Dietary Gross Energy Research Articles

Dietary isoacids effects on growth, nitrogen, and energy digestibility, and fecal volatile fatty acids and microbial ecology in finishing pigs.

Isoacids are branched ketoacids which when fed to ruminants have been shown to enhance the growth of fiber-digesting organisms. Ninety finishing gilts were individually fed dietary treatments consisting of diet type: corn-soybean meal (CSBM), a diet containing 40% distillers dried grains with solubles (DDGS), or a diet containing 40% sugar beet pulp (SBP); in combination with either no feed additive (CNT), the addition of 0.50% isobutyrate (IB), or the addition of a 0.88% mix of isobutyrate, isovalerate, and 2-methylbutyrate (MX). Gilts consumed an average of 2.171kg/d over the 28-d trial. On d 26, fresh fecal samples were collected for determination of apparent total tract digestibility (ATTD) of gross energy (GE) and nitrogen (N), determination of fecal volatile fatty acids (VFA), and evaluation of microbial ecology. There was no interaction between diet type and isoacid addition, and no main effect of isoacid or diet type on alpha or Shannon microbial diversity measures (P > 0.05). There was no interaction between isoacid addition and diet type, and no main effect of isoacid addition on microbial beta diversity (P > 0.05), but differences were observed in microbial beta diversity due to diet type (P ≤ 0.05). There was no interaction between diet type and isoacid addition observed in fecal VFA concentrations (P > 0.05), with only minor differences in fecal VFA concentrations noted due to isoacid addition (P ≤ 0.05). The interaction between diet type and isoacid addition on ATTD of dietary GE and N (P ≤ 0.01) was large because the addition of IB did not affect the ATTD of GE or N in pigs fed the CSBM diet, but increased ATTD of GE and N in pigs fed diets containing DDGS and decreased the ATTD of GE and N in pigs fed diets containing SBP. In contrast, adding a blend of isoacids (i.e., MX) reduced the ATTD of GE and N, regardless of diet type. There was no interaction between diet type and isoacid addition, and no effect of isoacid addition was observed on pig performance (P > 0.05). Diet type did not affect average daily gain (P > 0.05), but pigs fed diets containing DDGS or SBP consumed less feed (P = 0.01) and exhibited greater GF ratios compared to pigs fed the low-fiber CSBM diet (P ≤ 0.05). In conclusion, there was little to no effect of isoacid addition on microbial ecology, fecal VFA concentrations, ATTD of GE or N, or pig performance, but the improvement in ATTD of GE and N in pigs fed diets containing DDGS when IB was added warrants further investigation.

Evaluation of gross energy concentration of neutral detergent fiber contained in feed and fecal samples

Starch and NDF are usually assumed to contain the same concentration of gross energy (GE), but NDF is more variable in chemical composition and varies more in the extent of digestion. The variable chemical composition of NDF may have direct implications on dairy nutrition models that predict dietary GE and use this estimate for also predicting digestible energy. For example, when NDF is enriched in lignin and protein, the concentration of GE would increase, whereas NDF enriched in ash would have the opposite effect. Current nutritional models, such as the NASEM (2021) and CNCPS (6.55), assume a GE coefficient of 4.20 Mcal/kg for NDF. This study aimed to determine the heat of combustion of NDF and to consider if it is a contributing factor to the variance in digestible energy. To do so, NDF residues were isolated from 9 feed and 8 fecal samples and then combusted. Approximately 0.20 g of NDF residues from 16 feeds (corn silage, n = 2; grass hay, n = 2; alfalfa hay, n = 2; wheat straw, n = 1; cottonseed hulls, n = 1; soyhulls, n = 1; distillers dried grains with solubles, n = 1; and total mixed ration, n = 6) and 34 fecal samples were collected. A bomb calorimeter (Parr 6400 Calorimeter, Parr Instrument Company) was used to determine concentration of GE in each NDF residue sample. The GE concentration of feed NDF was observed to be 4.03 ± 0.245 Mcal/kg, which was similar to that of fecal NDF (3.94 ± 0.245 Mcal/kg). The lack of difference between feed and fecal NDF GE implies that digested NDF is of a similar GE concentration as total feed NDF and that current nutritional models are validated in their current approach in predicting digestible energy from NDF. However, our observed estimate of GE in NDF is lower than what is assumed and across feed types varied from 3.85 to 4.19 Mcal/kg.

