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Preparing for Breeding Season During Drought

Consider supplementation strategies to counter reduced quantity and quality of forages.

by Troy Smith for Angus Media

RUIDOSO, NEW MEXICO (Aug. 29, 2018) — In a rangeland environment blessed by adequate precipitation, nature does a pretty good job of providing adequate nutrition for the well-adapted bovine to thrive and reproduce. With sufficient rain, forage typically provides the needed nutrients. However, what about those times when moisture becomes scarce?

Eric Scholljegerdes

“Energy balance going into calving or up to breeding can have a profound impact on reproductive success,” stated Eric Scholljegerdes, New Mexico State University. “Although protein supplementation can liberate more energy from drought-stricken forages, during extensive drought supplemental energy is often needed and must be considered as part of a drought supplementation strategy.”

Speaking at the Applied Reproductive Strategies in Beef Cattle Workshop hosted Aug. 29-30 in Ruidoso, N.M., ruminant nutritionist Eric Scholljegerdes said forage quality and quantity can decline quickly after the onset of drought. The New Mexico State University animal scientist cited the sorry forage conditions resulting from the severe drought of 2010-2013, when crude protein content of forages on the university’s research ranch at Corona declined to as low as 3%. Energy values (total digestible nutrients, or TDN) hovered around 40%.

Scholljegerdes said vigilant monitoring of forage availability and quality are key to rancher survival under drought conditions. While little can be done to overcome diminished forage availability, aside from animal destocking, supplementation of sources of energy (fats and starches) can replace some forage in animal diets. However, ranchers must avoid overgrazing and damage to forage stands.

When forage availability is adequate, protein is often considered the first limiting nutrient in forage-based cattle production systems. According to Scholljegerdes, protein supplementation of ruminants can be complex and expensive. Depending on the source, protein supplements can be highly or lowly degraded by the rumen’s microbial population. To improve reproductive success during times of nutritional stress, the rancher must decide which type of protein to feed.

According to Scholljegerdes, when forage crude protein content is below 7%, supplementation with rumen degradable protein (RDP) is needed to “feed” the rumen bacteria that break down forage. Examples of good sources of RDP include urea, soybean meal, alfalfa and corn gluten feed. Supplemental RDP increases the digestibility of low-quality forages, thus increasing the energy value.

A second portion of dietary protein known as rumen undegradable protein (RUP), or bypass protein, is not utilized by rumen microbes, but is available to the animal through absorption in the small intestine. RUP and digested rumen microbes are the two sources of protein for the animal itself. Considering value of RDP and RUP, consideration must be given to protein supplementation programs that benefit rumen microbes and the ruminant directly.

Since drought-induced diets consisting of low-quality forages may also be deficient in TDN, producers may have to consider energy supplementation. Like protein, energy can come in various forms, including nonstructural carbohydrates (starch), structural carbohydrates and fat. Among the most common nonstructural carbohydrates are cereal grains. Structural carbohydrates are from co-products such as soy hulls, wheat middlings, distillers’ grains and beet pulp and can include high-quality hay. Fats can be in the form of tallow, oilseeds or vegetable oil.

Nonstructural carbohydrates, such as corn, can be used to replace a portion of forage in the diet, but must be managed carefully to avoid a negative impact to the rumen environment resulting in acidosis and bloat. Structural carbohydrates may have somewhat lower energy values, but they present little risk of rumen upset.

“Overall, energy supplementation is an important consideration when it comes to drought management. Energy balance going into calving or up to breeding can have a profound impact on reproductive success,” stated Scholljegerdes. “Although protein supplementation can liberate more energy from drought-stricken forages, during extensive drought supplemental energy is often needed and must be considered as part of a drought supplementation strategy.”

To read the proceedings, review the PowerPoint or listen to this presentation, visit the Newsroom at www.appliedreprostrategies.com.

Editor's Note: This article was written under contract or by staff of Angus Media. To request reprint permission and guidelines, contact the Angus Media editorial team at 816-383-5200.