Conversion Of Digestible Energy Research Articles

Effects of corn processing and cattle size on total tract digestion and energy and nitrogen balance.

This study used 18 calves (295 ± 29 kg) and 18 yearlings (521 ± 29 kg) fed whole, cracked, or steam-flaked corn (SFC) to evaluate nutrient digestion and energy balance across different types of processed corn and sizes of cattle. Cattle were fed a diet comprised of 75% corn (dry matter [DM]-basis) from whole, cracked, or SFC to 2.5-times maintenance energy requirements. Subsequently, cattle were placed in individual stanchions, and urine and feces were collected together with measures of gas production via indirect calorimetry. Data were analyzed using the MIXED procedure of SAS. There was no interaction between corn processing and cattle size (P ≥ 0.40). Time spent ruminating (min/d) and rumination rate (min/kg DM intake [DMI]) were not affected by corn processing or cattle size. The eating rate (min/kg DMI) was faster (P < 0.01) for yearlings compared with calves. Total tract starch digestion was greatest (P = 0.01) for cattle fed SFC (97.5%), intermediate in cattle fed cracked (92.4%), and least in cattle fed whole corn (89.5%). Dietary digestible energy and metabolizable energy (Mcal/kg DMI) were greater (P ≤ 0.05) for cattle fed SFC compared with cracked or whole. A greater proportion of digestible energy was lost to heat production (P = 0.01) in cattle fed whole corn compared with cracked and tended to be greater (P = 0.08) in cattle fed SFC than cracked. Conversion of digestible energy to metabolizable energy in this study was more closely related to a dynamic model used to estimate metabolizable energy of feeds to dairy cows than to a linear model used to predict metabolizable energy of feeds to beef cattle. If library estimates of net energy for maintenance are correct, then retained energy (Mcal/d) should have been similar between each type of processed corn; however, retained energy was greater (P < 0.01) for cattle fed cracked compared with whole corn and tended to be greater (P = 0.06) compared with SFC. Yet, observed amounts of net energy based on measures of retained energy were not different (P ≥ 0.60) between cracked and SFC. Nitrogen balance was not affected (P ≥ 0.30) by corn processing or cattle size, although cattle fed cracked had numerically greater (P ≤ 035) N retention. These data indicate that physical processing of corn provides greater net energy to cattle in comparison to whole corn.

The effects of the forage-to-concentrate ratio on the conversion of digestible energy to metabolizable energy in growing beef steers.

Metabolizable energy (ME) is calculated from digestible energy (DE) using a constant conversion factor of 0.82. Methane and urine energy losses vary across diets and dry matter intake (DMI), suggesting that a static conversion factor fails to describe the biology. To quantify the effects of the forage-to-concentrate ratio (F:C) on the efficiency of conversion of DE to ME, 10 Angus steers were used in a 5 × 5 replicated Latin square. Dry-rolled corn was included in experimental diets at 0%, 22.5%, 45.0%, 67.5%, and 83.8% on a dry matter (DM) basis, resulting in a high F:C (HF:C), intermediate F:C (IF:C), equal F:C (EF:C), low F:C (LF:C), and a very low F:C (VLF:C), respectively. Each experimental period consisted of a 23-d diet adaption followed by 5 d of total fecal and urine collections and a 24-h gas exchange collection. Contrasts were used to test the linear and quadratic effects of the F:C. There was a tendency (P = 0.06) for DMI to increase linearly as F:C decreased. As a result, gross energy intake (GEI) increased linearly (P = 0.04) as F:C decreased. Fecal energy loss expressed as Mcal/d (P = 0.02) or as a proportion of GEI (P < 0.01) decreased as F:C decreased, such that DE (Mcal/d and Mcal/kg) increased linearly (P < 0.01) as F:C decreased. As a proportion of GEI, urine energy decreased linearly (P = 0.03) as F:C decreased. Methane energy loss as a proportion of GEI responded quadratically (P < 0.01), increasing from HF:C to IF:C then decreasing thereafter. The efficiency of DE to ME conversion increased quadratically (P < 0.01) as F:C decreased, ranging from 0.86 to 0.92. Heat production (Mcal) increased linearly (P < 0.04) as F:C decreased but was not different as a proportion of GEI (P ≥ 0.22). As a proportion of GEI, retained energy responded quadratically (P = 0.03), decreasing from HF:C to IF:C and increasing thereafter. DM, organic matter, and neutral detergent fiber digestibility increased linearly (P < 0.01) and starch digestibility decreased linearly (P < 0.01) as the F:C decreased. Total N retained tended to increase linearly as the proportion of concentrate increased in the diet (P = 0.09). In conclusion, the efficiency of conversion of DE to ME increased with decreasing F:C due to decreasing methane and urine energy loss. The relationship between DE and ME is not static, especially when differing F:C.

