Supplementing to Stretch Pastures

– Jeff Lehmkuhler, PhD, PAS Associate Extension Professor, University of Kentucky

Drought continues to impact the high plains area stretching down to the pan handle of Texas. The dry conditions will continue to impact pastures potentially lowering beef cattle numbers at year’s end. The recent high temperatures and limited rain will dry out pastures and limit forage regrowth on recently cut hay fields here in the Commonwealth. As forage growth slows, supplementation may be needed to provide beef cattle adequate levels of nutrients to support target production levels and limit condition loss of lactating cows.

Fibrous coproduct feedstuffs that are low in starch but high digestible fiber work well for supplementingcattle on a high forage diet. Soybean hulls, corn gluten feed, beet pulp, distillers grains, wheat midds, and rice bran are a few commonly available feedstuffs that would be lower in starch and high digestible fiber. These feedstuffs would be higher in available energy than most pasture forages that are going or already dormant. Depending on the maturity and digestibility of the forages, supplements could provide twice as much energy on a dry weight basis. Therefore, supplementation would need to be limited and not offered free-choice to avoid over conditioning as well as to avoid digestive upsets.

Cottonseed hulls are lower in digestible energy than the supplements listed above and most cool-season forages. Cottonseed hulls would be deemed as more of a forage replacement than a supplement. The crude protein value is low ranging from 4-6% typically and the protein is relatively low in digestibility. The acid detergent value is reported to be high, near 65%, leading to a relatively low calculated Total Digestible Nutrient (TDN) value ranging 34-42%. Work at North Carolina has shown that self-fed diets containing 30% cottonseed hulls are effective for developing 2-6 month old dairy heifers. Many commercial precondition and creep feeds contain cottonseed hulls as a fiber source. The price of cottonseed hulls can be a limitation for their utilization. Having a nutrient content lower than typical fescue hay, the price paid should be similar or less than what one would pay for hay.

Starch containing feedstuffs such as wheat, barley, corn and oats are available to supplement energy to grazing cattle. Due to negative associative effects in the rumen when feeding starch supplements to cattle consuming a predominate forage-based diet, these feedstuffs should be limited if one wishes to avoid lowering fiber digestibility. Previously, summaries of supplementation research would indicate that offering 0.3% of body weight or less would minimize negative associative effects of starch supplementation. This would be equivalent of approximately 3-3.5 pounds of corn per 1,000 pounds of body weight. Supplementation with starch containing feeds can lead to a decrease in ruminally available nitrogen and amino acids needed by the microbes on low quality forage diets. Therefore, to mitigate negative associative effects protein supplementation may be necessary. Other researchers have demonstrated that providing protein supplementation with starch containing feedstuffs, levels as high as 6-8 pound/1,000 lb of body weight have had minimal impacts on fiber digestion.

Providing supplementation to cattle grazing pastures, the impact on forage intake will be dependent upon associative effects that may occur in the rumen. Providing protein to correct a ruminal nitrogen source deficiency may enhance fiber digestion and increase dry matter intake having a positive impact. Supplementing with excessive starch and reducing rumen pH and limiting available nitrogen sources for microbes will lead to lower intakes. In general, forage and supplement exchanges often average 2-3:1 in which forage intake decreases 2-3 pounds for each pound of supplement consumed at lower levels of supplementation. There is a wide degree of variability in the actual forage intake response and one should monitor cattle and observe body condition to ensure sufficient nutrient intake to support the desired level of performance.

If you are faced with limited pasture forage or hay, consult with your nutritionist or county Extension agent to develop a feeding program for your herd. There are many feedstuffs that can be utilized to develop the most cost-effective feeding program that delivers the nutrients the cattle need to achieve your desired level of performance. Here’s hoping you all get some timely rain.