CHAMPION TOC INDEX. Trace Minerals for Backgrounding and Finishing Beef Cattle. Rick Corbett. Take Home Message

Transcription

1 TOC INDEX CHAMPION Feed Services Ltd. Trace Minerals for Backgrounding and Finishing Beef Cattle Rick Corbett Take Home Message Trace mineral requirements are determined principally on the basis of need for promotion of normal growth rates and milk production. Little work has been done on requirements for optimal reproduction or health (immune function). Trace mineral nutrition is extremely complex with many interactions between the different trace elements and with other nutrients. Feeds grown in Alberta are deficient in several trace minerals that are required by growing and finishing beef cattle. Table 1. Average Trace Mineral Content of Selected Feedstuffs Grown in Alberta. mg/kg of dry matter Selenium Iron Copper Manganese Zinc Silage Barley Red Clover Triticale Alfalfa Oat Grain Barley Oat Triticale Wheat Hay Brome Mixed Grass Oat Source: (8) Alberta Feedlot Management Guide 1O1:1

2 Trace Minerals of Most Concern in Alberta Essential trace elements are necessary for the well being of the animal. These are needed in sufficient quantities to promote health and maximize growth rate. Table 2 is a summary of trace mineral allowances. These are approximations, since requirements and toxic levels are affected by numerous factors. The suggested allowances shown in this table, have margins of safety added to the minimum requirement for some of the trace minerals and it is recommended that these allowances be used to formulate rations. All trace elements are toxic when fed in excessive quantities. The maximum tolerable concentration of a mineral has been defined as, that dietary level that, when fed for a limited period, will not impair animal performance and should not produce unsafe residues in human food derived from the animal (5). Table 2. Minimum Requirement, Suggested Allowances and Maximum Tolerable Concentrations of Trace Minerals in the Diet DM of Growing/Finishing Cattle in Alberta. Chromium Minimum Suggested Maximum Tolerable Requirement 1 Allowance 2 Concentration mg/kg of dietary dry matter Chromium 1000 Cobalt Copper Iron Iodine Manganese Selenium Zinc Minimums and maximums are taken from (4). 2 Alberta Agriculture. Many symptoms of deficiency have been listed with each of the trace elements discussed. These symptoms are by no means complete as cattle may exhibit a wide range of symptoms depending on the severity of the deficiency and the length of time the animals have been deficient. Diagnosis of trace mineral deficiencies, can be very difficult, even for professionals. Most of the work has been done with individual elements and the effects of multiple trace element deficiencies has received little attention. Chromium is an essential part of the glucose tolerance factor which is needed to increase the action or efficiency of insulin. Although chromium is essential for beef cattle, the amount required is not known. The amount of chromium in feedstuffs and the chromium status of growing/finishing beef cattle is also unknown. Alberta Feedlot Management Guide 1O1:2

3 Calves that enter the feedlot have often been subjected to considerable stress from weaning, marketing and transportation. Mowat (3), summarized research conducted at the University of Guelph which reported significant improvements in growth rate, feed conversion efficiency and immune function as well as reduced sickness in stressed cattle supplemented with organic chromium. There is considerable evidence that chromium supplementation may be beneficial in preconditioning and receiving rations, particularly in highly stressed cattle. Mowat (3) suggested that reduction in sickness caused by bovine respiratory disease may be the biggest benefit seen from supplemental chromium for stressed feeder calves. Cattle experiencing more modest stress may not benefit. In contrast to the work reviewed by Mowat (3), Mathison and Engstrom (2) observed no improvement in rate and efficiency of gain or in the incidence of sickness when stressed calves were supplemented with chromium during the first 28 days after arrival in the feedlot. The differences in the results from the different experiments may be related to the degree of stress on the cattle. Other factors that may be influencing the results include differences in type of diet fed and differences in chromium status of the cattle prior to the stress. Based on conflicting results reported in the literature it is apparent that more work needs to be done to identify the conditions under which supplemental chromium will be beneficial. Current information suggests that 3 to 4 mg per head per day of organic chromium, should be fed prior to imposition of the stress or as early in the stress period as possible in order to obtain maximum benefits. Cobalt Cobalt content of feeds grown in Alberta has not been studied. Since the cobalt status of cattle produced in Alberta is unknown, it would be prudent to continue to supplement this element. Cobalt (Co) is needed by rumen bacteria to make Vitamin B12. Young, rapidly growing animals are more sensitive to cobalt deficiency than older cattle. High concentrate diets may depress ruminal synthesis of Vitamin B12, however there is no evidence that requirements are higher for animals fed high concentrate diets. Decreased appetite and failure to grow or moderate weight loss are early signs of cobalt deficiency. Deficiency of this element may impair immune function and result in reduced resistance to disease. Alberta Feedlot Management Guide 1O1:3

