Some Like It Hot, Some Not!

John F. Grimes, OSU Extension Beef Coordinator

As we move into August, we continue to experience a fairly typical seasonal weather pattern for most of Ohio.  Yes, it’s hot and humid!  We have been experiencing these conditions for the past couple of weeks and it appears that the trend will continue at least for the remainder of this week.  Maybe Mother Nature will improve her sense of humor and provide us some relief in the coming weeks.

Every cow-calf producer makes management decisions about their operations based on a wide variety of factors.  Some of these factors include access to land, feed resources, marketing goals, labor availability, etc.  In this article, I want to discuss another factor that significantly impacts management decisions for the cow-calf producer.  That factor is the weather.

The weather has a direct impact on nearly every management decision made by the cow-calf producer.  There are predictable seasonal trends that we can expect as we move from winter to spring to summer to fall.  There are also short-term weather anomalies that can complicate daily farm management from time to time.  While we expect colder temperatures during the winter months, very few of us expected to see the -10 to -20 degree F temperatures that we saw in February of 2014 and 2015.  Conversely, I would anticipate that many of us would lose several dollars if we tried to wager on the number of days we would see above 90 degrees F in a given summer.

I have always felt that the important management decisions of any cow-calf operation should be based upon the goals of optimizing conception rates, the percentage of live calves born, and ultimately the percentage of calves weaned.  Your choice for timing of the breeding season and eventual calving season will be influenced to some degree by the weather.  An interesting consideration in this process is the answer to this question: “Which is more important to you, the timing of your calving season or the timing of the breeding season?”  This can be a difficult question to answer.

I suspect many producers would prioritize the timing of their calving season based on less stressful environmental conditions.  In other words, many producers would prefer the warming temperatures and lush grass growth of spring over nearly any other season.  Spring “officially begins on March 20 and runs to June 20.  For this discussion, let’s assume that is your 90 day calving season.  I have heard this timing for the calving season widely promoted by some forage and grazing specialists as an ideal calving time as it works well with natural pasture growth and development.

I certainly cannot argue that the spring season typically provides a positive environment for the newborn calf.  However, this calving season can pose significant challenges during the breeding season.  If you follow the calving period we are using in this example, the breeding season that would coincide with this calving window would run from June 11 until September 11.  I would contend this may be one of the most difficult periods of the year to successfully get a beef female bred, especially if your primary pasture grass is fescue.

Think about the challenges faced in a breeding season during this timeframe.  Cows and bulls alike are certainly less active at grazing or other activity in the heat of the day in the summer.  The producer must reduce stress on the animals by providing aggressive fly control measures and insuring a plentiful supply of clean water.  If much of your pasture is based on traditional fescue varieties such as Kentucky 31, you may be subjecting the cow herd to the endophyte fungus that can negatively impact animal performance.

These and other factors can lead to a significant reduction in conception rates during the summer months.  Work done by Dr. Les Anderson of the University of Kentucky at the Research Center at Princeton, Kentucky demonstrated the negative impacts of a later summer breeding season.  In this study, the herd was divided into three distinct 45-day breeding seasons ranging from April 21-June 5, May 21- July 6, and June 19-August 4.  Subsequent conception rates for these three breeding seasons were 89%, 78%, and 59%, respectively.  Other research and anecdotal information would agree with the results from this study that conception rates will fall as temperatures rise.

Again, I respect those producers that want a favorable calving environment.  I believe that the best calving environment will have difficulty compensating for a potential 10-30% loss in conception rates from the breeding season.  The challenge for the cow-calf producer is finding the “sweet spot” that balances a timely breeding season that maximizes conception rates with a calving season with a less stressful calving environment. This is a difficult balance to achieve.

I would suggest that a fall calving season that includes the months of September and October can help provide such a balance between the breeding season and the calving environment.  These months provide similar environmental benefits to calving in April and May while providing a somewhat less stressful breeding season environment in November and December.  A relatively small number of the nation’s cow-calf operation will calve in the fall months but it does offer some potential advantages for improving conception rates and calving percentages.

A word of caution should be offered for those who are currently involved with or are considering fall calving.  This is especially true if your fall calving season creeps back into the month of August (as in the case of the author!).  Research has shown that fall calving cows can have shorter gestation lengths and lighter calves than their spring-calving counterparts.  This can be especially true in times where we see extended periods of extremely high temperatures.  It would not be unusual to observe actual calving dates occur 7-14 days or more earlier than expected based off a known breeding date.

The bottom line of this discussion is that appropriate timing of a breeding and calving season for the cow-calf producer is a difficult choice to make.  It certainly is not a “one size fits all” situation.  Choose the scenario that offers the potential for increasing the number of calves weaned from your herd in balance with feed and labor resources.