Not all minerals play nice, and some can create serious health problems in cattle.
“The thing that makes the phone ring the most are feed- or nutritional-related disease outbreaks,” Dr. Elizabeth Homerosky of Veterinary Agri-Health Services said at the recent virtual Red-Bow Ranching Conference.
“The most common thing, especially this time of year, are downer cows. Most of the time, when we run blood work, we find out those cows are low in magnesium.”
But that’s just one example of “minerals gone wrong,” said the veterinarian, who runs her own herd near Crossfield.
“Sometimes we just get generalized weight loss, issues with fertility, nothing really specific,” said Homerosky. “Minerals and vitamins, at the end of the day, are really important, especially when we’re going into the third trimester.
“It’s especially important for the health of those cows that they get supplemented adequately.”
Homerosky cited a 2014 case of a herd in which 29 of its 32 heifers that calved produced offspring with problems. Some were very small, weighing 40 pounds at most, others had short legs and domed heads.
“The calves could not get up and nurse because their joints were not allowing them to,” said Homerosky.
Further investigation confirmed joint laxity and dwarfism, but ruled out genetic abnormality as the cause. Adding to the mystery was that the 110 mature cows in the herd gave birth to normal calves.
A detailed investigation into what the herd was fed, their water source, and the causes of joint laxity and dwarfism eventually found a culprit.
“In Canada, we most commonly associate (these conditions) with silage, but we think it’s more commonly a result of low manganese,” said Homerosky. “Most of the time, this disease is seen in heifers that are calving in the spring.”
Manganese is an essential mineral and especially important for cartilage and growth plate formation. When animals get a proper amount, you don’t see these sorts of abnormalities, she said.
“Nutritionists recommend that cattle are supplemented with a total of 40 milligrams per kilogram of manganese on a dry matter basis. We know from research that cattle restricted to less than 17 mg per kg on a dry matter basis are likely to give birth to calves with these congenital abnormalities.”
Minerals can be quite antagonistic to each other. Iron, zinc, calcium and sulphur (all commonly found in well water) can reduce absorption of other minerals that cattle need.
“Just because we’re feeding the cow enough mineral doesn’t mean that she’s absorbing it,” said Homerosky.
Small calf, big neck
A similar mystery arose in 2018. The first few calves were weak or stillborn, others had masses on their necks and some had dwarfism (but no joint laxity).
“Out of 35 calves that hit the ground, 20 were affected,” said Homerosky. “The primary sign was a goiter on the neck.”
The cows were on native pasture until early November, and then received a ration of mixed grass hay and high-moisture barley greenfeed bales. But because the cattle weren’t eating free-choice vitamins, minerals or salt in spring, summer or fall, the producer decided they were getting enough minerals, and didn’t put them out in winter.
“The deficiencies that the calves actually had were as a result of not feeding any mineral throughout the winter,” said Homerosky. “The Canadian Prairies are pretty much deficient in cobalt and iodine and unless you’re supplementing it in some way, like blue salt, your cows are probably not getting much of any. We know that these cows are not getting cobalt if they’re all deficient, which they were. They’re probably not getting exposed to any iodine, either.”
Cows have no nutritional wisdom, and will just eat what they want, she emphasized.
“Don’t trust them,” she said. “If they’re not eating the mineral, find a way to force feed. We know that we’re going to get ourselves in quite a bit of trouble if we don’t get adequate mineral, especially in the second and third trimester. It’s a real high-risk period.”
In January 2018, Homerosky went out to a farm near Calgary to examine 11 dead cows that had all been walking around the day before.
There were 300 cows on native pasture, but the protein quality of the pasture was declining. Molasses-based protein lick tubs were available all the time, and supplemented with mineral twice a week. The cattle were fed mineral the day before, and the dead cattle were found near the protein lick tubs, their guts filled with gas. One live cow showed signs of inco-ordination, muscle tremors, salivation and belligerent behaviour consistent with neurotoxicity.
Again it took a detailed investigation — a post-mortem, tests for neurotoxicity, and pathology findings — to determine a cause: urea toxicity.
“You can feed a high level of urea to your cows as long as they stay acclimated,” said Homerosky. “You can’t stop and you can’t increase it dramatically. You have to be very consistent in the way you work those cows up on urea.”
Testing of the mineral in the tub found it was two-thirds urea — twice the level the producer thought he was feeding.
Two animals could feed at each tub — accounting for 11 dead cows and the other affected cow. They had likely been the boss cows that had pigged out on the mineral, and died shortly after.
“Do not feed urea free choice to cows,” said Homerosky. “There are people who do it and get away with it, but it’s kind of a game of Russian roulette.”
Yet another puzzler occurred in 2015 when a producer purchased a new ranch.
“Within six months of moving the entire herd, about 10 per cent had lost a significant amount of weight, and he’s really starting to get concerned,” said Homerosky. “This is a fairly young herd. They should be in their prime, but they’re just failing to thrive.”
Tests found five cows were low in manganese and copper, and while the cows had inconsistent minerals, their diet was excellent on paper. In the name of science, one cow was euthanized and a post-mortem found it has Johne’s disease. Later a heifer started having seizures, and then two more.
Homerosky noticed this was happening when there wasn’t a lot of snow on the ground. Perhaps, she reasoned, the cows had been using snow as a primary water source and there was something up with the regular water supply. Tests should see sulphate levels of about 1,200 mg per litre.
“With cows, you start to see clinical signs over 1,000 mg per litre. With calves, you’re going to have a hard time getting them to drink it. It tastes so bad to them that they will just refuse to drink it. You’ll start having issues with calves around 500 mg per litre.”
There was an error made when balancing rations, and the sulphates in the water weren’t taken into account. That meant total sulphur levels in the herd’s diet were far too high, causing weight loss. (The problem can also cause lesions in the intestinal tract that look like Johne’s and prevent cattle from absorbing selenium and copper as they should.)
A new water source solved this problem. But it’s a lesson for others, said Homerosky.
“It’s worthwhile to get your water tested if the herd is not performing at the level that it should.”