True Metabolizable Energy Values Research Articles

Pooling Excreta Prior to Calorimetry in the Bioassay for True Metabolizable Energy: The Effect on Estimates of Variance

Pooling excreta, within treatments, prior to calorimetry reduces the time and cost of the bioassay for true metabolizable energy (TME) and does not alter mean TME values. However, by ignoring the among-bird variance of the gross energy per unit weight of excreta (G) and its covariance with the weight of excreta (D), the standard errors of mean TME values are subject to bias. An additional factor for consideration is the effect of the sampling error from pooled aggregates. These factors were examined using data from TME bioassays of 20 feedingstuffs and by measuring the standard deviations of gross energy values for subsamples from pooled excreta.The standard deviation of G for each unit subsample from pooled excreta samples was .0381 kJ/g with 20 degrees of freedom. The resulting contribution to the standard errors of mean TME values was so small that replicate subsampling from the bulked excreta is of minor importance, although a useful precaution.However, ignoring the among-bird variation in G as a consequence of pooling excreta caused the standard errors of mean TME values to be incorrectly estimated by amounts ranging from −62 to + 64%. Although for these particular feedingstuffs the average discrepancy was small, the potential magnitude of the bias for an individual feedingstuff is too large to be discounted in a research laboratory.

EFFECT OF DOUBLE FORCE FEEDING ON TRUE METABOLIZABLE ENERGY

Four feedingstuffs were assayed for true metabolizable energy (TME) using a conventional single feeding or two feedings followed by a reduced fecal collection time. There was no significant (P < 0.05) difference in the TME values for any of the ingredients due to feeding technique. It is suggested that double force feeding could provide an alternative approach to TME results, allowing birds to increase the amount of feed in their gut, when compared to the amount of feed provided for the conventional assay. Key words: energy, feed intake, rate of passage

Comparison of Two Direct Bioassays Using Adult Cocks and Four Indirect Methods for Estimating the Metabolizable Energy-Content of Different Feedingstuffs ,

Ninety-six adult Single Comb White Leghorn males were divided into two 48-bird groups to assay feedingstuffs for apparent metabolizable energy (AME) and true metabolizable energy (TME). The metabolizable energy contents of corn, wheat, oats, rye, barley, glucose and soybean, rapeseed, sunflower, dehydrated alfalfa, feather, and fish and meat meals were evaluated. The experiment consisted of three replicates in a cross-over design. The excreta voided by birds in both assays was collected quantitatively at 24- and 48-hr intervals after feeding. A set of corrected AME values (AMEC) was obtained by correcting AME results for endogenous excreta losses. A prediction of AME results was also obtained by using the chemical composition of the 13 feedingstuffs.Birds trained for the AME assay to eat their feed requirements in 1 hr consumed less than ad libitum fed birds even after 14 days of training. Introduction of experimental diets caused a further reduction in intake even though all feeds were pelleted and of similar color. Thirty-nine of 117 AME values were discarded because intakes were less than 50 g/bird. Two TME values were discarded due to problems unrelated to feed. The AME values for the feedingstuffs tested were different (P<.05) from the AMEC and TME results; the latter were not different (P>.05) from each other. Differences (P>.05) in the AME, AMEC, and TME values between the 24-and 48-hr excreta collections indicated that there were differences in clearance rates of feed residues. When AME values were predicted from chemical composition, the error of prediction ranged from .28 to .40 kcal/g, depending upon the equation used.The results of this experiment show that the “rapid method” for AME determinations produces highly variable dat a due to variation in voluntary intake. Although chemical methods provide a more rapid estimation of AME values than bioassays, the results obtained are not reliable.

The Effect of Feeding Techniques on the True Metabolizable Energy Value of Yellow Corn

Thirty Single Comb White Leghorn (SCWL) roosters were utilized in five trials to evaluate the effect of various feeding techniques on the metabolizable energy (ME) value of yellow corn as measured by the true metabolizable energy (TME) scheme (Sibbald, 1976). Average weight of roosters was 1.6 kg. Roosters were paired (fed vs. nonfed) on the basis of weight. Feed preparations were: dry pellets, moist pellets, slurry, paste, or dry (ground) corn. The TME values (kcal/g [DM]) were: 4.107, 4.106, 4.106, 4.102 or 4.098, respectively, and did not significantly differ (P>.05) among feeding methods. Visual observations of fed birds indicated that moist pellets, slurry or paste forms produced less stressful postfeeding behavior (standing or reclining posture, ruffled feathers, etc.) than either dry pellets or ground corn.

