METABOLIZABLE ENERGY 0F CELLULOSE, THREE NATURAL FOODS AND ‘ THREE "DIETS FOR MALLARDS Thesis for the Degree of” M. S. MECHIGAN STATE UNIVERSITY DAVID A. PUROL‘ 1 9 75 ‘ “"i‘q \ ummmIllumujlnlwuwwlWI “mm . 312 Michigan Sum" U' ‘ty ABSTRACT METABOLIZABLE ENERGY OF CELLULOSE, THREE NATURAL FOODS AND THREE DIETS FOR MALLARDS BY David A. Purol The metabolizable energy (MEn) of cellulose, three natural foods and three diets was determined for semi— domestic mallards (Anas platyrhynchos) by ad libitum feeding trials in which food and water intake, excreta output and nitrogen retention of the diet was measured. The influence of sex, photoperiods and egg-laying status of the females on the determination of MEn values at a constant temperature of 20°C was examined. Mallards receive little MEn from low levels of cellulose ingestion and, like the domestic chicken (Gallus gallus), it appears that foods high in crude fiber are generally low in energetic quality. Duckweed (Lemna minor), solierfly larvae (Stratiomys Sppo) and proso millet (Panicum miliaceum) yielded 1.43, 2.39, and 3.57 Kcal/gm of MEn, respectively. No sex or photOperiod effect was noted; egg-laying resulted in a significant David A. Purol increase in MEn values, which for the practical purpose of assigning a single energy value to a food item could be ignored. Voluntary water intake was relatively stable in relation to the amount of food consumed. It is suggested that dietary weight or volume, as a regulatory mechanism of food intake, may have a similar magnitude of influence for both captive and free-living birds. Males, non-laying and laying (l egg/day) females metabolized 190, 176, and 333 Kcal/bird-day, respectively. Conservative estimates of free-living existence for mallards are given and the relative nutritional value of the three natural foods is discussed. METABOLIZABLE ENERGY OF CELLULOSE, THREE NATURAL FOODS AND THREE DIETS FOR MALLARDS BY David A. Purol A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Fisheries and Wildlife 1975 Q. r- ACKNOWLEDGMENTS I express my thanks to my committee members, Dr. Donald Polin, Dr. Thomas G. Bahr, and particularly my advisor, Dr. Harold H. Prince. My appreciation is extended to Dr. John L. Gill for his statistical advice and Mr. E. Paul Peloquin for his counsel. Without the guidance and assistance of these men this work would not have been possible. My wife, Irene, whose perserverance and encourage- ment made this work possible, deserves my sincerest gratitude. This study was financed by the Michigan Agricultural Experiment Station. ii TABLE OF INTRODUCTION . . . . . . MATERIALS AND METHODS . . . Test Item Procurement . . Diet Preparation . . . . Feeding Trials. . . . . MSULTS O O O I O O O 0 Dietary Energy Utilization. Metabolized Energy . . _. Water Consumption. . . . DISCUSSION. . . . . . . Evaluation of Test Items . Dietary Energy Utilization. Water Consumption. . . . Metabolized Energy . . . LITERATURE CITED. . . . . CONTENTS iii Page 16 21 23 23 26 26 28 30 31 35 Table 1. LIST OF TABLES Proximate analysis of food items and commercial diets expressed on a dry weight basis . . . Composition and calculated analysis of reference diets expressed on an air dry basis. . . . Egg production of female mallards fed com- mercial and experimental (reference and substituted reference) diets . . . . . . A split-plot analysis of variance for the MEn (meanis.e.) of Series I and II experimental (reference and substituted reference) diets fed to male and female mallards at photo- periods of 8 and 14 hours . . . . . . . Consumption and utilization of commercial and experimental (reference and substituted reference) diets by laying and non-laying female mallards expressed as a percent change (mean:s.e.) from males. . . . . . Metabolized energy, body weight response, egg production and water consumption (mean:s.e.) of male, laying and non-laying female mallards fed commercial and experimental (reference and substituted reference) diets . iv Page 17 18 22 24 LIST OF FIGURES Figure Page 1. Acrylic plastic drinking cup used to determine the ad libitum water intake of semi-domestic mallards. Cage mounting is illustrated . . 12 2. MEn of cellulose, three natural foods, an experimental diet and two commercial diets . 20 for semi-domestic mallards . . . . . INTRODUCTION Although a considerable amount of information is available regarding the types of foods eaten by waterfowl (Martin and Uhler, 1939; Anderson, 1959; Dillon 1959; and others), little is known about the nutritional or energetic quality of these foods. As indicated by Scott and Holm (1964), and more recently exemplified by Sudgen (1973), insight into the feeding activities and patterns of water- fowl can be gained by a better understanding of the nutritional quality of the foods eaten. The energetic quality of foods for birds is con- sidered to be best described by metabolizable energy (ME). Simply stated, ME is the gross energy (GB) of the diet intake minus the caloric equivalent of the excreta voided (Kendeigh, 1949). The term was first introduced by Armsby in the 19205 and is now the basic energy unit used in the feeding of domestic poultry. Sudgen (1971) has suggested that the composition of free-living waterfowl diets be described on the basis of ME. Studies evaluating the relative efficiency of waterfowl in utilizing the energetic components of foodstuffs are limited. In an early study, Holm and Scott (1954) found no appreciable differences between the nutritional requirements of several species of dabbler and diving ducks. Sudgen (1971) determined hand-reared mallards and domestic fowl to be essentially similar in metabolizing barley and wheat but not rye. Young black ducks (Anas rubripes) and American coot (Fulica americana) metabolized a commercial starter chow similarly and both increased their ability to utilize the energetic com- ponents of the diet during the initial eight weeks following hatching (Penney and Bailey, 