Effects of different defatted rice bran sources and processing technologies on nutrient digestibility in cannulated growing pigs.

The objective of this study was to evaluate the effects of different defatted rice bran (DFRB) sources and processing technologies on nutrient digestibility in different intestinal segments of pigs. Nine barrows with T-cannula in the distal ileum were randomly allotted to nine different sources in which oil was pressed extracted for seven sources and was solvent extracted for two sources. The experiment contained 6 periods of 12 d, including 8 d for diet adaptation, 2 d for fecal collection, and 2 d for digesta collection. The apparent ileal digestibility (AID) of dry matter (DM), ash, total dietary fiber (TDF), insoluble dietary fiber (IDF), neutral detergent fiber (NDF), acid detergent fiber (ADF), and hemicellulose in different sources of DFRB was quite variable. There were no differences in the AID of dietary gross energy (GE), organic matter (OM), ether extract (EE), crude protein (CP), and soluble dietary fiber (SDF) between different sources of DFRB. There were no differences in the AID of dietary EE, TDF, IDF, and hemicellulose between different processing technologies. Pressed DFRBs have greater (P < 0.05) average AID of dietary GE, DM, ash, OM, CP, SDF, and NDF and lower (P < 0.01) ADF compared with solvent-extracted DFRBs. The apparent total tract digestibility (ATTD) of most of the dietary nutrients, except for the ATTD of dietary EE, SDF, and hemicellulose, significantly varied in different sources of DFRB (P < 0.05). In addition, pressed DFRB had greater (P < 0.05) ATTD of dietary SDF, NDF, ADF, and hemicellulose compared with solvent-extracted DFRB. The apparent hindgut digestibility (AHD) of dietary DM, SDF, NDF, and ADF significantly varied (P <0.05) in different sources of DFRB. Exception with DM, there are no differences in the AHD of nutrients digestibility between pressed DFRB and solvent-extracted DFRB. In conclusion, DFRB in different sources and processing technologies with different physicochemical properties had different effects on nutrient digestibility in the foregut and hindgut of pigs.

Effects of fibre-degrading enzymes in combination with different fibre sources on ileal and total tract nutrient digestibility and fermentation products in pigs

ABSTRACT The study was conducted to determine effects of a complex of fibre-degrading enzymes (xylanase, cellulase and β-glucanase) on nutrient digestibility, fibre fermentation and concentrations of short chain fatty acids (SCFA) at different parts of digestive tract in pigs fed different fibre-rich ingredients. A total of 36 barrows fitted with T-cannulas in the distal ileum (initial body weight of 41.1 ± 2.7 kg) were randomly allotted to six dietary treatments with three different high-fibre diets including maize bran (MB), sugar beet pulp (SBP) and soybean hulls (SH) with or without supplementation of fibre-degrading enzymes. Enzyme supplementation improved (p < 0.05) apparent ileal digestibility (AID) of dietary gross energy (GE), crude protein, dry matter (DM), organic matter (OM), total dietary fibre (TDF), neutral detergent fibre (NDF) and apparent total tract digestibility (ATTD) of dietary GE, DM, OM, TDF, insoluble dietary fibre (IDF) when pigs were fed MB, SBP or SH diets. When compared to the SBP and SH diets, the AID of GE, DM, ash, OM and NDF in diet MB was higher (p < 0.05), but the hindgut disappearance and ATTD of nutrients, except for ether extract and crude ash, were lower (p < 0.05). Enzyme supplementation increased acetate and total SCFA concentrations in ileal digesta and faeces of pigs. In conclusion, enzyme addition improved IDF fermentation and SCFA concentration in the whole intestine of pigs, and there was a large variation of digestibility of fibre components among MB, SH and SBP owing to their different fibre composition. Therefore, fibre-degrading enzymes should be applied to fibrous diets to improve efficient production of swine, especially considering low fibre digestibility of fibre-rich ingredients.