Applicability of the True Metabolizable Energy System in Practical Feed Formulation

Two experiments were conducted to investigate whether values obtained using the true metabolizable energy (TME) assay are applicable in the formulation of practical diets for poultry.In the first study, five diets of increasing energy and nutrient density were assayed for TME and nitrogen corrected, apparent metabolizable energy. (AMEn). Chick response to each diet was evaluated in a 3-week growth trial. The determined TME of three practical diets exceeded the respective determined AMEn by 13 to 14%. A comparison between feed efficiency of chicks and the TME and AMEn content of the test diets indicated that TME values more closely reflected observed chick performance than did AMEn.In the second study, seven feed ingredients were assayed for TME and crude protein content. On the basis of these analyses, four isocaloric, isonitrogenous diets were prepared using the assayed lots of ingredients in varying proportions. In all diets, critical nutrients were included in excess of requirements, energy thus being limiting for optimal chick performance. In a 3-week growth study, chicks receiving each of the test diets exhibited virtually identical body weight gains and feed conversion ratios. Assays of the mixed diets indicated TME values of individual ingredients to be additive to within 1.6% of calculated totals. It was concluded that the TME system provided an accurate measure of metabolizable energy.

The Effect of Fasting Time of Mature, Nonlaying Female Embden Geese on True Metabolizable Energy of Corn ,

Mature, nonlaying, female Embden geese were fed either a 12% protein corn-soybean meal diet or alfalfa haylage for 5 months. Excreta collections over a 48-hr fasting period indicated that there was no difference in quantitative excretion due to previous diet and that 12 hr were sufficient to empty the digestive tract of a goose. However, cecal droppings were noted up to 48 hr of collection. In the second experiment, the true metabolizable energy (TME) value of corn was found to increase significantly between 6 and 12-hr periods of fasting prior to force-feeding 50 g of corn. Fasting up to 24 hr resulted in nonsignificant increases in the TME of corn. The TME of corn for geese previously fasted 24 hr was 4.169 kcal/g dry matter. Total metabolic fecal and endogenous urinary energy excretion of mature female geese, ranging from 3817 to 4857 g, was not correlated with body weight. The coefficient of variation was high. The mean metabolic fecal and endogenous urinary energy excretion of female Embden geese for a 24-hr period following an initial 24-hr fast was found to be 8.476 ± .822 kcal of energy per goose.

The Effect of Cecectomy and Extension of the Collection Period on the True Metabolizable Energy Values of Soybean Meal, Feather Meal, Fish Meal, and Blood Meal

Four experiments were conducted in which 30 g of test material were force-fed to both intact and cecectomized adult White Leghorn roosters. The length of the collection periods was as follows: soybean meal (49%), 24, 30, 48, and 60 hr; feather meal, 24 and 30 hr; fish meal, 24, 30, 48, and 60 hr; and blood meal, 24, 30, 48, 60, and 72 hr.There is no significant difference among the true metabolizable energy (TME) values for soybean meal (49%) for the extended collection periods. However, examination of the energy output (kcal/hr) data indicated that approximately 30 hr were required for complete passage of all undigested feed residues. The energy output (kcal/hr) and the TME data for the fish meal experiment are in agreement and indicate that 30 hr was the time required for complete passage. The TME data and the energy output (kcal/hr) data are also in agreement for the blood meal experiment and suggest that 48 hr were required for complete passage. In the feather meal experiment a collection period longer than 24 hr was required. A 48-hr collection period is suggested as a standard collection period for all ingredients force-fed using the “true metabolizable energy” system. Energy output (kcal/hr) is also proposed as an additional criteria for determining the time required for complete passage of an ingredient through the alimentary tract.The TME values for soybean meal (49%) for cecectomized roosters were significantly lower than the values for the intact roosters. When fish meal was force-fed, the TME values for the intact and cecectomized roosters were not significantly different.

Effect of Carrier on the True Metabolizable Energy of Corn Oil

The true metabolizable energy (TME) of corn oil was determined using both practical and purified carriers. When assayed with “high-fat” practical carriers (corn or mixed feed), the TME of corn oil averaged 9.21 kcal/g compared with a significantly (P≤.05) higher value of 9.66 kcal/g when assayed with “low-fat” carriers (soybean meal or ether-extracted feed). As the latter value exceeded the gross energy of fats, it was concluded that the addition of corn oil to the low fat carriers enhanced the absorption of these substances, and this was reflected in the TME of the corn oil by extrapolation.It was found that neither glucose nor corn starch alone was satisfactory as a carrier for determining the TME of corn oil. Combinations of glucose and corn starch had TME values equal to their gross energies, indicating virtually complete absorption. The TME of corn oil determined using these carriers was 8.90 kcal/g, which was not significantly different (P≤.05) than when high fat practical carriers were used. Glucose-corn starch carriers may find application in evaluating the interactions between supplemental fats and basal diets in energy determinations.