1970). Similiar relationships exist for young domestic fowl (Renner and Hill, 1960; Slinger et a1., 1964; and Begin, 1967). Baldini (1961) found that the ME content of a diet for domestic chicks may be influenced by dietary deficiencies and Sudgen (1971) further suggested that similarities in two species to metabolize a ration may deviate as one species departs from a balanced diet. Inherent inter- or intraspecies differences in the utilization of dietary energy would be expected to exist for birds with varying abilities to metabolize crude fiber (Inman, 1973). The efficiency of dietary energy utilization (ME/GE x 100) and ME determinations fluctuate in wild captive birds. The fluctuations have been associated to both exogenous and endogenous factors. The relationship of ambient temperatures and dietary energy utilization has been described for a variety of songbirds by Seibert (1949), Davis (1955), West (1960), Zimmerman (1965), and El-Wailly (1966). In addition, Seibert (1949) and Davis (1955) found indications that photoperiod length may influence energy retention. Although dietary energy utilization increased at both high and low temperatures for the blue-winged teal (Anas discors), photOperiods had little or not influence (Owen, 1970). Kendeigh (1949) attributed a decrease in the efficiency of utilization by English sparrows (Passer domesticus) at low ambient temperatures to less complete digestion and absorption when the mass of food ingested increased (Brody, 1945). West (1968) determined the change in efficiency of willow ptarmigan (Lagopus lagopus) held out-of-doors to be dependent upon the seasonal activities (molt, egg-laying) of the birds rather than environmental temperatures. Relatively large fluctuations in the ME content of a food item on the basis of ambient temperatures, photo- periods, or the birds seasonal activities would obviously limit the practical application of these data to the field situation. The amount of energy that is potentialIy available for heat production, that is, the katabolizable energy (Kleiber, 1961) portion of ME is calculated directly from the dietary nitrogen retention (Nr) of the bird (Hill and Anderson, 1958) which is in turn related to the birds seasonal activities and carcass nitrogen reserves. Correcting ME values to a state of nitrogen balance (MEn) is a standard procedure for evaluating the available energy in foodstuffs for domestic poultry (Scott et al., 1969). Although the factor is small, perhaps a similar correction for wild captive birds may explain some of the fluctuations observed in dietary energy utilization. The purpose of this study was to determine the MEn of cellulose, three natural foods and a commercial flight conditioner and breeder chow for mallards. The influence of sex, photOperiods and reproductive state of females in the determination of MEn values under constant temperature conditions was also examined. The three natural foods evaluated in this study were proso millet, soldierfly larvae and duckweed. They were chosen because they represented a seed, an animal and a plant food consumed by free-living mallards. MATERIALS AND METHODS Test Item Procurement Duckweed and soldierfly larvae were obtained from a waterfowl impoundment at the Rose Lake Wildlife Research Center, East Lansing, Michigan. Soldierfly larvae were collected during March and early April from wind-blown floating shoreline detritus which accumulated during the spring breakup of ice. Duckweed was obtained in June and July from the shallow bays in the impoundment. The test items were washed, sorted and held fresh frozen. They were prepared for diet mixing by drying at 70°C in a forced air oven and, along with proso millet, ground to particles which passed through a No. 20 US Standard Sieve. These natural foods represented items of diverse chemical com- position (Table 1). Solka Floc, the cellulose source used in this study, is guaranteed to contain at least 99.5 per- cent alpha cellulose. Proso millet was purchased com- mercially. Diet Preparation MEn values of the food items were determined by feeding trials of reference and substituted reference diets (Sibbald et al., 1960). Formulation of the reference m.>m m.HH o.v o.m m.m~ . . 3050 umpwmum m.mm H.a s.ma N.m o.H~ . . “macaufleaoo unmflam whoao Hmaoumasoo AHOGHE qumqv e.mm v.HH m.vH H.m m.mH m.va pomzxoso A.mmm mNEowumuumv H.om «.ma o.oa N.OH m.mv H.mm mm>umH mamuwfloaom AESmOMHHHE Esoflcmmv m.mn o.m m.n v.v o.ma H.om umHHwE Onoum EmuH coon w w w w w w EmuH mmz 2mm “when umm cflmuoum Hafiumumz ammum mo nwupmz who who m :0 Ummmmumxm mumflo .mwmmn unmflmz HMHoumEEoo pom mfimufl poo“ mo mammamcm ouwfifixoumll.a magma diets was based on an egg-laying poultry ration used by the Poultry Science Department, Michigan State University. The substituted diets were mixed from a reference diet by replacing, on a dry weight basis, a known quantity of glucose with an equal portion of the test item being analyzed. Glucose was assumed to contain 3.64 Kcal per gram of ME (Anderson et al., 1958). The substitution levels used (10 to 25 percent) were lower than generally recommended because of difficulties encountered in collecting large quantities of the natural foods, and in the case of cellulose, by the minimal level of 2.5 Kcal per gram of ME needed in the diet to permit the birds to adjust to an ad libitum energy intake (Scott, 1972). Two reference diets which met or exceeded the nutritional requirements of maintenance and egg-laying were formulated for evaluating the influence of sex and reproductive state of the females in the determination of ME values. The calcium level of Reference Diet II was formulated for egg production by replacing all of the cellulose in Reference Diet I with ground limestone (Table 2). The two diets were identical in all other aspects and were assumed to be isocaloric in ME content. Six substituted diets were mixed from these; proso millet and duckweed using both Reference Diets I and II, soldierfly larvae using only Reference Diet I, and cellulose using only Reference Diet II. The substituted diets along with the reference diets from which they were mixed formed a Table 2.