Impact of increasing the levels of insoluble fiber and on the method of diet formulation measures of energy and nutrient digestibility in growing pigs.

The objective of this study was to determine the differences in response to distillers dried grains with solubles (DDGS) level under constant nutrient or floating nutrient concentrations. A total of 21 ileal-cannulated gilts (33.1 ± 0.4 kg body weight) were randomly allotted to one of seven dietary treatments in a 3-period incomplete Latin square design (n = 9). Treatments consisted of a 0% DDGS basal diet, plus diets containing 15%, 30%, or 45% DDGS. Diets were formulated using one of two different formulation methods: 1) constant nutrient (CNU) where nutrients were held equal to the basal diet or 2) constant ingredients (CIN) where DDGS were added at the expense of corn and all other ingredients remained constant, so nutrient levels were allowed to “float.” Chromic oxide was added to the diets at 0.5% as an indigestible marker. Increasing the level of DDGS decreased the apparent ileal digestibility (AID) of dry matter (DM), gross energy (GE), starch, dispensable amino acids (AA), and fiber components (P < 0.050). The decrease in the AID of Lys, Met, Thr, and Trp was more pronounced under CNU compared with the CIN formulation method (P < 0.050). The decrease in the AID of hemicellulose was less pronounced under CNU compared with the CIN formulation method (P = 0.045). There was a DDGS level × formulation method interaction for the AID of acid hydrolyzed ether extract (AEE; P = 0.015); for the CNU formulation method, increasing level of DDGS decreased the AID of AEE from 0% to 30% and remained similar from 30% to 45% DDGS, whereas the CIN had no effect on the AID of AEE. Increasing the level of DDGS decreased the apparent total tract digestibility (ATTD) of DM, GE, and fiber components (P < 0.050), except for acid detergent fiber, which was not affected. The decrease in the ATTD of insoluble dietary fiber and total dietary fiber was less pronounced under CNU compared with CIN (P < 0.050). The ATTD of AEE decreased for CNU compared with CIN (P < 0.010). In conclusion, increasing the insoluble fiber level in the form of DDGS decreased the digestibility of most dietary components, including DM, GE, starch, insoluble fiber, and AA. The CNU and CIN formulation methods are equivalent when evaluating the digestibilities of DM, GE, starch, crude protein, and AA (when they were not added in purified synthetic forms). Differences between CNU and CIN formulation methods were detected for the digestibility of insoluble fiber, fat, and essential AA (when added as crystalline AA).

Using complete diet and Sibbald methods to determine the metabolizable energy of 5 Iranian wheat varieties

SUMMARY To determine the ME contents of 5 Iranian wheat varieties (Alvand, Zarrin, Sabalan, Sardari, and Azar2), 2 experiments were conducted. In experiment 1, the AMEn content of 5 wheat varieties was determined by complete diet method containing 62.06% of a test cereal grain (with or without an appropriate commercial enzyme). Diets were consumed ad libitum by sixty 21-d-old Ross 308 male broiler chicks. The AMEn values (kilocalories per kilogram of cereal grain, DM basis) were determined from gross energy of diet and collected excreta during 56 h at the end of the experiment. In experiment 2, 36 adult roosters were used to determine the TMEn content of the varieties by the precision feeding method. The AMEn content was not significantly affected by varieties. The AMEn of wheat varieties without enzyme supplementation varied from 3,120 to 3,191 kcal/kg. The AMEn was significantly affected by enzyme supplementation. Enzyme addition produced an average increase of 11.45% AMEn content of wheat varieties. The TMEn of wheat varieties varied from 3,788 (Sabalan variety) to 3,947 kcal/kg (Zarrin variety), and TMEn content was affected significantly by wheat varieties. Strong correlation was seen between broiler chick performance and AMEn of wheat varieties that determinate with the complete diet method in wheat-based diets. It is suggested that the AMEn obtained from the complete diet method should be applied in young broiler diets formulation.

