CALORIC VALUE OF PELLETING. BY LELAND MCKINNEY AND ROBERT TEETER Oklahoma State University, Department of Animal Science, Stillwater, OK 74078

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1 THREE Publication of Cobb-Vantress, Inc. CALORIC VALUE OF PELLETING BY LELAND MCKINNEY AND ROBERT TEETER Oklahoma State University, Department of Animal Science, Stillwater, OK INTRODUCTION: The benefits of feed processing have been long recognized by poultry industry personnel. Processing techniques, such as pelleting and extrusion, are frequently touted for their beneficial effects on feed-handling characteristics and animal performance. Though the magnitude and precise mode of action by which these benefits are realized is often debated, the majority of poultry rations utilized today undergo some form of post-mixing processing. The purpose of this treatise is to propose quantifiable methodology enabling greater interactivity between this aspect of bird management and nutrition. Presumably, the improved animal performance associated with processed feeds is attributable to enhanced feed value and/or altered nutrient need by the animal. Potential processing effects upon feed value include feed sterilization as well as increased product palatability and nutrient bioavailabililty. Concomitantly, processing may also alter animal nutrient need via the activity associated with feed consumption. Birds expending less energy for consumption would have more energy available for growth. The true value of pelleting may well be due to a combination of such variables. In any case, poultry rations which are processed to enhance profitability and information related to the mode of action may benefit its optimization. PROCESSING QUALITY RELATIONSHIPS: Final quality of the processed feed is the result of numerous factors influencing the feed form actually presented to the bird for consumption. As an example for pelleted feeds, it is the percentage of intact pellets at the feeder, and not the feed mill, that determines processing efficacy. Fundamentally, pellet integrity is affected by diet formulation, plant operation and feed handling during transport and delivery. Of these, diet formulation has the potential to divergently influence the nutritional value of the final product. Case in point, dietary fat supplementation negatively impacts pellet durability and lowers the proportion of intact pellets reaching the feeder. Consequently, efforts to increase the energy availability to the animal via fat supplementation may be partially offset by lowered pellet quality. Indeed, such divergent offsets have the potential to create formulization dead zones whereby bird performance seemingly lags behind that anticipated for the diet composition change. Nutritionists desiring to improve feed conversion commonly assume that combinations of pelleting and fat fortification will additively enable them to reach their goal. Indeed, increasing dietary fat has a significant impact upon feed conversion as displayed in Figure 1. However, from a mechanistic vantage it is well known that such fat addition Continued on page 2

2 Continued from page 1 degrades pellet quality. Feed manufacturers frequently attempt to modify processing parameters so as to lessen these adverse affects by added fat, but with varying success. The problem is highly interactive with other aspects of feed processing, as such efforts to counter fat addition may also slow product throughput. Since many plants operate at near capacity, adversely impacting product throughput is not an attractive option and pellet quality frequently declines. Ultimately, producers may be faced with the expense of increasing diet caloric density only to unknowingly have it partially or completely negated by feed form deterioration prior to bird consumption. But, how to place a value on these interacting processes has been a long-standing problem and the topic of this investigation. STUDIES: The principle project goal was to estimate the caloric value attributable to pelleting and further to determine the influence of pellet quality itself on calorific value. For the purpose of this discussion, pellet quality was defined according to the proportion of pellets and pellet fines available at the feeder for birds to consume. Experiment 1/Definition of Energy-Growth Relationships The first study was conducted to create an approach for predicting the caloric value of pelleting from feed conversion data. Since both bird body weight and dietary caloric density impact FCR, it was projected that the model must at a minimum account for these variables. If this objective could be achieved, then further work using treatments varying