It's no secret that feed costs are a major economic component of producing beef. Efficiency of feed and ration balancing are critical to optimizing profits. A balanced ration that's easy and affordable to provide will supply the proper nutrients needed for herd sustainability.

While fiber, mineral, vitamins and water are all important in ration consideration, crude protein (CP) and energy are the feed components most often considered, and confused, by livestock producers.

CP is determined by measuring the nitrogen content of feed and multiplying it by 6.25 because proteins typically contain 16% nitrogen, says Shane Gadberry, University of Arkansas livestock specialist.

But not all nitrogen-containing compounds are true proteins. These are called non-protein nitrogen (NPN) sources. Many of these NPN compounds can have their nitrogen converted to microbial protein in the rumen under proper conditions.

Generally, NPN sources such as urea aren't used as well as natural protein when cattle are on high-roughage rations or have high protein requirements, such as young cattle with high rates of growth, Gadberry explains. True protein sources should be used for the majority of the supplemental CP in these cases.

Recent Oregon State University research shows supplements containing urea or biuret as the primary source of supplemental nitrogen could be effectively used by cows consuming low-quality forage, even when provided every other day. Supplemented animals gained more weight prior to calving than non-supplemented animals. There were no effects of supplementation or source of supplemental NPN on calf birth weights.

More advanced ration balancing accounts for protein that is degradable in the rumen (DIP), and protein that isn't degraded in the rumen but is potentially degradable in the small intestine (UIP).

For optimal microbial production in the rumen, a balance exists between the amount of energy that's supplied and the amount of protein that can be utilized to support the microbial population. If DIP is insufficient in the diet, microbial growth will limit the intake and digestibility of the ration.

Energy isn't actually a nutrient, but is contained within protein, carbohydrates and fats. Several methods of indicating feed energy values are available, including digestible energy, net energy for maintenance and gain and total digestible nutrients (TDN). TDN is the value most commonly used in simple ration balancing.

Energy supplements can be subdivided into nonstructural and structural carbohydrate supplements. When choosing an energy supplement, consider its effect on the basal diet. The type of carbohydrate has a major effect on the rate and extent of forage digestion.

The overarching goal of supplementing beef cattle is to provide nutrients lacking in the basal diet, and to increase the intake and digestibility of lower quality forages and crop residues. John Paterson, Montana State University, says it's evident that reproduction is impacted the most by nutrient deficiencies.

Energy supplementation has been shown to improve reproductive performance. However, results appear to be dependent on the timing (pre- or post-partum) of supplementation. Research shows the level of energy fed during the winter can have a large effect on the interval between calving and first estrus.

Influence of inadequate dietary nutrient intake
Table 1. Influence of inadequate dietary nutrient intake
on reproduction in beef cattle
Select table to enlarge

Paterson says in drought conditions, or in late summer and early fall, range grasses can be deficient in both CP and energy for cows in lactation (Table 1).

Commercially available, self-fed products are nutritionally balanced to provide not only supplemental protein, but also vitamins and macro and trace minerals. These supplements can be provided in several different forms — liquid, pressed blocks, chemical blocks and low-moisture blocks.

Depending on the rancher's specific requirement, supplements can be formulated to provide additional ingredients such as fats, ionophores, coccidiostats, complex minerals and antibiotics.

Clint Peck is director, Beef Quality Assurance, Montana State University.

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