Correlations of Dietary Crude Protein and Gross Energy on Blood Glucose and Urea, Milk Urea and Lactose Concentrations in Lactating Ewes

Concentrations of serum glucose (SG) and urea (SU), milk lactose (ML) and urea (MU) and their relationships to dietary gross energy (GE) and crude protein (CP) were studied in 16 lactating ewes in Urmia, Iran. Ewes were aged 3 to 5 years and were bred in a closed pen. They were fed alfalfa hay, pasture grass, concentrate and corn silage. Each lactating ewe was nursing a single lamb. Five ml of blood from v. jugularis, 50 ml milk and 200 g feed mixture were collected at 15 day intervals up to 135 days (9 samples). Serum glucose and urea concentrations were evaluated using a spectrophotometer, milk lactose in Polarimeter, gross energy by calculation method and crude protein by Kjeldahl methods. The mean values for dietary GE, CP, SG, SU, MU and ML were 2.39 Mcal/kg/DM, 14.1% food/DM, 2.69, 4.65, 3.67 mmol/l and 4.8 mg/dl milk, respectively. Significant differences (P &lt; 0.01) were found for serum and milk indicators during the milking periods among the sampling times. Serum urea and milk urea irregularly increased while serum glucose and milk lactose irregularly decreased. Positive correlations were found (P &lt; 0.05) between SU/MU (r = 0.45), MU/GE (r = 0.75), MU/CP (r = 0.70) and SU/CP (r = 0.97). Negative correlations (P &lt; 0.05) were found between MU/SG (r = -0.17), SU/ML (r = -0.20) and MU/ML (r = -0.24). Based on results, it is concluded that urea, glucose and lactose would be appropriate variables in the prediction of crude protein and gross energy concentration of diet in lactating ewes.

Prediction of digestible energy content across feed ingredients and fish species by linear regression

In an attempt to develop predictive relationships, apparent digestible energy (ADE) content (n = 361) as biological dependent variable and dietary contents of crude protein (CP), lipid, ash and gross energy (GE) as independent variables, obtained in 40 studies with 65 different feed ingredients and evaluated with 26 fish species, were subjected to linear correlation and multiple linear regression analysis. With dietary CP and GE contents identified as significant predictors, only 58% of the variation in ADE content could be explained. No improvement in accuracy of regression equations was gained by classification of values according to either feed ingredient (animal proteins, plant proteins, cereals) or fish species (water type, water temperature, feed habit). An R (2)-value of 0.4570 and mean prediction error (MPE) of 0.2085 between predicted and observed ADE values from eight independent studies (n = 37) illustrated the inability of the derived regression equation to accurately predict ADE contents of feed ingredients. Inclusion of dietary crude fibre and nitrogen-free extract (NFE) contents as independent variables did not improve the accuracy of prediction equations. The inadequacy of the use of linear regression to predict DE content from dietary composition across feed ingredients and fish species with high accuracy is discussed.

Metabolizable energy intake during long-term calorie restriction in rhesus monkeys