4 Copper More than 90% of feeds grown in Alberta are deficient in copper. Copper requirements range from 4 to 15 mg/kg of diet dry matter depending on the amount of molybdenum and sulphur in the diet. Copper is needed for formation of red and white blood cells, deposition of minerals in the skeleton, heat regulation in the animal, heart and immune function. The recommended concentration of copper in the diet is 10 mg/kg of diet dry matter providing that sulphur in the diet does not exceed 0.25% sulphur and molybdenum is less than 2 mg/kg of diet dry matter. Less than 10 mg/kg of copper in the diet of finishing cattle may be adequate since copper is more available in high concentrate diets than in high forage diets. High levels of molybdenum and/or sulphur increase the requirement for copper by complexing the copper in the rumen, rendering it unavailable to the animal. Molybdenum concentration in feeds grown in Alberta are generally low, with only a few samples having levels high enough to cause problems. High concentrations of sulphur in feeds and in water are more common. High levels of sulphur in water will interfere with copper and increase requirements. High levels of zinc and iron may also increase the need for copper. Although Charolais and Simmental cattle are more susceptible to copper deficiency than are other breeds, the 10 mg/kg allowance should be adequate, providing that molybdenum and sulphur intake is not excessive. Copper deficiency symptoms include anaemia, reduced growth, diarrhea and impaired immune function resulting in increased susceptibility to disease. Iodine Although the requirement for iodine is not well defined, 0.50 mg/kg of diet dry matter is the suggested allowance. Few analyses for iodine have been done on feedstuffs grown in Alberta. However symptoms of deficiency have been seen in cattle and other animals throughout Alberta, and on this basis it appears prudent to assume that most or all of our feedstuffs will be low in iodine. Iodine is an integral component of the thyroid hormones which regulate body temperature, oxygen use and many other aspects which promote the physical well being of the animal. Alberta Feedlot Management Guide 1O1:4

5 Organic iodine, commonly called EDDI (ethylene diamine dihydriodide) has been used for many years as an aid in the control and prevention of footrot in cattle. In 1990, the regulations under the Feeds Act were changed to prohibit the sale of EDDI as a drug for control of footrot. EDDI may still be used, at nutritional levels, as a source of iodine. The range of dietary iodine permitted by the Feeds Act regulations is 0.1 to 10 mg/kg of diet dry matter. This range does allow enough EDDI to be fed to be useful as an aid in prevention of footrot. Feeding EDDI at 25 to 35 mg/head/day to backgrounding calves and 45 to 55 mg/head/day to finishing cattle would provide enough EDDI for footrot control and would be within the range allowed under the Feeds Act. Iron The requirement for iron is approximately 50 mg/kg of diet dry matter. Virtually all feedstuffs grown in Alberta contain adequate amounts of this element. Supplementation of ration for growing and finishing cattle should not be necessary. Some important functions of iron are formation of haemoglobin in red blood cells and energy transfer mechanisms in the animal. Manganese The manganese requirement of growing finishing cattle is approximately 20 mg/kg of diet dry matter. The requirement of manganese needed for maximum growth is considerably lower than that needed for reproduction and normal skeletal growth. Approximately 50% of the grain grown in Alberta contains less than 25 mg/kg of manganese whereas only 8 to 25% of forages fall in this category. Heifers that may be retained for breeding should be provided with a dietary allowance of 40 mg of manganese per kg of diet dry matter. Manganese is important for the connective tissue formation, brain function and for the prevention of accumulation of toxic oxygen molecules produced during metabolism which can cause tissue damage. Deficiency of manganese in young animals may result in bone abnormalities including stiffness, twisted legs, enlargement of the joints and reduction in strength of the bones. Alberta Feedlot Management Guide 1O1:5

