Trace elements. in cattle nutrition. Christian Punz Product Manager Nutritional Products

Transcription

1 Trace elements in cattle nutrition Christian Punz Product Manager Nutritional Products

2 Christian Punz Product Manager Nutritional Products Trace elements in cattle nutrition The importance of trace elements in livestock nutrition is undisputed. As the name implies, even small amounts of these elements have large and diverse effects on the animal organism. The function of enzymes and hormones is essentially linked to trace elements. This key role in metabolism cannot be replaced by other kinds of nutrients, that s why we call them essential (irreplaceable) trace elements. For cattle, copper, zinc, manganese, cobalt, iodine and selenium are among the most important and are usually added to various supplementary feed. Since iron has a decisive influence on the interactions between the elements, it will be discussed in later chapters as well. Regarding the bioavailability of trace elements from the feed, there are significant differences due to the binding form of the elements. In general, two main binding types can be distinguished: Inorganic bound trace elements (sulfates, oxides, chlorides, carbonates, ) Organic bound trace elements (chelates, proteinates, glycinates, polysaccharides, fatty acids, methionine-analogues, ) Inorganic bound trace elements are likely to have specific interactions and must be bound to transporters to be absorbed in the metabolism. Organic bound trace elements are absorbed into the small intestine via the amino acid peptide way. The most efficient absorption is when trace elements are bound to single amino acids. Trace elements bound in chelate form are a mixture of all naturally occurring amino acids and are absorbed through the different amino acids absorption mechanisms in the body. This article will provide guidance on the basic function of trace elements in ruminants, demonstrate the difference in bioavailability of different binding forms and show practical effects in examples from cattle. What are trace elements? Trace elements are defined by their extremely low concentrations in the body, such as less than 50 mg of iron per kg of tissue. Based on this, daily animal requirements of trace elements are in the milligram range as well. Needs for trace elements are determined by nutrient requirement models and nutrient response models. 2

3 Biological functions of trace elements Iron Iron is a part of hemoglobin, the pigment of red blood cells and myoglobin, the muscle pigment that is necessary for their formation. In addition, iron is responsible for oxygen storage and oxygen transport in the body. As an enzyme component iron plays an important role in energy metabolism as well as in the anti-oxidative system (immune system). Iron deficiency is not common in dairy cows because many feedstuffs (mainly forage) contain iron in sufficient amounts. However, it may lead to deficiency symptoms in calves supplemented with whole milk. Deficiency symptoms manifest themselves in the form of anemia, poor immunity and growth. In fact that iron is much more common than other trace elements, iron excess can lead to poor absorption for copper and manganese. Copper Copper is mainly stored in the liver and is an enzyme component that is part of many essential metabolic processes. As an enzyme activator, copper provides strong bones and joints and is heavily involved in the utilization of iron and thus the synthesis of hemoglobin. In addition, the pigmentation of the hair coat is fundamentally influenced by copper levels. Through the promotion of superoxid dismutase, which deactivates free oxygen radicals, copper is also involved in cell protection and thereby in a healthy immune system. Copper deficiency in dairy cows is often reflected in reduced fertility and poor immunity. Similarly, disturbances in pigmentation ( Copper glasses ), anemia and bone fragility may occur. Zinc Beside iron, zinc is the most common trace element. As an activator and a component of more than 300 enzymes and hormones, zinc plays an important role in metabolism. In particular, protein biosynthesis and the regulation of gene activity can be affected by zinc. Zinc is mainly stored in the liver, pancreas, bone, skin and hair. Zinc deficiency causes poor growth, loss of appetite, and a bad feed conversion rate. Due to its crucial function in defense enzymes (copper-zinc superoxid dismutase), zinc deficiency reduces resistance. In dairy cows, zinc deficiency is visible through bad hoof horn quality, reduced fertility and poor udder health. Manganese Manganese is mainly stored in the bone, liver, kidney and pancreas. It works as an enzyme activator and is crucial for energy-, protein- and fat metabolism. Furthermore, it has important enzymatic functions in cell protection. Deficiencies in manganese are reflected in reduced growth, skeletal deformities, poor fertility and birth defects in newborn calves. Iodine Iodine is located in the thyroid glands and is responsible for the formation of thyroid hormones (T3 and T4 hormone). These hormones in turn take over important control processes in the energy metabolism and are thus particularly important for growth, fertility and milk yield. Iodine deficiency can be detected by an enlarged thyroid gland and poor milk production. Cobalt Cobalt serves as a central atom of Vitamin B12 (Cobalamin). If ruminants are adequately supplied with Cobalt, they can synthesize their need for Vitamin B12 itself in the rumen. Vitamin B12 is necessary for a functioning energy- (utilization of propionic acid, gluco neogenesis) and protein metabolism (methionine formation) in the liver. A prolonged deficiency in cobalt leads to a decrease in feed intake, limited growth and reduced milk yield. Selenium Selenium is an essential component of the enzyme glutathion peroxidase, which deactivates harmful hydrogen peroxide radicals and is thus crucial in cell protection. In addition, it supports the effects of Vitamin E and vice versa. A slight lack of one element can be compensated by a higher supply of the other element to a certain extent. Moreover, Selenium also regulates the thyorid hormone metabolism and thus indirectly affects fertility in dairy cows. Selenium deficiency causes fertility disorders, muscle dystrophy and weak calves as well as retained placenta and mastitis in dairy cows. Also a sufficient selenium supply is important in dry cows because still births or aborts can otherwise occur. Source: Zinpro Figure 1: Copper glasses caused by copper deficiency 3