--Composition and calculated analysis of reference diets expressed on an air dry basis. Reference Diet I Reference Diet II Ingredient % % Dextrosea 36 . oo 36 . 00 Ground yellow corn 11.35 11.35 Soybean meal 49% 27.10 27.10 Alfalfa 17% 6.00 6.00 Stabilized corn oil 3.00 3.00 Celluloseb 4.80 . . Wheat middlings 5.00 5.00 Meat and bone meal 3.00 3.00 Dicalcium phosphate 1.60 1.60 Limestone 0.36 5.16 Iodized salt 0.30 0.30 Choline chloride 0.20 0.20 Methionine hydroxy analog 0.09 0.09 Vitamin mixc o. 50 o . 50 Mineral mixd 0.50 0.50 Cr203 0.20 0.20 100.00 100.00 Calculated Analysis Protein 17.72 17.72 Calcium 0.99 2.81 Available phosphorous 0.54 0.54 Metabolizable energy (Kcal/gm) 2.89 2.89 a . . . . "Clintose" dextrose, Clinton Corn Proce551ng Co., Clinton, Iowa. b Solka Floc, Brown Co., Berlin, New Hampshire. CVitamin mix contained per kg of diet: 10,000 IU Vitamin A, 1,000 ICU Vitamin D3, 10 IU Vitamin E, 4.0 mg Vitamin K, 10 mg niacin, 4.0 mg pyridoxine, 100 mcg biotin, 3.0 mcg Vitamin 312 and 125.0 mg ethoxyquin. dMineral mix contained per kg of diet: 500 mg magnesium, 55 mg manganese, 50 mg iron, 11 mg copper and 35 mg zinc. l‘rlll I.lu'l.lllllll"lll1lilllll,ll|lli.1ijl‘llillll III III. .llltllhll' I nllllllll Series I and II of experimental diets. During mixing Cr203 was added to the diets at 0.2 percent to measure metabolizability (Dansky and Hill, 1952). Following mixing, these experimental diets were moistened and passed through a power meat grinder fitted with a metal funnel for pelleting. The diets were com- pressed by the grinder and squeezed from the funnel as a long string 6 mm in diameter which was then cut into pellet sized pieces and dried at 70°C in a forced air oven. The pellets were allowed one week to adjust to air moisture just prior to feeding. The composition of the pelleted commercial flight conditioner and breeder chow was not altered (Table 1). No Cr203 was added to these diets; metabolizability was measured by the total collection of excreta only. FeedinggTrials An equal sex ratio of 24 semi-domestic mallards, obtained from the Max McGraw Wildlife Foundation, Dundee, Illinois, were used in the study. The birds were approxi— mately seven months old at the onset of the experiment and were held individually in 74 X 60 x 36 cm cages in a room where ambient temperatures were regulated to about 20°C. Photoperiods of 8 hours were used for the feeding of Experimental Diet Series I and flight conditioner and 14 hours were used for the feeding of Experimental Diet Series II and the breeder chow. Food was offered 10 ad libitum. No trials were conducted while the birds were actively molting. Four feeding trials, each lasting seven days, were conducted with the same group of 24 birds. Each trial corresponded to the feeding of one of the commercial or one of the Experimental Diet Series, so that each experimental diet was fed to 3 birds of each sex and each commercial diet to 12 of each sex. Paired observations, by bird, were taken for replicate diets in Series I and II. Water was provided to the birds by means of drinking cups specially built for this purpose (Fig. 1). The cups were designed to reduce food wastage in the drinking water and to restrict water spillage while still allowing ad libitum intake. Food and water consumption, maximum-minimum room temperatures and egg production was recorded each 24 hours during the last 4 days of each trial. If at least one egg was produced during the four day period a female was classified as an egg layer. No attempt was made to deter- mine the reproductive mode of male birds. Body weights were recorded at the start and finish of the four day period. Food consumption was corrected for diet spilled on the excreta trays and floor, and that lost in the drinking cups. Water consumption was measured as the sum of water intake and moisture consumed in the diet, minus the daily evaporative water loss from the drinking cups. Two drinking cups, filled to about the same level as that 11 Fig. 1. Acrylic plastic drinking cup used to determine the ad_1ibitum water intake of semi-domestic mallards. Cage mounting is illustrated. 13 provided the birds, were used to determine evaporative losses. Total dietary intake is defined as the sum of food and water consumption. A total collection of excreta was taken for all feeding trials regardless of whether or not the diets contained the Cr203 marker. The excreta collections were pooled for each duck for the four-day test period, dried at 70°C in a forced air oven, ground, and analyzed for gross energy (GE) in a Parr Adiabatic Calorimetor and for nitrogen by the semi-micro Kjeldahl technique. A diet sample taken during the feeding trials was ground and analyzed for moisture, gross energy and nitrogen. Diet and excreta samples containing Cr203 were analyzed by the method of Czarnocki et a1. (1961). Proximate analyses were performed by the Biochemistry Analytical Laboratory, Michigan State University, following AOAC methods (Horwitz, 1965). All data are expressed on a dry weight basis 1 unless stated otherwise. Metabolizability of the diets was calculated for the total collection and Crzo3 index method from the following equations adapted from Sibbald et a1. (1960): 0 indicator method: Cr2 3 CrZOB/gm diet Metatolizability in percent = 1 - Cr O3/gm excreta X 100 2 Total collection method: (I .‘l| 1 II. III 1" | 11." II, \II ‘1']! 1|!" .l'IIiII ilfli. 