Sunday, October 3, 2010

Trace mineral balance in poultry

Trace mineral balance in poultry
Monday, 01 December 2008 01:00
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Sheila E. SCHEIDELER, Dept. of Animal Science, University of Nebraska, Lincoln, NE, U.S.A.

Introduction

Trace mineral nutrition has a rich history of discovery and research in the field of poultry nutrition. Many of the early basic nutrient metabolism studies were conducted in chicks and then related to other livestock species and humans. The bulk of this work was conducted and reported in the era from 1960-1980. Nutrient requirements were established for each species of poultry and functions of those nutrients – trace minerals were also researched and reported. More recently, in the past 25 years, trace minerals role in immune function and related physiological roles have been studied. New organic sources of trace minerals have been patented and marketed providing a more available form of trace minerals for the chicken or turkey. The complexity of trace mineral nutrition requires a thorough review of functions, interactions and availability of sources from time to time by the poultry producer/nutritionist. The intent of this presentation is to do such a review of established functions and roles, as well as new opportunities for trace minerals in the field of poultry nutrition. The trace minerals of primary concern in poultry diets and having recommended levels of supplementation by the NRC (1994) Nutrient Requirements of Poultry include Zinc (Zn), Manganese (Mn), Copper (Cu), Iron (Fe), Selenium (Se) and Iodine (I). The trace minerals typically supplemented in poultry premixes include Zn, Mn, Cu, Fe and I. Selenium is very often supplemented either in the premix or separate from the premix formulation. Trace mineral premixes should be formulated and supplemented to poultry feeds separate from the vitamin premix due to potential vitamin oxidation by the trace minerals. Inclusion levels are often very small ranging from .05 to .50 percent which means that weighing (scales) needs to be quite accurate and mixing needs to be thorough for the trace mineral premix to be adequately distributed in a batch of poultry feed.

Functions of trace minerals

Zinc plays an important role in poultry, particularly for layers, as a component of a number of metalloenzymes such as carbonic anhydrase which is essential for eggshell formation in the hens shell gland. Other important zinc metalloenzymes in the hen include carboxypeptidases and DNA polymerases. These enzymes play important roles in the hens immune response, in skin and wound healing, and for hormone production (testosterone and corticosteroids). Classic deficiency symptoms of a zinc deficiency in poultry could include a suppressed immune system, poor feathering and dermatitis, infertility and poor shell quality.

Copper also plays an important role in a number of enzyme functions in the bird. Copper is closely associated with iron metabolism as it is a part of ceruloplasmin which is an enzyme that plays an important role in the oxidation of ferrous to ferric iron, controlling the movement of iron from the reticuloendothelium to liver and then plasma, affecting red blood cell formation. A copper deficiency can cause microcytic hypochromic anemia. Another important enzyme dependent on copper is lysyl oxidase which is an integral enzyme in elastin and collagen formation in birds. A deficiency of copper can cause bone abnormalities due to abnormal collagen synthesis. Tibial dyschondroplasia is an example of a leg disorder in poultry that can be caused by a copper deficiency. Poor collagen and/or elastin formation can also lead to cardiovascular lesions and aortic ruptures. Copper is also important for feather development as well as feather colour via it’s role in disulfide bond formation. Iron has a very specific function in all animals as a component of the protein heme found in the red blood cell’s protein haemoglobin and in the muscle cell’s protein myoglobin. Iron has a rapid turnover rate in the chicken – 10 X per day, so it must be provided in a highly available form in the bird’s diet on a daily basis. Any internal infection such as coccidiosis can also interfere with iron absorption and availability. Iron deficiency can result in microcytic, hypochromic anemia in poultry.

Manganese plays a significant role in the chicken’s body in the formation of chondroitin sulfate. This mucopolysaccharide is an important component of bone cartilage. Deficiencies of manganese in poultry will result in perosis, bone shortening and bowing and in poor eggshell quality in laying hens. Selenium is a very unique trace mineral in the chicken’s diet in that it’s inclusion rate is regulated and limited by the FDA. Selenium is considered a heavy metal in manure and is limited in its soil application. Selenium was recognized for its toxicity in animal diets before it’s essentiality was established.

