [Dairy Herd Improvement Association
], or for Western Canadian dairy producers, Can-West DHI [Western Canadian Dairy Herd Improvement
]). You can expect to pay anywhere from $3.00 to $4.50 per sample. The predominant company that can commercially perform this test for you is IDEXX Laboratories (via The IDEXX Laboratory Milk Pregnancy Test). The test itself and how it's done is exactly how PAGs in blood are tested, as described above.
- Results can be obtained within 3.5 hours from the start of testing, and sent to the producer just as soon via email. In the mail, though, you should expect to get lab results back in two to three business days. Testing can be done from 28 days post-breeding until cows are dried off, even though sensitivity and specificity averages increase when cows are around 60 days into gestation. For best optimum results and to reduce chances of false positives (or even false negatives), samples should be obtained when cows are at least 90 days post-calving.
- Recommended for herds with accurate breeding and artificial insemination (AI)
records. I's a test primarily for dairy herds, however research has found equally accurate results can be had with beef breeding herds as well. Samples must be sent to a laboratory that will do this test for you. Cost per sample depends on where you are sending samples to, and through whom (i.e., for dairy producers in the US, through DHIA [Dairy Herd Improvement Association
], or for Western Canadian dairy producers, Can-West DHI [Western Canadian Dairy Herd Improvement
]). You can expect to pay anywhere from $3.00 to $4.50 per sample. The predominant company that can commercially perform this test for you is IDEXX Laboratories (via The IDEXX Laboratory Milk Pregnancy Test). The test itself and how it's done is exactly how PAGs in blood are tested, as described above.
- Transrectal Ultrasonography.
Also known as ultrasound, this method not only determines status of pregnancy, but fetal age as well. The method utilizes a computerized unit that allows the operator to literally see what's inside the cow. There are two major parts to this ultrasound unit--the console which is the screen, and the transducer, or the probe that is inserted in the rectum of the cow. The electrically-powered console is connected to the probe via a cord so that the row of crystals in the probe can emit ultrasonic sound waves (the electricity actually causes them to change shape slightly allowing such sound waves to occur), which focuses on the tissues focused beneath the probe. The sound waves bouncing off the tissues back to the probe provides a visual image that can be seen on the console screen. The density of the tissues varies with bone, muscle, tendons, and fluids inside the body. The more dense the tissue, the more quickly sound waves return to the probe and the brighter they appear on the screen. Bone shows up bright white, whereas fluids like urine, follicles, amniotic fluid, blood vessels, etc., show up black. Because of the differences in tissue densities, the probe allows the operator to visually identify different structures, muscles and parts of the fetus.
- The optimal age to perform ultrasound is 26 days post-breeding in heifers and 28-days post-breeding in cows, however skilled operators can identify pregnancies with this method once the fetal heartbeat starts, which is around 21 to 22 days post-breeding.
- Ultrasound can detect fetal heartbeat and movement, which is a way to determine if the fetus is alive. Live fetuses indicate the cow or heifer is pregnant and is very likely to stay pregnant throughout the term. Dead fetuses mean that the cow or heifer will need to be rebred soon, and given a hormonal shot like Estrumate® or Lutalyse® may need to be given to get the female to abort so that she can be rebred soon. This is especially true with dairy herds.
- Fetal age can be determined by measuring, or estimating using what is seen on the screen, specific body parts like length of body (from the top of the head to the rump), and diameter of either the skull or the chest. Not all operators have the same preferred method for determining fetal age, some like to use more than one.
- Check with your veterinarian to see what age of fetus (and hence corresponding days post-breeding) they're comfortable with identifying. Note, though, that the measurements and age relationship are the most accurate in early pregnancy, and using that means that predictions of the anticipated calving date will also be more accurate.
- However, the exact time a fetus will be ready for birthing is highly variable among individuals, with frame size, fatness and other factors affecting when and if it will happen.
- With fetal age also comes the possibility of sexing fetuses. Fetal sexing techniques are highly precise, yet they depend on fetal age. Best times to sex a fetus is from day 60 to 65 to when it is too large or drops over the pelvic rim.