14 total weight excreta total weight diet Metabolizability in percent = l — x 100 A t test comparison of the total collection and Cr203 index method revealed no significant differences in metabolizability values (n=48; total collection 63.86: 0.81%; Crzo3 index 63.20:0.90%). Hence a mean value of the two methods was used for the experimental diets to determine ME and nitrogen retention (Nr) by the birds. The following expressions were modified from Sibbald et a1. (1960) for use: Cr203/gm diet total weight excreta Cr203/gm excreta total weight diet ME in Kcal/gm diet=GE/gm diet - 8 x GE/gm excreta Cr203/gm diet total weight excreta CrZOB/gm excreta total weight diet L Nr in gm N/gm diet=gm N/gm diet - 1 x gm.N/gm excreta ME and NI. were determined for the commercial diets by the total collection of excreta only. ME was corrected for nitrogen retention by the following formula (Hill and Anderson, 1958): Where 8.22 = Kcal/gm of uric acid nitrogen MEn values of the test items were calculated for each bird from the following equations modified from Hill and Anderson (1958): ,1 ‘1 II... ill I] l | I. I'll J ‘|l§C ‘ll‘ '1 I." ll [I'll 15 MEn of MEn of reference diet - substituted diet Proportion of test item substituted MEn in Kcal/gm = 3.64 - Where MEn of reference diet = mean value of reference diet for the sex and diet series being tested MEn of substituted diet = value measured for a single bird 3.64 = ME of glucose Metabolized energy was calculated by multiplying the average daily diet intake of a bird by the MEn content of the diet. Under non—reproductive conditions and constant body weight and composition this term is mainte- nance energy (Brody, 1945) expressed as Kcal of MEn/ bird-day. Statistical tests used in this study followed standard procedures (Snedecor and Cochran, 1973). Multiple comparisons were made using the Bonferroni t (Kirk, 1968). Unless specified otherwise the term significance applies to the 0.05 probability level. Variation about the mean is denoted by the standard error. RESULTS Complete control of the egg laying response of the females was not attained during the study. Some birds produced eggs while being fed flight conditioner and Experimental Diet Series I which were intended to be feeding trials under maintenance conditions, and some females st0pped producing eggs when offered Experimental Diet Series II which was intended to be an egg laying phase of the study (Table 3). Although this response by the females may have increased variability, a split-plot analysis of variance revealed significant differences in MEn values between diets and sex (Table 4). No detectable difference was found between phot0periods nor were there any photOperiod interactions. Females, including both layers and non-layers, metabolized significantly more energy per gram of diet than males. However, no signifi- cant interaction between diet X sex was found which suggests that the MEn values for the females, although higher, paralled the values of the males for the diets tested. Since MEn of a test item was calculated as the difference between the MEn of the reference and 16 17 Table 3.--Egg production of female mallards fed commercial and experimental (reference and substituted reference) diets. Females Laying Eggsa Rate of Layb Diet Type % No/day Commercial Diets Flight conditioner 33 .50 Breeder chow 100 1.00 Experimental Diets Series I .50 .25 Series II 42 .75 aTotal of 12 females per diet. bOf females laying eggs. substituted reference diets within a sex group, the parallel increases were not reflected in MEn values calculated for the test items. Based on these results test item values are reported as a single mean. Cellulose yielded a mean MEn content of 0.20:.17 Kcal/gm, which is not significantly different from zero (Fig. 2). The very low value of cellulose supports the assumption that paired diets of Series I and II were isocaloric in MEn content. When calculated as the differ- ence between the paired diets of the two series, cellulose yielded 0.01 Kcal/gm (n=18). Mean MEn values for the remaining diet items, expressed on a Kcal/gm basis, were 1.43:0.28 for duckweed, 2.39:0.33 for soldierfly larvae 18 mo.ovm¢ Hoo.ovm... .umfiu moccuomou ca mmoosav How wousuwumnsm macaw unwed 0000.0 NH m Houum Hv emoo.o ~ coauwmouonm x xmm x pogo ma.a voao.o a economouonm x xwm m¢.H emoo.o m nodummouonm x umao m~.m omHo.o H coaummouonm 0500.0 NH 0 uouum Hv omoo.o m xmm x amen «mm.m mamm.o A sum «44mm.- mama.o m amen m m: up ooccwwc> mo oouwom I. I. .I muoaaaa emoum mo mHo.o+m~o.m m amo.o+mmo.m m avo.o+qvo.m m vvo.o+mem.~ m mucoumumu eousuaumnsm I. .I mvow3xosu mo moo.o+amm.~ m mmo.o+aom.~ m emo.o+~eh.~ m «mo.o+vme.~ m uocououou wouauaumnam moo.QHHoo.m m mmo.quoma,m m mHo.QHmmm.~ m oeo.ommvo.m m mocououum musom ea a mason 0 c mucom «a c musom 0 c Down wamsmm can: 33380 cm: .mufloz «a van w No moowuumouonm um monHHmE mamawm can cams on com muowp Amocoucmcu cousuwumASm can mocmuommuv Housmaquomxo HH 0cm H mwwumm mo A.c.mflcmoav cm: can Hem coccwuc> mo mwmhaccc uoamuuwamm «II.v wands Fig. 2. l9 MEn of cellulose, three natural foods, an experi- mental diet and two commercial diets for semi- domestic mallards. Bar heights represent the mean, vertical lines show is.e. for each mean. Substitution level is percentage inclusion of test item at the expense of glucose in reference diet. Sample size is given; starred values (*) indicate replicate determinations for each of six birds. a Male E Non- laying Female . l6‘lo 25% Substitution Level l0% l0% 20 '0 " 3 '3? :3 E» x5 go oo “.4 (00 E W .5_ a ------ 3’3 =2; """""""" 2g 1: So: 0 .15. 2 0 e e O U is? .-:'.-;:.'::':EE!I:§i§§.‘£€:’3-'.L':!i-Tii:i'. 8 E” :2 0: {A a... g 7/////V//////////////////////////////////////// 83 “z .0 g (:2:///////////////////////// ”5 =3 1, .. a“ 8 0°) :2; zzy/WW 3 O 8 2 .2 a 0 l 1 l I l 1 l l I. l O O O O O O O 8 8 N o 9. 0. 3. “! 