Relationships between digestible energy and metabolizable energy in current feedlot diets.

It is commonplace that metabolizable energy (ME) is calculated from digestible energy (DE) as DE × 0.82. However, recent published literature suggests that the relationship between DE and ME is variable depending on the type of diet used, and is typically > 0.90 when high-concentrate diets are fed. Literature means were compiled from 23 respiration calorimetry studies where total fecal and urine collections were conducted and gaseous energy was measured. The relationship between experimentally observed and predicted ME (DE × 0.82) was evaluated using these previously reported treatment means. Additionally, a previously published linear regression equation for predicting ME from DE was also evaluated using a residual analysis. Published (Hales, K. E., A. P. Foote, T. M. Brown-Brandl, and H. C. Freetly. 2017. The effects of feeding increasing concentrations of corn oil on energy metabolism and nutrient balance in finishing beef steers. J. Anim. Sci. 95:939-948. doi:10.2527/jas.2016.0902 and Hemphill, C. N., T. A. Wickersham, J. E. Sawyer, T. M. Brown-Brandl, H. C. Freetly, and K. E. Hales. 2018. Effects of feeding monensin to bred heifers fed in a drylot on nutrient and energy balance. J. Anim. Sci. 96:1171-1180. doi:10.1093/jas/skx030) and unpublished data (K. E. Hales, unpublished data) were used to develop a new equation for estimating ME from DE (megacalories/kilogram [Mcal/kg] of DM; ME = -0.057 ± 0.022 DE2 + 1.3764 ± 0.1197 DE - 0.9483 ± 0.1605; r 2 = 0.9671, root mean square error = 0.12; P < 0.01 for intercept, P < 0.01 for linear term, and P < 0.01 for quadratic term). To establish a maximum biological threshold for the conversion of DE to ME, individual animal data were used (n = 234) to regress the ME:DE on DE concentration (1.53 to 3.79 Mcal DE/kg). When using experimentally derived data and solving for the first derivative, the maximum biological threshold for the conversion of DE to ME was 3.65 Mcal DE/kg. Additionally, the quadratic regression (equation 1) was used to predict ME from a wide range of DE (1.8 to 4.6 Mcal/kg). The ME:DE ratio was then calculated by dividing predicted ME by DE. The maximum biological threshold for the conversion of DE to ME was estimated by solving for the first derivative and was 3.96 Mcal DE/kg. In conclusion, this review suggests that the relationship between DE and ME is not static, especially in high-concentrate diets. The equation presented here is an alternative that can be used for the calculation of ME from DE in current feedlot diets, but it is not recommended for use in high-forage diets. The maximization of ME in current diets, maximum biological threshold, occurs between 3.65 and 3.96 Mcal DE/kg in the diet, which based on these data is approximately 3.43 to 3.65 Mcal/kg of ME consumption.