6 Zinc The requirement for zinc is 30 mg/kg of diet dry matter. Formulating diets to contain 40 mg/kg is recommended. Sixty five to 75% of forages grown in Alberta will contain less than the required amount of zinc needed to meet the needs of the cattle. Although grains tend to contain higher levels of this element than do forages, supplementation of most rations is necessary. Zinc is essential for translation of genetic material, for the development of the reproductive system and for proper functioning of the immune system. Subclinical deficiency of zinc can reduce growth rate and may contribute to an increased incidence of footrot and other foot infections. Zinc deficiency may also impair immune function. Selenium The selenium requirement of beef cattle is 0.10 mg/kg of diet dry matter. Formulating diets to contain 0.2 mg/kg is recommended. The selenium content of feeds grown in Alberta is quite variable. Approximately 20% of legume and grass-legume forages, and 50% of grass and cereal forages do not contain the required concentration of selenium. About 55% of cereal grains are deficient in this element. The likelihood that feedstuffs will be deficient in selenium is much lower in the area east of Highway 2 and south of Highway 16 than in the remainder of Alberta. Very little of the feed grown in this area is low in selenium. The majority of the feed grown in the northern and western parts of the province contain less than the required concentrations of selenium. Selenium is required for catalysing the destruction of toxic oxygen molecules produced during metabolism, thereby protecting the cells from damage and helps with the absorption of fat, including vitamin A and vitamin E, and in proper sperm formation. Deficiency symptoms include unthriftiness and reduced growth. Impaired immune response also occurs, which makes the animals more susceptible to disease. Alberta Feedlot Management Guide 1O1:6

7 Benefits of Trace Mineral Supplementation Trace Mineral Requirements of Stressed Cattle It is likely that most of the trace mineral deficiency problems experienced by cattle in Alberta are of a subclinical nature. Several Farming for the Future projects in Alberta have demonstrated 20 to 36 pound increases in weight gain in yearlings on pasture through trace mineral supplementation. In other projects where cow/calf pairs were provided with trace mineral supplements, improvements in weaning weights of 14 to 26 pounds have been seen. Its interesting to note that reduced growth rates were not recognized as a problem in these herds, lending credence to the observation of the subclinical nature of many deficiencies. The trace mineral requirements of stressed cattle do not appear to be different from those of non-stressed cattle (NRC 1996). Stress, whether it be caused by disease or by noninfectious stressors, dramatically alters the metabolism of copper, iron, manganese and zinc (1). Acute phase proteins are produced in the early stages of an immune response as tools for fighting disease and demand large amounts of several of these trace minerals for their production. Changes in the levels of these trace minerals circulating in the blood, increased losses from the body, decreased absorption from the diet and reduction in feed intake typically seen with stressed animals has been interpreted as evidence for an increased need for trace elements in the diet during episodes of disease or other stress. Reduced weight gain, or loss of weight due to the breakdown of muscle and bone, however, should decrease the requirements. The changes in levels circulating in the blood are largely taken care of by redistribution of these elements from the tissues into blood and by liberation of trace minerals due to loss of muscle and bone. The trace minerals liberated during muscle and bone breakdown, presumably, can be used for the production of acute phase proteins with the excess being excreted from the body. Selenium and vitamin E are needed for proper immune function. Both serve as antioxidants, protecting the cells of the body, and immune cells from damage by toxic oxygen molecules produced in large quantity during stress ( Nutrition and Immunity). Alberta Feedlot Management Guide 1O1:7