0°. s. 0. q! :6 «i oi N m - -— 0 0 0 ("16/ WW I“3w F light Conditioner L I Larvae TEST ITEMS DIETS 21 and 3.57:0.10 for proso millet. The relatively low substitution levels used in this study appears to be a major factor influencing the variance associated with MEn determinations of the test items. Variance associated with means of the test items was generally of a magnitude ten times greater than that associated with diet determinations which correSponds to the magnitude of substitution (Fig. 2). Stratification by sex and laying status of the females for MEn values of the diets indicated that the reSponse by laying females was greater than that of non- 1ayers and males (Fig. 2). Laying females metabolized 2.826:0.016 Kcal/gm and males 2.732:0.017 Kcal/gm of the breeder chow. Male, non-laying and laying female values for flight conditioner were 2.374:0.042, 2.340:0.047, and 2.487:0.035 Kcal/gm, respectively. The mean MEn value for the reference diets was 3.051:0.028 Kcal/gm which corre- sponds closely to the calculated analysis value of 3.07 Kcal/gm (Table 2), expressed on a dry weight basis. Dietary Energy Utilization Because of the variety of diets fed, each with characteristic energy values, an analysis of diet utilization by male and laying and non-laying females was made by comparing female values as a percent change to the mean value for males fed the same diet (Table 5). Any residual influence of photoPeriods was negated by this 22 Table 5.--Consumption and utilization of commercial and experimental (reference and substituted reference) diets by laying and non-laying female mallards expressed as a percent change (mean:s.e.) from males. Female Female Non-Layers Layers Item (n=21) (n=27) Food Consumptiona 0.04:5.49% 64.77:6.74%c Metabolizability l.74:l.65% l3.68:l.29%c GEe 2.11:0.53:h 10.53:1.08%° Nr 21.21:13.39% 92.281io.93%° ME -o.04:1.13% 5.14:0.80%c MEn -0.26:0.93% 3.18:0.64%c ent from.males and non-laying females. aFood consumption based on gm/Kgm body weight/day. Values with superscript are significantly differ- ent from males. cValues with superscript are significantly differ- analysis since comparisons were made between birds on the same day length. Diet utilization by non-laying females was similar to that of males, with the exception of a significant increase in GE content of the excreta (GEe). Laying females, however, exhibited a pattern of consumption and utilization significantly different than that of either males or non-layers. Correcting ME to MEn accounted for about 2 percent of the difference between laying females and males. 23 Metabolized Energy There was no significant difference between metabolized energy values of males and non-laying females (Table 6). Males metabolized l4 Kcals more per bird-day, which probably reflects their larger body weight and greater body weight gains for the 4 day test period. If metabolized energy is expressed on a per kg body weight or kg BW.744 basis male values are slightly lower than values for non-layers. The average metabolized energy value for all laying females was 289 Kcal/bird-day at a production level of 0.68 and body weight loss of 2.5 gm/bird/ day. Their MEn intake was significantly greater than the intake of either the males or non-layers. Body weight changes were highly variable between birds; however, this variation was not correlated with laying rates. Females that consistently produced one egg per day also lost 9 gms during the 4 day test period. Overall, the changes in body weight for each of the three groups were minor and amounted to less than 1 percent. For the purpose of discussion they are con- sidered to be constant. The average fresh, whole egg produced by the birds weighed 53 gms and contained 1.929 Kcal/gm of combustible energy on a wet weight basis. Water Consumption The specially designed drinking cups were successful in restricting water spillage in all but three cases, each involving egg-laying females. These 24 .ucmuommao maucoowmwcmwm mum mumfluomquSm pcouommwo sows casaoo a canoe: mosao> on oVNNCM m~.quom.m omnfloemm mm.o oHoHI «mumoofl oamummN am assume mcwmmH e~.o+mm.e nHm+o~m . . a+H o~+~ooa nm+mhfl an Iaoz mamsmm mH.oHe¢.v amauaam . . mum NAHNMHH nnHomH me . . mam: Iowan Assn lame\.ozc lasso e. lame “mac n moo: xmm ss\aac \euan\asc seq \euanxaoc new: \euanxfluosc maasmg mo ovum omcono hmuocm 00m 4 I emuaflonmuoz coaumasmcou noun: unmwoz moon .muowp Amocouomou pausuwumncm can mucouomwuv Hmucoawummxo can Hmwouoasoo pom mpuoaamfi oadfiom ocwmmalcoc can mcwmma can mama mo A.o.WHccmEv cofiumESmcoo uoum3 0cm cofluospoum 00m .mmcommou unowo3 anon .hmuoco wowuaonmuozII.m manna 25 measurements have been omitted from the results in Table 6. Although the natural aquatic feeding activities of the mallard, particularly "dabbling" make water intake measure- ments difficult, spillage was probably limited to less than 5-10 percent of the total. Consumption is expressed both as ml/gm of diet consumed as well as volume consumed per bird-day. Laying females consumed an average of 546 ml/bird/ day, a quantity significantly greater than the intake of either males or non-layers. As a percentage of body weight per day, consumption by males, non-layers and layers was approximately 27, 31, and 51 percent respectively. Total dietary intake (food + water) for males, non-layers, and layers was 381, 386, and 648 gm. Water consumed per gm of diet intake was relatively stable. DISCUSSION Evaluation of Test Items Cellulose yielded little useable energy for the mallards in this study when fed at low levels (4.8 to 14.8 percent) in diets which approximated the crude fiber levels of foods eaten by wild mallards (Junca et al., 1962). The domestic goose (Anser anser), which is primarily a grazing species, also apparently cannot digest cellulose (Mattocks, 1971). Similar results have been obtained for domestic poultry, where cellulose yielded values which ranged from slightly positive (Sibbald et al., 1960) to slightly negative (Potter et al., 1960). Deviations from zero were attributed to a physical inter- action of cellulose with the absorption of other nutrients in the diet. The duckweed collected for this study was also low in available energy for the mallards (1.43 Kcal/gm). Its proximate analysis (Table 1) roughly corresponds to that of roughage (alfalfa meals) used in the feeding of domestic poultry and its MEn content for mallards falls within the range of