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Determination of metabolizable energy contents of feed ingredients for ducks
Determination of Metabolizable Energy Contents of Feed Ingredients for Ducks1 DARRYL RAGLAND, DALE KING, and OLAYIWOLA ADEOLA2 Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907 dextrose in 100 mL of water at 48 and 54 h after feed withdrawal. The method of excreta collection utilized was surgical fixation of a collection apparatus to the vent area of ducks to facilitate total collection of excreta. Collection of excreta was initiated at the first feeding of test ingredients and was continued for a total of 54 h. In Experiment 1, the AMEn and TMEn of corn, barley, and pearl millet on an as-fed basis were determined to be 3.208 and 3.339, 2.730 and 2.863, and 3.350 and 3.484 kcal/g, respectively. In Experiment 2, the AMEn and TMEn of corn, sorghum, and triticale on an as-fed basis were determined to be 3.151 and 3.459, 3.260 and 3.567, and 2.757 and 3.065 kcal/g, respectively. In conclusion, the use of the modified TME assay, in addition to total collection of excreta from individual ducks, provides a means of accurately estimating the ME content of feed ingredients used to formulate diets for ducks.
(Key words: duck, true metabolizable energy, bioassay, nitrogen correction) 1997 Poultry Science 76:1287–1291
INTRODUCTION Certain nutrient requirement values, as well as amino acid digestibilities and energy contents of feedstuffs for chickens are commonly used in formulating diets for ducks because of the relatively limited nutritional information available on feedstuff digestibility and energy bioavailability for the duck (Elkin, 1987). One reason for the lack of information are the problems associated with the collection of duck excreta (Ostrowski-Meissner, 1984). Ducks consume water in much greater quantities than chickens (Siregar and Farrell, 1980b) and the result is a highly liquid excreta. Traditional excreta collection methods (OstrowskiMeissner, 1984) utilized collection pans, which are subject to errors from contamination with feathers and losses due to splatter when the forcefully ejected excreta contact the pan. The consequence of utilizing pan
Received for publication December 9, 1996. Accepted for publication April 17, 1997. 1Purdue University Agricultural Research Programs—Journal Paper Number 15284. 2To whom correspondence should be addressed.
collection is that sample loss and contamination result in reduced accuracy of estimation of bioavailable nutrients. The practice of applying nutrient bioavailability values determined from chicken nutritional studies to ducks would be feasible if both species metabolized nutrients in a similar manner. However, comparative studies of chickens and ducks suggest that differences in nutrient metabolism exist between the two species that should be considered when formulating diets for ducks based on values determined with chickens (Siregar and Farrell, 1980a). The present experiments were undertaken with the intent of contributing to the sparse pool of knowledge related to nutrient bioavailability in feed ingredients for the duck.
MATERIALS AND METHODS The approach adopted in this study was to use in part the modified TME bioassay described by McNab and Blair (1988), which differs from the method described by Sibbald (1976) in several aspects. The modifications to the bioassay described by Sibbald include: feed deprivation of all birds for 48 h prior to feeding test ingredients; administration of dextrose to all birds during the
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ABSTRACT The objective of the present experiments was to determine the AMEn and TMEn of various feed ingredients used in duck diets. In each of two experiments, 48 mature, male, White Pekin ducks were assigned in pairs to 24 cages based on initial weight. In each experiment, 12 ducks were assigned to each of three test ingredients and 12 ducks received dextrose for determination of endogenous losses of nitrogen and energy. The test ingredients were tube-fed in wet form and consisted of corn, barley, and pearl millet in Experiment 1, and corn, sorghum, and triticale in Experiment 2. Feed was withdrawn 48 h prior to feeding the test ingredients and ducks were tube-fed 30 g of dextrose in 100 mL of water at 8 and 32 h after feed withdrawal. Ducks were tube-fed 30 g of their assigned test ingredient in 100 mL of water at 48 and 54 h after feed withdrawal. Ducks used in estimating endogenous nitrogen and energy losses were tube-fed 30 g of
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Feeding Methodology The tube-feeding apparatus consisted of a 60-mL catheter-tip syringe, to which a 35-cm section of Nalgene tubing3 (8 mm inside diameter) was attached to facilitate delivery of the test ingredients to the ducks’ crop. Fortyeight hours prior to feeding the test ingredients, feed was withdrawn from all ducks. At 8 and 32 h after feed withdrawal, all ducks were tube-fed 30 g of dextrose in 100 mL of distilled water and allowed to purge their gastrointestinal tracts. At 48 and 54 h after feed withdrawal, all ducks were tube-fed 30 g of their assigned test ingredient in 100 mL of distilled water. All test ingredients were ground through a 0.5-mm screen prior to feeding. During a preliminary study to standardize the feeding methodology, birds were observed to regurgitate generous portions of test ingredients if too much was force-fed at one time. Based on these observations, it was decided that two 30-g feedings of test ingredients would be necessary in order to prevent exceeding the capacity of the crop due to the volume of water required to sufficiently mix the ingredients. Based on the necessity of the two feedings 6 h apart, it was decided that the collection period should be extended for an additional 6 h to 54 instead of 48 h. At 48 and 54 h after feed withdrawal, the ducks assigned to receive dextrose for estimation of endogenous losses were also tube-fed 30 g of dextrose in 100 mL of distilled water. All ducks were fitted with their respective collection vessels at the time of the first feeding of test ingredients and total collection of excreta was initiated for 54 h.