in pellet quality could be transformed into relevant calorific values. Subsequently, to evaluate the body weightdietary caloric density relationship, rations were formulated to contain a range of energy values (2,650 to 3,250 Kcal MEn/kg ration). These rations were then fed to Cobb 500 male broilers under conditions mimicking commercial starter, grower, and finisher periods. The intent was to create a mathematically defined response surface between the FCR, caloric density, and bird live weight variables for application. Bird live weight and feed consumption were tallied throughout the feeding period to 56 days of age. All rations were pelleted, transported to the test facility, stored, and fed in tube feeders such that pellet quality was maintained at 50 ± 10%. Results were then used to mathematically describe the relationship between caloric density, FCR, and bird body weight throughout the growth curve. Experiment 2 / Evaluation of Pellet Quality Influences Once the predictive methodology for estimating dietary calorific value was established, the second study was conducted to examine the impact of varying feed form (pellet quality) on calorific value. To achieve this, male Cobb 500 chicks were first reared to 38 days of age and then utilized in a 7-day feed conversion test. The five feed form treatments were derived from a single diet and incrementally ranged from 20% pellets with 80% pellet fines, to 100 % pellets and no fines. Unprocessed mash was also included as a treatment so that the overall impact of pelleting could be determined. Following the 7-day test period, body weight gain, feed consumption, and feed conversion ratio were determined. The remaining feed in each feeder was then sieved and the consumption of pellets and pellet fines determined for statistical analysis and modeling. RESULTS AND DISCUSSION Experiment 1 / Definition of Energy-Growth Relationships Results from the first study are presented in the following two ways, first in Figure 2, a conventional feed conversion Figure 2 Figure 3 Body Weight, g Diet Caloric density, MEn kcal/kg Body Weight, g Diet Caloric density, MEn kcal/kg Figure 2 Interrelationship between cumulative body weight and feed conversion ratio with dietary caloric density. Figure 3 Interrelationship between daily body weight gain and feed conversion ratio with dietary caloric density. Continued on page 3 2

3 Continued from page 2 made in the second study to convert feed form differences into dietary calorific values. Experiment 2 / Evaluation of Pellet Quality Influences Application of study 1 response surfaces, in the second experiment, enabled value assignment (as caloric density) to pellet quality and consequently to the value of feed processing. Results will be discussed first as performance and then as calorific value. Neither pelleting nor pellet quality significantly impacted feed consumption. The numerical feed intake elevation observed for birds consuming pelleted feed, compared to mash, is analogous to other published studies. Conversely, the proportion of post pelleting fines in the feeder did not influence feed consumption. However, birds did selectively consume pellets over pellet fines for some treatments. For example, birds offered a combination of 80% pellets and 20% pellet fines consumed on average 87% pellets and 13% pellet fines. This preferential consumption of pellets over pellet fines was dependent upon the ratio of pellets and fines in the feeder. As the proportion of pellet fines increased, and pellets decreased, the preference or ability for pellet consumption diminished and was not present below 40 percent pellets. At that point, birds consumed the pellet: fines ratio provided. The fact that feed intake did not differ across treatments lends credibility to the concept that performance differences for weight gain and feed efficiency, are due to either an enhanced nutrient bioavailabililty, or altered nutrient need of the bird. ratio was calculated based on cumulative feed consumption and body weight change during the starter, grower, and finisher intervals. The second approach created a more dynamic model by using daily feed intake and weight gain versus dietary caloric density (Figure 3). Note in both illustrations that body weight dominated the FCR relationship. Though caloric density exhibited significant influence on feed conversion, it was much less than bird body weight. Nonetheless, efficiency of gain increased steadily with caloric density to approximately 3100 Kcal MEn/kg, appearing to plateau thereafter. The impact of caloric density also tended to diminish as bird weight increased. Application of these surface relationships was Pellet quality