values reported for alfalfa meals fed to poultry (0.51 to 1.72 Kcal/gm) (Allen, 1973). Duckweed 26 27 contained about 16 percent crude protein; even at a con- centration over twice this percentage Sudgen (1973) found it to be deficient in three of nine essential amino acids. Green roughage is a good source of vitamins, primarily provitamin A, and perhaps this is related to the nutritional value of duckweed for free-living mallards. Apparently, unlike some gallinaceous gamebirds (Inman, 1973), mallards, like poultry, receive little energy from crude fiber digestion as evidenced by the MEn values for duckweed and cellulose. This appears to be consistent with the conclusion (Holm and Scott, 1954) that the nutritional requirements of captive mallards are similar to those of domestic ducks. Although the seeds of wild plants consumed by free-living waterfowl contain a greater proportion of crude fiber than do domestic cereal grains (Junca et al., 1962; Bardwell et al., 1962), based on this analysis, much of that energy is not available to the mallard for metabolism. In general, domestic grains appear not only to produce a greater biomass of edible material than annual wetland plants (Givens et al., 1964), but also to contain a greater concentration of useable energy. The estimated MEn of proso millet for chickens, calculated on the basis of its "percentage multiplier" values for poultry (Titus and Fritz, 1971) and proximate analysis (Table l) is 3.43 Kcal/gm which is slightly lower but not significantly different from 3.57 Kcal/gm, the 28 feeding value of proso millet determined for mallards in this study. Sudgen (1971) found a similar relationship between poultry and mallards in metabolizing other low fiber cereal grains. Proso millet has 95 to 100 percent the feeding value of corn for poultry (Schaible, 1970) and is thus a high energy feed grain. Relative to soldierfly larvae it contains little crude protein (Table 1). Soldierfly larvae are intermediate to duckweed and proso millet in MEn and very high in crude protein content. Animal proteins generally supply a better pattern of amino acids than plant sources (Scott et al., 1969; Sudgen, 1973); hence, they are of higher feeding quality. The intermediate energy content of soldierfly larvae would seem to be related to its high ash and fiber content. These factors not withstanding, I should point out that the determined MEn value is below what was originally antici- pated based on its proximate composition. No precautionary measures were taken to prevent the likelihood of accelerated fatty acid oxidation during the course of drying the insects for diet mixing, thus reducing their feeding value. The actual MEn value of soldierfly larvae for mallards may be slightly higher than that presented here. Dietary Energy Utilization Egg laying in females was found to significantly increase energy retained per gram of diet intake at both the ME and MEn level. The magnitude of the MEn difference 29 (+3 percent), however, was small and for the practical purpose of assigning a single MEn value to a food item can be ignored. In fact, values determined for laying females may have been biased slightly positive through the use of 8.22, the standard correction factor used for nitrogen retention in poultry (Scott et al., 1969). The validity of its use has been questioned (Vohra, 1966) and a larger value (28.7) has been suggested as being more appr0priate. Using a low value would tend to accentuate MEn differences between groups of birds where no difference exists particularly if Nr values diverge widely as in this case for laying versus non-laying and male birds. Axillary to and compounding this question are data (Stewart et al., 1969) that indicate that the proportions of nitrogenous compounds in duck and chicken urine are not similar. Although determining Nr values is a laborious task for a minor refinement in energy values, knowledge of the correct correction factor for ducks may be useful. At a constant temperature of 20°C no indication of a significant photoperiod or sex effect was noted. The pattern of GEe and ME values obtained for laying birds in this study is similar to that described by West (1968) for laying willow ptarmigan. Zebra finch (Taeniopygia castanotis) pairs increased energy retention (ME) during nest building and egg laying, however, the increase was not characterized by a significant change in GEe values (El-Wailly, 1966). The fluctuations in GEe levels during 30 laying periods is probably of minor energetic importance since they are influenced by the amount of dietary minerals, as well as protein, retained for the production of eggs. Water Consumption Very little data are available on the voluntary water intake of mallards. Research in this area on wild birds has been limited to terrestrial Species, particularly desert and semi-arid birds, or temperate species which are smaller than mallards (Bartholomew and Cade, 1963). In comparison to the voluntary water intake of domestic chickens (Medway and Kane, 1959), the male and non-laying mallards consumed roughly 2 times and egg-laying females 1.5 times the intake of pullets 16 weeks of age and mature laying hens on a ml/gm of diet consumed basis. To what extent water was consumed by the mallards to aid in diglutition of the pelleted diets is difficult to assess. The feeding pattern exhibited most often by the birds was one of constant movement from the feed tray to the water cup where extensive "dabbling" took place. Apparently the diets were well moistened before being swallowed. For domestic poultry, the influence of dietary factors in the regulation of food intake can be expressed by dry matter measurements (e.g., Gleaves et al., 1968) since the diets are usually presented to the birds in this form. The intake of free-living mallards, however, would be expected to fluctuate seasonally from high moisture 31 animal foods in the spring (Krapu, 1974) to low moisture seeds in the