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Getting the most out of your grass cattle

Nutrition with John McKinnon

As this issue comes to print, we are likely 40 to 60 days away from turning yearlings out to grass. The vast majority of these animals are last year’s calves weaned in the fall or early winter. If we examine how these animals are overwintered, two different management approaches are evident. The first is to buy or retain lightweight calves in the fall (i.e. 350 to 450 pounds) and grow them out over the winter at daily rates of gain ranging from 1.25 to 1.75 pounds. These cattle are typically on feed for 200 days or so. Target gains are achieved by feeding high-forage, relatively low-energy diets.

A second approach is to purchase calves in the early spring (i.e. late February, March) prior to pasture turnout. Typically, these are later-weaned calves that are somewhat heavier (i.e. 450 to 600 pounds). As with the first group, a backgrounding period (i.e. 70 to 90 days) is required to get them to an appropriate weight for grass. Daily gains of 1.5 to 1.75 pounds are typical.

For both groups, target weights going to grass will range from 650 to 800 pounds, depending on initial weight and days on feed. The goal of both programs is to turn “green” cattle out to grass with sufficient frame and muscle development such that they continue to grow efficiently on pasture. What we do not want is to turn “fleshy” cattle out to pasture that are showing early signs of laying down fat.

A question I often get is why do we worry about the condition of yearlings going to grass? In order to understand the relationship between gains in the feedlot and subsequent gains on pasture, one needs to examine the phenomena of compensatory gain. Much like heterosis, compensatory gain on pasture is one of nature’s gifts to the cattle industry. While heterosis refers to improved growth or function in crossbred versus purebred offspring, compensatory gain refers to the fact that cattle that have been moderately restricted in growth will gain at greater than expected rates once they have access to a “normal diet.”

In the two scenarios above, cattle are moderately restricted in their growth for various lengths of time prior to grass. Once they have access to spring grass with its dense nutrient content, these cattle will gain at significantly higher rates than predicted for the first 60 days or so of the grazing season. Contrast this with similar-weight yearlings that have been backgrounded over the winter at higher rates of gain (i.e. 2.25 to 2.75 pounds per day). Such cattle, particularly those with British breeding, will not only develop frame and muscle but will also start to lay down fat. As a result, they have a fleshy appearance going to grass. Such cattle are prone to losing condition when turned out on grass and do not get off to as fast a start as leaner cattle. Thus, in terms of maximizing pasture gains, the condition of your cattle going to grass is of paramount importance.

For those not enrolled in a natural beef program and wishing to maximize pasture gains, implanting yearlings going to grass is a no-brainer. Depending on the implant used, implanted grass cattle can gain 20 to 40 pounds or more than non-implanted cattle. There are a number of options, including implants that contain estrogen or its derivatives as the primary growth-promoting hormone to those that incorporate a combination of estrogen and trenblone acetate. These latter implants are typically more potent growth promoters.

One of the key considerations when choosing an implant is its payout period or the length of time it effectively releases hormones into the animal’s blood stream. Effective payout periods for many of the implants used with grass cattle range from 70 to 200 days. The goal is to match the payout period of the implant with the length of time you own or manage the cattle. For example, if cattle are implanted prior to grass turnout, implants with shorter payout periods are likely the best option. However, for cattle backgrounded over the winter where multiple implants are used, longer-acting implants — particularly when given in the early winter/spring — can eliminate the need for re-implanting and ensure coverage over the entire grazing season.

The use of an ionophore can also enhance pasture gains. In Canada, both monensin sodium and lasalocid sodium have label claims for increased weight gain of feeder cattle on pasture. The challenge is to ensure consistent daily consumption. According to their medicated ingredient brochures published by the CFIA, both products can be fed daily on pasture when incorporated as part of a hand-fed supplement specifically formulated to provide a targeted dose of either ionophore. As well, lasalocid sodium can be used in the formulation of registered free choice medicated mineral feeds.

Finally, choosing an appropriate mineral can help ensure the health and productivity of cattle on pasture. Depending on your situation, a simple trace mineral salt may suffice or you may need to look at a 2:1 or 1:1 mineral with specific trace mineral levels. A relatively recent innovation to the pasture mineral program is the inclusion of chemicals or ingredients that help control various classes of biting flies.

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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