Too Much of a Good Thing…Over Supplementation of Minerals in Cattle
By Dr. Jamie N. Henningson, DVM, PhD, DACVP
Minerals and vitamins are essential nutrients required for a diverse range of daily functions of the body. Minerals are important in cattle for maintaining health and reaching optimal growth and reproductive rates. The levels of minerals needed depend on age, stage of production, diet, and environmental availability. High quality forages and grains can provide large amounts of required minerals, and cattle need both macrominerals and trace minerals. Macrominerals include calcium, magnesium, phosphorus, potassium, sodium, chlorine and sulfur, while trace minerals include iron, manganese, copper, zinc, selenium, cobalt, iodine, chromium, molybdenum and nickel. Many minerals are available in the soil and therefore the need for supplementation can vary by geographic region.
At KSVDL we have recently seen several cases of acute hepatic necrosis in which the common thread in the history is mineral supplementation, sometimes higher than labeled recommendations. In case 1, calves were processed which included vaccination and supplementation with an injectable mineral product at 2.5 times the labeled dose. Within 48-72 hours, three calves died and the third one was submitted for necropsy. The cows had been supplemented with an oral mineral source. Case 2 consisted of cows with chronic wasting and a history of a liquid supplement being used. Case 3 was two calves that died 2 days after vaccination and administration of an injectable mineral supplement at higher than the labeled dose.
Figure 1. Liver from case 1 that is soft
Figure 2. A central area of liver necrosis
Over supplementation of minerals can cause various clinical signs, lesions and death. Acute selenium toxicosis is usually evident within a few hours to two days after overconsumption or injection. Major lesions can include pulmonary edema, pulmonary congestion, pulmonary hemorrhage, hepatic necrosis, myocardial necrosis, myocardial hemorrhage, and renal necrosis. Acute copper toxicity often causes severe hemorrhagic gastroenteritis and congestion of the liver, kidneys and spleen, while chronic copper toxicity results in gunmetal-colored kidneys, port-wine-colored urine, icterus, an enlarged spleen, and hepatic and renal necrosis. Toxicity from iron can result in enteritis, liver necrosis, icterus and hemoglobinuria. In addition, toxicity from zinc will result in lesions of gastroenteritis, renal necrosis and liver necrosis.
Many mineral toxicities can cause liver necrosis, and we have seen cases of this at KSVDL with histories that indicate mineral over supplementation. In many cattle operations, cows are supplemented with an oral source and calves are given an injectable. Multiple sources of mineral supplement and/or a large injectable dose can result in an overdose leading to acute liver necrosis and/or other lesions described above. It is important to consult a bovine nutritionist when considering mineral supplementation. If you suspect a case of mineral over supplementation, samples of formalin-fixed liver and kidney, fresh liver and kidney, and serum should be submitted to KSVDL to adequately evaluate lesions and mineral levels in the case.
1. Merck Veterinary Manual, http://www.merckvetmanual.com/mvm/toxicology/.
2. Maxie, G. Pathology of Domestic Animals. Fifth edition. Volume 2: Liver and biliary system. 2007.
3. Osweiler, Gary D. Toxicology. Chapter 17: Metals and Minerals. 1996. Pg 179-212.