As winter approaches and forage goes dormant understanding the nutritional requirements of your livestock is of great importance to maintaining a healthy cattle herd. On Average, nearly 40% of a producers total operating cost in a cow-calf enterprise are associated with nutrition because purchased and harvested hay and concentrate feeds make up the majority of the cost. Consequently, the nutritional program represents a major target to trim cost of production. However, it is widely recognized that the nutritional status of the cow is closely related to reproductive performance. If too many corners are cut in the nutritional program, pregnancy and calving rate dramatically suffer. With good management, forage is an extremely valuable renewable resource. As such, it represents the least expensive feed resource to maintain animal health and production in cow-calf and many stocker operations. A combination of excellent forage production and grazing management practices, cattle genetics that match the forage resources and a well-timed calving season results in minimum reliance on purchased and harvested feeds. Nevertheless, specific nutrients must be supplemented at times. The first step in implementing and maintaining an efficient supplementation program for grazing or forage fed cattle is to identify specific supplementation needs. In other words, the producer must identify specific forage nutrients not provided in adequate quantity to meet the animal’s nutrient requirements. The next step is to estimate the nutrient content of standing forage or hay. As mentioned earlier, these values also vary, depending on forage type, maturity and weathering. The most accurate method to determine supplementation needs for cows that will primarily receive a hay diet is to have the hay analyzed for nutrient concentration. Producers can bring your forage and hay samples into your local OSU extension office to be tested, and costs range from $15 to $70 per sample, but can save hundreds, even thousands of dollars in some cases. Cattle have a daily requirement for a certain quantity of specic nutrients such as protein, calcium and vitamin A. The necessary concentration of these nutrients in the diet is then determined by the amount of feed the animal is expected to consume given free-choice access to feed or forage. For example, steer calves gaining 2 pounds per day may require 1.6 pounds of protein per day. If they consume 15 pounds of DM daily, the protein requirement could be expressed as 10.7% of DM intake. On the other hand, if they are limited to consume only 10 pounds of DM daily, the protein requirement for 2 pounds of gain could be expressed as 16% of DM intake. Once nutrient requirements have been established and a reasonable estimate of the nutrient contribution of the forage has been made, determining supplemental needs is simply a comparison of the two. Again, this comparison is easily and perhaps more accurately made using computer software, such as OSU Cowculator. You can gain access to the OSU Cowculator at the following web address: https:// extension.okstate.edu/programs/cowculator.html. For this example, it is assumed cows will graze winter range with little to no hay supplementation. Let’s assume that the average cow weight will be 1,100 pounds and the average calving date is March 15. Consequently, these cows would be grazing low-quality winter range throughout the last one-third of gestation. Let’s also assume that a 1,100-pound cow requires about 1.62 pounds of protein and 11.7 pounds of total digestible nutrients (TDN) per day. Late-winter native range forage would be expected to contain only around 4% protein and 49% total digestible nutrients (TDN). These cows would be expected to consume around 2% of their body weight, or 22 pounds of diet dry matter (1,100 pounds x 2%), assuming adequate supplemental protein is provided. When hay or pasture nutrient concentration can actually be measured (samples collected and analyzed) and monitored, the methodical approach presented previously will be the most cost-effective way to determine the type and amount of supplement to feed. However, many low-cost producers do not feed hay and prefer to use their cows to harvest standing forage. If forage type and conditions are relatively constant from year to year, producers can develop a consistent supplementation program and fine-tune it when necessary. For example, when cattle graze native tallgrass prairie pastures, forage quality consistently declines through the summer, fall and winter months. Protein supplementation needs are quite predictable and may vary more from changing genetics or time of calving than forage conditions. More energy is necessary when wet, cold weather conditions persist for long periods of time. Therefore, feeding higher daily amounts of a moderate-protein supplement is advised when these conditions exist or anytime cows are observed to be losing weight and condition too rapidly. If you have questions about this article, please stop by your local extension office.