- A single scheduled ultrasound date for an entire cow herd to determine fetal sex would be very difficult because of variability in age of the fetus, even if the breeding season of said cow herd was confined to 60 days. It possibly would be best to fetal sex the entire herd when cows are at least 90 to 120 days post-breeding.
- Check with your veterinarian to see what age of fetus (and hence corresponding days post-breeding) they're comfortable with identifying. Note, though, that the measurements and age relationship are the most accurate in early pregnancy, and using that means that predictions of the anticipated calving date will also be more accurate.
- Historically transrectal ultrasound involved the technician to gain access to feel the reproductive tract of cattle via the rectum, very similar to rectal palpation described above. Recently several types of rigid probes and probe extenders have been developed to avoid risk of injury to technicians that have had to repeatedly place their arms inside of cows that have the potential to be quite uncooperative while being preg-checked. The increased safety is prevalent with optional use of a probe attached to a rigid wand, but some of the sensitivity and mobility required to perform all diagnostic techniques accurately is also lost.
- Ultrasound is expensive and requires hiring a technician or veterinarian to perform this type of pregnancy diagnosis.
- The optimal age to perform ultrasound is 26 days post-breeding in heifers and 28-days post-breeding in cows, however skilled operators can identify pregnancies with this method once the fetal heartbeat starts, which is around 21 to 22 days post-breeding.
- Rectal palpation.
More commonly referred to as "preg-checking." Please see the article How to Perform Rectal Palpation in Cows and Heifers
for more comprehensive information.
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Record the results. Records are important to keep so that you know not only which females don't need to be culled, but also how far along they are, especially if you have left preg-checking to less than 5 months post-conception, or need to confirm which females are bred (pregnant) and which are not.
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Release the cow/heifer. If all other things that needed to be done have been done--such as vaccinations, re-tagging, and deworming--the animal can be released back into the herd.
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Repeat with other cows and heifers as necessary. Ensure what you do with one female you try to do with all of your herd, and in a short period of time. The shorter the time between animals you have the sooner you can make the necessary decisions that need to be made. In other words, if you have to blood-test or preg-check 100 or 200 cows, make sure you do it in one day, not over an entire month. The key thing to remember is to never be in a rush to get things done: Quality takes far more precedence over quantity!
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Community Q&A
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QuestionWill a heifer start producing milk if a calf starts nursing?Community AnswerYes, a heifer other than the mother can start producing milk if nursed upon by another's calf.
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QuestionCan a heifer have an udder showing with their first pregnancy?Community AnswerYes. It's normal for a heifer to start showing a full udder when they're around four months away from calving. Some heifers don't show any udder until after they have calved, and that is normal too. Unlike cows, heifers are unpredictable with udder development and signs that they're ready to calve.
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QuestionWhat is the difference in an ox or oxen and a cow or heifer?KarinTop AnswererAn ox is a bovine that is used for work. Most commonly they are castrated male cattle, but they can be cows, heifers, steers, or even bulls. Cows are mature female bovines that have had a calf; a heifer is a young female bovine that has not yet had a calf.
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Tips
- No matter the method, records must be kept up to date and as accurate as possible to make the most out of any pregnancy checking method chosen. The more precise your records are, the better you know when cows will calve and how many remain pregnant to the start of calving season.Thanks
- Check all of your heifers and cows, no matter how certain you are that a particular female is pregnant or not. All cows and heifers need to be checked in one or two days, depending on the size of the herd and the method used. The larger the herd, the longer the time will needed to preg-check all females.Thanks
- Know your limitations and the limitations of each method of each pregnancy exam. Take on a method that you are confident will give you the results you want while keeping in mind the costs (financially and economically speaking) and availability of such a method. Don't decide on a method that you'll regret later one because of poor record keeping, missing ear tags, high cost, or risk of disease or injury to you or the operator.Thanks
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Warnings
- If bulls are with the cow herd on a continuous basis or are being pulled the same day as the pregnancy exam, you have no way of determining the true pregnancy status of all females. Cows that become pregnant early in the breeding season will be easily identified in these instances, whereas cows that are open may have been bred only recently. These newly-bred cows may have an embryo or fetus that is simply too young to feel with rectal palpation, to visualize with ultrasound, or is not producing sufficient levels of PAGs to be detected in the blood or milk.Thanks
- Risks are associated with any method used, and these risks vary from misdiagnosis to disease transfer. All of the methods mentioned above have the potential to carry these risks. Examples are if test tubes are not labelled properly (blood and milk pregnancy PAG ELISA tests), and if new needles or new gloves or sleeves are not used for every animal (blood test and rectal palpation).