LiGAPS-Beef, a mechanistic model to explore potential and feed-limited beef production 2: sensitivity analysis and evaluation of sub-models

The model LiGAPS-Beef (Livestock simulator for Generic analysis of Animal Production Systems – Beef cattle) has been developed to assess potential and feed-limited growth and production of beef cattle in different areas of the world and to identify the processes responsible for the yield gap. Sensitivity analysis and evaluation of model results with experimental data are important steps after model development. The first aim of this paper, therefore, is to identify which parameters affect the output of LiGAPS-Beef most by conducting sensitivity analyses. The second aim is to evaluate the accuracy of the thermoregulation sub-model and the feed intake and digestion sub-model with experimental data. Sensitivity analysis was conducted using a one-at-a-time approach. The upper critical temperature (UCT) simulated with the thermoregulation sub-model was most affected by the body core temperature and parameters affecting latent heat release from the skin. The lower critical temperature (LCT) and UCT were considerably affected by weather variables, especially ambient temperature and wind speed. Sensitivity analysis for the feed intake and digestion sub-model showed that the digested protein per kg feed intake was affected to a larger extent than the metabolisable energy (ME) content. Sensitivity analysis for LiGAPS-Beef was conducted for ¾ Brahman×¼ Shorthorn cattle in Australia and Hereford cattle in Uruguay. Body core temperature, conversion of digestible energy to ME, net energy requirements for maintenance, and several parameters associated with heat release affected feed efficiency at the herd level most. Sensitivity analyses have contributed, therefore, to insight which parameters are to be investigated in more detail when applying LiGAPS-Beef. Model evaluation was conducted by comparing model simulations with independent data from experiments. Measured heat production in experiments corresponded fairly well to the heat production simulated with the thermoregulation sub-model. Measured ME contents from two data sets corresponded well to the ME contents simulated with the feed intake and digestion sub-model. The relative mean absolute errors were 9.3% and 6.4% of the measured ME contents for the two data sets. In conclusion, model evaluation indicates the thermoregulation sub-model can deal with a wide range of weather conditions, and the feed intake and digestion sub-model with a variety of feeds, which corresponds to the aim of LiGAPS-Beef to simulate cattle in different beef production systems across the world.

Eficiência de utilização da energia alimentar para a produção de bezerros em vacas Nelore e mestiças

Objetivou-se avaliar a eficiência de conversão da matéria seca (MS) e da energia metabolizável (EM) da dieta em ganho de peso e em peso de bezerro desmamado por vaca. Utilizaram-se 13 vacas Nelore, 13 mestiças F1 Simental × Nelore (SN) e 13 F1 Limousin × Nelore (LN) com 5 a 9 anos de idade e suas respectivas crias. Entre 15 e 210 dias pós-parto, as vacas foram mantidas em baias individuais, juntamente com os bezerros. Utilizaram-se rações contendo, na MS, 30% de concentrado e 70% das silagens de milho e sorgo na primeira e segunda metades do período experimental, respectivamente. O conteúdo de energia metabolizável das dietas foi obtido utilizando-se o fator 0,82 na conversão da energia digestível, determinada experimentalmente, em energia metabolizável. A produção de leite foi determinada mensalmente utilizando-se o método da diferença de peso dos bezerros. A eficiência foi avaliada considerando as relações: kg de bezerro desmamado e kg de ganho de peso de bezerro por kg de MS; ou por Mcal de EM ingeridos pela vaca; ou pelo par vaca/bezerro no período de lactação: ou foram estimadas para todo o ano. Foi ainda considerada a relação peso do bezerro/peso da vaca (PB/PV) à desmama. As vacas mestiças apresentaram maior eficiência de conversão da MS e da energia alimentar em peso de bezerro desmamado e em ganho de peso de bezerro. Apresentaram ainda as mais elevadas relações PB/PV à desmama. Os dois grupos de mestiças não diferiram quanto à eficiência. A utilização de matrizes obtidas por cruzamento entre bovinos de raças européias e bovinos Nelore possibilita elevar a eficiência do sistema na fase de cria.

