A vitamin or mineral deficiency in bison may take two or more years to develop, but skimping on supplements can lead to problems in growth, diseases or parasites.Minerals are necessary for bone and muscle growth, reproduction and immune and enzyme function.Specific minerals are formulated for bison, but cattle minerals also come close to meeting a bison’s needs in many cases.Testing liver samples at post-mortem or with slaughter animals is the best way to check a specific mineral status. This is more accurate than taking blood samples.Animals cannot meet their mineral needs through regular feed because 75 to 95 percent of the feed grown in Alberta and probably in Western Canada is deficient.Nutritionists assume there are no minerals in the feed when they balance the feed ration. What is in the feed acts as a conservative cushion against deficiencies developing.A mineral deficiency will first cause retarded growth, followed by poor reproductive rates. Deficiencies are slow to develop, and correcting them is also slow because there is generally no magic shot.Supplementation over time is the answer. The first thing to calculate when delivering a balanced mineral regime is how to feed them to meet the recommended amount.For example, if the recommended daily amount is 40 grams, then a 25 kilogram bag of minerals has 625 daily doses.That means 30 head of mature bison should go through a bag every three weeks or so. They might not receive the exact amount, but the important point is to ensure that the animals consume at least some.Bison at pasture are indiscriminate grazers, and the variety of feed they eat helps provide minerals.If mineral consumption is really low, top dress it in feed whenever possible. Giving twice the daily requirements every two days in feed has worked well in cattle, but they should be consuming some minerals every two to three days if possible.Minerals in feeders can work, but the feeders must be solid or they will get either tipped over or broken.Bison grow slower than cattle, so we probably have overestimated the requirements, but young weaned calves and pregnant cows are the two most critical groups.Iodine deficiency causes goiter, which results in stillborn or weak calves at birth. The thyroid gland is visibly swollen in the throat, which makes diagnosis easy.Iodine is available in blue or red salt. Standard minerals contain 40 to 50 percent salt, which acts as an attraction so that the minerals are consumed when the animals are meeting their craving for salt.Copper deficiency can occur in two ways: an actual deficiency or a secondary deficiency, in which a surplus of sulfates or molybdenum in the diet compete with the copper. Sulfates in water can rise and fall, so it is a good idea to periodically check the water supply.Copper deficiency leads to poor growth and bleached hair, often with diarrhea and swollen bones around the joints. These swollen joints are the result of enlargements on the growth plates where the long bones grow.Selenium is deficient throughout Western Canada, and deficiencies particularly show up at handling time when bison run excessively and damage their muscles.The condition is called capture myopathy and we see this with white muscle disease in beef calves. Both conditions are greatly minimized if selenium is included in the minerals. The mineral label will identify the level of selenium.Many types of deficiencies exist.Producers must rely on their nutritionist to balance the package when using commercially prepared minerals. These preparations are developed for a certain region so a local veterinarian, feed mill or agriculturist should determine what is best for your area. However, remember that providing any minerals is better than providing none at all.
Roy Lewis is a veterinarian practising in Westlock, Alta.