Collection Methodology The present collection methodology was inspired in part by the technical note published by Revington et al. (1991), in which specimen container caps were nonsurgically secured to the vent of chickens, and specimen containers were attached to serve as a collection vessel. This approach to collection was tried and found to be unsuitable due to displacement of the specimen cap and container when the ducks assumed a squatting position. Surgical attachment of a collection apparatus to the vent of the ducks was considered to be a more suitable method because it provided better security against excreta loss. The collection apparatus did not appear to create any discomfort or impair the mobility of the birds in any way. The collection apparatus was constructed using materials from a Playtex4 baby nurser set. Prior to placement in cages, birds were surgically fitted with modified plastic retainer lids that were to serve as part of the collection apparatus. The plastic retainer lids from the nurser set were modified by drilling 12 holes, 2 mm in diameter in the ring similar to the 12 points on a clock. Surgical fixation of the retainer lids was accomplished by restraint of the duck in a plexiglass restraint box and local anesthesia of the vent area with 2% lidocaine hydrochloride. The ducks were restrained in the plexiglass box and a 5-cm zone of feathers adjacent to the vent was removed to expose the skin. The skin was then sanitized with a dilute solution of chlorhexidine diacetate (Nolvasan).5 The area to be sutured was then infused in the dorsal, ventral, and lateral quadrants around the vent with 2% lidocaine hydrochloride to desensitize the skin for suturing. The retainer lids were then sutured to the vent area using a continuous suture pattern with the retainer lid anchored in place by passing the needle and suture through holes placed in the retainer lid as the needle exited the skin. The plastic bottle of the nurser set was measured and cut to a length of 3 cm below the threads on the bottle. Whirl-pak bags6 with a capacity of 480 mL and covered with duct tape were then placed through the bore of the bottle and the flaps of the bag overlaid to the sides of the bottle covering the threads. The bottle and Whirl-pak bag were then screwed onto the modified retainer ring attached to the bird with the threads of the ring and bottle securing the bag in place and completing the collection apparatus. The Whirl-pak bags containing excreta were changed within the first 6 h and every 12 h thereafter during the 54-h collection period. All of the feeding and surgical collection protocols in the present study were approved by the Purdue University Animal Care and Use Committee.
Analysis 3Fisher Scientific, Itasca, IL 60143. 4Playtex Products, Dover, DE 19901. 5Fort Dodge Laboratories, Inc., Fort 6Nasco, Fort Atkinson, WI 53583.
Dodge, IA 50501.
All excreta samples were frozen immediately after collection. After completion of the experiment, all samples were thawed, dried at 55 C for 48 h, and ground through a
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 28, 2015
48-h period without feed; a 48-h period of excreta collection; and birds assigned for determination of endogenous losses are administered dextrose instead of no feed at all. These modifications to the Sibbald method appear to improve the precision of the assay as well as decrease the stress on the birds used for determination of endogenous losses. In each experiment, 48 mature, male, White Pekin ducks were sorted according to weight and placed in 24 cages with two ducks per cage (0.66 m × 0.66 m). Twelve birds were assigned to each of three test ingredients and 12 birds were assigned to receive dextrose for estimation of endogenous losses of nitrogen and energy. Test ingredients consisted of corn, barley, and pearl millet in Experiment 1 and corn, sorghum, and triticale in Experiment 2. An additional 500 mL of water/d was offered to each cage during the experiment.
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0.5-mm screen prior to analysis. Dry matter contents of the test ingredients and all samples were determined by drying the samples at 110 C for 24 h. Nitrogen content of test ingredients and excreta was determined by the combustion method using the Model FP2000 combustion analyzer.7 Energy content of test ingredients and excreta was determined by bomb calorimetry using the Adiabatic calorimeter.8
Statistical Analysis Statistical analysis of the data as a completely randomized design was accomplished using the General Linear Models procedure of SAS (SAS Institute, 1986). Differences between means were determined using the least significant difference mean separation procedure.
Experiment 1 The dry matter, gross energy, and crude protein contents of the test ingredients are summarized in Table 1. Endogenous losses and animal performance based on assigned treatments are summarized in Table 2. Initial and final body weights were fairly uniform across all treatments; thus, weight losses were similar (P > 0.05) across treatments. Mean fasting energy loss was estimated to be 13.57 kcal per duck per 54 h and the mean fasting nitrogen loss was estimated to be 0.63 g per duck per 54 h. Nutrient metabolism and MEn determinations are summarized in Table 3. The highest nitrogen intake, energy intake, and nitrogen retention were observed in the group fed pearl millet, and the highest outputs of nitrogen and energy were observed for the group fed barley. The AMEn, TME, and TMEn values for pearl millet numerically exceeded that of corn, but were not significantly different (P > 0.05). The AMEn, TME, TMEn, and dry matter digestibility for barley were significantly less (P < 0.05) than those of corn.
Experiment 2 The dry matter, gross energy, and crude protein of the test ingredients are summarized in Table 1. Endogenous losses and animal performance based on assigned treatments are summarized in Table 4. Initial and final body weights, as well as weight losses were similar across all treatments. Mean fasting energy loss was estimated to be 22.26 kcal per duck per 54 h and the mean fasting nitrogen loss was estimated to be 0.461 g per duck per 54 h. The nutrient metabolism and MEn determinations are summarized in Table 5. The highest nitrogen intake was observed in the group fed triticale. The highest energy intake and nitrogen retention values were observed in the group fed sorghum, and the highest outputs of nitrogen and energy were observed for the group fed triticale. The AME,
7LECO Corp., St. 8Parr Instrument
Joseph, MI 49085. Co., Moline, IL 61265.