4 Christian Punz Product Manager Nutritional Products They are responsible for specific functions in the organism for certain metabolic processes and must be regularly supplied with feed.. An essential function of trace elements is that they act as an activator and part of many enzymes. Furthermore they are present in proteins and carry out several tasks in the hormonal system. Therefore, basic functions such as reproduction of dairy cows depend a lot on the supply of trace elements. trace elements, macro elements or other food sources. For example phytate can build complexes with zinc, copper, manganese and iron and negatively impair their absorption into the body. Crude fibre can block the absorption of metal ions. Hg Te Ca Co Cu Regulation of absorption and excretion For a functioning metabolism, trace elements always have to be present at a specific concentration in the target tissue. To avoid an over-concentration and thus the risk of poisoning, the trace element metabolism is strictly controlled by the homeostatic regulation. This means that the input and outflow are regulated such that the interior of the body always has the same concentration in different target tissues. The processes of acquisition, storage and excretion of trace elements are overlapping and always in a dynamic equilibrium. I Zn S Mn Al Na F K W Se Cd Mg Interactions of trace elements In the uptake of trace elements, it is always important to consider certain adverse interactions with other Mo Pb Fe As P Figure 2: Interactions between micro- and macro minerals (Graphic: Punz; Source: Miller, 1979) Table 1: Trace element content of the most important forages and concentrates in Austria. (ÖAG-Futterwerttabellen für das Grundfutter im Alpenraum, Resch et al. 2006; Daten aus dem Futtermittellabor Rosenau ) Feed stuff Trace element content (mg/kg DM) Iron Manganese Zinc Copper Forages Grass silage, 1st cut Grass silage, 2nd -5th cut Corn silage Concentrates Barley Corn Triticale Dried beet pulp Wheat Brewers' grain (dried) Peas Rape seed extracted Rape seed cake (8-12% fat) DDGS (from bioethanol production) Soy bean full fat Soy bean extracted Soy bean extracted HP Sunflower seed extracted (dehulled)

5 Diets rich in calcium, and drinking water or silages high in iron can build hardly soluble complexes with copper or manganese and reduce their availability dramatically. In the presence of high levels of molybdenum and sulfates, copper sulfide can occur which is hardly soluble as well and nearly unusable for ruminants. If the diet contains too much sulfur, the uptake of Selenium in the body is negatively affected. Calcium and phosphorus inhibit zinc absorption. Figure 2 shows an overview of the various antagonsims between minerals. Trace element concentrations in forages and concentrates In principle it should be noted that forages and concentrates do not contain enough trace elements to cover the needs of high yielding dairy cows. Therefore the total rations have to be supplemented with additional trace elements. Analyses show that corn silage has lower levels of trace elements than grass silage. In pastures, the location, plant population, utilization intensity and fertilization have a big influence on trace element contents. Energy concentrates are different from protein concentrates. Protein concentrates are richer in trace elements than energy concentrates. Are my cows adequately supplied? The need for trace elements is mainly determined by the growth stage, milk or beef usage and performance of cattle. Thus, calves and growing cattle have quantitatively different demands than a high yielding dairy cow. Trace element recommendations are derived from dose-response studies. In consideration of bioavailability and intermediate interactions, safety margins are conducted to ensure an adequate trace element supply. On the other hand, there are legal limits on maximum values for trace elements in cattle. An overview of recommendations and legal limits can be found in Table 2. From a practical point of view, demand for trace elements increase at certain production stages of a cow. In times of high temperatures (heat stress), in stressful situations (around calving, disease) and in times of high performance we can expect increased trace element requirements. The meaning of the term bioavailability is fairly ambiguous, but it generally describes mineral absorption by and/or retention within the animal. Theoretically, a mineral supplement that is more bioavailable than another will provide a greater proportion of absorbed minerals to support animal production and health. Table 2: Recommendations and legal limits for trace elements in dairy cows Recommendations (mg/kg DM) Jeroch et al. 2008; GfE 2001 NRC 2001 Legal limits (mg/kg complete feed) Iron Zinc Manganese Copper Iodine 0,5 0,4-0,77 5 Cobalt 0,1-0,2 0,11 2 Selenium 0,2-0,25 0,3 0,5 One tool to check the efficiency of the trace element supply is the analysis of blood serum. For this, some representative dairy cows of the herd (including healthy cows, high lactating, low lactating and dry cows) were selected to have their blood samples taken by a veterinarian. Depending on the results of the analysis, any lack can be balanced and oversupply prevented. In some cases it makes sense to analyse forages for their trace element contents as well. By calculating minerals intake based on the animal s diet, specific levels can be supplemented to meet the animal s needs. Organic bound trace elements To avoid negative interactions between inorganic minerals and trace elements, organic bound trace elements are increasingly used in cattle diets successfully. In particular, amino acid chelates work very efficiently as a binding partner for trace elements. This means that a trace element ion is bound to an amino acid chelate. The target is to improve the bioavailability and thus the intake of trace elements. Thereby the organic binding form uses a separate resorption process in the intestinal tract resulting in higher trace element contents in the blood, tissue, etc. An improved trace element content in the metabolism is the basis for healthy and highly productive cattle. Numerous studies have proven that organic bound trace elements are absorbed more effectively. For example Wolfram (1999) documented that different forms of selenium have different pathways into the body. Furthermore Kincaid et al. (1999) reported higher zinc values in the liver of calves after supplementing them with organic bound zinc. However, the different transport mechanisms of various trace element sources from the feed into the body are not completely known.