An Evaluation of the Nitrogen Correction in the True Metabolizable Energy Assay

This paper examined the effect of N-correction on the true metabolizable energy (TME) values of mixed diets and single ingredients using mature White Leghorn roosters. The N-corrected TME (TMEn) values were consistently higher than the corresponding TME values, the results being significant (P<.05) in about one-half of the samples tested. This indicated a net loss in body N in the birds during the experiments. The correlations between N input and N correction were highly (P<.01) significant. This, however, explained only 46 to 48% of the variation in the TMEn data as being due to differences in the amount of N input.In view of the present results and the abnormal condition (fasted birds) in the TME assay, it is doubtful that birds would retain enough N from a single feeding to revert to a positive body N equilibrium. Therefore, positive N retention in such an assay would be indicative of incomplete feed passage through the birds. This appears to be the only valid reason for applying N correction to TME values. However, the variations associated with N correction of TME data raise some doubt concerning the validity of this assay as compared with the conventional apparent metabolizable energy assay.

A Comparison of the True and Apparent Metabolizable Energy Measures Using Corn and Soybean Meal Samples

This study was designed to compare the results of the true metabolizable energy (TME) and the conventional apparent metabolizable energy (AME) assays in detecting differences in the metabolizable energy content of different samples of corn and soybean meal. The samples assayed were three pairs of high and low protein soybean meals (SBM) and six corn samples of varying bushel weight. Also included in the study were two additional corn samples of a single variety of which one was a normal crop (corn ND) and the other (corn D) was obtained from plants earlier afflicted with ‘eye spot’ fungal disease (Kabatiella zeae) so that the grain kernels did not fully mature. A somewhat larger difference was apparent in the metabolizable energy content of two of the three pairs of the high and low protein SBM using the AME assay as compared to using TME as a measure. Because of insufficient material the AME of two of the six corns that differed most in bushel weight could not be determined. The TME values for the six corns were very similar and so were the AME values for the four samples with sufficient assay material. In the case of the two corns of the same variety, corn ND showed an appreciably higher AME than corn D while the TMEs of these two samples were essentially the same. The multiplication factors for converting N-corrected AME to TME were greater for the low protein, high fiber SBM than for the high protein, low fiber samples, while the factors for corn samples were substantially smaller than those for either the high or low protein SBM. These results indicate that there may be no consistent relationship between AME and TME, although theoretically there should be a consistent relationship between these two energy measures regardless of the feedstuff assayed.

Influence of an Indigestible Material on Energy Excretion by Roosters and on True Metabolizable Energy of Corn

The influence of an indigestible and noncombustible material, silica gel (SG), on the excretion of energy by roosters and on the true metabolizable energy (TME) of corn was determined. Energy excretion by fasted roosters increased linearly with each increment of SG force-fed. The equation, energy excreted (kcal/24 hr) = 9.87 + (.47 × g SG) described this effect of SG. The data also showed that 24 hr was insufficient time for SG to completely clear the digestive tract, irrespective of amount force-fed. The TME of corn was 4.05 kcal/g dry matter when the grain was force-fed alone to roosters. When corn was force-fed in mixtures containing increasing proportions of SG, the TME of corn decreased with each increment of SG in the mixture. It was concluded that the extra energy excreted as a consequence of the presence of SG in mixtures with corn caused an underestimation of corn's TME. The regression coefficient relating energy excretion to amount of SG force-fed in the previous trial was used to correct energy excretion by roosters fed corn-SG mixtures, and corrected TME's for corn were calculated. The average corrected TME of corn was 3.97 kcal/g dry matter. These data illustrated that an indigestible material passing through the gastrointestinal tract of the chicken changed the amount of fecal metabolic energy excreted and, consequently, influenced the TME value of companion feedstuffs when the conventional TME assay procedure was used.