Selenium is an important constituent of the enzyme glutathione peroxidase. Glutathione peroxidase functions in the cell as its first line of defence against oxidation. Other selenoproteins in poultry play an important role in prevention of exudative diathesis, normal pancreatic function, and fertility. Levels of selenium supplementation are limited by the FDA to only .30 ppm in poultry diets. Levels of selenium in feedstuffs for poultry can vary considerably dependent on soil content of selenium the crops are grown on. Soils in the Dakotas and Canada can contain high levels of selenium resulting in higher grain levels of selenium. Often times, total selenium of poultry diets in our plains states will reach levels of .40 to .50 ppm when corn and soybean levels are combined with .30 ppm supplementation levels. These high levels can to be beneficial to the immune status and performance of poultry flocks without being toxic. Dietary selenium works with Vitamin E in boosting the immune status of poultry.

Interactions

A number of negative interactions can occur such that an excess of one trace mineral will interfere with another trace mineral’s availability. The most common antagonism occurs between zinc and copper. High levels of dietary zinc will inhibit copper absorption, hepatic accumulation and deposition in the egg. Ratios greater than 4:1 of zinc:copper can be considered antagonistic. High levels of copper and iron can interfere with zinc availability and potentially could induce anemia. Excess dietary phosphorus will interfere with manganese availability in poultry. Environmental factors such as water, equipment and or soil conditions for crops may also contribute to a birds exposure to excessive trace minerals. Many soils in the Midwest have an abundance of manganese and zinc which can correspond to sometimes higher levels in the corn grown on these soils as well as high drinking water levels of some of the trace minerals. All of these potential sources need to be accounted for when calculating the birds consumption rate of trace minerals.

Dietary sources of trace minerals

Traditionally, inorganic sources of trace minerals have been utilized in poultry feed supplements. Trace minerals as inorganic salts such as chlorides, sulfates, carbonates and oxides have all been supplemented to poultry diets. In general, the chloride and sulfate forms are more available than the carbonates, with the oxides having the poorest availability. During recent years, organic chelates and bioplexes of trace minerals have become available for supplementation in poultry diets. A trace mineral bioplex is defined as a trace mineral with ligands to amino acids or proteins. A number of companies have patented organic trace mineral products. Research has indicated that these inorganic sources are more bioavailable than their inorganic counterparts due to the following reasons:

1. The ring structure protects the mineral from unwanted chemical reactions in the gut
2. Chelates are absorbed more efficiently in the gut.
3. Fewer interactions occur between competing minerals for absorption sites.

Numerous studies have reported beneficial effects of chelated organic trace mineral supplementation on bird health and production parameters as well as product quality.

Research (UNL):

Study 1. Trace mineral supplementation effects on eggshell strength.
Supplemental trace minerals play a significant role in eggshell formation as co-factors and/or structural components of enzyme systems such as carbonic anhydrase which are inherently involved in eggshell formation. Ceylan and Scheideler, (1999) reported significant positive effects of zinc and manganese supplementation from Bioplex Zn and Mn (Alltech) on carbonic anhydrase activity levels in the shell gland of laying hens and a correlated improvement in percent dry shell of eggs laid. Percent cracked eggs during processing, was also reduced by supplementation of zinc and manganese to the layer diets. Increasing dietary calcium from 3.5 % to 4.0 % (Ceylan and Scheideler, 1999) also improved eggshell quality and carbonic anhydrase activity in the shell gland.

