In all livestock operations, the production performance depends very heavily on just how well the diet provided meets the nutritional requirements of the animals. There are many aspects of feed quality, feed manufacturing practice and feeding management that interact to secure success in this area but fundamental to the equation is the control of ingredient quality. The whole effort of feed formulation becomes futile if the nutrient composition and integrity of raw materials is not as assumed in the computer matrix.
The stockfeed industry has long been frustrated by the time delay in wet chemistry analysis of feedstuffs with much of the received material being consumed before results are available. Bioassay of materials is not a practical method of routine raw materials assessment/grading on a day-to-day basis. Near infrared reflectance (NIR) has emerged as a "real time" method of evaluation but this too has its limitations.
The classical textbook tabulation of nutrient requirements of various animal species has been shown
to be too insensitive to accommodate the needs of modern intensive livestock operations. The
differentiation of requirements by age, sex, genetics, environmental conditions, different production
systems, different market requirements, and dynamic market economics, has proven too complicated
to the simple fixed nutrient requirements table approach. Most intensive livestock industries have
developed simulation models which allow the definition of optimum nutrient supply levels for each
specific production situation. The efficiency of the practical application of these recommendations
however still depends on the accuracy of the descriptions we apply to the feedstuffs employed.
Ingredient quality has many aspects, some of which are discussed below,
Variation In Basic Proximate Analysis
[protein, fat, fibre, NFE (carbohydrates), minerals]
The protein content of grain is often discounted as being secondary to that of the protein meals. Yet in most diets the grain component supplies approximately one third to one half of the dietary protein. In the Australian context wheat is the dominant feed grain and each percentage unit of protein has a value of approximately A$4/tonne so it is important to specify this accurately. This is not only important from an economic stand point but also from an amino acid supply standpoint since protein increases generally involve a changing mix of proteins eg. a constant level of metabolic proteins (albumin and globulins of high essential amino acid content) and variable levels of the storage protein (gliadins and glutelins of low essential amino acid content). Hence the proportion of essential amino acids in the protein declines with rising protein control. These can be largely predicted from regression equations based on protein. Total and digestible amino acid levels in feedstuffs can be measured by NIR technologies but despite some very positive research (Jackson et al. 1996, Kempen and Boden 1998, Leeson 1997) commercial adoption has been limited due to concern with the errors involved with some feedstuffs. As more robust calibration sets are developed this technique will no doubt emerge as the most rapid and cost effective means of monitoring amino acid content in feedstuffs.
Variation in the fat content of feedstuffs (natural levels or residual levels following processing) and their fatty acid profiles profoundly influences the energy value, hence to achieve precise formulation, fat levels and composition need to be consistent or at least closely monitored.
c) Fibre And Other Carbohydrates
The available carbohydrate (starch and sugars) component of feedstuffs contributes positively to the energy value of the material while the crude fibre acts as a diluent and the non-starch polysaccharide fractions interfere with nutrient utilization. Since the negative effects of NSP's and oligiosaccharides can to some extent be countered with specific enzyme supplementation, the relative proportions of starch and fibre remains the major influence on the energy available to poultry from cereal grains (Black, 2001).
In a summary of feed grains in Australia Van Barneveld (1999) revealed a wide range in energy values (eg. DE/kg DM for pigs of 13.3 - 17.0 for wheat, 11.7 - 16.0 for barley, and AME for broilers of 10.4 - 15.9 for wheat, 10.4 -13.8 for barley and 8.6 - 16.6 for triticale). Most of the variance was explained by gross chemical composition. Prominent was the influence of total cellulose or faecal DE and total arabinoxylans on ileal DE.
The trace mineral content of feedstuffs is notoriously variable and it is for this reason that the traditional approach to meeting trace mineral requirements has been to largely ignore their contribution and meet the known requirement by supplementation via the vitamin/mineral premix. However, with the mineral depletion of high performance breeding stock over time even when fed "adequate" diets by NRC standards (Mahan and Newton, 1995) and concern re the bioavailability of inorganic supplements (Close, 2000) there is now more interest in the base mineral contributions from feedstuffs, to make organic mineral supplementation more cost effective.
