Feed Lot

JUN 2018

Feedlots and cow/calf operations in the beef industry who feed 500 or more has annually on grains and concentrates; maintain 500 or more beef cows; backgrounder, stocker/grower, preconditioner; veterinarian, nutritionist, consultant

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20 FEED•LOT June 2018 stored in the body. Therefore, it is im- portant that cattle on pastures with an elevated risk for tetany receive a high Mg mineral and that pro- ducers ensure daily consumption of the mineral supplement. Copper (Cu) is the most com- mon trace mineral deficiency in grazing cattle. Indications of cop- per deficiency most often include reduced fertility, depressed im- munity (for example, increases in cases of summer pneumonia or scouring calves), and dulling of hair coat. Not surprisingly, 52% of pasture samples were found to be deficient in copper. Even if dietary levels of Cu are adequate (10 ppm), secondary deficiencies are likely if elevated levels of Sulfur, zinc (Zn), Iron (Fe), or molybdenum (Mo) are present. These minerals affect Cu absorption. Due to the complexities of mineral interactions, Cu should be supplemented in a form that is bioavailable. Copper oxide is commonly found in inexpensive mineral supplements, however this form of Cu is poorly absorbed and may not help to correct a primary or secondary deficiency. Sulfate and chloride forms have greater availability than oxides, but may still complex with other minerals It takes more than just ener- gy and protein to ensure optimal health and performance of beef cattle. Vitamins and minerals are required to maintain vital biolog- ical processes and even moderate deficiencies can have significant economic impacts. It is well accepted that native rangeland is deficient in vitamins and minerals, and that supplemen- tation under these circumstances is necessary. However, it is important to recognize that cattle grazing managed pastures, cereal grains, and hayfields, which often include high quality forages, also require mineral supplementation. It may be tempting to assume that cows or stocker calves grazing tall, lush forages are getting all the nutrients they need. While this might be true for protein and energy, it is unlikely that all mineral requirements are being met. A frequency analysis was con- ducted on 2,631 pasture samples sent in by Agri-King clients, over a 5 year period, to evaluate the proportion of pastures which fail to meet minimum NRC requirements for macro and trace minerals. Pas- tures were composed of grasses, legumes, grass/legume mixes, cere- al grains, and brassicas. All months of the year were represented, but 92% of the samples were taken during common grazing months (April through October). Fifteen states were in- cluded in the analysis, with the majority of samples coming from the upper Midwest and Northeast. Most pastures provided ade- quate concentrations of calcium (Ca), phosphorus (P), potassium (K), and sulfur (S) for mature cows. However, 30% of these pastures had Ca:P ratios that were outside of the recommended ratios. Sodium had the greatest fre- quency of deficiency of any mineral in the pasture samples evaluated, where 70 - 87 % of pastures were deficient. Due to its relationship with water balance in the body, a deficiency in sodium can result in decreased milk production in lac- tating cows. Salt should always be included as part of a mineral pro- gram, and is often used to encour- age and control the consumption of free choice mineral products. Magnesium (Mg) was deficient for lactating cows in 24% of the pastures tested. Pastures with low magnesium and sodium (NA), and high potassium (K) concen- trations are where issues with grass tetany (hypomagnesemia) are most likely to occur. Cool sea- son grasses grazed in early spring and wheat pasture in the fall pose the most risk. Cattle have a daily requirement for Mg, as it is not COW/CALF CORNER Evaluating Your Mineral Program BY DR. AIMEE N. HAFLA, PH.D., P.A.S., BEEF CATTLE NUTRITIONIST, AGRI-KING, INC As we begin to think about green grass and grazing cattle, it is a good time to evaluate your mineral supplementation program

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