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Tips For Winter Supplementation Of Cattle

Identify what the cows need and what they don't.

Developing a cost-effective supplementation program depends on just two things – first, identify the nutrient (or nutrients) most limiting to productivity and provide it at the lowest cost. Just as important, however, is identifying what your cows don’t need, so you’re not paying for more nutrition than necessary.

If protein is deficient, evaluate supplements on cost/lb. of protein. Similarly, if forage supply is limited and energy is deficient, look at supplements based on cost/lb. of total digestible nutrients (TDN; energy). Sometimes both energy and protein are limiting, so a balanced approach to provide supplemental protein and energy is recommended.

Generally, high-protein commercial supplements and byproduct feedstuffs are more expensive than feeds that are lower in protein content. However, it is still important to evaluate potential supplements based on cost/unit of nutrient needed (i.e., $/lb. protein or $/lb. TDN), recognizing that a cost/unit of nutrient comparison does not account for practicality of use, the starch or fiber content of energy supplements, the dynamic nature of commodity prices, or the broad variation in nutrient content inherent to many byproduct feedstuffs.

Commercially available processed supplements and feeds (i.e., cubes, small pellets, blocks, tubs and liquids) are designed to be safe and easy to store and deliver to the livestock. The practicality of using commercial supplements has significant monetary value.

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Nonetheless, when protein supplementation is needed, consider comparing the price/lb. of protein for traditional supplements to that of products like canola meal (~38% crude protein – CP), dried distillers grains (~27% CP), and corn gluten feed (~21% CP). If you’re going to feed byproducts on the ground, include an adjustment for 10-25% wastage.

When energy supplementation is needed, products high in digestible fiber are most desirable, so up to 7 lbs. of soybean hulls (69% TDN); wheat middlings (~73% TDN); and even corn gluten feed (~72% TDN, max of 5 lbs./day without sulfur analysis) may be cost-effective when compared to traditional supplements.

When it’s necessary to use energy replacement to reduce intake of pasture forage or extend grazing days, low-cost byproducts like cotton motes or cotton burrs can be offered free choice and may be a less expensive approach than feeding hay. However, these byproducts are low in energy (40-45% TDN), so don’t expect any weight gain when these are fed.

It is important to be aware, however, that the appeal of lower-cost byproduct feedstuffs is usually partially offset by increased storage and delivery challenges. In addition, many byproducts have anti-nutritional factors which dictate that they can only be used in moderation.

Frequency of supplementation

Feeding frequency (daily vs. three times/week vs. once/week) of some supplements may affect animal response. Feeding smaller amounts of protein or energy supplements more frequently decreases the potential for negative impacts on forage intake. However, feeding high-protein supplements once a week results in no significant reduction in performance when compared to feeding supplements three times/week or daily. Additionally, transportation and labor costs are reduced with less frequent feed delivery.

Conversely, research shows that heifer weight gain and conception rate declined when the frequency of energy supplementation was decreased from daily to twice/week. Collectively, these findings indicate that protein supplements (i.e., ≥ 30% CP) can be delivered as infrequently as once or twice/week, while energy supplements (≤ 20% CP) should be offered no less frequently than every other day.

Supplements containing 30-40% protein can be delivered less frequently than every day. In fact, research has shown that the delivery of a week’s supply of a high-protein supplement all at once can be as effective as feeding the same weekly supply in equal proportion on a daily basis. A conservative approach to reducing labor and delivery costs associated with feeding high-protein supplements is to feed twice/week. For example, target 1 lb./head/day by feeding 3.5 lbs. twice a week.

And don’t overlook crop aftermath. When available, corn stalks or alfalfa stubble may be great feed sources that can help get cattle through for a few weeks or months at a relatively low cost.

Urea (non-protein nitrogen)

As range forage matures, it becomes lower in nutritive value. When the protein content of forages in cattle diets declines to less than about 7%, both forage intake and digestion are usually suppressed and animal performance is reduced. Providing supplemental protein to offset deficiencies in the forage protein can help optimize forage intake and utilization.

