It’s not just a matter of she is or isn’t pregnant.
The ritual of fall pregnancy checking can and should be much more than a simple yes or no. Beef producers, with their veterinarian at the end of the chute, get feedback on potential calving dates, body condition scores, eye lesions, feet and udder problems, health, behaviour and weaning success. The exchange makes individual culling decisions easier and more fertile.
Though relatively simple, collecting and keeping basic production information, the kind ultimately aligned with practical economics and marketing, shuttles producers toward the common goal of developing trouble-free cow herds. A key to getting there is sound management of herd reproduction and recognition it’s based on good habits and good habits don’t come remotely via a lab report.
Our industry doesn’t run as efficiently as it could. On average, about 25 per cent more cows and yearling replacements are kept every year than the number of calves entering feedlots. An important step in narrowing the gap is culling non-performers and culling the right cows — the open, dry and wild cows; the high-maintenance cow; those that wean poor calves; and cows with common problems like bad eyes, poor udders and lame.
According to USDA’s 2007-08 National Animal Health Monitoring System’s (NAHMS) Beef Study, producers were surveyed and the nine top reasons for culling females included:
- Age or bad teeth;
- Pregnancy status (open or aborted);
- Other reproductive problems;
- Economics (drought, herd reduction, market conditions);
- Producing poor calves;
- Physical unsoundness;
- Udder problem;
- Bad eyes.
Over 50 per cent of the time, reproductive issues were listed as the main reason for culling. Factors that make or break a brood cow’s contribution to profit include: ability to rebreed; weaning a live calf; pounds of calf weaned; conception early in the breeding season; and the ability to maintain body condition compared to herdmates. It’s generally agreed that cows that get pregnant and wean a calf every year may not wean the heaviest calves, but from a herd perspective, may wean more pounds of calf per acre. Making chute-side culling decisions, or adjustments to management practices like feeding through cold weather, or changes in vaccination programs are best answered when veterinarian and producer work together. “Do we keep or cull?” is a team decision that often happens once a year at “preg-checking” time.
Traditional methods of pregnancy diagnosis are presumptive based on non-return to estrus, abdominal enlargement, and onset of lactation. While non-invasive and requiring only basic knowledge, errors and lack of accuracy make presumption a poor choice and more expensive in the long term.
Great advances have been made in diagnosing pregnancy. The standard for many years was rectal palpation of the uterine contents and the ovaries. It remained the standard until ultrasonography of the reproductive tract became widespread. Rectal palpation is still a very important diagnostic method used in cattle. A positive diagnosis of pregnancy and stage of gestation can be made by identifying pregnancy-associated structures like the amniotic vesicle; fetal membranes; placentomes on the uterine wall; and the fetus itself. It can be done safely.
Technological advances brought the application of ultrasonography to diagnose pregnancy into the everyday realm of service to cattle producers and introduced portable ultrasound equipment for field use. Decreasing cost and increasing availability of high-quality equipment made possible earlier diagnosis of pregnancy, and the ability to determine fetal gender, viability, and most importantly, fetal age. Trans-rectal ultrasound is very safe. With a 5.0-MHz transducer applied trans-rectally, an amniotic vesicle (AV) can be detected at day 13 to 14 and an embryo by day 26 to 29. Under ideal circumstances, accuracy approaches 100 per cent by day 22. Typically, heifers may be diagnosed pregnant up to three days earlier than cows. In the hands of an experienced practitioner ultrasound is relatively quick and the stage of pregnancy easily determined.
Chemical assays include:
1. Progesterone Assay in blood and milk: Progesterone, a hormone required to maintain early pregnancy, can be detected in blood and milk 20 to 23 days after breeding. Progesterone testing accurately predicts non-pregnancy, but is only a fair test for diagnosing pregnancy.
2. BioPRYN measures the presence of pregnancy-specific protein B (PSPB), a protein produced by the placenta of a growing fetus and detected by an ELISA-based assay (Enzyme Linked Immunosorbent Assay). Pregnancy can be detected as early as 28 days. Blood samples are collected from the tail vein using red stopper vials, or by using the TEGO™ Blood Collection Kits, a blood spot absorption kit marketed and sold by TEGO. Labs routinely conducting BioPRYN assays are located in Saskatoon (PDS) and Lethbridge (BioChek).
3. DG29 test, another ELISA-based assay is used to detect one of the 20 or so placental proteins linked to pregnancy. The manufacturer recommends that DG29 be used from 29 days after breeding and 100 days, or more, after calving to avoid false positives resulting from the high amount of the placental protein at calving.
Advantages of utilizing blood tests for pregnancy diagnosis over palpation or ultrasonography are limited. Blood testing can be more economical than traditional testing in smaller operations with fewer cattle to be tested, especially in remote areas located long distances from a veterinarian. Blood tests for pregnancy can help maximize the efficiency of artificial breeding and estrus synchronization programs when a simple “yes or no” is required. Knowing whether conception occurred following breeding aids making decisions on estrus-induction for another cycle — a choice that should not be made without veterinary oversight. There are challenges with inexperienced people collecting blood samples, partially overcome by the TEGO Blood Collection Kits. Because several days lapse between collecting samples and receiving results, cattle often need to be handled more than once.