Effects of Fatty Acid Supplements on Milk Yield and Energy Balance of Lactating Dairy Cows

Saturated and unsaturated fatty acid supplements (FS) were evaluated for effects on yield of milk and milk components, concentration of milk components including milk fatty acid profile, and energy balance. Eight ruminally and duodenally cannulated cows and 8 noncannulated cows were used in a replicated 4×4 Latin square design experiment with 21-d periods. Treatments were control and a linear substitution of 2.5% fatty acids from saturated FS (SAT; prilled, hydrogenated free fatty acids) for partially unsaturated FS (UNS; calcium soaps of long-chain fatty acids). The SAT treatment did not change milk fat concentration, but UNS linearly decreased milk fat in cannulated cows and tended to decrease milk fat in noncannulated cows compared with control. Milk fat depression with UNS corresponded to increased concentrations of trans-10, cis-12 conjugated linoleic acid and trans C18:1 fatty acids in milk. Milk fat profile was similar for SAT and control, but UNS decreased concentration of short- and medium-chain FA. Digestible energy intake tended to decrease linearly with increasing unsaturated FS in cannulated and noncannulated cows. Increasing unsaturated FS linearly increased empty body weight and net energy gain in cannulated cows, whereas increasing saturated FS linearly increased plasma insulin. Efficiency of conversion of digestible energy to milk tended to decrease linearly with increasing unsaturated FS for cannulated cows only. Addition of SAT provided little benefit to production and energy balance, whereas UNS decreased energy intake and milk energy yield.

Determination of digestible energy values and fermentabilities of dietary fibre supplements: a European interlaboratory study in vivo

The performance of methods to determine energy conversion factors for dietary fibre (DF) supplements and fermentability (D) values of their non-starch polysaccharides (NSP) was investigated. Heats of combustion, digestible energy (DE) and D values were determined on five DF supplements in five European laboratories on five separate occasions. In each instance the DF supplements were fed to juvenile male Wistar rats at two doses, 50 and 100 g/kg basal diet, for 3 weeks with food and faeces collected in the 3rd week. Among-laboratory variations in heats of combustion (delta Hc) were < 2%. DE values (kJ/g dry weight) at the upper and lower doses respectively were: 10.4 and 9.9 for a high-methoxyl apple pectin, 9.5 and 9.4 for a sugar-beet DF supplement, 12.2 and 12.7 for soyabean DF supplement, 3.8 and 4.0 for maize bran, and 0.3 and 0.3 for Solka-floc cellulose. Variations among laboratories, among occasions and among animals were < 1, < 2 and < 2.5 kJ/g respectively. The among-occasion: among-laboratory variance ratio for DE was 0.5, suggesting the method performed equally well in all laboratories. There was no evidence of learning of fatigue or fatigue in the performance of the method. D values were also independent of dose and at the high and lower doses were: pectin 0.92 and 0.95, sugar-beet NSP 0.68 and 0.68, soyabean NSP 0.86 and 0.88, maize bran 0.17 and 0.18, cellulose 0.07 and 0.06. Among-laboratory variance tended to increase with decreasing fermentability and ranged from 0.03 to 0.18. The DE and D data were not significantly different from a previously proposed relationship DE = 0.7 x delta Hc x D, where delta Hc is the heat of combustion of the supplement. We conclude that while the among-laboratory variation in the D of difficult-to-ferment NSP is too large for the reliable prediction of energy value the method for the direction determination of DE is both reproducible and repeatable, that DE is independent of dosage of DF supplement up to 100 g/kg diet, and that it is safe to discriminate between energy values with a precision of 3 kJ/g. The conversion of both DE and D to net metabolizable energy for the purpose of food labelling, tables and databases is described.

