Editors’ Note: This article was drawn from a piece by Ann Perry of the USDA-ARS. The article was published in the July 2014 Issue of their Agriculture Research magazine. The research is part of Pasture, Forage and Rangeland Systems (#215) and Climate Change, Soils and Emissions (#212), two ARS national programs.
For decades, Agricultural Research Service scientists in the northern plains have kept meticulous records on cattle weight gains during the growing season. Although their main focus was on trends in livestock and forage production, they also tracked weather conditions as part of their studies. Then, a few years ago, ARS rangeland management specialist Justin Derner assembled a team from three ARS locations in Wyoming, North Dakota, and Montana and used the data to see if it might give us a clue about how increased seasonal weather variability might affect cattle production.
Wet Winters and Springs Are Better For Weight Gain
Looking at cow-calf production in Cheyenne, Wyoming from 1975 to 2012 on both Herefords and Red Angus crossbred cattle the data showed that wet winters and/or wet springs increase soil moisture levels, likely helping provide ample forage throughout the growing season. The result was better cattle production in those years. That’s not too surprising. The data also showed that the Hereford stock were more sensitive to the seasonal variations than the crossbred animals. This supports the idea of raising animals that fit your environment as they’ll be more resilient when conditions are less than perfect.
What About Stocking Rate and Weather Variations?
Based on 30 years of data on yearling steers in Cheyenne, the team concluded that if you’re stocking your range very lightly, you’ll be unaffected by seasonal weather variability. You’ll have enough forage, even when the weather doesn’t cooperate. But when we get cool, wet springs and warm, wet summers, producers with moderate and heavy stocking rates will see upticks in beef production that those stocking lightly won’t experience. Again, there’s no real surprise here. But the team did point to the need for seasonal weather forecasts that could help reduce rancher risk. Knowing when to expect a dry spell lets ranchers de-stock ahead of time and guards against rangeland degradation.
What Happens When Invasive Grasses Arrive?
The team used data collected from 1936 to 2005 to look at how the Kentucky bluegrass invasion of the Dakotas that began in the 1980s affected production. What they learned is that though spring temperatures did not affect cattle production before the arrival of Kentucky bluegrass, afterwards, whenever there were hotter spring temperatures there was also a decline in beef production. This means that by knowing your plant communities and how seasonal weather conditions might affect forage production, you’ll know more about how to adjust stocking rates.
Timing of Weather Affects Weaning Weights
Ecologist Lance Vermeire and animal scientist Mike MacNeil (retired) conducted a related study that used 76 years of data to evaluate links between weather patterns and the growth of Hereford calves at the ARS Fort Keogh Livestock and Range Research Laboratory in Miles City, Montana. Their data was unique; all the animal records were obtained from one closed and pedigree-recorded population that has been maintained at the Miles City location throughout its history.
The scientists found that calves reared in years with longer, cooler growing seasons and typical seasonal precipitation grew faster from birth to weaning than calves reared under other conditions, regardless of previous seasonal precipitation patterns. In the model, they identified two critical weather periods that affected weight from birth to weaning. Additional precipitation from February 8 to February 22—almost certainly in the form of snow—reduced weight gain by nearly 3.4 pounds per 1/10 inch of precipitation. Vermeire and MacNeil think the pregnant cows, which became increasingly wet as the snow accumulated, responded to the wintry conditions with a decrease in body temperature that affected the unborn calves.
During the second critical weather period, from June 23 to July 7, model results indicated that every 1˚F increase in temperature reduced growth from birth to weaning by around 1.1 pounds. Since 90 percent of annual plant productivity for this region typically occurs by July, the researchers think the increasing temperatures reduced forage quality by speeding up the rate of plant senescence and reducing forage digestibility and nitrogen content. These results indicated that a general increase in temperature could result in decreased growth in suckling calves in the U.S. northern Great Plains, the scientists say. This research was published in Agricultural
Sciences in 2012.
While these weather periods that affect weight gain will be different in different parts of the country and the world, they might help you understand better what is happening in your area and what you can expect from your calves. It also gives us all a sense for what can happen as the planet continues to warm.
