Extension Education: Ways to Prevent Calving Difficulty in the Beef Herd
As we enter the new year and move closer to spring, many ranchers are thinking ahead to calving season. This rewarding, yet challenging, time on the ranch comes with plenty of difficulties and worries, one of which is potential calving difficulties or dystocia.
Most operations expect to deal with dystocia, especially in heifers and younger cows and have a contingency plan in place. However, as with most things, the best treatment is always prevention.
Dystocia can be brought on by several factors, some of which are more difficult to manage than others. This article briefly discusses a few of the factors producers can manage to deter calving difficulties.
The largest contributor to dystocia is the age of the cow.
In many cases, two percent or less of calving problems occur in mature cows.
Studies by the U.S. Meat Animal Research Center in Nebraska showed less than five percent of cows five years of age and older required calving assistance, whereas 54 percent of two-year-old heifers experienced difficulty calving.
This proves what many already know – heifers are where the trouble usually comes from. Selecting the right replacements can help curtail this trouble.
When it comes to decreasing dystocia, using heifers with proven genetic merit is a good idea. This is often accomplished using the sire’s maternal expected progeny differences (EPDs), such as calving ease maternal (CEM).
Genomic testing can also be used to predict heifer performance.
Pelvic measurements are another great tool in selecting heifers less likely to need calving assistance. However, a good pelvic measurement will not eliminate dystocia, as it is the relationship between pelvic size and calf weight which influences how easy delivery is.
The benefits of a good pelvic area measurement can be negated by a calf that is too big. It is also helpful to keep first-calf heifers close and, if possible, in a separate pasture from mature cows to monitor and assist in birth if needed.
Many ranchers are well aware of the effect the bull can have on the delivery of the calf.
Certain bulls will yield bigger calves which are more likely to cause trouble.
The bull’s breed is one selection criterion which allows ranchers to influence calf birthweight. Typically, British breeds like Angus and Herefords yield lighter birthweight calves than Continental breeds.
Looking at a bull’s EPDs allows a more fine-tuned approach to assess the expected difficulty a sire’s calves will pose.
The birthweight (BW) EPD, expressed in pounds, is the expected difference in a bull’s calves at birth, with lower values indicating lower birthweights. Many producers utilize this EPD in selecting bulls to decrease dystocia, especially for first-calf heifers.
However, birthweight is not the only factor controlling calving ease. Many geneticists suggest focusing instead on the calving ease direct (CED) EPD, as this utilizes BW as well as other factors in its calculation.
CED is the difference in percentage of unassisted births when a sire is bred to first-calf heifers. A higher CED value means when a sire is bred to first-calf heifers, a higher percent are expected to calve without intervention.
Expected progeny differences are a great tool for predicting how much calving difficulty to expect, especially when looking for a sire to pair with heifers.
Generally, pregnant two-year-old heifers need about nine to 13 pounds of total digestible nutrients (TDN) per day. This is greater than a mature pregnant cow’s requirement of eight to 12 pounds per day despite their smaller size, because the heifers are still developing themselves while growing a calf at the same time.
A misconception persists underfeeding cows and heifers during late pregnancy will lead to a smaller calf and lessen the likelihood of calving difficulty. This is not the case. Genetics are the predominant determinant of calf size.
Underfeeding the mother can cause her to be weakened at calving, which increases the chance of dystocia.
Research shows feeding the recommended level of TDN does lead to a slightly heavier birthweight than underfeeding but does not cause a greater instance of dystocia.
Underfeeding will especially hinder two-year-old heifers pregnant with their first calf by jeopardizing skeletal growth and therefore, pelvic area. It can also decrease milk yield, increase calf scours and most importantly, decrease pregnancy rates the following breeding season.
Research trials at the U.S. Department of Agricultureʼs Agricultural Marketing Service research station in Miles City, Mont. show the relationship between dystocia and nutrition – cows receiving a low plane of nutrition had higher percentages of dystocia than those on a high plane of nutrition, despite the high plane group having a higher calving weight.
Overfeeding a heifer or cow to the point of obesity can lead to dystocia due to fat obstructing the pelvic canal and hampering her ability to physically strain, but this usually only occurs at a body condition score (BCS) of eight or more.
Obese cows are rarely a problem on Wyoming ranches, but both underfeeding and overfeeding can be monitored by keeping cows and heifers at a BCS of five to six.
For help in determining BCS, University of Wyoming Extension has published a three-step guide for body condition scoring range cows which can be found at wyoextension.org/publications/. This is a simple method of monitoring the nutrition of the herd as a whole.
The battle against dystocia in cattle requires a comprehensive approach, from strategic heifer and sire selection to good nutritional management. There are other factors determining how likely it is a producer will have to pull a calf, but understanding how to manage the cow herd can improve the chances of easy births each spring.
Even the best management is not bulletproof against dystocia, and calving problems will still rear their head from time to time so it is best to remain prepared to address the issue when it arises.
Dagan Montgomery is a University of Wyoming Agriculture and Natural Resources Extension educator. He can be reached at email@example.com.