8 Over supplementation of iron and zinc during disease or periods of stress may impair the immune response and worsen the situation, while extra copper and manganese may have minimal effect. Animals with low trace mineral status caused by chronic dietary deficiency may also suffer from impairment of immune function. It appears that supplementation of trace minerals above the levels required under normal conditions may be useful prior to the time when stress is expected, for example, before cattle are shipped to the feedlot or auction market. This strategy is advised when the trace mineral status of the animal is questionable or unknown. The objective is to ensure that the animals have adequate body reserves of these nutrients. This strategy is likely of little value for animals that have been on a good trace minerals supplementation program. Extra supplemental trace elements may also be advantageous during the convalescence period following the stress response. The objective in this case is to provide the extra minerals to allow the animal to rebuild body reserves and to provide for the compensatory or catch-up growth which typically occurs following periods of reduced growth or weight loss. There is less agreement on the need for extra supplementation of trace minerals during the stress, particularly, stress caused by infectious disease. During infectious disease, the low circulating levels of iron and zinc have a protective value to the animal (1). For further discussion on this, see Nutrition and Immunity of Feedlot Cattle. Table 3. Suggested Trace Mineral Concentrations for Receiving Diets for Stressed Calves (NRC, 1996). Suggested Range Daily Intake (mg) for a 250 d Calf a mg/kg of Diet DM 0-7 Days 0-14 Days DM Intake, kg Copper Iron Manganese Zinc Cobalt Selenium Iodine a Average dry matter intake are based on 1.55% of body weight for a 0 through 7 days and 1.9% for days 0 through 14. Alberta Feedlot Management Guide 1O1:8

9 Stress usually results in reduced feed intake. Increasing the concentration of trace minerals during periods of low feed intake may be beneficial. Table 3 gives the nutrient concentrations of receiving diets of stressed cattle that are suggested in NRC Nutrient Requirements of Beef Cattle (4). These recommendations are for the first two weeks after arrival or until the cattle are consuming feed at 2% or more of body weight on a dry matter basis. Chelated Trace Minerals Most trace minerals used as supplements in the diets of growing and finishing cattle are in an inorganic form such as carbonates, sulphates and oxides. Chelated and proteinated trace minerals are organic forms, bound to amino acids (protein). Several of the chelated trace minerals have been shown to have higher bioavailability (1 to 2.5 times) than the inorganic forms. However the chelated forms cost from 5 to 16 times as much per unit of trace mineral than the common inorganic forms (7). There is evidence that some of the chelated trace minerals are metabolized differently than the inorganic forms. However, until specific modes of action are clarified, it is not possible to optimize any benefit of organic forms over the inorganic forms of a mineral (6). References 1. Klasing, Kirk C Nutrition and metabolism of trace minerals during stress. California Animal Nutrition Conference, Fresno, California 1990: Mathison, G.W. and D.F. Engstrom, Chromium and protein supplements for growing-finishing beef steers fed barley based diets. Can. J. Anim. Sci. 75: Mowat, D.N Organic Chromium in Animal Nutrition. Proceedings of the Asia Pacific Lecture Tour. Alltech Inc. Lexington Kentucky. 4. National Research Council Nutrient Requirements of Beef Cattle. 7th Revised Edition. National Academy of Sciences, Washington, D.C. 5. National Research Council Mineral tolerance of domestic animals. Washington D.C. National Academy of Sciences. 6. Nelson, J Review of trace minerals chelates and complexes available to the feed industry. Western Nutrition Conference, Winnipeg, Manitoba. 7. Owens, Fred, Don Gill and Chuck Strasia, Trace minerals for feedlot cattle - an update. Proceedings of the Southwest Nutrition and Management Conference, Phoenix, Arizona. 8. Suleiman, Abdullatif I. H Ten Year Average Analyses of Alberta Feeds Alberta Agriculture, Food and Rural Development, Edmonton, Alberta, T6H 4P2. Alberta Feedlot Management Guide 1O1:9