6 Christian Punz Product Manager Nutritional Products effect on a variety of fertility parameters could be scientifically demonstrated, as shown in Table 3. Source: Zinpro Figure 3: Molecule structure of a trace element amino acid chelate bond (Metal Ion= Copper, Zinc or Manganese) Results from practice In practice, the supply with trace minerals from dairy cows can be measured with certain parameters. Supplementing trace elements in organic form over a longer period results in beneficial effects as described in the previous chapters. Technically it is possible, to supplement copper, zinc and manganese in organic form. Moreover it is also very common to use selenium in a rumen stable form in cattle diets. Lameness In a trial, 150 Holstein cows were supplemented either with inorganic trace elements (sulfates) or with organic bound trace elements (copper-, zinc- and manganese chelates). The experimental period lasted 21 days prior to calving until 250 days after calving. The use of organic bound trace elements significantly reduced the incidence of lameness 75 days after calving. At 250 days after calving, it was observed that there were even fewer cows with claw disease. Cows with claw disorders, % Influence of different trace element sources on the incidence of lameness 34,1 a 23,6 b Mean values with different superscripts are significantly different (P=0,15) Ballantine et al., Professional Animal Scientist 18: Fertility In the same study, the infl uence of organic bound trace elements (copper-, zinc- and manganese chelate) in comparison to inorganic trace elements (sulfates) on fertility was investigated. Through the supplementation with organic bound trace minerals a positive 17,7 75 d after calving 250 d after calving Inorganic trace elements 10 Zinpro Performance Minerals Source: Zinpro Figure 4: Lame cows show poor fertility and low milk production Table 3: Effect of trace element sources on the fertility of lactating dairy cows Parameter Trace elements Inorganic a Organic b Days to first insemination Pregnant cows 150 days 42,7 54,8 after calving, % 21 day pregnancy rate, % 18,4 27,4 Insemination index 2,6 2,3 Days open a Application of sulfates Application of organic bound trace elements (Zinpro Performance Minerals ) Ballantine et al., Professional Animal Scientist 18: Udder health In a study with 306 Holstein cows the effect of different trace element sources on udder health was inves- Somatic cell count in the milk, 1000/ml Influence of different trace element sources on the somatic cell count in the milk 183 Inorganic trace elements 136 Somatic cell count in the milk Zinpro Performance Minerals DeFrain et al., Professional Animal Scientist 25:

7 tigated. The experimental period lasted 21 days prior to calving until 250 days after calving. The application of organic bound trace elements resulted in a significant decrease in the somatic cell count in the milk. Figure 5: A healthy udder requires an adequate supply of highly available trace elements Conclusion It is important to ensure high performing cattle receive an adequate level of trace minerals in their diets. This requires knowledge of the contents in forages, concentrates and mineral feed as well as their specific usage in feeding. The possible negative interactions due to an oversupply of a certain element also have to be considered. Therefore it is crucial that all minerals and trace elements are supplemented completely to meet the animal s needs. A toxification has to be avoided in any case. Applications of organic bound trace elements have shown clear positive effects in practice, and their usage prevents any negative interactions. Trials demonstrate that bioavailability increased and thus the performance and health status in dairy cows could be improved as well. There is a positive effect on claw and udder health. Furthermore organic bound trace elements support fertility in dairy cows. With higher bioavailability of trace elements, it is possible to reduce the levels of trace element supplementation. This also ensures a lower discharge in the manure which benefits the farming environment.

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