Calving in late winter as opposed to spring maximizes calf growth by supplying high-quality forage when it’s most needed, confirmed a recent study by the USDA Agricultural Research Service.
Using rangelands is a cost effective way for ranchers to lower the cost of beef production, and selecting the right calving time is one factor ranchers can adjust to affect the efficiency of production, USDA said.
The long-term study was completed by researchers in Miles City, MT, and published in the journal Rangeland Ecology and Management. USDA researchers analyzed more than 80 years of data from more than 39,000 calves to obtain accurate data on the effect of calving date on calf weight gain.
“The long-term data allowed us to estimate the relationship between calving date and calf weight averaged over many years. The average relationship helps producers determine the best calving date over the long term. This must be considered because the calving date of a herd is difficult to adjust once set,” explained Matthew Rinella, research rangeland management specialist and lead author of the study.
The team found that calves born in early March averaged about 13 percent heavier at 180 days of age than those born in early May. Calves born in March are older and larger and can better utilize high-quality forage in summer. May calves reach 180 days old in early November, when forage quality has typically declined.
“When calves are born earlier, they typically experience a better match between their nutrient requirements and the timing of protein and energy supplied by forage,” Rinella said.
The data involved in the study allowed researchers to look at the cold mortality rate of beef calves born during late winter. Some ranchers prefer waiting until spring to avoid the risk, but even when considering the risk, researchers found early calving increases overall beef production.
The risk of cold weather mortality has also declined since the 1940s due to warming winter temperatures, and this trend is likely to continue, the scientists said. The beginning of plant growth also appears to be shifting earlier in the West, giving more of an incentive to calve earlier.
“This study puts numbers to calf weight and beef production resulting from different calving dates so that ranchers can factor these things into their decision-making,” Rinella concluded. — Anna Miller, WLJ managing editor