Experiment 1 Corn Barley Pearl millet 2 Corn Sorghum Triticale
Dry matter
Gross energy
Crude protein
(%)
(kcal/g)
(%)
88.54 88.10 89.91
3.951 3.875 4.257
8.07 11.94 13.05
88.54 91.15 90.16
3.986 4.180 3.938
6.99 10.92 11.55
AMEn, TME, TMEn, and dry matter digestibility for triticale were observed to be significantly less (P < 0.05) than those of corn. The AME, AMEn, TME, and TMEn of sorghum numerically exceeded those of corn, but were not significantly different (P > 0.05).
DISCUSSION The TMEn bioassay for estimating energy contents of feedstuffs was developed by Sibbald (1976). Although criticized in theory (Pesti and Edwards, 1983), it is considered to be suitable for determining the ME content of feedstuffs because it incorporates a nitrogen correction for endogenous losses. Due to the feed restriction associated with the TME assay, endogenous losses assume greater importance due to constant output of fecal and urinary energy in the face of decreased intake of feed energy. Nitrogen-corrected and uncorrected apparent values determined from the TME assay are prone to considerable variation because significant endogenous losses may exceed energy intake and result in depression of the AME (Sibbald, 1975). Corn has long been the predominant cereal grain used in formulating diets for poultry, due in part to its high AME content. In considering alternative cereal grains for poultry feeding, the AME content of corn is typically the standard to which all other prospective grains are compared. In Experiment 1, the AMEn and TMEn of barley and pearl millet were determined and compared to those of corn. The AMEn and TMEn of corn was observed to exceed those of barley in the present study (P < 0.05). This observation is in agreement with previous comparative ME studies in which corn and barley were fed to ducklings and chicks (Mohamed et al., 1984). The other cereal grain under consideration in Experiment 1 was pearl millet. Produced for human consumption, pearl millet is a drought-resistant cereal grain grown predominately in Africa and Asia (Lawrence et al., 1995). Pearl millet is considered to have an amino acid profile superior to corn, a higher crude protein content, and higher ether extract content. A comparative study conducted by Adeola et al. (1994) utilizing ducks, evaluated the performance, nutrient utilization, and carcass composition of ducks fed pearl millet and corn and found pearl millet to have nutritive value similar to
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RESULTS
TABLE 1. Analysis of the test ingredients
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RAGLAND ET AL. TABLE 2. Animal performance and endogenous losses, Experiment 1 Item
Dextrose
Corn
Barley
Pearl millet
SD
Initial weight, g Final weight, g Weight gain, g Fasting energy loss, kcal/54 h Fasting nitrogen loss, g/54 h n
3,813 3,203 –610 13.57 0.63 12
3,814 3,220 –594
3,833 3,223 –610
3,820 3,292 –528
576 392 207 3.38 0.30
12
12
12
TABLE 3. Nutrient metabolism and MEn determination, Experiment 1 Feedstuff Corn
Barley
Pearl millet
SD
Nitrogen intake, g/54 h Nitrogen output, g/54 h N retained (apparent), g/54 h N retained (true), g/54 h Energy intake, kcal/54 h Energy output, kcal/54 h AME, kcal/g AMEn, kcal/g TME, kcal/g TMEn, kcal/g Apparent dry matter utilization, % n1
0.735 0.734 0 0.630 236.49 44.12 3.207a 3.208a 3.427a 3.339a 78.55a 12
1.122 0.953 0.169 0.799 231.77 66.59 2.753b 2.730b 2.973b 2.863b 70.57b 12
1.160 0.860 0.300 0.930 258.92 55.40 3.392a 3.350a 3.612a 3.484a 74.32a,b 12
0.027 0.297 0.293 0.293 2.11 12.31 0.21 0.18 0.21 0.18 5.79
a–cMeans 1Final
in the same row with no common superscript differ significantly (P < 0.05). weights for ducks fed corn, barley, and pearl millet were 3,220, 3,223, and 3,292 g, respectively.
TABLE 4. Animal performance and endogenous losses, Experiment 2 Treatment Item
Dextrose
Corn
Sorghum
Triticale
SD
Initial weight, g Final weight, g Weight gain, g Fasting energy loss, kcal/54 h Fasting nitrogen loss, g/54 h n
3,761 3,287 –474 22.26 0.46 12
3,671 3,254 –477
3,724 3,318 –406
3,618 3,256 –362
372 306 120 2.84 0.33
12
12
12
TABLE 5. Nutrient metabolism and MEn determination, Experiment 2 Feedstuff Item
Corn
Sorghum
Triticale
SD
Nitrogen intake, g/54 h Nitrogen output, g/54 h N retained (apparent), g/54 h N retained (true), g/54 h Energy intake, kcal/54 h Energy output, kcal/54 h AME, kcal/g AMEn, kcal/g TME, kcal/g TMEn, kcal/g Apparent dry matter utilization, % n1
0.671 0.577 0.094 0.555 239.13 49.30 3.164a 3.151a 3.535a 3.459a 78.05a 12
1.048 0.668 0.381 0.842 250.78 52.05 3.312a 3.260a 3.682a 3.567a 77.11a,b 12
1.108 0.796 0.315 0.773 236.25 68.27 2.800b 2.757b 3.170b 3.065b 70.36b 12
0.000 0.272 0.272 0.272 0.000 19.3 0.32 0.29 0.32 0.29 8.28
a–cMeans 1Final
in the same row with no common superscript differ significantly (P < 0.05). weights for ducks fed corn, sorghum, and triticale were 3,254, 3,318, and 3,256 g, respectively.
