by Terry Lidral in collaboration with John Gilliam, DVM, MS, DACVIM, DABVP, Oklahoma State University, College of Veterinary Medicine
BST: What are the health preparations that should be made for a cow or heifer prior to breeding?
Dr. Gilliam: Cows and heifers should have customized vaccine programs, parasite control programs, nutrition programs and a biosecurity plan. Herd health plans should be customized for each herd to account for management differences and variations in disease challenge. A bull fertility evaluation should be conducted prior to each breeding season to reduce the risk that bull fertility issues pose to herd reproductive efficiency.
Biosecurity is an important part of a healthy and successful breeding program. It consists of good sanitation, disease monitoring and prevention, proper introduction of new animals to avoid both health and adaptation issues, and the keeping of reliable records.
Supplements are not generally needed as long as cows/heifers are on an adequate nutritional program. Feeding a ration that supplies adequate energy and protein along with a balanced source of minerals is generally all that is required for optimum reproductive success.
BST: What are the percentages of pregnancy with live cover?
Dr. Gilliam: When both the cow and bull are healthy and fertile, pregnancy rate from a single breeding opportunity usually runs about 65% to70%. (Pregnancy rate is different than conception rate. Conception rate is generally thought to be higher, but some conceptions don’t result in a detectable pregnancy. We actually don’t have a way to truly measure conception rate.) Depending on the length of the breeding season, with natural service, herd pregnancy rates for healthy animals should be 90% to 95% . This includes repeat breedings for cows and heifers who did not become pregnant on the first pairing. Herd pregnancy rates below 85% to 90% could indicate a need for an investigation.
BST: What are the percentages of pregnancy with artificial insemination (AI)? What are the factors affecting pregnancy rates?
Dr. Gilliam: Pregnancy rates from artificial insemination (AI) depend on several factors. With appropriate estrus detection, AI typically achieves pregnancy rates around 60% for a single breeding. Many people claim AI success in the 85% to 90% range but these percentages aren’t realistic. They may happen occasionally but are not the norm and create unrealistic expectations.
Timed artificial insemination (TAI) is a program of AI that uses a synchronized estrus in a herd to breed all cows at the same time. With TAI, breeding is based synchronized timed breeding without estrus detection. For TAI, pregnancy rates generally fall in the 50% to 55% range for a single breeding.
There are numerous infectious diseases that can impact pregnancy success but breeding failure is more commonly caused by poor nutrition than disease.
If gender sorted or sexed semen is used, pregnancy expectations should be reduced by 10% to 15%. Generally speaking, TIA with sexed semen is not recommended due to the low probability of success. Pregnancies can be achieved but it’s important to start with realistic expectations.
BST: What are the percentages of pregnancy with in-vitro fertilization?
Dr. Gilliam: For in-vitro fertilization, fertilization rates of about 40% are expected. This means that 40% of the harvested oocytes will fertilize to make an embryo. Generally, about 50% of those fertilized oocytes result in a pregnancy. A good estimate for pregnancy rate following IVF is about 20% of the number of harvested oocytes.
BST: How does stress affect pregnancy in cows and heifers?
Dr. Gilliam: Stress can negatively impact pregnancy although the level of stress generally has to be at a high level. Cortisol is the primary hormone released in response to stress. Cortisol released by the fetus is actually the trigger for parturition (calving) so high levels of cortisol in the cow due to stress could result in pregnancy loss.
BST: Are there weather conditions that affect the probability of pregnancy in cows?
Dr. Gilliam: Extreme heat can certainly impact breeding success by negatively impacting the fertility of both the cow and the bull. Heat stress can negatively impact sperm quality in the bull and oocyte quality in the cow. Once heat stress occurs, it can take up to 60 days for recovery of fertility once the heat stress subsides.
Timing breeding seasons to avoid the hottest part of the year and ensuring access to clean water and shade can minimize the impacts of heat stress but may not completely eliminate them. Once a pregnancy is established, heat stress has less effect on the pregnancy but may still cause occasional pregnancy loss.
Handling cattle during hot weather can increase the risk of pregnancy loss due to heat stress.
Cold stress has less impact on female fertility and pregnancy maintenance as long as nutrition is adequate. Severe cold can lead to frostbite of the scrotum resulting in inflammation that can reduce sperm quality in bulls.
BST: What are some things that can cause a cow or heifer to abort?
Dr. Gilliam: Abortion can be caused by a number of things. There are several infectious diseases that can directly infect the fetus or placenta leading to abortion. Many other infectious diseases may not directly infect the fetus or placenta but may still result in abortion if the cow/heifer becomes sick.
Anaplasmosis is an example of a disease that can cause abortion. The fetus can die due to lack of oxygen caused by severe anemia in the cow.
There are some opportunistic infections that may result in occasional abortions without making the cow visibly sick. A variety of plant toxins have the capability of causing an abortion as can trauma due to crowding or cows fighting over feed. Stress from handling, transport, or adverse weather may also result in pregnancy loss.