Anti-Nutritional Factors (ANF's)
Many feedstuffs contain inherent ANF's such as trypsin inhibitors, lectins, gossypol, amylase inhibitors, tannins, phytate, alkaloids, saponins, conglycinin, vicine, convicine, glucosinolates, arabinoxylans, B-glucans, oligosacchrides, etc. These all have the potential to cause nutritional disorders and impair performance. Their influence needs to be either deactivated by heat treatment, mineral binding, enzymic hydrolysis, etc and where this is not possible their levels need to be quantitated to allow appropriate formulation limits to be applied.
Field crops such as cereal and grain legumes can be subject to weather damage in the growing phase (rain, flooding, hail, and frost). This can create shot and sprung, leached and pinched grain that can be markedly compromised in its feed value. In the initial stages of sprouting the hydrolysis of starch to sugars by endogenous enzymes in the sprung grain can actually enhance its feed value by improving the digestibility of starch. However, as the process proceeds to shooting, the nutrient content of the seed is consumed by the developing shoots and roots creating a drop in nutritional value.
In the case of frosted grain the seed development is often arrested at an immature stage leading to pinched, grain with reduced starch content and elevated NSP levels. Table 1 (from Van Barneveld and Edwards, 2001) demonstrates the drop in starch and bulk density in various grains due to frosting and the compromise to faecal and more dramatically ileal digestibility energy in pigs. Due to the absences of any significant hindgut activity in poultry the energy values for broilers, layers or ducks would parallel those for the ileal responses in pigs.
Moulds And Mycotoxins
These are a constant hazard in tropical climates. Feeds that are not intended for immediate use should be protected with an effective mould inhibitor. Materials of uncertain history should be considered as potentially hazardous and subjected to routine mycotoxin analysis. Any positive analysis should raise an alarm, as there are no safe levels of mycotoxins. The variable nature of their production means that even the detection of minor levels could signal the presence of far greater problems due to sampling errors. Further to this it has been shown that many of the mycotoxins have synergistic activity in that small amounts of several mycotoxins each below the recognised threshold of toxic effects when activity alone, can result in severe performance depression when operating in combinations (Smith et al., 2000).
Much of the grain used in Asia is imported from other regions. Often it will have been treated with preserving compounds. It is therefore important that they be monitored for potentially hazardous residues such as organochlorides or organophosphates as well as illegal compounds such as DDT or even appropriate compounds at excessive rates.
The tropical climate is very conducive to oxidative degradation. Once this process initiates the climate will tend to accelerate its development. High fat components such as oils, full fat soya, rice-bran, meatmeal, fishmeal, as well as finished feeds are all vulnerable. Oxidative fats are known to reduce growth and feed efficiency via various mechanisms such as impaired gastrointestinal structure, liver damage, reduced immuno-incompetence, vitamin destruction, and lowered hematorcrits (Shermer et al., 1995).
Consequently antioxidant treatments of feeds not intended for immediate use is recommended. The use of Vitamin E as a natural antioxidant is both expensive and hazardous as a Vitamin E deficiency can quickly compound into an immuno-inadequate situation as well as other direct illnesses (eg encephalomalacia, transudative diathesis).
Putrifaction And Processing Of Animal Proteins
Camden et al (2000) conducted a survey of 20 meatmeal samples in New Zealand and recorded a range in AME from 5.75 to 12.33 MJ/kg DM, and a range of a true digestibility of essential amino acids from 26.7 to 88.8%. The AME and total amino acid value are indicative of the raw materials processed and hence the primary analysis of the meals (protein, fat and ash) while the amino acid digestibility variation is reflective of the processing conditions in different plants.
Biogenic amines form from the degradation of amino acids to their corresponding amines, usually due to bacterial spoilage. This can occur either prior to processing or in subsequent storage of the meal. Birds fed high levels of biogenic amines develop symptoms such as enlarged proventriculus, gizzard lining erosion, undigested food in the excreta and pathological changes in the gut mucosa, kidneys and liver. Den Brinken et al (1997) conducted a survey of 81 Australian meatmeal samples and found a wide range of putrescine, cadaverine and histamine up to a total of 558 mg/kg. Meatmeals and fishmeals traded in Asia can often spend a long time in storage so it is important that they be screened for oxidative or microbial damage.