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2. Effects of supplemental selenium on vitelline membrane strength (UNL)
Monsalve and Scheideler (2004) studied the effects of 2 selenium sources (selenium selenite and Sel-plex) at 2 dietary levels (0.55 or 0.75 ppm) in laying hen diets and their effects on production and vitelline membrane strength. The higher level of dietary selenium resulted in a 2 percent increase in egg production and a 1 gram increase in egg mass produced during this short trial. Increasing dietary selenium improved vitelline membrane strength in both fresh and stored (aged) eggs. Dietary source of selenium had no effect on vitelline membrane strength, but did affect yolk selenium content. Yolks from hens fed the Sel-plex source of selenium had greater amounts of selenium deposited in the egg yolk compared to yolks from hens fed the inorganic source of selenium, indicating improved availability of selenium from the organic source – Sel-plex. Research is on-going at a number of institutions regarding the improved bioavailability of trace minerals from organic sources and their role in the poultry diet. Leeson (2005) boldly proposed reducing the overall amount of trace mineral supplementation to 20 % of the regular level of inorganic level of supplementation with reduced performance criteria.

Summary

With new research being published showing improved utilization of organic trace minerals, the poultry nutritionist has to contemplate the validity of the NRC Nutrient Recommendations for Poultry (1994) and how one can formulate rations more responsibly using organic trace minerals. With the stress to reduce flow of waste nutrients into the environment, poultry producers may be able to reduce overall supplementation of trace minerals, yet still receive optimum performance when using organic trace elements.

References

Leeson, S., 2005. Trace mineral requirements of poultry – validity of the NRC recommendations. Published in “Re-defining Mineral Nutrition” edited by JA Taylor-Pickard and LA Tucker, Nottingham University Press, Nottingham, United Kingdom.

Monsalve, D., G. Froning, M. Beck and S.E. Scheideler, 2004. The effects of supplemental dietary Vitamin E and selenium from two sources on egg production and vitelline membrane strength in laying hens. Poultry Sci. 83: Supplement 1, p. 168.

Ceylan, N. and S.E. Scheideler, 1999. Effects of Eggshell 49, dietary calcium level and hen age on performance and egg shell quality. Proceedings of Alltech’s 15th Annual Symposium, Biotechnology in the Feed Industry.

From Proceedings of the “Midwest Poultry Federation Convention”, St. Paul, Minnesota, U.S.A.

How valid are the National Research Council nutrient requirement estimates for poultry?

How valid are the National Research Council nutrient requirement estimates for poultry?
PUBLICATION DATE: 06/03/2007
RATING
AUTHOR: STEVEN LEESON - University of Guelph (Courtesy of Alltech Inc.)
The National Research Council (NRC) is the last surviving independent organization to publish nutrient requirement data for farm, pet and lab animal species.


The published values are often accepted as ‘standards’ especially in developing countries, and by government organizations charged with establishing guidelines for legislation. The question often asked is “are NRC values of commercial relevance today?” and if not, “what is the basis for such discrepancies?”


The National Research Council operates under the mandate of the National Academy of Sciences based in Washington, D.C. Over the last 50 years, the NRC has itself formed subcommittees in order to define the nutrient requirements of various animal species including most of the important farmed animals together with needs for laboratory animals, cats and dogs. Over the last 20 years, the Poultry Subcommittee has published recommendations on nutrient requirements each 7-10 years (1977, 1984, 1994). In Europe, the now defunct Agricultural Research Council likewise published nutrient recommendations for farm animals, again every 10 years or so.


The mandate of the NRC species subcommittees is to provide unbiased reviews and recommendations regarding the nutrient requirements of the various animal species. The last NRC Poultry Subcommittee was established in 1990, the outcome of which was the 9th Revised Edition of Nutrient Requirements of Poultry published in 1994. Within this publication are nutrient requirements for egg-layers, breeders, broilers, turkeys, pheasant and waterfowl. In establishing any nutrient requirement value, the committee members are given one simple, albeit very restrictive directive, and that is to base such values only on data published in referred journals. The idea behind this mandate is to prevent the use of potentially biased commercial data. This directive is particularly restrictive to estimating certain nutrient needs, since there has been a lack of scientific research and publication on many topics over the last 40 years.


This situation dictates the reliance on very dated literature estimates of certain nutrient needs. On the other hand, everyone recognizes the increase in growth rate of broilers and turkeys that has occurred over the last 40 years, and the increased egg output of modern layer strains. For this reason, the NRC estimates are often criticized as not representing the needs of modern strains of commercial poultry.


