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Good trace mineral status in cows leads to good rebreeding economics

Profitable cow-calf operations achieve a calf crop of more than 90 per cent, while herds struggling to meet a threshold calf crop of 85 per cent will likely not meet most production expenses. The root of reproductive success often lies in cows consuming proper post-calving diets, which encompass a good supply of essential trace minerals.

As part of this post-partum trace mineral package, there are four principal trace elements which are very important for good cow reproduction — copper, zinc, manganese, and selenium. All too often in nature, they are either low or marginally deficient in soils and forages or are bound up by inorganic antagonistic compounds that make them “biologically unavailable” to even the most fertile cows.


For example, even the most promising cows truly marginally or clinically copper-deficient will often suffer from poor first-service conception rates and poor embryonic survival. Some of these copper-deficient cows may actually show normal estrus behaviour, but normal ovulation does not occur and may lead to future estrus retardation.

Such erratic heat cycles might also be caused by antagonistic minerals such as molybdenum or high levels of zinc affecting copper metabolism. Unfortunately, producers could have a hard time pinpointing copper, and the other three essential trace mineral deficiencies, because of many nutritional and other unrelated reasons that cause poor reproductive performance.

Sometimes, cow trace mineral-linked reproductive problems are caused by producers not providing on a regular basis of a well-balanced commercial cattle mineral fortified with bio-available copper, manganese, zinc and selenium. Failure to invest as little as 15 cents per cow per day to assure good trace mineral status after calving, and into subsequent breeding season has dire consequences.


It may start with a good portion of the cow herd having one delayed estrus cycle by 80-85 days post-partum. The delay of only one heat cycle offsets the birth of their respective calves by a corresponding 21 days. Because they were born later, these calves lose a potential 21 days of growth and if they should have gained two lbs. per head; results in 42 lbs. of lost weaning weight on any specific sale date. Assuming $1.55/lb. for a 600-lb. weaned calf translates into $65 of lost revenue per late-born calf. These calves from delayed mothers might still be sold at a targeted weaning weight at a later date, but there is always a likelihood of off-season discounted markets.

Fortunately, producers can still recoup some revenue from selling late-weaned calves, but if the same cows continually fail to cycle due to poor mineral status, they may become “open” cows. A cow that does not cycle, conceive and produce a calf for the fiscal year produces no revenue and her feed and management costs become a financial burden to the rest of the herd.

We might choose to illustrate an un-pregnant cow’s liability to rest of the operation in the following way: (1) assume it costs about $2 to feed a brood cow during a 200-day winter, and $1 per day to feed her on summer pasture and these feed costs account for 65 per cent of her total costs (housing, medical, fuel, etc). Consequently, the total costs per cow would be about $870 per year, (2) we pencil in that X per cent calf-crop produces: X multiplied by 600-lb. calves = sold lbs., and (3) there is no open cow salvage value.

By using only these three parameters and regardless of the sale price of the present calf crop, the “additional” cost of keeping open cows, which must be covered by actual sold lbs. of weaned calves, increases dramatically; 90 per cent calf-crop = $0.16/lb.: 85 per cent calf-crop = $0.25/lb.: and 75 per cent calf-crop = $0.48/lb.!

This is an undesirable trend that dictates: as the herd’s calf crop shrinks, an open cow’s liabilities dramatically increases and inherently must be covered by diminished revenues.


How easy it would be to prevent such reproductive drama and chaos, if a good mineral-feeding program was established in the first place!

Consequently, the following nutritional and management suggestions are helpful in assuring that fertile cows build good trace mineral status for the breeding season, when commercial cattle mineral is poured into their feeders:

  •  Target cow herd mineral consumption. The best well-formulated mineral containing adequate copper levels cannot do its job unless cattle eat it. Target the above mentioned 50-100 grams per head per day. If cattle are not eating enough or too much, add 1/3 portion salt to the mineral mixture.
  •  Know the dietary trace mineral sources in your mineral. This is particularly important when purchasing cattle mineral. For example, knowing copper’s final concentration of your cows’ diet without knowing the source of supplemental copper is of little value. Copper comes in many forms such as copper oxide, copper sulphate, and chelated copper forms, which respectively have relative biological availabilities of five per cent, 100 per cent and 125-150 per cent in cattle.
  •  Feed a “breeder mineral” all winter long. Some producers feed a more fortified breeder mineral (with more bio-available organic trace minerals) all winter long. The cost-difference between a basic gestation and calving/breeding mineral calculates to about $4 per head premium for the first half of the winter.
  •  Fill your mineral feeders regularly. Mineral feeders should be filled every two to three days and hardened old mineral should be removed. It’s also important to remove snow and debris that prevents good mineral consumption.

Success of taking such conscious trace mineral-feeding actions to build good trace mineral status for good rebreeding in cows is easily visible; post-partum cows cycle one or two times before a limited breeding season actually begin and tend to get pregnant by breeding bulls within weeks of release. These cows also tend to give birth and nurse healthy calves, which in turn are heavier and thus more profitable on an established weaning date. †

About the author


Peter Vitti is an independent livestock nutritionist and consultant based in Winnipeg. To reach him call 204-254-7497 or by email at [email protected]



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