An Evaluation of the True Metabolizable Energy Assay for Monitoring the Apparent Metabolizable Energy Values of Poultry Diets

Samples of 35 diets were obtained from five different regions of Canada. The true metabolizable energy (TME) of these diets was measured with mature White Leghorn cockerels. The N-corrected apparent metabolizable energy (MEn) values, calculated from average analysis figures, were supplied by the feed manufacturers. The relationship between TME and MEn was examined in two ways. First, the MEn values were multiplied by 1.097, the factor to convert MEn to TME derived by Sibbald (1977), and the results were compared with the corresponding determined TME values. The percent difference between the estimated and determined TME values was for Alberta from −7.1 to 3.1; for Manitoba from −9.8 to 5.4; for the Maritimes from −.3 to 10.8; for Ontario from −3.9 to 14.7, and for Saskatchewan from −4.2 to 5.7. Second, the ratio of determined TME:MEn for the various diets was calculated. The ratios varied considerably both within a region and between regions, ranging for Alberta from 1.063 to 1.176; for Manitoba from 1.041 to 1.204; for the Maritimes from .990 to 1.102; for Ontario from .957 to 1.141, and for Saskatchewan from 1.036 to 1.144. These data suggest that the TME assay could not be used to accurately monitor the MEn content of diets in commercial practice. However, this may have been due to imprecision in the TME data or in the MEn values or both.

True Metabolizable Energy Values of a Number of Feedingstuffs and Complete Diets as Determined in Two Laboratories

True metabolizable energy (TME) values were measured on six samples of soybean meal (SBM), two samples of corn, and five laying hen rations mixed at two different times. The determinations were carried out in two different laboratories, the University of Guelph (UG) and Canada Packers (CP) Research Centre, with a view to checking interlaboratory agreement. The TME values of four out of the six SBM samples agreed very well between the two laboratories. For the two samples with results that did not agree well, the difference was as much as 8%. The TME values of the two corn samples determined at the UG laboratory were about 6 to 9% higher than those obtained at the CP Centre depending on whether these were fed alone or mixed with a basal diet. In the case of the layer rations mixed at two different times, reasonably good interlaboratory agreement of the TME results occurred for only three of the five rations at each of the two mixings. The results of the remaining two rations varied by about 7 to 9% between laboratories. These results indicate the need to improve the reproducibility of TME values between laboratories before the method can have practical application. A number of factors possibly contributing to the significant interlaboratory differences noted are duscussed.

True Metabolizable Energy Values of Corn and Different Varieties of Wheat and Barley Using Normal and Dwarf Single Comb White Leghorn Roosters

An experiment with four trials was conducted to measure the true metabolizable energy value of corn and different varieties of wheat and barley using normal and dwarf Single Comb White Leghorn (SCWL) roosters.Maxigene, Purple, Red, and Yamhill wheats and corn were assayed for TME using normal sized and dwarf roosters in Trials 1 and 2, respectively. Hannchen, No. 2 Western, Lady Godiva, and Hiproly barleys were assayed using normal sized and dwarf SCWL roosters in Trials 3 and 4, respectively. The pooled results indicated that normal sized roosters gave (P<.01) significantly higher TME values than dwarf roosters. There was no significant difference in TME found between wheat and barley cultivars, although both types of grain were significantly (P<.01) lower in TME than the value found for corn. Average dry matter TME values for corn, wheat, and barley were 4.17, 3.70, and 3.54, respectively. A bird X grain interaction was found to be significant (P<.05).

Additivity of True Metabolizable Energy Values as Measured with Roosters, Broiler Chicks, and Poults

True metabolizable energy (TME) values were determined for five feed ingredients (yellow corn, dehulled soybean meal, corn gluten meal, menhaden fish meal, and poultry byproduct meal), and three combinations of these ingredients, using Single Comb White Leghorn roosters, 6-week-old broiler males (Cobb), and 6-week-old male turkey poults (Large White).There was generally good agreement in the TME values between roosters, broilers, and poults although the values for broilers tended to be slightly lower than for roosters or poults. Values for the ingredient combinations as assayed with the three classes of birds showed differences of 3% or less between “predicted” and “determined” in seven of nine comparisons, indicating a satisfactory degree of additivity of TME values for these ingredients.

The Effects of Fractions of Yellow Corn on the True Metabolizable Energy Value of Beef Tallow

An experiment was made to study the effect of diet composition on the utilization of beef tallow by adult cockerels. The diets were based on wheat and soybean meal with portions of the wheat being replaced by either yellow corn, degermed corn, corn germ, extracted germ, crude corn oil, soapstock, or refined corn oil. The birds were starved for 24 hr and then force fed one of 8 basal diets (30 g) supplemented with 0, 1.5, 3.0, or 4.5 g of beef tallow. Excreta voided during the subsequent 24 hr were collected. The true metabolizable energy values (TME) of the tallow were measured.The TME value of tallow decreased with the level of input (P<.01). A corn based diet permitted greater TME values for tallow than did a wheat based diet at the lowest level of tallow inclusion. However, when corn products (degermed corn, germ, extracted germ, crude oil, soapstock, refined oil) were substituted in the wheat basal at levels similar to those in the corn basal, it appeared that all fractions except soapstock had some ability to enhance tallow utilization. Comparisons of TME values with lipid composition data failed to identify the factor(s) which increases tallow utilization.