effects on weight gain and feed to gain ratio are presented in Figure 4. Note that regardless of pellet quality, pelleting improved both rate and efficiency of gain. In analysis, where the results of the pellet treatments were pooled and compared with mash, pelleting increased (P <.01) weight gain 6% and improved (P <.05) efficiency of gain 5%. Birds that received 100% pellets were excluded from the computation to avoid inflating the pelleting effects with a practically unattainable pellet quality. Generally, field pellet qualities at the feeder are in the 40 to 80% range. As the proportion of pellets to pellet fines increased, birds gained more weight and did so more efficiently (Figure 5). The responses to pellet quality appeared to be biphasic with an intermediate plateau in the 40 to 60% pellet quality range. This would suggest there is little need to improve pellet quality above Continued on page 4 3

4 Continued from page 3 such, the data were first transformed into dietary caloric density and then examined as deviations from the mash diet to produce an estimate of the Kcal/Kg added to the nonpelleted mash diet. Calorific estimates of pelleting and pellet quality are displayed in Figure 6. Note that as pellet quality increases, the apparent caloric value of the diet becomes greater. Considering proposed modes of action suggest that as pellet quality increases, either the bird expends less energy for consumption or the bioavailabililty of nutrients and/or energy increases. Regarding this latter point, most reported literature examining pelleting effects on digestibility indicate that pelleting does not greatly impact nutrient bioavailabililty. In that respect, increasing pellet quality may be viewed as decreasing bird activity associated with feed consumption, thereby diverting calories from activity to tissue accretion (Jensen et al. 1962). In this study, energy sparing attributable to pelleting peaked at 187 Kcal MEn/kg feed consumed for the 100% pellet quality treatment. The estimated energy sparing values diminish as the proportion of pellets to fines decreases, but still appears greater than zero for the 20% pellets (76 Kcal/kg diet). 40%, unless it will also be in excess of 60%. However, keep in mind that if possible, birds will selectively consume pellets. Therefore, in all likelihood the more aggressive birds would consume mostly pellets leaving the more timid birds with pellet fines. Consequently, the proportion of pellets and pellet fines consumed could vary from bird to bird. Using the daily results from study 1 to enhance precision, the body weight and FCR data associated with pelleting were transformed into a caloric density. As a test, the 40 to 60% pellet quality data were averaged to simulate the approximately 50 ± 10% pellet quality achieved in study 1. When this was done, the approach predicted 3225 Kcal MEn/kg diet, exactly matching the dietary energy concentration used in the second study. Consequently, the surface relationship was accepted as a methodology to estimate the caloric value associated with pellet quality. As Lipid addition to diets is the usual approach to elevate dietary caloric density. However, dietary fat inclusion (prior to pelleting) also has the potential to reduce pellet quality (Behnke, 1994). Consequently, the reduction in pellet quality associated with dietary fat fortification has the potential to at least partially offset the caloric boost attributable to fat inclusion. Indeed, under some circumstances it could potentially eliminate the added fat value. To ascertain the net caloric value (energy attributable to fat inclusion minus energy lost due to pellet degradation) of fat fortified-pelleted diets, both the caloric gain attributable to fat supplementation and the caloric consequence of altered pellet quality must be considered. Continued on page 5 4

5 Continued from page 5 APPLICATION: As practical applications of results presented herein, two scenarios are discussed. Both examples suggest a stepwise method for determination of true or net dietary caloric value of pelleting. The method also enables dynamic evaluation of the nutrition-feed form interface with quantifiable calorific value. Scenario 1. In this scenario, a producer has an opportunity to decrease ingredient costs via use of a lower quality fat source (Fat B). The fat currently used (Fat A) is included at 4% of the ration. After this ration is pelleted, approximately 70% of the pellets are intact at the feeder. In maintaining a constant dietary caloric density, it is required that the cheaper fat source be included at 6% of the ration. Despite the additional Fat B required, ingredient costs are still lower, however