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Nutrition with John McKinnon

Cows coming into calving in poor shape is a consequence of how they are fed over the winter.

I attended a producer meeting in Weyburn where speakers addressed issues with winter feeding. One of the speakers, Leah Clark, a livestock agrologist with the Saskatchewan Ministry of Agriculture gave an excellent presentation on body condition scoring (BCS). Her focus was the relationship between a cow’s body energy stores, nutrition program and the subsequent impact on reproductive success and performance of offspring. The message resonated with me and I thought I would pass on a few of the points that were raised, as they apply to beef producers across the country.

As we have discussed many times in this column, thin cows at calving or those that lose weight through the breeding season are at risk of a longer anestrus period and/or poor first service conception rates. In either case, both the breeding season and subsequent calving season are extended. The consequences of which can include an increase in the number of open cows and negative effects on calf growth both for the current as well as next year’s calf crop. For example, newborn calves will receive less milk as the cow is not milking to potential while next year’s calf crop will be lighter due to the fact that more calves are born later in the calving season and have less time to grow through weaning. In all cases, these issues can be traced back to inadequate nutrition at some point over the last six months of the cow’s life. The fact that cows are coming into calving in poor shape is a consequence of how they have been fed over the winter. Either they have come off pasture in thin condition and were not fed to regain weight, or they have lost weight due to an inadequate winter feeding program. Similarly, cows that are not fed to meet lactation requirements will lose weight from calving through breeding and pasture turnout.

The key to preventing these issues is to develop a winter feeding program that matches the cow’s requirements for pregnancy, particularly in the last trimester and for milk production after calving. From a nutrient perspective, requirements for energy, protein, minerals and vitamins peak during these periods. Failure to meet requirements will result in the negative effects discussed above. Complicating matters is that some cows may come off pasture in thin condition and need to gain weight over the winter, first and second calf heifers have both pregnancy and growth requirements; and in all likelihood at least once or twice a winter, extreme cold weather will increase the animal’s maintenance energy needs and if not accounted for will result in weight loss. Clark’s presentation pointed out the need to account for these factors by grouping animals according to age, body condition (thin, normal or over-conditioned) and stage of pregnancy, and to develop targeted feeding programs for each group. Body condition scoring is a tool that can help you achieve this goal.

Body condition scoring is a means of physically assessing the amount of fat an animal is carrying and by proxy, its nutritional status. Scores range from 1 (extremely thin) to 3 (normal body condition) to 5 (over-conditioned or “fat”), and are assigned by physically feeling for evidence of fat over the short ribs, along the backbone and in areas such as the hooks, pins and tail head where only bone and fat is present under the hide. In under-conditioned animals (BCS 2 or less), it will be very easy to feel the ends of the short ribs, while in over-conditioned animals (BCS 4 or 5) it will be very difficult to feel any bone in the areas of the skeleton mentioned above.

By gaining experience with this system, you will gain the ability to sort your cows into groups that need to gain weight, those that can maintain weight and those that are over-conditioned. Implementing a condition scoring system at appropriate times such as at pregnancy checking, and taking into account factors such as age (first or second calf heifers and older cows) and pregnancy status, it is possible to group cows according to nutritional needs and develop a feeding program accordingly. For example, cows that have a BCS of 2 or less in the fall will need to be fed to gain weight over the winter such that they are in a BSC of 2.5 to 3 at calving. Depending on the animal this can involve a gain of 100 to 200 pounds and will require a ration that has appropriate energy and protein levels to support this level of weight gain. In contrast, cows with a BCS of 2.5 or higher can be maintained on a lower-quality diet for much of the winter before addressing the needs of the last trimester of pregnancy. Those with excess condition can actually be allowed to lose condition during the early part of winter without jeopardizing health or pregnancy. In short, BCS can help you fine-tune your feeding program. For more details on implementing a BCS system, consult the Beef Cattle Research Council website, or one of the many outstanding young agrologists in the public and private sectors.

About the author


John McKinnon

John McKinnon is a Professor Emeritus at the University of Saskatchewan and a consulting nutritionist who can be reached at [email protected].



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