Since essential mineral and vitamin status of many brood cows were run down by the the summer drought in parts of Western Canada, it is important producers do not overlook the value of good mineral intake particularly at a time of year when good mineral consumption is very important — just before calving.
Good mineral intake by gestating beef cows helps supplement the essential minerals and vitamins often deficient or biologically unavailable in many forage-based diets, and helps cows maintain or build good mineral status in many areas of metabolism. Three main areas in the beef cow’s body that require good mineral intake in order of their respective demands are: (1) the immune system; (2) good reproductive performance; and (3) vital body tissues.
When insufficient mineral intake lowers mineral status in cows to a marginal state, immune response to disease tends to be compromised first, well before reproduction performance suffers (poor heat cycles, and low conception rates) and any disruption to general body functions. It is believed the overall mineral requirements for immunity are much greater, respectively.
Important for the calf
It is also no secret that good mineral intake by the cow herd not only affects the mineral status of each cow, but that of each unborn calf as well.
The developing calf fetus is depends on the availability of essential minerals travelling through the placenta from its mother’s blood. Subsequently, the fetus has a natural ability to concentrate certain trace minerals such as iron, copper, zinc, manganese, and selenium. It’s an instinctive means of post-calving survival, since colostrum and milk can be low in these micro-minerals. For example, selenium status in the fetal and newborn calf is only a reflection of the selenium status of its mother during gestation — white muscle disease in newborn calves is cited as a direct result of selenium deficiency in freshened cows.
The general daily recommendation to meet these nutrient requirements is to feed commercial cattle mineral so each cow consumes between 56 and 112 grams (two to four ounces) of salt-free mineral per day. If salt makes up at least 25 per cent of this mineral, one should adjust suggested mineral intakes accordingly.
Since most producers feed loose granular cattle mineral and fill a mineral feeder, bunk or tub by the 25-kg bag: a 200-cow herd targeted for 85 g (3.0 oz.) mineral intake per head should eat about 17 kg of mineral per day, which means the cow herd would consume about two bags (50 kg) every three days (17 x 3 = 51 kg).
Without using a calculator, another good mineral consumption rule of thumb is that each beef cow should consume one-half 25-kg bag of cattle mineral for a six-month (November 1 to May 1) winter. That means a producer that owns 200 beef cows should purchase about 100 bags of commercial cattle mineral by next year’s calving season, regardless of what type of cattle mineral program that is chosen.
One should realize that mineral consumption among beef cows is likely not an exact science and therefore producers may encounter little, some or significant variation. Here is an illustration of some the leading causes of mineral intake variation:
- Natural variability. It is generally accepted that given a group of cattle, mineral intake plotted on a graph forms the shape of a bell curve. This means that about half or more of the cows should consume about the target mineral intake amount, while a small fraction eat less than desired, while the remainder eat more than their fair share. The only concern is that some cows may not be meeting their entire total mineral and vitamin requirements.
- Individual cow variation. While it assumed mature cows should eat more than replacement heifers, practical experience says there is no rhyme or reason to how much mineral some individuals consume.
- Day-to-day variation. Individual cattle and the whole cow herd will likely not consume the same amount of mineral every day. Target mineral intakes (56 to 112 g) should be based on averaging targeted intakes over a weekly or biweekly.
- Water quality. Cattle drinking water with high total dissolved solids (TDS) tend to consume less mineral than water of lower TDS. Also, cattle tend to reject commercial mineral if they drinking high-saline water.
Regardless of intake variability, beef producers should still be able to target their beef herd toward the standard recommendations for good mineral intake. Fortunately, there are options to correct a possible mineral consumption shortfall. One common practice is to mix 1/3 salt with 2/3 commercial cattle minerals to either increase or decrease the amount of mineral cattle are consuming.
Adding distillers’ dried grains or dried molasses at four to five per cent of the mineral has also become routine to stimulate mineral intake. In many cases, when mineral intake is low or high, it is a good idea to review the rest of the cattle diet and insure a well-balanced ration for beef cows is fed.
Some mineral consumption troubles are not product-, diet- or cattle-related, but due to the way mineral feeding is managed. The condition, stocking rate, and location of mineral feeders have been implicated in many troublesome herds. Experience dictates a mineral feeding station be provided for every 25 to 30 cows and mineral feeders located near (but not too close to) a water source. Cattle mineral should also be checked every couple of days, never allowed to harden like concrete and be kept out of any bad weather. †