Calorie restriction (CR) is a dietary intervention shown to increase maximum life-span. The aim of this study was to compare the metabolizable energy of the pelleted semi-purified diet with estimated energy intake from food weight. Energy density of diet, urine and feces were measured by bomb calorimetry in rhesus monkeys (23–29 years old) on CR (CR, n = 11) and control (C, n = 9). Food moisture was measured to be 2-fold higher (9 ± 1%) than indicated on the label (∼5%). The measured gross energy of diet was 4.4 kcal/g dry weight of CR and 4.5 kcal/g dry weight of C diets. In a two-day trial, food intake (mean ± SD) was 112 ± 20 g and 136 ± 26 g of dry mass/d in the CR and C monkeys, respectively ( p = 0.003). The fraction of the diet absorbed (CR = 0.91; C = 0.95) was different ( p < 0.001) between CR and C monkeys. Using these coefficients, the metabolizable energy intake averaged over 6 months was 450 ± 53 and 534 ± 97 kcal/d in CR and C monkeys, respectively (Diff = 16%; p = 0.03). These values were compared with energy expenditure (EE), as measured annually by indirect calorimetry (490 ± 61 kcal/d in CR and 532 ± 62 kcal/d in C monkeys). Adjusted for changes in body composition (2 ± 10 kcal/d in CR and −7 ± 12 kcal/d in C), energy balance was not different from zero in CR (−42 ± 42 kcal/d) and C (9 ± 61 kcal/d) monkeys. Use of diet weight is a reasonable estimate of the level of CR when food waste is assessed.

Effects of variable feed allowance with constant energy and ratio of energy to protein in a diet for constant protein input on the growth of common carp Cyprinus carpio L.

An 11-week feeding trial was conducted to evaluate the effects of dietary protein and/or energy levels on growth, feed efficiency and proximate composition of juvenile (average weight: 21.5 g) common carp (Cyprinus carpio L.) fed various diets based on constant daily protein input. Five experimental diets were prepared. One group of diets (diets 1, 2 and 3) contained three crude protein (P) levels (35%, 40% and 45%) with a constant gross energy (GE) of 3.8 kcal g−1 diet. The second group of diets (diets 4 and 5) were formulated to contain a GE of 4.3 or 4.9 kcal g−1 diet and 40% or 45% protein levels, respectively, where GE/P was constant at 10.8 kcal g−1 protein. Fish receiving diet 1 served as the control; they were hand-fed to visual satiety. Feed allowance for diets 2 and 4 was 87.5% of the control. Feed allowance for fish receiving diets 3 and 5 was 77.8% of the control. Thus, all tanks received the same daily protein input. When gross energy in the diets was constant, 3.8 kcal g−1 diet, weight gain of fish fed diet 2 at 87.5% satiation was significantly higher than that of fish fed diet 3 at 77.8% of satiation. When the GE/P in the diets was constant, 10.8 kcal g−1 protein, weight gain of fish fed diet 1 was significantly higher than that of fish fed diet 5 at 77.8% satiation. The feed efficiency ratio (FER) for diets 2–5 was significantly higher than for diet 1 at constant GE and GE/P, and this improved linearly as dietary protein levels increased. The protein efficiency ratio (PER) for diet 2 was significantly higher than for diet 3 at constant GE. However, PER was not significantly different at constant GE/P. Protein retention of fish fed diet 2 was significantly higher than that of fish fed diet 3 at constant GE. Protein retention of fish linearly decreased at constant GE/P. The energy efficiency ratios (EER) for diets 2 and 3 were significantly higher than for diet 1 at constant GE. Moisture and protein contents of the whole body of fish were not significantly different at constant GE, but they decreased linearly at constant GE/P. The lipid content of fish fed diet 1 was significantly lower than that of fish fed diet 2 at constant GE, and body lipid content linearly increased at constant GE/P. These results indicate that growth and feed efficiency for common carp fed a 40% protein diet with 3.8 kcal g−1 diet GE at 87.5% satiation rate was superior to those for the fish fed either a 35% protein diet with 3.8 kcal g−1 diet GE at 100% satiation rate or a 45% protein diet with either a 3.8 or 4.9 kcal g−1 diet GE at 77.8% satiation rate.

