Maintaining good nutrition in beef cows after calving largely involves continuing with the well-balanced diets that were fed to them as late-gestation cows.
Years of beef research demonstrate that cows that calve out in optimum body condition score of between five and six, compared to thin fresh cows, have a greater chance of an easier calving, of producing large quantities of colostrum with more immune antibodies and producing more milk for their newborn calves. (The nine-point body condition score ranges from one being emaciated and nine being obese).
If optimum body condition is maintained through to breeding season, cows show a quick return to fertile estrus, which leads to high rates of conception with next year’s calf.
Maintaining optimum body condition in breeding beef cows can be viewed as the specific amount of dietary energy that is surplus from meeting the energy requirements for vital functions and milk production as well as replacement heifer growth. It is stored as layers of body fat in beef cows.
Postpartum beef cows’ requirement for dietary energy increases 25 to 35 per cent and for crude protein increases 10 to 15 per cent compared to late-gestation beef cows of the same stature. Both of these nutrients are largely utilized for milk production. About 75 per cent of the milk produced by fresh cows and consumed by their calves is produced in the first 60 days after calving. Therefore, most nursing cows require about 60 – 62 per cent TDN (total digestible nutrients) and about 11-12 per cent crude protein in their diet by the time they are milking at their highest levels. Growing first-calf heifers need a similar amount of these nutrients too.
In addition to extra energy and protein, beef cows after calving require a more fortified mineral and vitamin feeding program. For example, bovine research shows that an average cow producing 10 to 15 lbs. of milk per day requires about two times more calcium compared to a non-milking, late-gestating beef cow. They also proved that phosphorus deficiencies reduce milk production as well as reduce utilization of dietary energy to maintain optimum body condition. There is also work that shows deficiencies in both minerals delays post-calving estrus as well as puberty in unbred first-calf heifers.
Don’t forget the trace minerals
Trace minerals are also documented to play significant roles in beef cows’ milk production but their heavy focus tends to be preparing beef cows for the upcoming breeding season. For example, copper, zinc, manganese and selenium (and vitamin E) are part of important enzyme systems that are linked to good reproductive activity.
As a beef nutritionist, I have formulated many post-calving cow diets to meet each of these required major nutrients. Here is an outline of each important nutrient group as it relates to my dietary advice:
- Energy — Lactating beef cows consume 30-40 lbs. of feed (dm, basis), each day. So, I often develop a diet based upon a 90 per cent forage base, which should be of good quality and mould-free until cows are released onto spring pastures. Until then I would also supplement with one to two pounds of high-energy grain such as corn or barley. Limit alternative ensiled forages such as corn silage to avoid over-conditioning of beef cows.
- Dietary protein — Postpartum beef cows need a 11 to 12 per cent protein diet. A mixed legume-grass hay can fill this demand. Although alfalfa hay or silage can be used, feeding a sole 18 to 20 per cent hay is not recommended. This could lead to diarrhea and possible loss of body condition. In contrast, avoid feeding low-quality straw as the main forage, because they are typically deficient in both protein and energy.
- Mineral/vitamin program — A well-balanced program should either maintain or build up adequate mineral and vitamin status of the postpartum cow. It should compliment macro-minerals found in the forages and assure that trace minerals are consumed in adequate amounts.
By following good dietary parameters, it really showed me the right direction to put together well-balanced post-calving cow diets. It also taught me the value of meeting the much higher dietary requirements, as beef cows change from gestating into lactating fertile cows.