Determining Pregnancy Status in Your Beef Herd
She Looks Pregnant To Me: Determining Pregnancy Status in Your Beef Herd
Figure 1. An image from an ultrasound machine showing the early bovine pregnancy with the presence of a fetus in the center.
The eyes can be deceiving at times, especially when you’re hoping that high performing mother cow in your herd is pregnant. It is important to determine pregnancy status for a multitude of reasons, including to evaluate herd reproductive efficiency and bull fertility, estimate calving dates to assist with strategic management of calving groups, and to improve flexibility with marketing options of late calvers and non-pregnant females. Early detection of pregnancy status can be particularly useful to identify females that conceived in the first cycle of the breeding season, and to identify those that conceived via artificial insemination from those breed by the clean-up bulls. Early detection can assist with selecting future replacement heifers and bulls, along with identifying future options for marketing of calves. It can also be beneficial for detecting issues that occurred during the breeding season, such as individual bull fertility, poor estrus response, human error such as poor semen handling, synchronization protocol event timing, or insemination. Low pregnancy rates in one breeding group may indicate poor nutrition, or an individual bull fertility issue, while whole herd rates may be due to an issue with the current breeding program, poor nutritional status at pre-breeding and throughout the breeding season, ingestion of poisonous plants, or infectious disease. In years of drought and limited resources, early detection of pregnancy status and strict culling can assist with flexible marketing and prevents the use precious resources on overwintering open cows.
One misconception is that heat detection alone can be used to determine pregnancy status; however, some bred females can continue to express signs associated with estrus (such as riding herd mates) due to changes in hormonal changes that occur early in pregnancy or prior to calving heat. Therefore, more accurate pregnancy testing methods should be used to determine individual status.
Pregnancy status in beef cattle can be determined by several different methods including blood analysis, rectal palpation, and ultrasonography. Each method varies in cost and skill associated with accurately evaluating pregnancy status.
Blood collection can be a very convenient and cost-effective means of pregnancy testing. The blood is drawn using a needle and syringe, or a needle, needle hub, and blood tube from the coccygeal vein in the tail or from the jugular vein in the neck. Care should be taken to use a new needle for each female as cross contamination can occur and lead to inaccurate results. There are several options in terms of companies, cost, and means of blood analysis for pregnancy testing. Blood analysis will only be able to categorize a female as pregnant or open, and in the case of a recent abortion, the female may be deemed pregnant as the hormones of pregnancy and the fetus are still lingering.
Rectal palpation involves the veterinarian or skilled technician inserting a hand into the rectum and palpating through the rectal wall and locating the reproductive tract. Once the reproductive tract is located, then symmetry or asymmetry of the uterine horns, size of the tract, absence or presence of fetal fluid, fetal membranes and the fetus, or the presence of placentomes in later stage pregnancies, are used as indicators of pregnancy status. It takes a skilled palpator to accurately assess pregnancy status depending on the stage of gestation, and this takes numerous palpation events to become proficient. Untrained individuals should not attempt to perform pregnancy checking as they can cause unnecessary stress and damage on the female and could injure themselves. Producers should seek out pregnancy diagnostic services with their local veterinarian or skilled technician. Using a defined breeding season and scheduling the examination either 30 days after artificial insemination, or at least 30 days after the clean-up bulls have been removed will assist your palpator. Early bred (less than 30 days) can be questionable and may be deemed open when they are simply too early to call accurately. Determining pregnancy status can be achieved by a veterinarian or skilled technician at a high accuracy, they can estimate the stage of gestation starting at around one month post-breeding with the best accuracy occurring between 45 – 120 days post insemination and during the third trimester. As gestation progresses, the pregnant tract can drop into the body cavity of the female and make it increasingly difficult for the palpatory to reach, thus creating opportunity for error. In these times the palpator will use the presence or absence of fetal fluid and placentomes, and the inability to easily pick up the complete reproductive tract as an indication of pregnancy status.
The use of ultrasonography is another method of pregnancy testing and is very accurate to determine pregnancy status. Early pregnancy testing with an ultrasound can identify a pregnancy with high accuracy as early as 30 days post breeding. Additional information such as viability of the fetus, age of the fetus, sex of the fetus, and the presence of multiple fetuses can be determined with an ultrasound. Sex of the fetus can be determined with high accuracy between 55 – 90 days post breeding. Since the cost to purchase and maintain ultrasonography equipment is an expensive investment to the veterinarian, it is the most expensive method of pregnancy testing but is also the most accurate.
Blood analysis is typically more cost effective than ultrasound and more accurate than rectal palpation. The most strategic means of pregnancy testing your herd is to assess at early pregnancy, again at the end of the season, and when cattle are located where you can gather, such as weaning time. Abortion and resorption of the pregnancy can occur prior to calving season, so record keeping is imperative to determine the occurrence of pregnancy loss and to assist with determining the cause. Contact your county Extension agent or Carla Sanford (firstname.lastname@example.org) for more information about how you can determine pregnancy status in your herd.