the proportion of intact pellets at the feeder deteriorates to 30%. QUESTION: Does Fat B use still offer an economic advantage? To compute this the net dietary caloric value must be computed. STEPS: (Refer to Table 1) Estimate dietary caloric changes attributable to each fat source inclusion. The dietary caloric density did not change as the diets were formulated to be iso-caloric. Estimate fat source and fat inclusion level effects on pellet quality. Fat B use resulted in a 40% reduction in pellet quality (from 70 to 30% pellet quality). Sum the caloric change due to fat source and/or fat inclusion with the caloric consequence of altering pellet quality. In this case, neither fat source nor inclusion level affected dietary caloric value per se. However, pellet quality degradation (from 70 to 30%) resulted in a loss of 55 Kcal 5 MEn/kg diet. To overcome this, inclusion of Fat B must be elevated further, with additional degradation of pellet quality. Though Fat B is lower in cost/kg, it may well be the most expensive when fed at equalized energy value. Scenario 2: In this scenario, a producer desires to increase dietary caloric density utilizing supplemental fat. The current ration is formulated to provide 3120 Kcal MEn/kg diet and contains 4% animal fat. Additionally, intact pellets at the feeder average around 68%. Increasing animal fat inclusion to 5% achieves the producer s goal in elevating the rations caloric value to 3157 Kcal MEn/kg diet. However it also results in a reduction of pellet quality (49%). QUESTION: Does pellet quality degradation offset the caloric gain attributable to the additional 1% inclusion of animal fat? STEPS: (Refer to Table 2) Estimate the dietary caloric change associated with diet formula modification. The additional 1% animal fat inclusion increased the dietary energy concentration 37 Kcal MEn/kg diet (from 3120 to 3157 Kcal MEn/kg diet). Determine pellet quality change attributable to diet formula modification. The additional 1% animal fat resulted in a 19% decline in pellet quality (from 68 to 49%). Sum the caloric change due to additional animal fat inclusion and the caloric consequence of altering pellet quality. For this example, the diet formula modification resulted in a caloric gain of 37 Kcal MEn/kg diet. However, this was offset by a 37 Kcal MEn/kg diet loss associated pellet quality degradation. Consequently, the proposed change falls in a Continued on page 6

6 Continued from page 5 calorific nutritional-feed form dead zone and the caloric value of the additional 1% fat is forfeited. SUMMARY: The interface between nutrition and management is complex. Many companies have evolved their own view of ingredient nutrient value for eliciting a level of bird performance. When the full range of bird management, postmixing processing and nutritional formulization practices are considered, it should not be surprising that subtle interactions may negate the best of intentions. In such cases it may be necessary for personnel to step outside the realm of practical individual experiences to gain a quantifiable appreciation for the true or net value of their production system. Leland McKinney Leland McKinney received his B.S. and M.S. degree at Kansas State University. He is currently pursuing his Ph.D. in poultry nutrition at Oklahoma State University. LITERATURE CITED Behnke, K. C Factors affecting pellet quality. Maryland Nutrition Conference. Dept. of Poultry Science and Animal Science, College of Agriculture, University of Maryland. College Park. Jensen, L. S., L. H. Merrill, C. V. Reddy, and J. McGinnis Observations on eating patterns and rate of food passage of birds fed pelleted and unpelleted diets. Poultry Science 41:1414. Richardson, W., E. J. Day Effect of varying levels of added fat in broiler diets on pellet quality. Feedstuffs 48(20):24. Submitted for publication with the permission of the Director, Oklahoma Agricultural Experiment Station, Stillwater, OK Support provided by the Oklahoma Agricultural Experiment Station, State of Oklahoma, and Cobb-Vantress. Dr. Robert Teeter Dr. Robert Teeter has led a poultry research program at Oklahoma State University since His research interests are directed at describing metabolic association with feed conversion, stress management and energetic efficiency throughout the growth curve. COBB-VANTRESS,INC. PO BOX 1030, SILOAM SPRINGS, ARKANSAS 72761, USA TEL: FAX: info@cobb-vantress.com COBB EUROPE MIDDEN ENGWEG 13, 3882 TS PUTTEN, THE NETHERLANDS TEL: FAX: info@cobb-europe.com WEBSITE: COBB-VANTRESS BRASIL,LTDA. RODOVIA ASSIS CHATEAUBRIAND, KM 10 CEP: /CAIXA POSTAL 2, GUAPIAÇU-SP-BRASIL TEL: +55 (17) FAX: +55 (17) cobb.info@cobb-vantress.com.br