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Publication #AN314

Understanding Pregnancy Diagnosis in Beef Cattle1

G. Cliff Lamb, Darren D. Henry, Nicolas DiLorenzo, Francine M. Ciriaco, Pedro L. P. Fontes, Vitor R. G. Mercadante, and Doug Mayo2

Overview

Generally, 55 to 70 percent of the input costs associated with a beef cattle operation are related to nutrition, primarily from stored feed. Culling non-pregnant, or open, cows is an essential management practice that reduces feed costs. Only cattle that will produce calves the subsequent year should be given feed resources. In order to cull effectively and reduce costs, however, producers must be able to diagnose pregnancy in their cattle quickly, economically, and accurately.

Surveys indicate that many producers still do not use pregnancy diagnosis methods after the breeding season. The National Animal Health Monitoring System (NAHMS) survey indicates that less than 20 percent of producers use a form of pregnancy diagnosis. These numbers are surprisingly low, considering the financial opportunity that the diagnosis of non-pregnant cows presents. Generally, herd pregnancy rates after a 60- to 120-day breeding season tend to range from 80 to 94 percent. Pregnancy diagnosis identifies the 6 to 20 percent of open cows in the herd so they can be culled after their calves are weaned, instead of waiting until the end of the subsequent calving season. Considering that the annual feed/forage costs associated with maintaining a mature cow can be as high as $400 to $500 per year, culling open cows can save as much as $200 per head, which can then be diverted to the purchase or development of replacement females, sire selection, increased nutritional management, and/or other management-related costs.

Pregnancy diagnosis can be performed simply at the time that producers work their cattle during their vaccination schedule or even at the time of weaning. There are three practical methods to diagnose pregnancy in beef cows: 1) rectal palpation, 2) transrectal ultrasonography, or 3) use of a blood sample that is submitted to a laboratory for analysis (labs return results within a few days).

Methods of Pregnancy Diagnosis

Palpation

Rectal palpation is an accurate form of pregnancy diagnosis that can be performed by a skilled technician after day 35 of pregnancy. Most veterinarians are proficient at pregnancy diagnosis through rectal palpation, which is a simple procedure that requires little time in the cattle-handling facility. However, rectal palpation does not provide any information about the viability of the embryo/fetus. Therefore, some animals with a nonviable embryo/fetus or an embryo/fetus in the process of degenerating might be diagnosed as pregnant. Costs of rectal palpation vary widely based on the number of females to be handled, the distance that a veterinarian must travel, or the time and facilities used. Generally, rectal palpation costs will range from $2.50 to $15.00 per female. A primary advantage of rectal palpation is that the result is chute-side, with an immediate diagnosis that allows a producer to make a decision while the cow is in the chute.

Ultrasound

Transrectal ultrasonography, more commonly called ultrasound, can be used to detect pregnancy as early as day 26 of gestation for heifers and day 28 of gestation for cows with a high degree of accuracy (Figure 1). For a skilled technician, the procedure is as fast as rectal palpation and may provide additional information in terms of embryo/fetus viability, incidence of twins, and potentially the sex of the fetus (usually performed around day 55 of gestation). Prior to the development of ultrasound for pregnancy diagnosis in cattle, technicians were unable to accurately determine the viability or number of embryos/fetuses. Since the heartbeat of a fetus can be detected at approximately 22 days of age, one can accurately assess whether or not the pregnancy is viable. Producers also should be aware that early embryonic loss is a natural occurrence in cattle and may be evident between the time of pregnancy diagnosis and calving, and that this is not the result of the actual pregnancy diagnosis procedure. For example, we have observed a 4.2 percent incidence of embryonic loss in beef heifers initially examined through ultrasound at day 30 of gestation and subsequently palpated rectally between day 60 and day 90 after insemination. In beef cows, embryonic loss ranges from 3 to 8 percent from 30 to 75 days of gestation, whereas in dairy cattle, pregnancy loss from 28 to 56 days after artificial insemination is 13.5 percent. Therefore, ultrasonography provides a tool to accurately differentiate between the failure of a female to conceive and the incidence of embryonic mortality, because a heartbeat is detectable at 22 days of gestation.

Figure 1. 

Ultrasound images of the bovine fetus at various stages of development.


[Click thumbnail to enlarge.]

Ultrasound also gives producers an opportunity to identify the sex of the fetus, which becomes distinguishable between day 55 and day 80 of gestation. Many cattle operations are developing strategies to use fetal sexing as either a marketing or purchasing tool. At approximately day 55 of gestation, male and female fetuses can be differentiated by the relative location of the genital tubercle and development of the genital swellings like the scrotum in male fetuses and the vulva in female fetuses. Ultrasound was used in an experiment conducted by the authors, in which the sex of 112 fetuses in Angus heifers was determined with 98.2 percent accuracy. For beef cattle producers, fetal sexing remains limited to purebred operations, especially in conjunction with an embryo transfer program. Determination of sex, especially after the successful transfer of embryos to recipients, allows marketing of male and female embryos before the pregnancy is carried to term. This strategy can be used effectively in dairy operations trying to produce bull calves of a particular mating for sale to bull studs. From a commercial standpoint, heifer development operations use fetal sexing as a marketing tool to provide potential buyers with females pregnant with fetuses of a specific sex. As more technicians become proficient at fetal sexing, commercial operations will use this technology to enhance the marketability and efficiency of their cattle operations. As with the costs of rectal palpation, ultrasound costs vary widely for many reasons, such as the number of females to be handled, the distance that a veterinarian must travel, or the time and facilities used. Generally, ultrasound costs will range from $4.00 to $25.00 per female. As with rectal palpation, ultrasound provides an immediate diagnosis that allows a producer to make a decision while the cow is in the chute.

