Ensuring mineral status of mother cows helps improve early calf health, improve breed-back
A wave of cold weather in late February welcomed 2018’s calving season for many ranchers in Wyoming. As ranchers begin calving, Jeffrey Hall of Utah State University noted that a calf’s mineral status is directly related to the mineral status of the cow.
“Calves have to be born with more reserves than an adult animal,” he said. “A cow will actually deplete her own system to make sure the calf has enough.”
“The cow pushes enough mineral into the calf, so it has enough body reserves to maintain health until it starts grazing on its own,” said Hall. “In the first 90 days of life, the calf will triple its birthweight, and just by dilution alone, the amount of nutrients available will not be sufficient.”
He further explained, “The only reason a calf would be deficient is if its mama is deficient. The only way a calf will be born without a body reserve is if mama runs out.”
Maternal deficiencies are due to inadequate intake of minerals, he said, and often, forages are not sufficient to meet the needs of cows. As a result, the last trimester of gestation is critical for calf health as it relates to minerals.
From a dietary standpoint, 98 percent of the calves’ intake comes in the form of milk for the first 90 days, yet the amount of copper or selenium, for example, in milk is low enough that it doesn’t meet the body’s needs.
“When we think about colostrum, most people think of it as important for the immune system, but we also have to look at it as a source of fat-soluble vitamins,” Hall commented.
Only 10 percent of a calf’s required vitamin E and vitamin A are delivered to the fetus prior to birth. Nearly 70 percent comes in the first colostrum.
“It gets a bolus dose of vitamin E and vitamin A that are already bound to the carrier proteins to be functional at the time it’s ingested and readily absorbed,” he said.
Cows retain a four- to seven-month supply of vitamin E and only four to five months of vitamin A.
“She is at the point when she is running out of vitamin E and A when she’s making the bolus of milk for her calf, so we see vitamin E and A deficiencies in calves following drought when the cow didn’t get enough to maintain her supply,” Hall said.
“We can optimize production efficiency if we rebuild the mineral stores in the cow,” Hall said. “If mama depletes herself in the last three months of gestation, the three months from calving to breed-back are critical to build her system back up to improve her reproductive efficiency.”
In breeding back, cows that aren’t at a sufficient plane of mineral nutrition are much more likely to come up open at preg-checking, he continued, which may explain why first- and second-calvers come up open more frequently.
First- and second-calvers have a higher dietary requirement for mineral for several reasons, Hall added, noting they are moving mineral to the fetus, they have mineral needs for maintenance and they are also growing.
“Our mature cows have a slight advantage of not needing quite as much mineral in the diet to get by because they are not growing,” he said.
Neo-natal health will improve while sick calves, labor costs and medicine costs will decline with appropriate mineral supplementation, Hall said.
“We also increase the number of live calves we have to sell at the end of the year,” he explained. “I looked at our university data and found that 93 percent of summer pneumonia cases came from calves that were copper or selenium deficient or both. These calves are immune compromised. That’s why they get pneumonia to start with.”
If a calf is born with reserves that aren’t quite what they need to be, if they only get 60 percent of their requirements in the ration, the body stores will continue to deplete.
“Then, their immune system isn’t able to fight off disease like it should be,” he said. “As a result, we see more sick calves.”
“The biggest thing – and the thing that producers can see as an immediate return – is weaning weight changes,” said Hall. “If we have a sick calf, it doesn’t eat well.”
Even if they don’t seem clinically ill, sub-clinical presentation comes in decreased weight gain from resulting lowered consumption.
“It’s not uncommon for me to see a 25- to 30-pound decreased weaning weight across mineral deficient calves,” he said. “With severe deficiencies, it’s not uncommon to see over 50 pounds in decreased weaning weights.”
Hall continued, “This ignores the other profits from having more live calves with better reproduction efficiency, not having to cull as many cows and not having to keep as many replacements.”
Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at firstname.lastname@example.org.