The fall calving season is just around the corner for several producers around the state. While a minority of Ohio's cow-calf producers utilize fall calving as a management practice, there are several valid reasons to calve in this less traditional setting. As with just about any management practice, there are drawbacks that need to be considered as well. Producers must understand that there are unique characteristics associated with fall calving and they should be prepared for the differences when compared to a spring calving season.
I believe there are some very distinct advantages to calving in the late summer or early fall. Probably the biggest advantage for calving at this time of year is the fact that we have typically see warmer, drier conditions in the calving environment. Yes, it can be downright hot during this time, but let's not forget the challenges of calving in the first quarter of the year. We simply do not see the cold, wet, and muddy conditions that pose very real threats to calf health that we see in January through March.
The summer heat can actually provide some beneficial aspects to fall calving. While there is not a wealth of information on this subject, researchers at Oklahoma State University have examined the effects of temperatures on gestation length and birth weights of calves born in the fall. In one study, cows from were bred to calve in August or October to compare gestation length. Results from this five-year study showed that the August calving group averaged a four day shorter gestation length when compared to the October calving group. Another two-year Oklahoma State University study examined the effects of August versus October calving on birth weights. In year one, August born calves were 3.74 pounds lighter than the October born calves. In year two, the August born calves were 9.68 pounds lighter.
Dr. Glenn Selk, Oklahoma State University Emeritus Extension Animal Scientist, offers the following explanation for these results: "The reason that early fall calving cows have lighter birth weights is generally attributed to the fact that the cows are gestating in hot weather. Blood flow patterns of cattle during periods of high temperatures change in an effort to dissipate heat from the body. Blood (and the nutrients that it carries) is shunted to the outer extremities during hot weather to dissipate heat. Therefore less blood flow is sent to the inner core of the cow where the fetus is gestating. This subtle change in blood flow is commonly thought to be the reason that lighter birth weights occur to cattle that are in the last trimester of pregnancy in June, July, and August."