Protein is vital because the rumen microorganisms require the nitrogen in proteins to grow and digest feeds in the rumen. The primary sources of protein in traditional range supplements fed to cattle in the West and Southwest are plant proteins like cottonseed meal and soybean meal. However, it is possible to reduce the cost of range supplements without compromising performance by replacing a portion of the plant protein (nitrogen) with urea or other non-protein nitrogen (NPN) sources.

Urea is almost always less expensive per unit of nitrogen than plant protein sources. However, excessive levels of urea can impair animal performance, so urea should be incorporated into range-cattle supplements in moderation. For example, a cottonseed meal-based protein supplement formulated to be 38% protein should not contain more than about 4% CP equivalence from urea if fed less frequently than every other day and/or if fed to lactating cows.

The real question is: How much urea can be included in a protein supplement without negatively impacting performance? To answer this question, it is important to note that CP can be categorized into two parts—that which is degraded in the rumen by microorganisms (ruminally degradable protein), and that which escapes the rumen without being altered by the microbes. The ruminally undegradable protein is commonly referred to as escape protein or bypass protein.

Generally, 55-70% of the protein in high-protein feedstuffs of plant origin is ruminally degradable protein, and thus is used by the rumen microorganisms as a source of nitrogen. Urea is completely degraded in the rumen (100% ruminally degradable protein).

The most appropriate way to determine the optimal amount of urea in a protein supplement is to evaluate the proportion of the ruminally degradable protein that urea supplies. This can be challenging, because feed tags generally express the percentage units of CP equivalence coming from NPN.

Based on the findings of numerous research trials, a conservative target level of urea inclusion in protein supplements for gestating cows grazing low-quality forage is about 25% of the ruminally degradable protein in the supplement, if the supplement is fed on a daily basis. If fed less frequently, 20% may be a safer target.

There is limited research evaluating the impact of feeding urea-containing protein supplements to postpartum cows. However, some results indicate that high levels of urea inclusion in supplements during this period may have a negative effect on fertility.

Based on those trials, postpartum protein supplements should be formulated so that urea does not supply more than about 15-20% of the ruminally degradable protein in the supplement. Most of the research trials evaluating NPN content in supplements utilized feeding rates of 4 lbs./day or greater.

In New Mexico and West Texas, it is much more common to provide protein supplements at rates of 1 to 3 lbs./day. If producers are supplementing at lower rates (i.e., < 3 lbs./day) they can likely avoid negative impacts of supplying a higher concentration of NPN in a supplement. In fact, it is often smaller meal sizes and increased meal frequencies that allow for self-fed liquid and tub products to include NPN at such a high proportion of the total protein in the supplement.

It is also important to note that supplements including urea or other sources of NPN should contain at least one unit of sulfur for every unit of nitrogen. This is generally not a problem in the Southwest because sulfur content of drinking water is often high.

Urea inclusion in protein supplements can be a successful means to reduce supplement cost without negatively impacting performance, as long as urea is included in moderation. Urea inclusion can reduce supplement cost by 5-15% when supplements are formulated so that urea supplies 15-25% of the ruminally degradable protein. In a cottonseed meal-based protein supplement, this amount of urea inclusion would equate to about 3-6% of the CP equivalence supplied by urea.

Clay Mathis is executive director of the King Ranch Institute for Ranch Management at Texas A&M University-Kingsville.

Summary of NPN (urea) supplementation recommendations

If attempting to identify a single feed for the entire dormant season supplementation period while feeding three times/week or less, a conservative target of 20% of the ruminally degradable protein in the supplement (about 4 to 5 CP equivalents from NPN) should reduce feed cost and minimize the risk of suppressed performance.

Higher NPN inclusion rates (20-50% of the supplement rumen degradable protein from NPN) may be safe when supplementation rate is low (1-2 lbs./day) and meals are consumed frequently.

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