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Item
METABOLIZABLE ENERGY IN FEED INGREDIENTS FOR DUCKS
research with ducks in which collection and analysis of excreta is required.
ACKNOWLEDGMENTS The authors thank Maple Leaf Farms Inc. (Syracuse, IN 46567) for their generous contribution of ducks and feed. The authors also acknowledge the technical assistance of Brian Ford and Charles Thomas. Support provided by the Indiana Institute of Agriculture, Food, and Nutrition, Inc. is thankfully acknowledged.
REFERENCES Adeola, O., J. C. Rogler, and T. W. Sullivan, 1994. Pearl millet in diets of White Pekin ducks. Poultry Sci. 73:425–435. Elkin, R. G., 1987. A review of duck nutrition research. World’s Poult. Sci. J. 43:84–106. Gualtieri, M., and S. Rapaccini, 1990. Sorghum grain in poultry feeding. World’s Poult. Sci. J. 46:246–254. Johnson, R. J., and P. Eason, 1988. Evaluation of triticale for use in diets for meat-type chickens. J. Sci. Food Agric. 42: 95–108. Lawrence, B. V., O. Adeola, and J. C. Rogler, 1995. Nutrient digestibility and growth performance of pigs fed pearl millet as a replacement for corn. J. Anim. Sci. 73: 2026–2032. McNab, J. M., and J. C. Blair, 1988. Modified assay for true and apparent metabolisable energy based on tube feeding. Br. Poult. Sci. 29:697–707. Mohamed, K., B. Leclercq, A. Anwar, H. El-Alaily, and H. Soliman, 1984. A comparative study of metabolisable energy in ducklings and domestic chicks. Anim. Feed Sci. Technol. 11:199–209. Ostrowski-Meissner, H. T., 1984. A method of simultaneous measurement of apparent (AME) and true (TME) metabolizable energy with ducks and comparisons of data obtained with drakes and cockerels. Nutr. Rep. Int. 29: 1239–1248. Pesti, G. M., and H. M. Edwards, Jr., 1983. Metabolizable energy nomenclature for poultry feedstuffs. Poultry Sci. 62:1275–1280. Revington, W. H., N. Acar, and E. T. Moran, Jr., 1991. Research note: Cup versus tray excreta collections in metabolizable energy assays. Poultry Sci. 70:1265–1268. SAS Institute, 1986. SAS User’s Guide: Statistics. SAS Institute Inc., Cary, NC. Sibbald, I. R., 1975. The effect of level of intake on metabolizable energy values measured with adult roosters. Poultry Sci. 54:1990–1997. Sibbald, I. R., 1976. A bioassay for true metabolizable energy in feedstuffs. Poultry Sci. 55:303–308. Siregar, A. P., and D. J. Farrell, 1980a. A comparison of the energy and nitrogen metabolism of starved ducklings and chickens. Br Poult. Sci. 21:203–211. Siregar, A. P., and D. J. Farrell, 1980b. A comparison of the energy and nitrogen metabolism of fed ducklings and chickens. Br Poult. Sci. 21:213–227. Smith, R. L., L. S. Jensen, C. S. Hoveland, and W. W. Hanna, 1989. Use of pearl millet, sorghum, and triticale grain in broiler diets. J. Prod. Agric. 2:78–82. Sugden, L. G., 1974. Energy metabolized by bantam chickens and blue winged teal. Poultry Sci. 53:2227–2228.
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that of corn. In the present study, the AMEn and TMEn of pearl millet and corn were observed to be similar (P > 0.05). In Experiment 2, the AMEn and TMEn of sorghum and triticale were determined and compared to corn. Although recognized for its effect on protein, the elevated tannin content of some varieties of sorghum have been shown to exert a negative effect on ME. Studies by Gualtieri and Rapaccini (1990) revealed that ME decreases approximately 40 kcal for every 0.1% increase in tannin over 0.23%. The AMEn and TMEn of sorghum numerically exceeded that of corn in the present study, but the difference was not significant (P > 0.05). Triticale, produced from crossing wheat (genus Triticum) and rye (genus Secale), was the other cereal grain under consideration in Experiment 2. Studies with triticale have yielded mixed results as variation in ME of triticale cultivars is considered to be due to higher acid detergent fiber associated with certain cultivars in addition to the presence of trypsin inhibitors (Johnson and Eason, 1988). Other antinutritional factors, such as pectins and alkyl resorcinols, have also been proposed to account for the variation in nutritive value of triticale (Smith et al., 1989). The AMEn and TMEn of corn was observed to exceed that of triticale in Experiment 2 (P < 0.05). Siregar and Farrell (1980a), through a series of comparative studies utilizing metabolism chambers, demonstrated that ducks and chickens differ in basal metabolism and their ability to metabolize dietary nutrients. It was observed that feed-deprived ducks have higher starvation heat production, nitrogen excretion, weight loss, and fat mobilization than feeddeprived chickens. Fed ducks were observed to exhibit greater ME and water intakes with higher rates of nitrogen and fat retention than chickens. It was suggested from the results of the comparative study that duck growth exceeds that of chickens due to the ability of the duck to consume and efficiently retain higher amounts of ME in the diet. A brief technical note by Sugden (1974) demonstrated that differences in energy metabolism do exist between poultry species and have been observed in birds within the same species as well as across species. It was concluded that ME coefficients from one species cannot be confidently applied to another. The results of the present study as well as that of others demonstrate the need for more research to clarify the differences in nutrient utilization and bioavailability as it relates to ducks. The use of nutrient bioavailability data determined with chickens to formulate duck diets can be considered a questionable practice in light of the metabolic differences between ducks and chickens. These differences create a dilemma for the poultry nutritionist based on the sparse amount of information available specifically for ducks in the area of nutrient bioavailability. The method of excreta collection described in this communication provides a viable alternative to pan collection and minimizes one of the problems associated with nutrient bioavailability
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(Key words: duck, true metabolizable energy, bioassay, nitrogen correction) 1997 Poultry Science 76:1287–1291
INTRODUCTION Certain nutrient requirement values, as well as amino acid digestibilities and energy contents of feedstuffs for chickens are commonly used in formulating diets for ducks because of the relatively limited nutritional information available on feedstuff digestibility and energy bioavailability for the duck (Elkin, 1987). One reason for the lack of information are the problems associated with the collection of duck excreta (Ostrowski-Meissner, 1984). Ducks consume water in much greater quantities than chickens (Siregar and Farrell, 1980b) and the result is a highly liquid excreta. Traditional excreta collection methods (OstrowskiMeissner, 1984) utilized collection pans, which are subject to errors from contamination with feathers and losses due to splatter when the forcefully ejected excreta contact the pan. The consequence of utilizing pan
Received for publication December 9, 1996. Accepted for publication April 17, 1997. 1Purdue University Agricultural Research Programs—Journal Paper Number 15284. 2To whom correspondence should be addressed.