fall. Hence, the dietary intake of captive birds is probably more realistically compared to that of wild birds as total intake (food + water), and percentages thereof, rather than dry matter intake alone. Percent dry matter of total dietary intake for the male, non-laying and laying females during the study remained fairly constant at 18, 17, and 16 percent, reSpectively. These percentages fall within the range of values for soldierfly larvae and duckweed (Table l), which seems to indicate that dietary intake and capacity of captive birds, at least on a volumetric or weight basis, may be similar to that of free-living mallards. Metabolized Energy_ Wild mallard females usually lay one egg per day when completing a clutch of eggs. Birds at this rate of lay during the study metabolized 333 Kcal/bird-day (n=12), an increase in MEn intake of 89 percent above that of non- layers. At this rate of lay the females deposited 102 Kcals in egg tissue per day at an intake of 157 Kcals greater than non-layers, yielding an estimated net effici— ency value of 65 percent. Brody (1945) determined the net efficiency of egg production in chickens to be 77 percent based on the intake of total digestible nutrients. A recalculation of his data to a MEn base yielded a net 32 efficiency value of 82 percent which is considerably larger than the value obtained here for mallards. A convenient method of representing energy intake above basal metabolic needs is by a factor of increase. King (1972) predicted the energy requirements of maintenance and egg-laying for gallinaceous birds to be 1.7 and 2.8 times the basal metabolic rate when energy requirements are ‘5 expressed on a base of total digestible nutrients. 1 Estimated basal metabolic needs of the males, non-layers E“ and layers are 100, 91, and 100 Kcals/bird-day (Smith and Prince, 1973). The numerical relationship of metabolized energy to basal metabolic needs is 1.9, 1.9, and 3.3 for the three groups, reSpectively. West (1968) used the estimate of Kendeigh (1.5 X maintenance) to predict the free living energy requirements of willow ptarmigan for intermediate temperatures. Estimated on this same basis the cost of non-reproductive, free-living existence for mallards would be about 274 Kcal/bird-day. The cost of egg laying and free existence combined might approximate 431 Kcal/bird-day. These estimates appear to be realistic. In a current study at this laboratory a group of about 31 female mallards held out-of-doors in a large pen and offered the commercial breeder chow analyzed in this study, metabolized approxi— mately 405 Kcal/bird-day during peak egg production in May when ambient temperatures were about 13°C (unpublished). Under the same conditions energy intake by a group of about iii' All! I‘. ‘ 'I'Iillr .lul 33 35 males was fairly stable through the year at about 240 Kcal/bird-day. In comparison to these two values the ‘ estimated requirements for free existence appear to be at least conservative figures that are not outside the range of expected values. King (1972) speculated that free- living energy requirements were not below 1.5 nor above 4.0 times the maintenance level. Based on these estimates and previous discussion on the nutritional value of the natural food items, the importance of duckweed as a major source of energy for mallards is questionable. A voluminous wet weight amount would have to be ingested if day-to-day energy demands of the levels estimated were to be met. Certainly proso millet or soldierfly larvae would supply a greater con- centration of useable energy than duckweed. Low to moderate levels of duckweed ingestion, in combination with high energy foods, would approximate dietary energy levels fed to captive birds (Scott, 1972). For mallards to minimize the mass of food ingested while maintaining a balanced energy/protein intake, it appears a distinct advantage would be gained by the con- sumption of a mixed diet of foods represented by soldierfly larvae (high protein) and proso millet (high energy), particularly during egg-laying when both of the nutrients are required in large amounts. Deviations from balanced energy intake would be reflected in body fat dynamics and concurrent changes in body weight similar to that recorded IIIII 34 by Folk et a1. (1966). These fluctuations may in turn indicate physiological adaptations of the bird to seasonal changes in the quality and quantity of available nutrients. LITERATURE CITED LITERATURE CITED Allen, R. D. 1973. Ingredient analysis table (1973). Feedstuffs 45(39):24-30. Anderson, D. L., F. W. Hill, and R. Renner. 1958. Studies of the metabolizable and productive energy of glucose for the growing chick. J. Nutrition 65(4):561—574. Anderson, H. G. 1959. Food habits of migratory ducks in Illinois. Illinois Nat. Hist. Surv. Bull. 27: 289-344. Armsby, H. P. 1922. The nutrition of farm animals. MacMillan Co., New York. 743pp. Baldini, J. T. 1961. The effect of dietary deficiency on the energy metabolism of the chick. Poultry Sci. 40(5):ll77-1183. Bardwell, J. L., L. L. Glasgow, and E. A. Epps, Jr. 1962. Nutritional analyses of foods eaten by pintail and teal in Southern Louisiana. 16th Conf. S. E. Assoc. Game and Fish Comm., Charleston, South Carolina. 209—217. Bartholomew, G. A., and T. J. Cade. 1963. The water economy of land birds. Auk 80(4):504-539. Begin, J. J. 1967. The relation of breed and sex of chickens to the utilization of energy. Poultry Sci. 46(2):379-383. » Brody, S. 1945. Bioenergetics and growth. Reinhold Publ. Co., New York. 1023pp. Collias, N. E., and E C. Collias. 1963. Selective feeding by wild ducklings of different species. Wilson Bull. 75(1):6-14. 35 36 Czarnocki, J., I. R. Sibbald, and E. V. Evans. 