The effect of autoclaving a yeast culture of Saccharomyces cerevisiae on turkey poult performance and the retention of gross energy, and selected minerals

A study was conducted to determine the effects on nutrient retention in turkey poults fed a diet containing an untreated or autoclaved yeast culture (YC). Isonitrogenous and isocalorific diets consisting of corn-soybean meal (CS, control), CS + YC (10 g kg−1 XP yeast culture®, Saccharomyces cerevisiae) or CS + 10 g kg−1 autoclaved YC (CS + AYC; autoclaved at 121 °C and 0.8 kg cm−2 for 35 min) were fed to Wrolstad Medium White poults from Days 1 to 28. Between Days 21 and 28, the diets were marked with 3 g kg−1 chromic oxide and feed and excreta samples were collected between Days 26 and 28. The samples were analyzed for gross energy (GE), Ca, P, B, Cu, Fe, K, Mg, Mn, and Zn. The addition of the untreated and autoclaved yeast culture to the poult diets had no effect (P > 0.05) on weight gains or feed conversion measured between Days 1 and 28. There were increased (P < 0.05) retentions of dietary GE, Ca, P, B, K, Mg, and Mn observed only in poults fed the CS + YC diet when compared with the CS and CS + AYC diets. These results indicate that autoclaving impairs the ability of the YC to increase the utilization of selected nutrients in starting poults.

The effect of autoclaving a yeast culture of Saccharomyces cerevisiae on turkey poult performance and the retention of gross energy, and selected minerals

A study was conducted to determine the effects on nutrient retention in turkey poults fed a diet containing an untreated or autoclaved yeast culture (YC). Isonitrogenous and isocalorific diets consisting of corn-soybean meal (CS, control), CS + YC (10 g kg −1 XP yeast culture®, Saccharomyces cerevisiae) or CS + 10 g kg −1 autoclaved YC (CS + AYC; autoclaved at 121 °C and 0.8 kg cm −2 for 35 min) were fed to Wrolstad Medium White poults from Days 1 to 28. Between Days 21 and 28, the diets were marked with 3 g kg −1 chromic oxide and feed and excreta samples were collected between Days 26 and 28. The samples were analyzed for gross energy (GE), Ca, P, B, Cu, Fe, K, Mg, Mn, and Zn. The addition of the untreated and autoclaved yeast culture to the poult diets had no effect ( P > 0.05) on weight gains or feed conversion measured between Days 1 and 28. There were increased ( P < 0.05) retentions of dietary GE, Ca, P, B, K, Mg, and Mn observed only in poults fed the CS + YC diet when compared with the CS and CS + AYC diets. These results indicate that autoclaving impairs the ability of the YC to increase the utilization of selected nutrients in starting poults.

The antinutritive effect of proanthocyanidin-rich and proanthocyanidin-free hulls from field beans on digestion of nutrients and metabolisable energy in intact and caecectomised cockerels

Three white flowered (proanthocyanidin-free) and three coloured flowered (proanthocyanidinrich) varieties of field beans were dehulled to give pure cotyledons and pure hulls. Cockerels that had been starved for 48 h received directly into the crop the following three diets with cotyledon to hull ratios of 100:0, 80:20 or 50:50 in amounts of 30, 37.5 and 60 g, respectively. A control group of birds received 50 g glucose only. Excreta voided over 72 h were quantitatively collected and freeze dried. True metabolisable energy values for the diets were calculated from the gross energy of diets and excreta. True digestibility of protein, starch and lipid was calculated from the quantitative measurement of amino acids, starch and lipid in diets and excreta. Proanthocyanidin-free hulls were mainly composed of non-starch polysaccharides and their ingestion caused a small reduction in the digestibility of protein and starch, the highest level of hulls causing the largest reductions, 3.1 and 3.5%, respectively. Proanthocyanidin-rich hulls greatly reduced the digestibility of protein, starch and lipid, the highest level of hulls causing the largest reductions, 22.0, 23.5 and 9.3%, respectively. The true metabolisable energy values of diets were greatly reduced by the inclusion of both types of hulls, although proanthocyanidin-rich hulls caused the greatest reductions in metabolisable energy values. Caecectomy did not appear to affect the true metabolisable energy of diets nor the digestion of protein, starch or lipid.

