Take time to evaluate your calving distribution this spring
Record calf birthdates this calving season to track calving distribution.
Calving distribution provides valuable insight into the reproductive performance and productivity of the herd, says University of Missouri Extension veterinarian specialist Craig Payne.
Calving distribution represents when calves are born during the calving season. It is often based on the percentage of calves born at 21-day intervals since 21 days is the average length of the estrous cycle in cattle.
Payne tracks calving distributions as part of a three-year project to help beef producers improve whole-herd record keeping.
This is important for two reasons, says Payne. First, dams of early-born calves enjoy a longer recovery period before the next breeding season They will likely be cycling at the beginning of the breeding season and have a greater chance of becoming pregnant. Second, earlier born calves have longer to gain weight. This results in more pounds of calf sold at marketing time, and more profits for the owner.
Payne points to weaning weights collected from a northwest Missouri operation in the fall of 2020. They show that steer calves born in the first 21 days were 47 pounds heavier at weaning than calves born during days 22 – 42 (537 vs. 490). The number of calves in this group is relatively small (47 steers born in the first 21 days and 12 born during days 22 - 42). However, the reported weight difference in this herd is similar to other studies, says Payne.
Begin tracking calving distribution by establishing the date of the initial counting period. One option is to start the first period 283 days from bull turn-in or AI. If this information is not available, begin the first 21-day period when the third calf is born. Both methods work, says Payne, but use the same method to be consistent. Once you have the start date, count the number of calves born in the first 21 days of the calving season and divide that number by the total number of calves born, says Payne. Repeat the process for days 22-42, 43– 63, and greater than 63 days. Count all full-term calves born, dead or alive. Also, include calves born before the beginning date in the first 21 days. Finally, evaluate the calving distribution of first-calf heifers (two-year-old cows) separately from the mature herd. Their breeding season is often earlier or managed differently. Once you know your herd’s distribution percentage, compare it to the industry standard. Benchmarks for the first, second, and third 21-day period are 65%, 23%, and 7%. The remaining 5% of calves are born at greater than 63 days.
The following is the calving distribution of 142 calves from a 2020 spring calving herd in northwest Missouri. Day of calving season and percentage: 1-21, 66%; 22-42, 28%; 43-63, 6%; and over 63, none. Therefore, this herd performed better than the industry standard.
To achieve the targets, all cows must cycle at the beginning of the breeding season and bulls must be fertile. “If your distribution is unfavorable, meaning a higher percentage of calves are born later in the calving season, it could indicate one or more problems and will require more investigation,” says Payne. Factors to consider are the nutritional program, inadequate bull power or fertility, disease or conditions that cause early embryonic loss or infertility, or a mismatch between herd genetics and environment. Also, look at the calving distribution for each age category, pasture, etc. to see if a specific group is responsible for differences.
The following distributions are from two groups of cows owned and managed by the same beef producer. Day of calving and percentage for the 2019 fall calving group (44 calves): 1 - 22, 45%; 22 - 42, 34%; 43 – 63, 16%; >63, 5% and 2020 spring calving group (66 calves): 1 – 21, 74%; 22 – 42, 24%; 43 – 63, 2%; >63, none. Notice the differences, with the 2019 fall calving herd being unfavorable and the 2020 spring calving herd exceeding the industry benchmark. According to the producer, this difference can be explained by management intensity. The spring herd is intensely managed for reproductive success whereas the fall herd is a mixture of purchased cows of unknown origin, late fall calving cows purchased from another producer and cows that were carried over from the spring herd.
“Evaluating a calving distribution takes very little time but can provide valuable insight into reproductive performance and productivity of the herd,” says Payne. For more information on the record-keeping project, contact Payne at 573-882-8236; livestock specialist Shawn Deering at 660-726-5610; livestock specialist Jim Humphrey at 816-324-3147; or state beef nutritionist Eric Bailey at 573-884-7873.