collection is that sample loss and contamination result in reduced accuracy of estimation of bioavailable nutrients. The practice of applying nutrient bioavailability values determined from chicken nutritional studies to ducks would be feasible if both species metabolized nutrients in a similar manner. However, comparative studies of chickens and ducks suggest that differences in nutrient metabolism exist between the two species that should be considered when formulating diets for ducks based on values determined with chickens (Siregar and Farrell, 1980a). The present experiments were undertaken with the intent of contributing to the sparse pool of knowledge related to nutrient bioavailability in feed ingredients for the duck.
MATERIALS AND METHODS The approach adopted in this study was to use in part the modified TME bioassay described by McNab and Blair (1988), which differs from the method described by Sibbald (1976) in several aspects. The modifications to the bioassay described by Sibbald include: feed deprivation of all birds for 48 h prior to feeding test ingredients; administration of dextrose to all birds during the
1287
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 28, 2015
ABSTRACT The objective of the present experiments was to determine the AMEn and TMEn of various feed ingredients used in duck diets. In each of two experiments, 48 mature, male, White Pekin ducks were assigned in pairs to 24 cages based on initial weight. In each experiment, 12 ducks were assigned to each of three test ingredients and 12 ducks received dextrose for determination of endogenous losses of nitrogen and energy. The test ingredients were tube-fed in wet form and consisted of corn, barley, and pearl millet in Experiment 1, and corn, sorghum, and triticale in Experiment 2. Feed was withdrawn 48 h prior to feeding the test ingredients and ducks were tube-fed 30 g of dextrose in 100 mL of water at 8 and 32 h after feed withdrawal. Ducks were tube-fed 30 g of their assigned test ingredient in 100 mL of water at 48 and 54 h after feed withdrawal. Ducks used in estimating endogenous nitrogen and energy losses were tube-fed 30 g of
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RAGLAND ET AL.
Feeding Methodology The tube-feeding apparatus consisted of a 60-mL catheter-tip syringe, to which a 35-cm section of Nalgene tubing3 (8 mm inside diameter) was attached to facilitate delivery of the test ingredients to the ducks’ crop. Fortyeight hours prior to feeding the test ingredients, feed was withdrawn from all ducks. At 8 and 32 h after feed withdrawal, all ducks were tube-fed 30 g of dextrose in 100 mL of distilled water and allowed to purge their gastrointestinal tracts. At 48 and 54 h after feed withdrawal, all ducks were tube-fed 30 g of their assigned test ingredient in 100 mL of distilled water. All test ingredients were ground through a 0.5-mm screen prior to feeding. During a preliminary study to standardize the feeding methodology, birds were observed to regurgitate generous portions of test ingredients if too much was force-fed at one time. Based on these observations, it was decided that two 30-g feedings of test ingredients would be necessary in order to prevent exceeding the capacity of the crop due to the volume of water required to sufficiently mix the ingredients. Based on the necessity of the two feedings 6 h apart, it was decided that the collection period should be extended for an additional 6 h to 54 instead of 48 h. At 48 and 54 h after feed withdrawal, the ducks assigned to receive dextrose for estimation of endogenous losses were also tube-fed 30 g of dextrose in 100 mL of distilled water. All ducks were fitted with their respective collection vessels at the time of the first feeding of test ingredients and total collection of excreta was initiated for 54 h.