1961. The determination of chromic oxide in samples of feed and excreta by acid digestion and spectrOphotometry. Can. J. Animal Sci. 41(2):167-179. Dansky, L. M., and F. W. Hill. 1952. Application of the chromic oxide indicator method to balance studies with growing chickens. J. Nutrition 47(3):449-459. Davis, E. A., Jr. 1955. Seasonal changes in the energy .balance of the English sparrow. Auk 72(4):385-411. Dillon, 0. W., Jr. 1959. Food habits of wild mallard ducks in three Louisiana parishes. Trans. N. Am. Wildl. Conf. 24:374-382. El-Wailly, A. J. 1966. Energy requirements for egg-laying and incubation in the zebra finch (TaeniOpygia castanolis). Condor 68(6):582-594. Folk, C., K. Hudec, and J. Toufar. 1966. The weight of the mallard, Anas platyrhynchos, and its changes in the course of the year. Zool. Listy 15(3): 249-260. Givens, L. S., M. C. Nelson, and V. Ekedahl. 1964. Farming for waterfowl. Pages 599-610 Ia J. P. Linduska, ed. Waterfowl tomorrow. U.S. Government Printing Office, Washington, D.C. 770pp. Gleaves, E. W., L. V. Tonkinson, J. D. Wolf, C. K. Harman, R. H. Thayer, and R. D. Morrison. 1968. The action and interaction of physiological food intake regulators in the laying hen. I Effects of dietary factors upon feed consumption and production responses. Poultry Sci. 47(1):38-67. Hill, F. W., and D. L. Anderson. 1958. Comparison of metabolizable energy and productive energy deter— minations with growing chicks. J. Nutrition 64(4):587-603. Holm, E. R., and M. L. Scott. 1954. Studies on the nutrition of wild waterfowl. N. Y. Fish and Game J. l(2):l7l-187. Horwitz, W. (ed.). 1965. Official methods of analysis. Assoc. of Official Agr. Chemists, Washigton, D.C. 957pp. 37 Inman, D. L. 1973. Cellulose digestion in ruffed grouse, chukar partridge and bobwhite quail. J. Wildl. Manage. 37(1):1l4-121. Junca, H. A., E. A. Epps, and L. L. Glasgow. 1962. A quantitative study of the nutrient content of food removed from the crops of wild mallards in Louisiana. Trans. N. A. Wildl. and Nat. Res. Conf. 27:114-121. Kendeigh, C. S. 1949. Effect of temperature and season on energy resources of the English Sparrow. Auk 66(2):113-127. King, J. R. 1972. Energetics of reproduction in birds. Pages 78-107 In D. S. Farner, ed. Breeding biology of birds. NaEIonal Academy of Sciences, Washington, D.C. 515pp. Kirk, R. E. 1968. Experimental design: procedures for the behavioral sciences. Wadsworth Publishing Co., Belmont, California. 577pp. Kleiber, M. 1961. The fire of life. John Wiley & Sons, Inc., New York. 454pp. Krapu, G. L. 1974. Feeding ecology of pintail hens during reproduction. Auk 91(2):278-290. Martin, A. C., and F. M. Uhler. 1939. Food of game ducks in the United States and Canada. 0.8. Dept. Agr. Tech. Bull. 634. 156pp. Mattocks, J. G. 1971. Goose feeding and cellulose digestion. Wildfowl 22:107-113. Medway, W., and M. R. Kare. 1959. Water metabolism of the growing domestic fowl with specific reference to water balance. Poultry Sci. 38(3):631-637. Owen, R. B., Jr. 1970. The bioenergetics of captive blue- winged teal under controlled and outdoor conditions. Condor 72(2):153-163. Penney, J. G., and E. D. Bailey. 1970. Comparison of the energy requirements of fledgling black ducks and American coots. J. Wildl. Manage. 34(1):105-ll3. Pirnie, M. D. 1935. Michigan waterfowl management. Mich. Dept. Cons., Lansing. Franklin DeKleine Co., Lansing, Michigan. 401pp. 38 Potter, L. M., L. D. Matterson, A. W. Arnold, W. J. Pudelkiewicz, and E. P. Singsen. 1960. Studies in evaluating energy content of feeds for the chick. I. The evaluation of the metabolizable energy and productive energy of alpha cellulose. Poultry Sci. 39(5):ll66-1178. Renner, R., and F. W. Hill. 1960. The utilization of cornoil, lard and tallow by chickens of various ages. Poultry Sci. 39(4):849-854. Schaible, P. J. 1970. Poultry: feeds and nutrition. The Avi Publishing Co., Inc., Westport, Connecticut. 636pp. Scott, M. L., and E. R. Holm. 1964. Nutrition of wild waterfowl, pp. 149-155. Proc. of Cornell Nutrition Conf. for Feed Manufacturers. 165pp. Scott, M. L., M. C. Nesheim, and R. J. Young. 1969. Nutrition of the chicken. M. L. Scott and Associates, Publishers, Ithaca, New York. 511pp. Scott, M. L. 1972. Nutrition in reproduction--direct effects and predictive functions. pp. 46-59 {a D. S. Farner, ed. Breeding biology of birds. National Academy of Sciences, Washington, D.C. 515pp. Seibert, H. C. 1949. Differences between migrant and non- migrant birds in food and water intake at various temperatures and photOperiods. Auk 66(2):128-153. Sibbald, I. R., J. D. Summers, and S. J. Slinger. 1960. Factors affecting the metabolizable energy content of poultry feeds. Poultry Sci. 39(3):544-556. Slinger, S. J., I. R. Sibbald, and W. F. Pepper. 1964. The relative abilities of two breeds of chickens and two varieties of turkeys to metabolize dietary energy and dietary nitrogen. Poultry Sci. 43(2): 329-333. Smith, K. G., and H. H. Prince. 1973. The fasting, metabolism of subadult mallards acclimitized to low ambient temperatures. Condor 75(3):330-335. Snedecor, G. W., and W. G. Cochran. 1973. Statistical methods. 6th ed. Iowa State University Press, Ames, Iowa. 593pp. 39 Stewart, D. J., W. N. Holmes, and G. Fletcher. 1969. The renal excretion of nitrogenous compounds by the duck (Anas platyrhynchos) maintained on freshwater and onfihypertonic saline. J. Exp. Biol. 50(2): 527-539. Sudgen, L. G. 1971. Metabolizable energy of small grains for mallards. J. Wildl. Manage. 35(4):781-785. Sudgen, L. G. 1973. Feeding ecology of pintail, gadwall, American widgeon and lesser scaup ducklings. Can. Wildl. Serv. Rep. No. 24. 45pp. Titus, H. W., and J. C. Fritz. 1971. The scientific *‘ feeding of chickens. 5th ed. The Interstate Printers & Publishers, Inc., Danville, Illinois. 336pp. 1!“. Vohra, P. 1966. Energy concepts for poultry nutrition. World's Poultry Sci. J. 22(1):6-24. West, G. C. 1960. Seasonal variation in the energy balance of the tree sparrow in relation to migration. Auk 77(3):306-329. West, G. C. 1968. Bioenergetics of captive willow ptarmigan under natural conditions. Ecology 49(6): 1035-1045. Zimmerman, J. L. 1965. Bioenergetics of the dickcissel, Spiza americana. Physiol. 2001. 38(4):370-389.