Consequences Of Ingredient Quality Shortfalls
Where ingredient quality shortfalls are detected prior to feed manufacture the cost of the shortfall can be calculated by the cost of any remedial action eg. reformulation, supplementation, rejection and organisation of alternative supply, treatment or insurance strategy (eg. mycotoxin binder). These exercises tend to be far less expensive than the situation where the quality shortfall is undetected and is unwittingly incorporated into the feed and goes on to compromise livestock production or the market value of the produce.
These compromises come in many forms and have varying effects on profitability.
Some examples are discussed below,
Where metabolisable energy values are reduced due to shifts in the proportions of starch, fats, fibre and mineral content, or reduced digestibility of specific components due to NSP levels, inadequate processing, heat denaturation, etc. the primary effect is a compromise on feed conversion efficiency as the birds increase their intake to compensate. However, the flow-on effects can be more far reaching eg. increased faecal volume, wet droppings, protein:energy imbalance, reduced essential fatty acids depressing growth or egg size, etc.
Conversely where there is an energy overshoot due to elevated fat levels, intake may drop leading to a protein and mineral shortfall, compromising muscle growth, rate of lay, egg size, shell strength, and maybe inducing fatty liver problems. The growing cycle of broilers is so tight that there is no time for compensatory growth if the birds suffer a setback due to inappropriate nutrition. The cost of the episode will be reflected in extended growing time, reduced average sale weight, increased variability and increased mortality. In layers any interruption to the laying curve can prove difficult to restore and hence a short-term interruption can result in extended depression of performance In breeders, even if rate of lay is not affected subtle compromises to fertility, hatchability, egg size or shell integrity can prove very expensive. Due to the extended production cycle of layers and breeders and the need for persistence in lay and maximum egg quality, the issue of consistent feed quality is more critical in these birds.
Amino acid responses in poultry have been extensively studied and generally involve curvilinear responses with increasing specific amino acid inputs up to a plateau. The economic optimisation of these curves varies with the parameter under study. For example the optimum lysine level in the diet for maximum growth, maximum efficiency, breast meat yield, rate of lay, egg size, etc may all be different. As the dietary adequacy falls back from the target due to shortfalls in total amino acid content, lower digestibility or bioavailability then assumed, antogonism/interference from phytate, NSP, amino acid imbalance, etc then each of the parameters will be progressively eroded, with increasing economic compromise.
Hoehler (2000) in a review of several publications demonstrated the nature of the responses to lysine and the descending sensitivity of breast meat yield, FCR and weight gain. (Figure 1) The commercial cost of these shortfalls in performance far exceeds the cost of adjusting the diet to restore lysine levels, if the compromise was identified prior to feed manufacture.
Attempts to optimise responses to amino acids will prove futile where there is no control over the amino acid contributions from specific raw materials.
Contaminants And Toxins
Toxic components in feeds such as mycotoxins, alkaloids, mineral excesses, and contra-indicated medications can have a profound and immediate effect on performance and profitability. However, of even greater concern is the risk of carcass or egg condemnation due to bruising or chemical residues (eg. antibiotics, dioxins, heavy metals, other hazardous chemical residues, etc.).
Bacterial contamination of feedstuffs also presents public health risks and any episode of food poisoning can seriously erode consumer confidence and depress sales volumes and prices for extended periods.
Quality Control In The Feedmill
This subject has been reviewed extensively in previous ASA Bulletins (Beggs, 1995 Mc Ellkiney, 1996 and Leslie, 1997) and the importance of this function cannot be over emphasised. Quality control embraces the procedures in the feed milling process from ingredient receival to finished feed delivery, and the final result is dependent on all areas being managed satisfactorily. If control is lost early in the process due to poor or variable feed ingredient quality then subsequent efforts can prove futile no matter how diligently applied.