Collection Methodology The present collection methodology was inspired in part by the technical note published by Revington et al. (1991), in which specimen container caps were nonsurgically secured to the vent of chickens, and specimen containers were attached to serve as a collection vessel. This approach to collection was tried and found to be unsuitable due to displacement of the specimen cap and container when the ducks assumed a squatting position. Surgical attachment of a collection apparatus to the vent of the ducks was considered to be a more suitable method because it provided better security against excreta loss. The collection apparatus did not appear to create any discomfort or impair the mobility of the birds in any way. The collection apparatus was constructed using materials from a Playtex4 baby nurser set. Prior to placement in cages, birds were surgically fitted with modified plastic retainer lids that were to serve as part of the collection apparatus. The plastic retainer lids from the nurser set were modified by drilling 12 holes, 2 mm in diameter in the ring similar to the 12 points on a clock. Surgical fixation of the retainer lids was accomplished by restraint of the duck in a plexiglass restraint box and local anesthesia of the vent area with 2% lidocaine hydrochloride. The ducks were restrained in the plexiglass box and a 5-cm zone of feathers adjacent to the vent was removed to expose the skin. The skin was then sanitized with a dilute solution of chlorhexidine diacetate (Nolvasan).5 The area to be sutured was then infused in the dorsal, ventral, and lateral quadrants around the vent with 2% lidocaine hydrochloride to desensitize the skin for suturing. The retainer lids were then sutured to the vent area using a continuous suture pattern with the retainer lid anchored in place by passing the needle and suture through holes placed in the retainer lid as the needle exited the skin. The plastic bottle of the nurser set was measured and cut to a length of 3 cm below the threads on the bottle. Whirl-pak bags6 with a capacity of 480 mL and covered with duct tape were then placed through the bore of the bottle and the flaps of the bag overlaid to the sides of the bottle covering the threads. The bottle and Whirl-pak bag were then screwed onto the modified retainer ring attached to the bird with the threads of the ring and bottle securing the bag in place and completing the collection apparatus. The Whirl-pak bags containing excreta were changed within the first 6 h and every 12 h thereafter during the 54-h collection period. All of the feeding and surgical collection protocols in the present study were approved by the Purdue University Animal Care and Use Committee.
Analysis 3Fisher Scientific, Itasca, IL 60143. 4Playtex Products, Dover, DE 19901. 5Fort Dodge Laboratories, Inc., Fort 6Nasco, Fort Atkinson, WI 53583.
Dodge, IA 50501.
All excreta samples were frozen immediately after collection. After completion of the experiment, all samples were thawed, dried at 55 C for 48 h, and ground through a
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 28, 2015
48-h period without feed; a 48-h period of excreta collection; and birds assigned for determination of endogenous losses are administered dextrose instead of no feed at all. These modifications to the Sibbald method appear to improve the precision of the assay as well as decrease the stress on the birds used for determination of endogenous losses. In each experiment, 48 mature, male, White Pekin ducks were sorted according to weight and placed in 24 cages with two ducks per cage (0.66 m × 0.66 m). Twelve birds were assigned to each of three test ingredients and 12 birds were assigned to receive dextrose for estimation of endogenous losses of nitrogen and energy. Test ingredients consisted of corn, barley, and pearl millet in Experiment 1 and corn, sorghum, and triticale in Experiment 2. An additional 500 mL of water/d was offered to each cage during the experiment.
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METABOLIZABLE ENERGY IN FEED INGREDIENTS FOR DUCKS
0.5-mm screen prior to analysis. Dry matter contents of the test ingredients and all samples were determined by drying the samples at 110 C for 24 h. Nitrogen content of test ingredients and excreta was determined by the combustion method using the Model FP2000 combustion analyzer.7 Energy content of test ingredients and excreta was determined by bomb calorimetry using the Adiabatic calorimeter.8
Statistical Analysis Statistical analysis of the data as a completely randomized design was accomplished using the General Linear Models procedure of SAS (SAS Institute, 1986). Differences between means were determined using the least significant difference mean separation procedure.
Experiment 1 The dry matter, gross energy, and crude protein contents of the test ingredients are summarized in Table 1. Endogenous losses and animal performance based on assigned treatments are summarized in Table 2. Initial and final body weights were fairly uniform across all treatments; thus, weight losses were similar (P > 0.05) across treatments. Mean fasting energy loss was estimated to be 13.57 kcal per duck per 54 h and the mean fasting nitrogen loss was estimated to be 0.63 g per duck per 54 h. Nutrient metabolism and MEn determinations are summarized in Table 3. The highest nitrogen intake, energy intake, and nitrogen retention were observed in the group fed pearl millet, and the highest outputs of nitrogen and energy were observed for the group fed barley. The AMEn, TME, and TMEn values for pearl millet numerically exceeded that of corn, but were not significantly different (P > 0.05). The AMEn, TME, TMEn, and dry matter digestibility for barley were significantly less (P < 0.05) than those of corn.
Experiment 2 The dry matter, gross energy, and crude protein of the test ingredients are summarized in Table 1. Endogenous losses and animal performance based on assigned treatments are summarized in Table 4. Initial and final body weights, as well as weight losses were similar across all treatments. Mean fasting energy loss was estimated to be 22.26 kcal per duck per 54 h and the mean fasting nitrogen loss was estimated to be 0.461 g per duck per 54 h. The nutrient metabolism and MEn determinations are summarized in Table 5. The highest nitrogen intake was observed in the group fed triticale. The highest energy intake and nitrogen retention values were observed in the group fed sorghum, and the highest outputs of nitrogen and energy were observed for the group fed triticale. The AME,
7LECO Corp., St. 8Parr Instrument
Joseph, MI 49085. Co., Moline, IL 61265.
Experiment 1 Corn Barley Pearl millet 2 Corn Sorghum Triticale
Dry matter
Gross energy
Crude protein
(%)
(kcal/g)
(%)
88.54 88.10 89.91
3.951 3.875 4.257
8.07 11.94 13.05
88.54 91.15 90.16
3.986 4.180 3.938
6.99 10.92 11.55
AMEn, TME, TMEn, and dry matter digestibility for triticale were observed to be significantly less (P < 0.05) than those of corn. The AME, AMEn, TME, and TMEn of sorghum numerically exceeded those of corn, but were not significantly different (P > 0.05).
