From inclement weather to dealing with dystocia cases, spring calving season has felt longer and more difficult in 2019 than in previous years combined, and thanks to unforeseen nutritional deficiencies, cattlemen’s tough luck is more reality than perception.
During the Beef and Forage Field Day at the Southeast Research Center in Parsons, Kansas, Kansas State University veterinarian Greg Hanzlicek addressed the issues found in his statewide calf death field investigations.
“I’ve been a veterinarian for over 30 years and in talking to other veterinarians and producers, no one has ever experienced a year like we did this year,” Hanzlicek said. “Frankly, we hope we never experience a year like this again.”
While Hanzlicek said he prepares himself for common cases of calving difficulty, 2019 was different not just in the number of calf death losses but also in their causes of death.
“As veterinarians going into the spring, one of the things we are most concerned about is abortion storms — how many and how extensive,” Hanzlicek said. “I tell you in 2019, looking back on our records, the number of abortions was not higher than any other year, but the number of cases of stillborn calves and/or weak calves being born was more than you could count.”
More than 20 ranches across the state had losses significant enough to warrant full-fledged investigations, Hanzlicek said.
All of these cases had the same complaints — either the calves were stillborn or they were too weak to get up and nurse. In the case of stillborn cases, a vet validated during the necropsy that the calf had not taken a breath, and the cases with weak calves were validated by the client witnessing their symptoms.
Dystocia, bovine viral diarrhea, leptospirosis and low-grade nitrate toxicity were all ruled out during the investigations. With the most common culprits ruled out, Hanzlicek looked to nutritional deficiencies as a probable root cause.
“Our nutritional deficiencies that we think about in these cases would be protein or energy deficiencies in the cow or heifer or vitamin A which is a major issue in stillborn or weak calves, and then maybe selenium, vitamin E or trace minerals,” Hanzlicek said. “We did have one selenium and vitamin E deficient herd in the investigations, so that was a classic issue that was responsible for their weak calves being born.”
Hanzlicek said vitamin A deficiency consistently rose to the top in the investigations. While the nutrient is abundant in growing pastures, its potency and availability declines rapidly outside of a natural setting.
“Vitamin A is found in green forages,” Hanzlicek said. “In your pastures before that grass becomes brown and dormant, the amount of vitamin A in the pasture is huge — it supplies vastly more vitamin A than the cow needs.
“The good thing is cows can store the excess vitamin A in their livers and that’s where they will store most other trace minerals as well,” Hanzlicek said. “But that liver can only hold a two-to-four month supply of Vitamin A.”
Some studies show up to 18,000 IU of Vitamin A in a single pound of dry matter in a green pasture, where baled alfalfa would only contain around 1,300 IU, Hanzlicek said. Some common mineral supplements provide even lower numbers of vitamin A, so awareness of natural levels and supplementation rates can be key.
In some of the problem herds examined, mineral was removed once the herd came off of green pasture and was being fed cake and hay, Hanzlicek said. In a very short period of time, those cows were vitamin A deficient and then the calves were also.
“Vitamin A is very unstable and oxidizes very easily,” Hanzlicek said. “Any time that we store hay, depending on how it’s stored, we lose a lot of the vitamin A over time.”
For every month in storage, hay loses about 7 percent of its vitamin A content, Hanzlicek said.
“The same thing occurs in trace mineral products that contain Vitamin A,” Hanzlicek said. “Some of the herds we work with had purchased a multi-year supply of trace minerals and over time the amount of vitamin A in those products was much less than was listed on the tag.”
Mineral products with lower-than-required vitamin A levels or lesser bioavailability could also cause the deficiency issues. Hanzlieck said a mineral supply issue in recent years that led to more imported vitamin A might have led to mineral sources utilizing vitamin A sources not formulated to give cattle maximum absorption of the mineral into their system. In some of the studied cases herds were fed mineral at an appropriate rate and were still found to be vitamin A deficient.
Most of the investigated cases showed protein, energy or vitamin deficiencies in the cows’ diets. Vitamin A and protein deficiencies were identified through blood testing while energy deficiencies were found by examining calf body fat during necropsy.
While causation in most herds could be narrowed down to a single nutritional deficiency, in some of the herds a cocktail of causes rendered the results.
“We had some herds that were both protein and energy deficient,” Hanzlicek said. “These herds are what we would call classic PEM, or protein energy malnutrition, herds where we had down cows close to calving.”
For the most part, the cows were normal in these cases but the calves were either stillborn or very weak upon delivery.
Hanzlicek encouraged producers to check recommended values of nutrients and minerals required by cattle against the diets they are feeding to avoid preventable calving issues like vitamin A deficiency.