A comparison of offering meal from a self-feed hopper having built-in watering with some conventional systems of offering meal and pellets to finishing pigs

In two experiments, involving 624 and 480 pigs, a system of meal-feeding from a novel self-feed hopper with nipple drinkers positioned within the trough was compared with meal or pellets given ad libitum through conventional self-feed hoppers, or a high-oil meal (50 g soya oil kg −1 meal) offered ad libitum through conventional hoppers, or a restricted allowance of wet meal presented in troughs. In Experiment 1, an additional treatment comprised a medium-oil meal which had been treated with soya oil at 25 g kg −1 meal and which was given ad libitum through conventional hoppers, while in Experiment 2 a restricted allowance of pellets was given through conventional hoppers. Offering meal through the novel hoppers, as compared with conventional hoppers, gave the highest rates of live-weight gain, and improved the apparent conversion of digestible energy to carcass gain by 2.5%. The comparable improvement in efficiency with a restricted allowance of meal given in wet form in a trough was 5.4%. Treating the meal with oil also improved the efficiency of conversion of digestible energy to carcass gain in comparison with untreated meal, and the improvement was greater than was obtained with meal given through the novel hopper. Pelleted meal gave the most efficient conversion of DE to carcass gain in both experiments.

A comparison of wheat- or barley-based diets given ad libitum as meal or pellets to finishing pigs

A total of 480 crossbred pigs, penned in groups of 4 boars plus 4 gilts, were fed ad libitum from hopper feeders on cereal and soya-bean meal diets in either pellet or dry meal forms from 36 to 88 kg live weight. The sole cereal was either wheat or barley milled through the same equipment. Pigs on the wheat diets grew faster ( P < 0.01) than those on the barley diets (764 v. 737 g day −1), but there was not difference between cereals in the conversion of digestible energy to carcase weight. The latter variable was 12% better ( P < 0.001) with pellets than with meal, in spite of careful management of the feed hoppers.

Digestion and metabolism of high-tanninEucalyptus foliage by the brushtail possum (Trichosurus vulpecula) (Marsupialia: Phalangeridae)

The digestion and metabolism of Eucalyptus melliodora foliage was studied in captive brushtail possums (Trichosurus vulpecula). The foliage was low in nitrogen and silica but high in lignified fibre and phenolics compared with diets consumed by most other herbivores. The high lignin content was suggested as the main cause of the low digestibility of E. melliodora cell walls (24%); microscopic observations of plant fragments in the caecum and faeces revealed few bacteria attached to lignified tissues. The conversion of digestible energy (0.34 MJ X kg-0.75 X d-1) to metabolizable energy (0.26 MJ X kg-0.75 X d-1) was low compared to most other herbivores, probably because of excretion of metabolites of leaf essential oils and phenolics in the urine. When the inhibitory effect of leaf tannins on fibre digestion was blocked by supplementing the animals with polyethylene glycol (PEG), intake of dry matter, metabolizable energy and digestible fibre increased. These effects were attributed to the reversal by PEG of tannin-microbial enzyme complexes. It was concluded that the gut-filling effect of a bulk of indigestible fibre is a major reason why the brushtail possum does not feed exclusively on Eucalyptus foliage in the wild.

Growth of body components in young weaned pigs

SummaryFour experiments with 133 piglets of between 21 and 55 days of age were used to examine, by slaughter and chemical analysis, the composition of the body of young pigs. Following removal from the sow, the lipid content of the empty body decreased from about 15 to 7·6%, and in the subsequent 4 weeks had recovered only slightly to between 7·7 and 10·9%; with the exception of pigs with a particularly high intake of energy whose 42-day lipid content had increased to 13·2%. Where Y3 was the lipid gain, X1 the digestible energy intake (MJ) and X2 the ratio of digestible energy to digestible crude protein (g), over all experiments Y3 = 7·83X1 + 4945X2−1260. There was little change in the protein content of pigs consequent upon the effects of either removal from the sow, pig age, diet type or nutrient intake. Over all experiments and slaughter weights; P = 0·164W−100, where P was the protein content of the body (g) and W the empty body weight (g). The efficiencies of conversion of digestible energy to energy gain in body protein and lipid were 0·36 and 0·33 respectively, associated with a constant (daily maintenance) term of 0·462 MJ ME/kg LW0·75. The low value for lipid is as would be expected for animals catabolizing lipid within the experimental period.