DISCUSSION The TMEn bioassay for estimating energy contents of feedstuffs was developed by Sibbald (1976). Although criticized in theory (Pesti and Edwards, 1983), it is considered to be suitable for determining the ME content of feedstuffs because it incorporates a nitrogen correction for endogenous losses. Due to the feed restriction associated with the TME assay, endogenous losses assume greater importance due to constant output of fecal and urinary energy in the face of decreased intake of feed energy. Nitrogen-corrected and uncorrected apparent values determined from the TME assay are prone to considerable variation because significant endogenous losses may exceed energy intake and result in depression of the AME (Sibbald, 1975). Corn has long been the predominant cereal grain used in formulating diets for poultry, due in part to its high AME content. In considering alternative cereal grains for poultry feeding, the AME content of corn is typically the standard to which all other prospective grains are compared. In Experiment 1, the AMEn and TMEn of barley and pearl millet were determined and compared to those of corn. The AMEn and TMEn of corn was observed to exceed those of barley in the present study (P < 0.05). This observation is in agreement with previous comparative ME studies in which corn and barley were fed to ducklings and chicks (Mohamed et al., 1984). The other cereal grain under consideration in Experiment 1 was pearl millet. Produced for human consumption, pearl millet is a drought-resistant cereal grain grown predominately in Africa and Asia (Lawrence et al., 1995). Pearl millet is considered to have an amino acid profile superior to corn, a higher crude protein content, and higher ether extract content. A comparative study conducted by Adeola et al. (1994) utilizing ducks, evaluated the performance, nutrient utilization, and carcass composition of ducks fed pearl millet and corn and found pearl millet to have nutritive value similar to
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RESULTS
TABLE 1. Analysis of the test ingredients
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RAGLAND ET AL. TABLE 2. Animal performance and endogenous losses, Experiment 1 Item
Dextrose
Corn
Barley
Pearl millet
SD
Initial weight, g Final weight, g Weight gain, g Fasting energy loss, kcal/54 h Fasting nitrogen loss, g/54 h n
3,813 3,203 –610 13.57 0.63 12
3,814 3,220 –594
3,833 3,223 –610
3,820 3,292 –528
576 392 207 3.38 0.30
12
12
12
TABLE 3. Nutrient metabolism and MEn determination, Experiment 1 Feedstuff Corn
Barley
Pearl millet
SD
Nitrogen intake, g/54 h Nitrogen output, g/54 h N retained (apparent), g/54 h N retained (true), g/54 h Energy intake, kcal/54 h Energy output, kcal/54 h AME, kcal/g AMEn, kcal/g TME, kcal/g TMEn, kcal/g Apparent dry matter utilization, % n1
0.735 0.734 0 0.630 236.49 44.12 3.207a 3.208a 3.427a 3.339a 78.55a 12
1.122 0.953 0.169 0.799 231.77 66.59 2.753b 2.730b 2.973b 2.863b 70.57b 12
1.160 0.860 0.300 0.930 258.92 55.40 3.392a 3.350a 3.612a 3.484a 74.32a,b 12
0.027 0.297 0.293 0.293 2.11 12.31 0.21 0.18 0.21 0.18 5.79
a–cMeans 1Final
in the same row with no common superscript differ significantly (P < 0.05). weights for ducks fed corn, barley, and pearl millet were 3,220, 3,223, and 3,292 g, respectively.
TABLE 4. Animal performance and endogenous losses, Experiment 2 Treatment Item
Dextrose
Corn
Sorghum
Triticale
SD
Initial weight, g Final weight, g Weight gain, g Fasting energy loss, kcal/54 h Fasting nitrogen loss, g/54 h n
3,761 3,287 –474 22.26 0.46 12
3,671 3,254 –477
3,724 3,318 –406
3,618 3,256 –362
372 306 120 2.84 0.33
12
12
12
TABLE 5. Nutrient metabolism and MEn determination, Experiment 2 Feedstuff Item
Corn
Sorghum
Triticale
SD
Nitrogen intake, g/54 h Nitrogen output, g/54 h N retained (apparent), g/54 h N retained (true), g/54 h Energy intake, kcal/54 h Energy output, kcal/54 h AME, kcal/g AMEn, kcal/g TME, kcal/g TMEn, kcal/g Apparent dry matter utilization, % n1
0.671 0.577 0.094 0.555 239.13 49.30 3.164a 3.151a 3.535a 3.459a 78.05a 12
1.048 0.668 0.381 0.842 250.78 52.05 3.312a 3.260a 3.682a 3.567a 77.11a,b 12
1.108 0.796 0.315 0.773 236.25 68.27 2.800b 2.757b 3.170b 3.065b 70.36b 12
0.000 0.272 0.272 0.272 0.000 19.3 0.32 0.29 0.32 0.29 8.28
a–cMeans 1Final
in the same row with no common superscript differ significantly (P < 0.05). weights for ducks fed corn, sorghum, and triticale were 3,254, 3,318, and 3,256 g, respectively.
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Item
METABOLIZABLE ENERGY IN FEED INGREDIENTS FOR DUCKS
research with ducks in which collection and analysis of excreta is required.
ACKNOWLEDGMENTS The authors thank Maple Leaf Farms Inc. (Syracuse, IN 46567) for their generous contribution of ducks and feed. The authors also acknowledge the technical assistance of Brian Ford and Charles Thomas. Support provided by the Indiana Institute of Agriculture, Food, and Nutrition, Inc. is thankfully acknowledged.
