As reported in High Plains Journal ask any new or soon-to-be mother and they’ll tell you they only want the best for their child’s health, development and future. Cattle producers feel the same way about their stock and they only want to make sound, practical decisions for each calf crop. Those management practices in question often center on topics such as breed, calving season, nutrition, health protocol, and breeding techniques.
Several Oklahoma State University professors—including Paul Beck, associate professor and Extension specialist for beef nutrition, and David Lalman, professor and Extension beef cattle specialist—decided to put these questions to the test in a four-year study conducted through OSU’s Department of Animal and Food Sciences. They set out to compare the effects of calving season for steer feedlot performance in the carcass characteristics. The study started in 2016 and Angus cows were randomly assigned to be bred to Angus and Hereford bulls through artificial insemination. Then Angus and Charolais clean up bulls were turned out for natural service on the open cows. Spring born calves were weaned in early October, backgrounded on native range, hay, and 3 pounds of DDGS supplement per day for 60 days, then grazed on wheat pasture through spring before being shipped to a commercial feedlot. Fall born calves were weaned between May and June, grazed on native range for 70 to 90 days, backgrounded in a dry lot during late summer for 30 days, then shipped to a commercial feedlot in August or September.
Fall versus spring
One aspect of the study focused on fall versus spring calving. Since nutritional deficiencies occur at different times during their production cycles, Lalman expected this to affect the overall performance of the offspring at slaughter.
“With good grazing management, most spring calving cows will be in moderate body condition—a body condition score of 4 to 5 using a scale of 1 to 9—when their calves are weaned in the fall,” Lalman said. “From that time until calving approaches again during the spring, these cows are managed to target a body condition score of 5 on average, at the time of calving. Through the fall and winter months, cattle producers adjust the amount and type of supplemental feed to keep cows in good condition. Calving occurs just before or during spring green up. This results in a relatively good synchrony between the increased nutrient requirements associated with lactation and diet quality. Therefore, there is not a tremendous amount of variation throughout the annual production cycle for a spring-calving cow. She stays relatively constant in body condition.”
Contrast this to conditions in a fall-calving system, cows calving in September or October normally calve in a body condition score of 6 to 7, Lalman said. As forage quality declines during fall, nutrient requirements associated with lactation are at their peak. Thus, cows lose body condition going into the breeding season and through the first and second trimesters. Commercial cow-calf operations generally provide supplemental feed with the objective of slowing the rate of body condition loss. This trend is reversed late in the second trimester and through the third trimester in a fall-calving operation. Under good grazing management and moisture conditions, spring and early summer forage is at its peak at the time the cows’ nutrient requirements are gradually declining during late-lactation. These conditions result in fall-calving calving cows gaining weight rapidly during summer.
“Under normal management conditions, the fall calving cow experiences substantially more body condition variation compared to a spring calving cow,” Lalman said. “We thought the wide differences in maternal nutrient availability and other environmental conditions might influence the performance of those calves once they reached the feedyard and might influence their carcass quality.”
When the effects of calving season were examined, spring calves weighed an average of 880 pounds when they entered the feedlot, while fall calves weighed 770 pounds. Lalmans said the difference in stocker phase forage quality can explain the majority of the differences with wheat pasture calves gaining at a faster rate compared to fall-born calves grazing mid to late-summer native range forage. The out weights for the spring calves averaged out to 1,500 pounds and the fall calves weighed 1,470 pounds. Fall calves had lower average daily gains than spring calves and thus required more days on feed to reach finishing. For example, fall-born Angus steers needed 163 days on feed versus spring-born Angus steers, which only required 146 days.
“I was surprised that the calves from the fall system ended up having more days on feed than the calves in the spring system,” Beck said. “The combination of lighter entry weight and slower gain in the feedlot combined to require about an extra two to three weeks to achieve the same backfat thickness.”
To Lalman, the main revelation was that there was almost no influence of calving season on marbling. Spring calves averaged out to a marbling score of 6 and fall calves averaged 5.9.
“I thought the fall-born steers might have lower marbling because those calves are exposed to a modest negative energy balance in-utero mid-gestation,” he explained. “Also, these calves were finished in northern Colorado each year. So lower feedlot ADG in fall-born calves fed through the harsh conditions of winter is no surprise, compared to spring-born calves fed through the spring and summer months. We expected the spring-born calves to have better feed efficiency, but there was no difference.”
When it came to calculating overall net revenue for fall versus spring calving systems, fall-born calves were about $20 per head more profitable during the finishing phase.
“In our study, the price margins slightly favored the fall-calving system, and that was mostly due to higher finished cattle prices during March and April,” Lalman said.
Beck said cattle producers should look at their environment when making the decision to raise fall or spring calves.
“Logically, most of us in the southern Great Plains look at the quality of forage and that fits a spring calving cow herd really nicely,” he said. “When we start putting these cows into a fall calving cow herd, it’s surprising how well those cows do on a predominately warm season forage base. There’s a lot of demand for calves at weaning in May or June. It just really fits nicely with economics because there’s not as many fall calving cows in our national cow herd. It’s something to look at and consider if you can make it work in your production system.”