Much of the older data are based on research studies involving purified or semi-purified diets. In fact, the NRC (1994) publication has a section solely related to description of reference diets used in classical requirement studies. These diets often contain isolated soybean protein or casein as a source of protein and amino acids, and dextrose, starch and sucrose as a source of energy. Cellulose was often used as non-nutritive filler in these purified diets. Such diets are highly digestible, and are not encumbered with facets of variable nutrient availability, yet can be criticized as not being of relevance to commercial feeding. It is very difficult to crumble/pellet diets with these purified ingredients, and today mash diets are obviously of little relevance to the broiler and turkey industries.


Although the foregoing discussion highlights inadequacies in NRC published values, NRC still provides the best unbiased assessment. The reader has to be aware of the relevant potential confounding factors, and adjust actual feeding levels accordingly. Just as no two commercial broiler starter diets will ever be identical, formulating all nutrients within a diet solely to NRC (1984) levels shows a lack of understanding of nutrition and feed management.


Another factor of relevance today in establishing diet nutrient specifications is the trend towards specialization in nutrition. Certainly, many broiler nutritionists will never formulate diets for laying hens, while turkey nutritionists have little interest in specifications for egg laying stock. Our degree of specialization leads us to source more specific material, while NRC provides a general overview of all species. In research, specialization tends to be even more extreme, where researchers in amino acid metabolism, for example, at best pay cursory attention to trace mineral levels in their diets. In fact the complexity of research today dictates that we can answer questions on at best a very limited number of nutrients at any one time.


While the requirement tables were eventually published in 1994, the information base for the latest Nutrient Requirements of Poultry were collated in 1991, making the ‘current’ information now some 14 years old. Fourteen years is a long time in terms of productive performance of layers, broilers and turkeys. Obviously growth rate and egg mass output have increased in this period, and for some traits this is in the order of +20%. All research becomes ‘dated’ quite quickly, relative to the ongoing changes in genetic gain, and this situation must be a consideration in reviewing historical dated information.


Another major factor to consider in reviewing NRC (1994) data is the assessment criteria used to establish various nutrient requirements. For broiler chickens, virtually all nutrients are assessed in terms of optimizing growth rate, while for layers, the measurement criteria is simply egg production and egg weight. Over the last 20 years, commercial goals have evolved, and these impinge on nutrient needs and feeding programs. For the broiler chicken, the needs for lysine now relate to not merely growth and feed utilization, but also breast meat yield and carcass quality per se. Broiler chickens today are marketed over a vast range of weights/ages and in some instances these may be as mixed-sex or separate sex flocks. Most broiler genetic companies also have stock with different growth and carcass characteristics. In the future, we may also produce broilers with enhanced meat nutrient profile relative to human nutrition. Yet another major change has been the move to controlled environment housing of broilers, which itself impinges on the birds’ nutrient needs and growth potential. Of late, there has been the impetus to consider manure loading of nutrients during formulation of most poultry diets.


An interesting scenario has occurred with broilers since 1994, and that highlights the importance of continual need for reappraisal of feeding systems. In the mid-1990s, metabolic disorders such as ascites, sudden death syndrome, and leg disorders together accounted for 3-5% mortality in male broilers. In order to counteract such problems, it was common to feed lower energy and/or lower nutrient dense diets, at least for part of the grow-out period. Today such disorders are much less problematic, due to genetic selection, and consequently there is little need for any period of under nutrition. Consequently over a 15 year period we have gone from a situation of selecting nutrients for maximum growth followed by a 5-6 year period of consideration for tempering growth, back to today’s goal of maximum growth rate.


For egg production we no longer have the luxury of formulating solely for egg numbers per se, which is the basis for much of the NRC published nutrient values. There is now interest in egg composition, both in terms of nutrient profile as it impacts human nutrition, as well as component/solid yield for egg processing. There has always been concern about optimizing egg shell quality, and this becomes more critical today with white egg strains capable of producing 330 eggs in 365 days within reasonably large commercial flocks. The current trend of maintaining layers at 26- 28oC in modern housing systems imposes a fairly predictable limit to feed intake, and so allows for greater precision in selection of diet nutrient levels.