Blood Test

Blood samples are now a suitable tool that can assist in the determination of pregnancy. There are at least two primary blood-sample pregnancy test kits (BioPRYN and PG29), both of which work effectively. Blood samples are taken and screened for pregnancy-associated glycoproteins (PAG). The contact information for both kit manufacturers is listed on the sample sheets.

Heifers and lactating cows can be tested 30 days or later after breeding. Lactating cows carry residual PAG from the previous pregnancy until 90 days after calving. To avoid receiving a false-positive test result, producers should sample blood 30 days or more after the conclusion of the breeding season and 90 days or more after calving. Thus, if a cow is bred 60 days after calving, it is appropriate to take the sample 30 days post-breeding, which is 90 days after calving.

The blood tests are more than 99 percent accurate if the result is negative or not pregnant, with less than 1 percent showing false-open (false-negative). The false-pregnant (false-positive) rate for the test is approximately 5 percent. High-producing dairy cows tend to show slightly higher false-positive rates of 7 to 8 percent, especially during periods of extremely hot weather. It is presumed that a portion of this variance is due to greater early embryonic death and not to the inaccuracy of the blood test.

The tests cost between $2.40 to $4.00 per cow from the laboratory that processes and conducts the test, plus the cost of a sample tube and needle. Shipping expenses also must be added if the tests are not processed locally. When the laboratory sends the results, both the PAG concentration and pregnancy diagnosis are included. A primary drawback of this method of pregnancy diagnosis is that results are not immediate. A producer must wait for 2 to 5 days for the results to be sent before a diagnosis is confirmed, depending on when the laboratory receives the samples.

Producers interested in using a blood test can find additional information on the following websites:

http://www.biotracking.com/?q=beef (BioPRYN)

http://genex.crinet.com/page3429/DG29BloodPregnancyTest (DG29™)

Figure 2. 

Picture depicting the correct location for collection of blood samples from the tail vein.


[Click thumbnail to enlarge.]

Reproductive Management Days

An in-service training event was held at the UF/IFAS North Florida Research and Education Center in Marianna, FL, where 22 Extension agents and producers from multiple counties participated in pregnancy diagnosis of cattle using blood tests. From June until October 2014, hands-on demonstrations were performed at four producers’ locations. Extension agents from the University of Florida and Florida A&M University were essential in developing unique Reproductive Management Days (RMD) in their respective counties, which consisted of hands-on training to equip producers with the skills needed to sample and handle blood for pregnancy diagnosis. One hundred nine participants from 11 counties in northwest Florida and 1 county in Alabama attended the RMD.

A wide variety of beef producers attended the RMD from operations ranging from 0 head to more than 500 head of cattle. Of the attendees, 48 percent reported currently using a breeding season with an average length of 87 days. After the RMDs, 88 percent of surveyed participants reported that they felt comfortable collecting blood samples from cattle at the conclusion of each session. This shows a marked increase from the 27 percent who reported prior knowledge of blood sampling. Preceding the RMD, 73 percent of producers revealed that they did not utilize pregnancy diagnosis methods; of these, 72 percent claimed that they planned on diagnosing pregnancy after the RMD. The producers’ intent to diagnose pregnancy on their respective ranches indicates that the information provided by Extension was not only absorbed, but also valuable to the producers. Participants of RMD reported an expected average increase of $295 per cow when pregnancy diagnosis was performed.

To demonstrate the efficacy of pregnancy diagnosis via blood testing, the authors also used ultrasonography to determine pregnancy status. Throughout the course of 5 months, data was collected on 65 head of beef cows. The cattle evaluated had an overall pregnancy rate of 85 percent, which was determined by a skilled technician using ultrasonography. When evaluating the blood tests, the researchers determined that the ultrasonography data matched the blood data 100 percent. The findings suggest that blood tests (when used according to the described instructions) were equally accurate at determining whether a female was pregnant or not pregnant.

Figure 3. 

Blood pregnancy-associated glycoproteins (PAG) concentration from cattle at one ranch location signifying non-pregnant (open; white bars) and pregnant (black bars) females.


[Click thumbnail to enlarge.]

Summary

Cattle producers should consider pregnancy diagnosis for the cattle in their herds. This simple management practice will allow the producers to make critical management and economic decisions based on pregnancy status several months before calving. Precious feed resources can be reserved for cattle that will be productive in the year ahead. Replacement animals can be retained or purchased in advance to maintain the total production of the herd. Contact your local UF/IFAS Extension Livestock Agent if you have any questions related to pregnancy diagnosis for a beef cattle operation.

Footnotes

1.

This document is AN314, one of a series of the Animal Sciences Department, UF/IFAS Extension. Original publication date November 2014. Revised October 2015. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

G. Cliff Lamb, professor; Darren D. Henry, PhD candidate; Nicolas DiLorenzo, departmental associate; Francine M. Ciriaco; Pedro L. P. Fontes; Vitor R. G. Mercadante, PhD candidate, Department of Animal Sciences, North Florida Research and Education Center; and Doug Mayo, Extension agent III, UF/IFAS Extension Jackson County; UF/IFAS Extension, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.