Comparison of Metabolizable Energy Methods on Identical Ingredient Samples

Individual samples of corn, dehydrated alfalfa meal, and menhaden fish meal were assayed for nitrogen-corrected metabolizable energy (MEn) and for true metabolizable energy (TME) on identical samples. The MEn values were 3.51, 1.43, and 3.18 kcal/g dry matter, respectively. The TME values were 4.08, 1.60, and 3.66 kcal/g dry matter, respectively. These resulted in the following TME:MEn ratios: 1.16, 1.12, and 1.15, respectively.

Variability in Metabolic Plus Endogenous Energy Losses of Adult Cockerels and in the True Metabolizable Energy Values and Rates of Passage of Dehydrated Alfalfa

An experiment with four groups of 12 adult cockerels allowed true metabolizable energy (TME) to be estimated in several ways. The birds were alternately fed one of two samples of dehydrated alfalfa meal or starved to serve as a negative control for the measurement of metabolic and endogenous energy loss (FEm + UEe). Each bird was fed twice and served as a control twice. The correction for FEm + UEe, therefore, could be estimated from the same bird, at a different period, or from a different bird at the same period.The FEm + UEe was largely characteristic of the bird. The correlation of the first observation with the second observation for each bird was .744 (44 DF). Variation in body weight did little to explain variation in FEm + UEe (r = .069, 90 DF).The most precise TME estimates were obtained by using each bird as its own negative control. A group mean value for FEm + UEe was somewhat inferior but the decrease in precision may be offset by reduced time and cost. The TME values provided additional evidence that the FEm + UEe output is characteristic of the bird.Although some birds consistently voided alfalfa residues more slowly than other birds, the pattern was not sufficiently consistent between birds to be significant.

Predicting True Metabolizable Energy, Gross Energy, Carbohydrate, and Proximate Analysis Values by Assuming Additivity

Seven feedingstuffs and 42 mixtures thereof were assayed under routine quality control conditions for true metabolizable energy (TME), gross energy, proximate constituents, and starch plus sugars expressed as glucose. Comparisons were made between the observed analytical values of the mixtures and the values predicted from the data describing their constituent parts by assuming additivity.The largest differences between observed and predicted values were associated with a small number of mixtures and may have resulted from errors in mixing, changes in moisture content, or analytical variation. The differences between observed and predicted TME values were similar to the differences in the other analytical values; the average standard error of prediction was about 2.5% of the observed TME value.

The Effects of Dietary Cellulose and Sand on the Combined Metabolic Plus Endogenous Energy and Amino Acid Outputs of Adult Cockerels

Two experiments were made with adult, Leghorn cockerels to measure the effects of inert materials on metabolic plus endogenous (M+E) excretions. In the first experiment birds starved for 24 hr were force-fed 25 g of either a laying hen diet (OHR) or corn supplemented with 0, 1, 2, 3, or 4 g of cellulose. Excreta voided were collected quantitatively during the two 24 hr periods postfeeding. A group of 4 birds was maintained unfed. Diets and excreta were assayed for amino acids (AA) and gross energy (GE). Supplemental cellulose had no effects on AA excretion nor on the availabilities of the AA within the OHR and corn. All AA, in the form of feed residues, were excreted within 24 hr of feeding. During the period 24 to 48 hr postfeeding the OHR fed birds excreted more AA than did the corn fed birds, probably because they were less depleted in protein. The AA excretions of the unfed birds decreased with the duration of starvation. The true available AA values for the diets were calculated using a series of three corrections for M+E AA outputs. The true metabolizable energy (TME) values of the OHR and corn were unchanged by the cellulose which indicates that the cellulose contained no available energy and had no effect on the availability of the energy within the OHR and corn. It also demonstrated that the cellulose did not change the M+E energy excretion.The second experiment was a 4 × 4 factorial with four diets: nil, corn, wheat, oats (25 g/bird), and four levels of sand: 0, 1, 2, 3 g/bird. The birds were starved for 24 hr prior to feeding and excreta were collected quantitatively during the two 24 hr periods postfeeding. Feeding sand to the birds had no effect on their GE outputs but it was noted that little sand was voided within 48 hr postfeeding. The TME values were determined for the grains. A number of significant differences were observed but there was no evidence that the sand altered the TME values. It was therefore concluded that the sand had no effect on the M+E energy excretion of the assay birds.It is concluded that supplemental cellulose had no effect on the AA excretions of adult Leghorn cockerels. Neither cellulose nor sand, in the levels fed, altered M+E energy excretion. Neither diluent appeared to alter the utilization of the materials with which they were fed.