- PAG ELISA tests can reveal false positives or false negatives if tests are taken at the wrong time in a cow or heifer's pregnancy state. False positives (tests revealing that a cow is pregnant when she is in fact open) can occur if a sample is taken when a cow is less than 90 days post-calving, no matter if she has been re-bred or is still open. PAGs stay in a cow's system for 6 to 12 weeks (~45 to 90 days) after she has calved, and return to the system 15 to 20 days post-breeding. Hence, false negatives (tests revealing that a cow is open when she is in fact bred or pregnant) come about when a cow has passed the 90-day post-calving mark, but has been bred less than 28 to 32 days ago.
- Mislabelling can result in certain females being kept back that end up being open, or females being culled that are in fact pregnant. Mislabelling can result if identification numbers of females are similar, test tubes are not labelled sequentially (and how the sequences identify with which cow [via identification number[s] and/or name or letter[s]] the numbered sample came from), labels are not legible, or ear or brisket tags have fallen off prior to or after testing (and before tests, like blood, have come back) and guesses have to be made on what identification name/number[s]/letter[s] a cow is. The latter is a significant issue if herds are over 100 head and the producer doesn't know each cow or heifer individually with features other than what they read on the ear tag, or can't tell the difference because they are all one breed (such as with the Angus breed).
- Rectal palpation can be rife with risks. Injury to the operator, disease transfer, abortion, and misdiagnosis due to inexperience of the technician are primary associated risks.
- Risk of injury to the technician not only comes from the potential of an unruly animal not standing still while being palpated, but wear on the bones, muscles and ligaments of the tech's palpating arm can cause pain and tissue damage as well as fatigue from having to palpate a lot of cows in one day (for example, if a technician or veterinarian had to rectally palpate 400 cows in one day, that means a very tired arm indeed.) The cows themselves are unpredictable in their reactions to having a human stick their arm in their anus, and could react violently causing a dislocated shoulder or broken arm to that human.
- Disease transfer is a significant risk of the operator isn't disposing of used gloves after checking every cow or heifer. Disease transfer risk is more significant if one or more new heifers or cows have been introduced into the existing breeding herd and have not been tested for sexually transmitted diseases like BVD (Bovine Viral Diarrhea), trichomoniasis, anaplasmosis, and others, prior to being preg-checked along with the rest of the herd. Those untested cows could have BVD, for instance, and preg-checking without switching new gloves every time could result in the spreading of this disease.
- Abortions can occur in females that have been preg-checked. Depending on the technician, the risk of abortion in a herd may be associated with how the cows were treated before and during the palpation process. If palpation was very stressful and/or painful for the female, she may abort (or experience early embryonic death if she's less than 45 days pregnant) due to hormone production, including cortisol, which in turn may cause her to go into premature labour. Heifers are more prone to abortions with preg-checking than cows are, especially with rougher handling.
- Misdiagnosis by an inexperienced technician or veterinarian can result in cows that may actually be pregnant be put on the cull list, or cows that are not pregnant be confirmed as so and kept back. This can cost a producer, because these mistakes can mean cows that are open are "allowed" to be free-loaders, in a manner of speaking, or cows that have potential return are sent to the auction mart as "open" cows.
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References
- ↑ http://www.wdmc.org/2015/Fricke.pdf
- ↑ http://www.canwestdhi.com/pdf_files/IDEXX%20milk%20pregnancy%20test%20validation%20summary%20poster.pdf
- Preg Checking via Blood Test is Gaining Popularity - CattleToday.com
- Pregnancy Checking Tips by Heather Smith Thomas - BEEF Magazine
- Milk vs. Blood - Which is Best for PAG Pregnancy Prediction? Fricke et. al. University of Wisconsin-Madison
- Pregnancy Analysis: Milk ELISA Testing - Lancaster DHIA
- IDEXX Milk Pregnancy Test—a New Tool for Pregnancy Diagnosis in Cattle ]
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