The Efficiency of Food Utilization and Energy Requirements of Captive Female Fishers

Sixteen complete digestibility, energy and nitrogen balance trials were carried out to determine the nutritive value of 4 diets fed to 4 captive female fishers (Martes pennanti). Diets consisting of snowshoe hares (Lepus americanus), white-tailed deer (Odocoileus virginianus), small mammals (Microtus pennsylvanicus, Blarina brevicauda, and Peromyscus leucopus or maniculatus), and coturnix quails (Coturnix coturnix) were fed separately in 4 series (time periods) to the experimental animals. Gross energy of diets generally was related positively to ether extract (fats) and negatively to ash percentages in diet dry matter. Dry matter intake per kilogram body weighto075 did not differ significantly (P < 0.05) among treatments. Gross energy intake per kgWo.75 was higher (P < 0.05) on diets of deer and quails. Digestible, metabolizable, and net energy values per gram of dry matter intake were higher (P < 0.05) for deer (5.98, 5.54, 4.30 kcal/g) and quails (6.12, 5.86, 5.27) than for hares (4.32, 3.64, 2.57) and small mammals (4.15, 3.80, 2.69). Efficiency of conversion of dietary nitrogen to body tissue was significantly greater on the hare ration. J. WILDL. MANAGE. 42(4):811-821 The existence of the fisher in New Hampshire is threatened by the destruction of habitat due to development of open and wild lands and overtrapping. The success of restocking efforts, and the accurate assessment of the impact of fishers on game species require better understanding of the many aspects of predation. Studies of the fisher's status and distribution (Hagmeier 1956, Coulter 1960, Dodds and Martell 1971), reproductive potential (Eadie and Hamilton 1958, Wright and Coulter 1967), and food habits (DeVos 1951, Hamilton and Cook 1955, Stevens unpublished data) have contributed to understanding the fisher. However, part of understanding its relationships with prey requires determinations of this carnivore's energy requirements and the nutritive worth of its food, particularly those ingested in winter. This information will help to determine the minimum amounts of prey needed to sustain fishers and to evaluate the relative importance of different prey to fishers. There are numerous reports of feeding trials which dealt with the digestibility, and relative value of commerical feeds for ranch minks (Mustela vison) and foxes (Vulpes spp.) (Bezeau 1950, Inman and Smith 1941, Leoschke 1959, Roberts and Kirk 1964, Seier et al. 1970, Smith 1942). The digestible energy and protein requirements of these ranch animals were also studied (Farrell and Wood 1968b, Harris et al. 1951, Kosko 1968, Kumeno et al. 1970). However, there have been no nutritional studies with fishers and relatively few with other wild carnivores which were fed their natural foods or approximations of such foods (Golley 1960, Golley et al. 1965, Jense 1968, Underwood 1971, Vogtsberger and Barrett 1973). While there have been no determinations of the energy expenditure of fishers, there are reports of the basal and resting metabolic rates of a number of mustelids and other carnivores (Perel'dik ' Published with the approval of the Director of the New Hampshire Agricultural Experiment Station as Scientific Contribution No. 155. 2 Present address: Department of Wildlife Science, Utah State University, Logan 84322. J. Wildl. Manage. 42(4):1978 811 This content downloaded from 207.46.13.83 on Fri, 13 May 2016 07:26:51 UTC All use subject to http://about.jstor.org/terms 812 FISHER ENERGY AND FOOD EFFICIENCY* Davison et al. and Titova 1950, Scholander et al. 1950, Farrell and Wood 1968a, Underwood 1971, Brown and Lasiewski 1972, Iversen 1972). The objectives of this investigation were to evaluate the relative nutritive value for the fisher of 4 diets (snowshoe hares, white-tailed deer meat and viscera, small mammals [meadow voles, short-tailed shrews, white-footed mice], and coturnix quail), and to estimate the fisher's energy requirements for