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Brood cow nutrition part of fall planning

The best indicator we have for assessing the nutritional status of beef cows is body condition and all measures of production are tied to this. Thin cows produce poorer-quality colostrum, have weaker calves, wean lighter calves and are less likely to breed back in the first 21 days of the breeding season producing more open cows in the fall. Because 50 per cent of fetal growth occurs during the last 60 days of pregnancy, managing body condition through the last three months of gestation becomes important.

Poor body condition can influence the size of two calf crops: this year’s and next. Using body condition scores this fall to assess the nutritional status of cows as they come off pasture is the right place to start planning nutrition programs for the winter. Having cows in optimum condition for calving season next spring will impact things like the length of calving season the following year. When the breeding herd is in good condition, producers make better use of their bull inventory and benefit from better response to vaccines used in both cows and calves.

For example, going from a BCS 2.0 (thin) to a BCS 3.0 at calving, gains up to 30 days in return to heat after calving. In other words, a cow between BCS 3.0 and 3.5 will start cycling about a month earlier than a herd mate at BCS 2. This single step helps maintain a 365-day calving interval and the reproductive momentum herds need to maximize profit.

The body condition of a brood cow significantly impacts her economic contribution to the bottom line. Tracking body condition scores and monitoring the year-to-year productivity it influences allows producers to makes performance-based decisions on matters like adjustments to rations, time of weaning, managing the breeding herd in groups through fall and winter, and culling strategies. Planning ahead puts producers in a position to manage, rather than react, when a tough winter or poor feed compromises the health and condition of brood cows.

Optimal targets for body condition scores (BCS) at key times are:

  • Fall pregnancy check, or start of winter feeding program — BCS 3.0
  • At calving — BCS optimum for mature cows is 2.5; optimum score for first-calf heifers is 3.0
  • Thirty days before the start of breeding season — BCS 2.5

A key factor when looking at a group of cows is the number that are thin and below optimum body condition. Small numbers may be indicative of cattle that simply don’t fit your environment or management system; larger numbers are symptomatic of feed shortages, or poor-quality feed. Groups falling outside optimum ranges should be sorted and managed separately. Larger percentages of thin cows indicate a general requirement for additional inputs and a significant change to ration management. Producers should consult an animal health professional (veterinarian, nutritionist) for help.

When rations need adjustment, the sooner they start the easier it is to reach desired targets for weight gain. To move one full point on the five-point body condition scale, say from BCS 2.0 to BCS 3.0, requires 160 pounds additional weight in medium-framed cows and 200 pounds in large-framed cows. Twenty per cent more energy is needed to accomplish this in a 90-day period; 30 per cent more over 60 days.

These figures do not take into account the weight of the fetus. Fetal membranes and fluid, can add up to another 130 to 180 pounds through late gestation. A cow that is just maintaining weight during late gestation is actually losing body mass, and possibly body condition because the fetus is growing by at least one pound per day.

Feed analysis provides important information on the nutrient levels of the feed and is necessary to accurately formulate rations. As much as underfeeding affects body condition and poor performance in the breeding herd, overfeeding is costly and wastes feed.

Important points to remember:

  • The body condition of cows at the start of the winter feeding period has a major effect on the amount and quality of feed required.
  • Cows have greater difficulty gaining weight during cold winter conditions. Thin cows must gain weight through winter. First- and second-calf heifers require additional feed to support growth.
  • Cows coming off grass thin in the fall stand to be thin going onto grass the following spring unless winter rations are adjusted for energy and protein.
  • Cows reach peak lactation around six weeks post-calving. Energy and protein demands also peak at this time.
  • Early-spring grazing is not always the answer. New pasture growth can be affected. Each day grazing is delayed in the spring two or more days of grazing are added in the fall.
  • Cows eat what they like, not what they need. Cows will eat until full, given voluntary free-choice access to feed. Cows do not balance nutrients needs, only feed intake.
  • Nutrient levels of forages and grasses fluctuate widely from year to year (as much as 30 per cent).
  • A cow’s nutrient requirements (energy, protein, minerals) will increase about 30 to 40 per cent with calving. Forage intake will generally increase about 30 per cent.
  • Feed costs represent 50 to 70 per cent of total production costs for cows and the major factor influencing reproductive performance.
  • For a beef female to reproduce, requirements for maintenance, growth and milk production must be met first.

Total body energy reserves greatly affect reproductive performance and profit. Thin cows at calving mean reproductive performance in the subsequent breeding season will suffer. Therefore, as winter approaches and you look forward to optimal reproductive performance in the spring, managing winter rations based on feed quality and nutritional requirements of the cow herd becomes a part of fall planning.

Seek professional help with questions about nutrition and feed analysis. It’s important to remember that all measures of production are affected to some extent by nutrition, and that is the very thing BCS is all about.

Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be emailed to Canadian Cattlemen or WCABP.

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Dr. Ron Clarke

Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen ([email protected]) or WCABP ([email protected]).

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