In the September issue we discussed formulating rations for backgrounding cattle and focused on the importance of targeting performance. The take-home message is, if one wants to target a specific rate of gain regardless of the class of cattle you are feeding, a nutrition program needs to be developed that meets the nutrient requirements of the cattle for the expected level of performance with an emphasis on appropriate dietary energy content. However, developing such a program, particularly if you feed a variety of classes of cattle (i.e. different ages, weights, sexes) is not easy, particularly if you want to keep the feeding program relatively simple and easy to implement.
The approach that the vast majority of larger finishing operations employ and which I find can be easily implemented on smaller operations is to develop a step-up feeding program. These programs are a series of rations that increase in energy content at each step. The number of steps is determined by the nature of the operation and the type of feed available. For example, I find that a 4- to 5-step program can work well for backgrounding operations, while finishing operations can utilize up to eight steps. Each step is formulated to a defined energy content and is achieved by manipulating the dietary forage-to-concentrate (grain plus supplement) ratio.
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The following program is one that I like to follow for backgrounding newly weaned calves. The starter ration (step 1) is typically 55 per cent forage and 45 per cent concentrate on a dry matter (DM) basis. In terms of total digestible nutrients (TDN per cent), the energy content is 67 to 68 per cent TDN or approximately 1.55 and 0.95 megacalories per kilogram DM of net energy for maintenance (NEm) and gain (NEg), respectively. With respect to makeup of the forage, I like to see an equal proportion of silage and hay (DM basis). This helps to promote feeding behavior with the goal of having newly weaned calves eating at 2.5 to 2.7 per cent of body weight (DM basis) within three weeks of arrival.
Once the cattle are eating at a level I am comfortable with, it is time to move to the next step. The nature of this move, however, will depend on the weight of the calves and the target gains for the pen. For light weight calves, step 2 is formulated to higher forage content (i.e. 60 to 65 per cent forage, DM basis) and as a result, a lower dietary energy content (i.e. 65 per cent TDN or lower). This step is used when it is necessary to limit gains to less than two pounds per day. An example of its use would be for backgrounding lightweight calves that are destined for grass in the spring or for growing out replacement heifers. With such cattle, one typically targets overwintering gains of 1.5 to 1.75 pounds per day.
Heavier calves are typically backgrounded over the winter at higher rates of gain (i.e. 2.2 to 2.75 pounds per day) and destined for finishing in the spring. For such cattle, step 2 is typically not required. Once these calves are adapted to feed, they typically move from the starter ration to higher energy diets. This is accomplished by reducing the forage-to-concentrate ratio in a defined fashion. For example, step 3 might be formulated to 50 per cent forage and 50 per cent concentrate (DM basis) and a TDN content of 69 per cent. The forage content would decrease to 40 and 30 per cent (DM basis) in steps 4 and 5, while TDN content increases to 71 and 73 per cent, respectively. Further, if one wanted to finish cattle, each succeeding step (i.e. steps 6 through 8) would continue to decrease the forage content by five to 10 per cent and increase the concentrate until the final finishing ration is reached at approximately 10 per cent forage on a DM basis.
There are several advantages to using such programs. Perhaps the most important is the knowledge that at each step you are dealing with a specific dietary energy content that can be expressed as TDN or as net energy. With this knowledge it is possible to match energy needs of a specific pen of cattle with the appropriate ration. Cattle performance becomes much more predictable and you have more faith in your break-even analysis. A second benefit is that it becomes easier to transition cattle to higher energy rations. Since each step is set in terms of forage-to-concentrate ratio, moving from one ration to the next can be done smoothly by providing a minimum of three to four days on each step of the program. This helps to minimize potential digestive upsets such as sub-acute acidosis and bloat. Finally these programs allow one to set protein, mineral and vitamin levels at each step of the program that matches the requirements for the class of cattle that will spend the greatest period of time on each step.
For those interested in developing a step-up feeding program, I would suggest that you work with your nutritionist or feed company representative. These professionals can work with you to develop the nutrient specifications at each step and formulate the rations using your feed resources. They can also provide helpful advice regarding feeding and bunk management.