Various strategies have evolved to accommodate variability in raw materials. Some mills choose to increase the specification of the diet to ensure that minimum specifications are met but this can prove expensive. If data is available on the variance of individual ingredients then it is more appropriate to maintain normal dietary specs but reduce the nutrient levels of each ingredient by say 0.5 - 1.0 std. deviation. This then focuses the economic pressure in the least cost formulations on the more variable components, with little compromise to the consistent products, and with the same confidence of achieving the final diet specification.
In commercial poultry production it is essential to achieve consistent and uniform growth in growing birds and persistence in lay for layers and breeders. This requires that every batch of feed is right up to the mark in terms of quality and its ability to meet the nutrient requirements of the stock. Fundamental to this is control of the nutrient content and quality of ingredients employed. This alone will not ensure success as there are many downstream process of milling, mixing, pelleting, delivery, feeding out, bird health and shed management, etc that influence the final outcome but none of these downstream events can correct for initial shortfalls in ingredient quality.
When it comes to product quality, consistency from batch to batch, tight coefficients of variation on content and digestibility, high biological value, freedom from contaminants and mycotoxins, 48% US Soybeanmeal sets the standard.
Beggs, W. A. 1995. Quality Control in the Feedmill. ASA Technical Bulletin FT 27 1995.
Black, J. L. 2001. Variation in nutritional value of cereal grains across livestock species. Proceedings Australian Poultry Science Symposium. 13: 22-29.
Camden, B. J., Thomas, D. V., Voon H and Ravindran, V. 2000. Variation in the protein quality of New Zealand meat and bonemeals. Proceedings Australian Poultry Science Symposium. 12:199
Close, W. H. 1999. Organic minerals for pigs: an update. In: Biotechnology in the Feed Industry. Proceedings 15th Alltech Symposium. Eds: Lyons and Jaques.
Den Brinker, C. N., Rayner, C. J., Kerr, M. G. and Bryden, W. L. 1997. Biogenic amines in meatmeals. Proceedings Australian Poultry Science Symposium. 9:230.
Hoehler, D. 2000. Evaluation of amino acid dose response data and implications for commercial formulation of broiler diets. Amino News 4/2000 Degussa-HULS.
Jackson, D. A., Bodin, J. C. and Maillard, R. 1996. Determination of total and digestible amino acids by near infrared reflectoscopy. Proceedings Australian Poultry Science Symposium. 8:46-52.
Kempen, T. Van and Bodin J. C. 1998. Near infrared reflectance spectroscopy (NIRS) appears to be superior to nitrogen based regression as a tool in predicting the poultry digestible amino acid content of commonly used feed stuffs. Animal Feed Science Technology. 76:139-147.
Leeson, S. 1997. Potential for real time ingredient quality control procedures. Journal Applied Poultry Research. 6:501-506.
Leslie, A. J. 1997. Quality control in feedmilling, procedures for an effective Programme. ASA Technical Bulletin. FT39-1997.
Mc Ellhiney, R. R. 1996. Quality control in feed manufacturing. ASA Technical Bulletin. FT34-1996.
Mahon, D. and Newton, C. A. 1995. Effect of initial breeding weight on macro and micro mineral composition over a three parity period using a high producing Sow genotype. Journal of Animal Science. 73:151.
Shermer, W. D., Ivey, F. J., Andrews, J. T., Atwell, C. A., Kitchell, M. L. and Dibner, J. J. 1995. Biological effects of lipid peroxides and their by-products in feed. Proceedings Australian Poultry Science Symposium. 7:153-159.
Smith, T. K., Modirsanei, M. and Macdonald, E.J. 2000. The use of binding agents and amino acid supplements for dietary treatment of Fusarium mycotoxicosis. In: Biotechnology in the Feed Industry. Proceedings of 16th Allthech Symposium. Eds. Lyons and Jacques. pp. 383 - 390.
Van Barneveld, R. J. 1999. Chemical and physical characterisation of grain related to variability in energy and amino acid availability in pigs: a review. Australian Journal Agricultural Research. 50:667-687. Van Barneveld, R. J. and Edwards, A. C. 2001. Weather damaged cereal grains in pig diets. Australian Pork Journal. January 2001. pp12-14.