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More questions on mineral nutrition (part 2)

Nutrition with John McKinnon

cows at a mineral feeding trough

With this column, I want to continue our discussion on mineral feeding. Last month I addressed questions regarding the adequacy/availability of trace minerals naturally found in tame and native grasses and how effective they were in meeting requirements; the role of sulphur and molybdenum in copper deficiency, and the need to understand your mineral tag when purchasing the correct mineral for your situation. In this column, I want to address the need for year-round mineral feeding and management of the mineral feeder.

One of the more common questions I get involving mineral supplementation goes something like this: “Do I need to feed minerals year-round?” The simple answer is yes! While requirements for specific minerals will vary with stage of pregnancy, breeding status, age of the animal and body reserves, your cows still require appropriate supplementation throughout the year.

Remember that in last month’s column I wrote that many minerals in forages are poorly absorbed by adult cattle. Failure to supplement at strategic times such as during the spring and/or summer or over the winter will simply deplete an animal’s reserves and lead to deficiency situations. For cows that have calved and are attempting to return to normal breeding status, such deficiencies can be difficult to correct and lead to reproductive issues such as delayed estrus and/or poor conception rates.

Short-term fixes such as supplying a mineral post-calving do not always work. A more realistic approach is to work with your feed company or nutritionist to develop an understanding of your forage base in terms of their macro (i.e. calcium, magnesium) and trace (i.e. copper, zinc, manganese) mineral content as well as soil molybdenum levels and water quality (i.e. sulphate levels). With this information you and your nutritionist can develop a mineral feeding program that meets the requirements of your cow herd 365 days a year! Such a program can include a mineral designed for early as well as late fall range conditions, a mid-gestation mineral for feeding over the winter and, finally, a pre/post-calving mineral that may include a percentage of chelated trace minerals to ensure optimal reproductive performance.

Management of the mineral feeder is another area producers often have questions about.

One common complaint is: “I can’t get cows to eat mineral, or they eat it like candy and won’t stop!” Poor mineral consumption can in some cases be related to specific commercial mineral mixes. Some are less palatable than others, which can be related to a high phosphorus content, the presence or absence of specific flavou­ring agents or salt content.

Location of the feeder on pasture can also influence intake, depending on where it is situated in relation to salt blocks, water sources and supplemental feed. If the mineral is low in salt and located on the other side of the pasture from your salt blocks, consumption is likely to be poor.

How often do you refill your mineral feeder? It’s hard for cows to consume mineral consistently if your feeder is empty half of the summer.

As to the comment that cows won’t stop eating mineral, the first question that should come to your mind is: “When was the last time they had access to mineral?” Cows that have not seen mineral for a prolonged period will likely overeat when they get fresh mineral and may take two or three weeks to get their fill. If you continue to have issues with over-consumption, my advice would be to provide a two- or three-week supply (based on the recommended daily per head intake found on the tag) in multiple feeders so that all cows have access. Regardless of how quickly the mineral disappears, do not refill the feeder until the two- or three-week period is up. In other words, limit feed to recommended intake levels.

Finally, let’s look at troubleshooting a mineral problem. First and foremost, don’t wait for a wreck to occur before seeking professional help. Once you start seeing issues with milk fever, lameness, retained placentas or open cows, it is too late. At this stage you are dealing with deficient cows and, as discussed above, it is difficult to identify and correct the issue in a short time frame.

Secondly, if you are seeing thin or open cows or infertile bulls, make sure it is a mineral problem and not just a lack of energy or protein. Confirmation of a deficiency is best achieved through a blood sample and/or liver biopsy taken by a veterinarian from suspect animals. Troubleshooting a program also involves knowledge of mineral intake at different stages of the production cycle, which implies keeping track of how much mineral is purchased and fed throughout the year. Such knowledge can lead to recommendations related to the placement/management of the mineral feeder, the need for salt supplementation and potential palatability issues. Working with your nutritionist will also help you evaluate if you are feeding the right mineral for your operation, taking into account forage species, soil molybdenum levels as well as water quality.

About the author


John McKinnon

John McKinnon is a Professor Emeritus at the University of Saskatchewan and a consulting nutritionist who can be reached at [email protected].



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