These evolving on-farm conditions, together with advances in feed processing, mean that nutritionists cannot expect that single nutrient values, whatever the source, will be applicable to feeding birds under all farm conditions.


To this point, this paper has focused on the validity of NRC (1994) values for the major nutrients. We invariably question these nutrient values most frequently, since they are the most expensive nutrients, and usually have greatest impact on performance and there is continuous release of ‘new’ information. Over the last few years, we have been re-evaluating trace mineral needs of poultry, and in this instance NRC (1994) is essentially the only reference. There has been a dearth of information on requirements for trace minerals, essentially due to the fact that they usually contribute less than 0.5% to the cost of a diet. There has been little trace mineral research conducted in the last 10 years, and even within the NRC (1994) publication, many trace mineral requirement values are based on quite dated research. Most commercial diets provide 2-5× the level of trace minerals relative to NRC (1994) values. While NRC (1994) values are often referred to as minimal values, for other nutrients such as amino acids, we do not usually provide such 2-5× levels of ‘insurance’ as occurs with the trace minerals (and vitamins). One reason for concern with trace minerals is consistency of quality and availability of the mineral within inorganic salts.


We have previously reported on the success in using drastically lower levels of trace minerals (80% less in the diet) provided by BioplexTM proteinates of consistently high and predictable bioavailability. The impetus for this work was reduction in manure loading of minerals, especially zinc and copper (Leeson, 2003).


Broilers grew at comparable rates, while excreting 38% less zinc and 20% less copper in the manure. We have confirmed these results in a subsequent study, in which broilers were fed inorganic trace minerals or just 7% of the same level of minerals as a BioplexTM source, and again observed comparable performance. We have subsequently conducted a trial with laying hens, again using BioplexTM vs inorganic sources of trace minerals (Table 1). In this 32 week study, layers were fed conventional inorganic trace minerals, just 20% of these levels as BioplexTM minerals, or diets totally devoid of trace minerals. Birds fed inorganics or BioplexTM minerals performed the same, while those fed diets devoid of minerals produced slightly fewer eggs with reduced egg size. Layers fed BioplexTM or no trace minerals produced manure with identical levels of Zn, Mn and Cu. In both cases, the levels of zinc in manure were reduced by 67% while for manganese and copper, manure output was reduced by 80% and 10%, respectively.


Table 1. Effect of trace mineral source on egg production (28-60 weeks age).

To enlarge the image, click here
NS, no significant difference.
1- 28 day period.
2- 20% of inorganic mineral level.



These recent findings with trace minerals suggest that the ‘low’ values published by NRC (1994) are probably more appropriate today than they were at time of publication, when environmental issues were not being considered.


The NRC (1994) values for nutrient requirement are a sound starting point for formulation of commercial poultry diets. A single source of requirement values is unlikely to be considered by any nutritionist, and this situation applies to NRC values. Likewise no one set of standards can be applicable to the array of commercial situations that arise during feeding, and it is evident that all requirement values must be periodically scrutinized so as to accommodate improved genetic potential of birds. Nutrient needs also must be reassessed as our end-point goals change, and this is exemplified with impending legislation in metal accumulation in manure.



References

Leeson, S. 2003. A new look at trace mineral nutrition of poultry. In: Nutritional Biotechnology in the Feed and Food Industries. (T.P. Lyons and K.A. Jacques, eds) Nottingham Univ. Press, Notts, UK.


National Research Council. 1994. Nutrient Requirements of Poultry. 9th Rev. Ed. NAS-NRC, Washington, D.C.




Author: STEVEN LEESON
Animal & Poultry Science, University of Guelph, Ontario, Canada
PUBLICATION DATE: 06/03/2007
RATING
AUTHOR: STEVEN LEESON - University of Guelph (Courtesy of Alltech Inc.)