REFERENCES Adeola, O., J. C. Rogler, and T. W. Sullivan, 1994. Pearl millet in diets of White Pekin ducks. Poultry Sci. 73:425–435. Elkin, R. G., 1987. A review of duck nutrition research. World’s Poult. Sci. J. 43:84–106. Gualtieri, M., and S. Rapaccini, 1990. Sorghum grain in poultry feeding. World’s Poult. Sci. J. 46:246–254. Johnson, R. J., and P. Eason, 1988. Evaluation of triticale for use in diets for meat-type chickens. J. Sci. Food Agric. 42: 95–108. Lawrence, B. V., O. Adeola, and J. C. Rogler, 1995. Nutrient digestibility and growth performance of pigs fed pearl millet as a replacement for corn. J. Anim. Sci. 73: 2026–2032. McNab, J. M., and J. C. Blair, 1988. Modified assay for true and apparent metabolisable energy based on tube feeding. Br. Poult. Sci. 29:697–707. Mohamed, K., B. Leclercq, A. Anwar, H. El-Alaily, and H. Soliman, 1984. A comparative study of metabolisable energy in ducklings and domestic chicks. Anim. Feed Sci. Technol. 11:199–209. Ostrowski-Meissner, H. T., 1984. A method of simultaneous measurement of apparent (AME) and true (TME) metabolizable energy with ducks and comparisons of data obtained with drakes and cockerels. Nutr. Rep. Int. 29: 1239–1248. Pesti, G. M., and H. M. Edwards, Jr., 1983. Metabolizable energy nomenclature for poultry feedstuffs. Poultry Sci. 62:1275–1280. Revington, W. H., N. Acar, and E. T. Moran, Jr., 1991. Research note: Cup versus tray excreta collections in metabolizable energy assays. Poultry Sci. 70:1265–1268. SAS Institute, 1986. SAS User’s Guide: Statistics. SAS Institute Inc., Cary, NC. Sibbald, I. R., 1975. The effect of level of intake on metabolizable energy values measured with adult roosters. Poultry Sci. 54:1990–1997. Sibbald, I. R., 1976. A bioassay for true metabolizable energy in feedstuffs. Poultry Sci. 55:303–308. Siregar, A. P., and D. J. Farrell, 1980a. A comparison of the energy and nitrogen metabolism of starved ducklings and chickens. Br Poult. Sci. 21:203–211. Siregar, A. P., and D. J. Farrell, 1980b. A comparison of the energy and nitrogen metabolism of fed ducklings and chickens. Br Poult. Sci. 21:213–227. Smith, R. L., L. S. Jensen, C. S. Hoveland, and W. W. Hanna, 1989. Use of pearl millet, sorghum, and triticale grain in broiler diets. J. Prod. Agric. 2:78–82. Sugden, L. G., 1974. Energy metabolized by bantam chickens and blue winged teal. Poultry Sci. 53:2227–2228.
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that of corn. In the present study, the AMEn and TMEn of pearl millet and corn were observed to be similar (P > 0.05). In Experiment 2, the AMEn and TMEn of sorghum and triticale were determined and compared to corn. Although recognized for its effect on protein, the elevated tannin content of some varieties of sorghum have been shown to exert a negative effect on ME. Studies by Gualtieri and Rapaccini (1990) revealed that ME decreases approximately 40 kcal for every 0.1% increase in tannin over 0.23%. The AMEn and TMEn of sorghum numerically exceeded that of corn in the present study, but the difference was not significant (P > 0.05). Triticale, produced from crossing wheat (genus Triticum) and rye (genus Secale), was the other cereal grain under consideration in Experiment 2. Studies with triticale have yielded mixed results as variation in ME of triticale cultivars is considered to be due to higher acid detergent fiber associated with certain cultivars in addition to the presence of trypsin inhibitors (Johnson and Eason, 1988). Other antinutritional factors, such as pectins and alkyl resorcinols, have also been proposed to account for the variation in nutritive value of triticale (Smith et al., 1989). The AMEn and TMEn of corn was observed to exceed that of triticale in Experiment 2 (P < 0.05). Siregar and Farrell (1980a), through a series of comparative studies utilizing metabolism chambers, demonstrated that ducks and chickens differ in basal metabolism and their ability to metabolize dietary nutrients. It was observed that feed-deprived ducks have higher starvation heat production, nitrogen excretion, weight loss, and fat mobilization than feeddeprived chickens. Fed ducks were observed to exhibit greater ME and water intakes with higher rates of nitrogen and fat retention than chickens. It was suggested from the results of the comparative study that duck growth exceeds that of chickens due to the ability of the duck to consume and efficiently retain higher amounts of ME in the diet. A brief technical note by Sugden (1974) demonstrated that differences in energy metabolism do exist between poultry species and have been observed in birds within the same species as well as across species. It was concluded that ME coefficients from one species cannot be confidently applied to another. The results of the present study as well as that of others demonstrate the need for more research to clarify the differences in nutrient utilization and bioavailability as it relates to ducks. The use of nutrient bioavailability data determined with chickens to formulate duck diets can be considered a questionable practice in light of the metabolic differences between ducks and chickens. These differences create a dilemma for the poultry nutritionist based on the sparse amount of information available specifically for ducks in the area of nutrient bioavailability. The method of excreta collection described in this communication provides a viable alternative to pan collection and minimizes one of the problems associated with nutrient bioavailability
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