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Most forages fall short of nutrients at calving

This is not a typical Prairie winter for pregnant beef cows ready to calve.

Right after New Year’s, Calgary smashed a 100-year weather record of 12.8 C. The next day, Manitoba shattered 11 temperature records. Saskatchewan wasn’t left out; Maple Creek reported a record of 16 C. What does this mean for beef cows just weeks or a month away from calving?

Although we slipped in to a few days of very cold (more seasonal temperatures) in mid-January, it means most cattle probably began winter in pretty good shape. That means chances are good beef cows, overwintered on a nutritious feeding program, should not be hampered by the typical cold Canadian days and should be in good body condition for a successful calving season. It also means producers should continue to feed a good post-calving diet so there is enough milk for calves, and at the same time cows can maintain proper body condition for successful re-breeding.

Part of the feeding challenge is to meet the high nutrient needs of the individual nursing cow, which represents the greatest demand for nutrients by the cowherd compared to any other time of the year.


Dietary energy and protein requirements of a beef cow nursing a calf nearly double, compared to the start of the winter season. Similarly, mineral and vitamin requirements grow too. The demand for calcium (re: milk contains about 0.12 per cent Ca) increases by 80-90 per cent, while related phosphorus and trace mineral usage grows by a conservative 50-60 per cent. Vitamin requirements (Vitamin E is sometimes called the “fertility” vitamin) tend to double or triple. In addition, milk contains about 87 per cent water, and therefore a milking cow can now easily drink 45-50 litres from a waterer per day, up from a normal 25-30 litres before calving.

According to the National Research Council, a 600-kg mature cow maintaining a descent body condition score of 2.5 (re: 1 = thin to 5 = obese) and producing 10 litres of milk for her calf should consume about 14-15 kg of dry matter feed containing at no less than 58-60 per cent TDN (total digestible nutrients) and about 10-11 per cent crude protein with a full complement of macro- (calcium and phosphorus), trace-minerals (i.e.: copper, zinc, selenium) and vitamins (A,D and E).

Furthermore, although first-calf heifers often do not eat as much or produce as much milk as older cows, their dietary concentrations for the same nutrients are slightly higher because they are still growing to full bodyweight. A compliment of 62-63 per cent TDN for dietary energy and 11-13 per cent protein should be formulated into their diets.


Under normal circumstances, it’s not that difficult to develop respective lactation feeding programs as long as we remember energy and then protein are the first and second limiting nutrients for all post-calving cows.

Of the two nutrients, energy is the largest and more dynamic nutrient to meet, but after the basic body functions of the cow herd are achieved, milk production is given a top priority for this precious nutrient. Any leftover energy is spent on growth, building back loss body condition and finally on reproduction. (As a footnote, it is nearly impossible to put back body condition on thin post-partum cows, and if cold weather is a significant factor, a lot of dietary energy is used by cows just to keep warm!).

Next protein requirements must also be met in order to prevent a loss of milk production for nursing calves, which in turn could directly affect their growth and future weaning weights. A lack of protein can also delay a return to estrus by cows, which is often complicated by a energy deficiency.

In addition, part of any good feeding program for lactating beef cows also should include well-balanced mineral (and vitamin) levels that tend to maintain or improve good cow mineral status. Macro-minerals, trace minerals and Vitamins A, D and E play a wide range of metabolic roles in the cow after calving from visible basic body functions and lactation performance to what we cannot see, such as healthy follicular development and commencement of the estrus cycle for rebreeding.


Regardless as to how lactation diets are formulated with minerals or any other nutrients on paper, meeting these requirements on a practical basis really comes down to the type and quality of forages available on the farm. Since forage makes up nearly 90 per cent of the pre- and post-calving diets, it will determine the type and amount of nutrient supplementation required by the lactating beef cows.

For example, with the exception of corn and barley silage (re: high-energy forage), most common dry forage such as grass, mixed or alfalfa hay have a dietary energy, range from 55-60 per cent TDN and protein ranging from nine to 18 per cent. As a result, nearly all forages don’t meet the energy requirements of post-calving and nursing cows and need to be supplemented with an energy supplement such as feeding high-energy grains or byproducts. And if you have lower-quality forages they will require added protein.

Consequently, the most economical supplementation of encompassing lactation diets are those that need less nutrient supplementation and closely matches the nutrient shortages found in the forages. Consider the following three lactation-feeding programs and average/estimated costs:

  •  12 kg good quality alfalfa-mixed grass hay (58 per cent TDN, 15 per cent protein) supplemented with 1.5 kg of barley grain. 100 g of a 2:1 mineral w salt. Estimated cost: $1.48/head/day.
  •  12 kg grass hay (52 per cent TDN) supplemented with 3.0 kg of distillers’ grain. 100 g of a 2:1 mineral w salt. Estimated cost: $1.59/head/day.
  •  10 kg of barley silage (65 per cent TDN, 9 per cent protein), 8 kg of grass hay with 1.0 kg of distillers grains, 100 g of 2:1 mineral w salt. Estimated cost: $ 1.25/head/day.

Despite their total feeding costs, most post-calving cow feeding programs are usually a continuation of late-gestation beef cow diets. Only this time, the demand for dietary energy, protein, minerals, vitamins (and water) must be fed in greater quantities. Assuring such feeding challenges are met should generate good milk production for profitable growing calves and good reproductive performance for profitable once-again pregnant beef cows. †

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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