Determining the specific cause of an abortion is often very difficult. If a single abortion occurs, it generally isn’t worth the expense to pursue a diagnosis. However, multiple abortions should certainly trigger an investigation. Fresh placenta and a fresh fetus (not frozen) are the best samples for diagnosing an abortion. However, even with these samples, diagnosing the cause of an abortion is not guaranteed.
BST: What are some of the problems cows and heifers can encounter with delivery and what are the signs they might happen?
Dr. Gilliam: The most common cause of dystocia (inability to deliver a calf) is called feto-pelvic disproportion. This occurs when the calf is too big to fit through the pelvic canal of the cow/heifer. Dystocia due to calf size is more common in heifers but can occur in cows as well.
Generally, brahman and longhorn influenced cattle have lower rates of dystocia due to calf size than other cattle breeds so this problem seems to be less of an issue with bucking stock but it is still possible.
The next most common cause of dystocia is a calf that is in the wrong position for birth. The most common abnormal positions include having the head turned back, having one of both limbs turned back or being in a breech position which means the calf is coming out tail first.
A backward (meaning the rear feet are coming first) birth is considered normal. But these deliveries are higher risk for the calf. Suffocation can occur if the umbilical cord becomes pinched off or breaks.
Pronged labor is the primary sign that dystocia is occurring. Labor is divided into three stages. Stage 1 is primarily dilation of the cervix and this stage may last several hours. The cow/heifer may be restless, hold her tail up and seem uncomfortable. She may also isolate herself from the rest of the herd.
A backwards calf will need assistance at birth. Read more here: https://news.okstate.edu/articles/agriculture/2021/stotts_backwards-calves.html
Stage 2 begins with active abdominal contractions. Often, the first sign observed is placenta or feet visible in the vulva. Stage 2 should be short. A heifer in stage 2 labor should be examined if she goes more than an hour without making progress. A cow should be examined if she goes more than 30-45 minutes without making progress. If the cow/heifer is making progress, she can be given time. Prompt examination is warranted if progress is not made in the described time frame because the risk of losing the calf becomes substantial as stage 2 becomes prolonged.
Stage 3 is passage of the placenta and should occur within about 12 hours of birth. Retained placenta in the cow is not a major concern as long as the cow is acting normal otherwise.
Establishing a relationship with a nearby veterinarian can be extremely important so that help can be available in a timely manner in the event of a dystocia.
BST: Is there a risk in transporting pregnant cows and heifers? Does the stage of pregnancy matter?
Dr. Gilliam: Transporting cows and heifers during very early or late pregnancy can result in pregnancy loss. Such losses are generally thought to be due to stress or possibly trauma from overcrowding.
BST: What do you consider to be one of the most essential elements of a successful breeding program?
Dr. Gilliam: The primary thing I would stress is the need to develop a working relationship with a local veterinarian. A qualified bovine vet is the most appropriate source for assistance with all of the different aspects of herd management in a healthy and successful breeding program.
Find more health related articles in the Keeping Em Fit section of BST: https://buckingstocktalk.com/topics/keeping-em-fit/
You might find this article about labor surveillance interesting: https://www.grainews.ca/cattlemans-corner/tips-on-when-and-how-to-check-cows-during-calving/
Dr. JOHN GILLIAM, DVM, MS, DACVIM, DABVP
Dr. Gilliam is currently a Clinical Professor in the College of Veterinary Medicine Boren Veterinary Medical Teaching Hospital where he teaches livestock medicine and surgery. He grew up in rural Oklahoma and completed a BS in Animal Science and Doctor of Veterinary Medicine degree at Oklahoma State before entering veterinary practice. After a few years of practice, he completed a residency in Large Animal Internal Medicine and an MS in Veterinary Biomedical Sciences at OSU before joining the OSU faculty in 2009. He is a Diplomate of the American College of Veterinary Internalm Medicine-Large Animal and a Diplomate of the American Board of Veterinary Practitioners-Food Animal. Since 2009, he has served as the food animal production medicine and field service clinician for the Boren Veterinary Medical Teaching Hospital at OSU. His research interests focus primarily on the
welfare of food producing animals.
Author: Terry Lidral
Terry Lidral is a western writer/journalist who lives in Idaho. She is the publisher and editor of the online magazine Bucking Stock Talk and the online magazine Western Living Journal. Her publishing credits include Storyteller for Real American Cowboy Magazine, writing feature articles for Humps N Horns Magazine as well as a wide variety of national and international web sites, historical magazines and news publications. She is known for her "up close and personal" profiles of celebrities and industry moguls such as NPR's Tom Bodett; PBR's Wiley Petersen and D.H. Page, PRCA's Sammy Andrews, Cindy Rosser and Julio Moreno to name a few. She has been applauded for her way of making a personal connection between her readers and her subjects. She indulges in her love of rodeo by serving as an associate board member for the Caldwell Night Rodeo. She is also an accomplished trainer and handler in dog agility. Her shelties Amelie and Milo are titled in NADAC, USDAA and AKC.