Relationships between levels of feeding and certain blood metabolites in dairy cows in mid lactation

SUMMARYFollowing a 14-day uniformity period when they were stall-fed to appetite on a grass silage-grass ration, 18 cows in mid lactation were allocated to three treatments on which they received during the following 28 days either 100%, 75% or 50% of their previous voluntary feed intakes.Treatment effects were measured on milk yield and composition, live weight, liveweight change and fasted live-weight change. Twice during uniformity period, and on the 7th, 14th, 22nd and 26th days of the treatment period, samples of jugular blood were obtained from each cow immediately before and 3 h after the first meal of the day. These were analysed for percentage packed cell volume, blood acetone and β-hydroxybutyrate levels, plasma glucose, non-esterified fatty acid, and total fatty acid concentrations.Alternative methods of collecting blood samples, involving cannulation of the vein and venipuncture, were compared. Obtaining samples through cannulae took nearly three times as long as by venipuncture, but the method of sampling did not significantly affect the concentrations of individual blood metabolites. Blood samples collected before as contrasted with after feeding had significantly higher concentrations of nonesterified fatty acids and glucose, and lower concentrations of acetone and β-hydroxybutyrate.The feed requirements of the cows were assessed using data on live weights, fasted live-weight change and milk production by calculating the regression of estimated net attributable energy/kg LW0·75 on digestible energy intake/kg LW0·75, from data for the full 28-day period. The maintenance requirement was 124 kcal net energy/kg LW0·75, and the efficiency of conversion of digestible energy to milk and body-tissue loss or gain was 60%. These data were used with each animal's live weight, milk yield and liveweight change appropriate to each blood-sampling day to calculate individual feed requirements on every occasion. Ratios of actual feed consumed to estimated requirements were calculated subsequently to provide quantitative indices involving all cows and feeding levels. Regressions of these indices on individual blood metabolites were examined to assess the value of the latter as predictors of the relative nutritional status of the cows as defined in this way. Of the blood metabolites studied, only plasma NEFA were consistently significantly correlated with these indices, and relationships were specific to each feeding level. Thus although, at a common feeding level, plasma NEFA can be used to categorize lactating cows according to degree of nutritional stress, they will have limited values as predictors if applied indiscriminately to the wide range of feed availabilities and intakes which exist between herds at similar stages of lactation.The results have been discussed relative to previously published work, mainly with sheep and beef cattle.

Responses to variations in dietary energy intakes by growing pigs 3. Effect of level of intake of diets of differing protein and fat content on the performance of growing pigs

SUMMARYThree diets were given separately, each at four levels of digestible energy (DE) intake, to gilts, castrates and boars growing from 21 to 92 kg live weight. The energy levels were those suggested by the Agricultural Research Council, compared with a 5% increase or 10% or 20% decreases in daily allowance. One diet (ME 18) had 3·0 Meal DE/kg and 18·2% crude protein; the other two (HE 16 and HE 19) had 3·26 Meal DE/kg and 16·1% or 19·3% crude protein.They were given unchanged throughout the experiment. Responses to change in daily DE intake were not affected by sex or diet, except in shoulder fat thickness. Feed eaten per kg gain did not vary by more than 4% over the intake levels investigated, and no difference was significant. On average, each reduction in daily intake below the ARC+5% allowance led to an increase of 1·2 percentage units of carcass lean and a decrease of 1·3 percentage units of carcass fat.In comparison with HE 16, the higher protein diet HE 19 gave improved feed conversion efficiency and growth rate, particularly in gilts. It did not cause significant changes in carcass measurements. In comparison with ME 18, HE 19 gave more efficient conversion of DE to weight gain, and faster growth.Boars required less feed per kg gain and had faster growth rates and leaner carcasses than gilts, which were superior to castrates. There was a high incidence of unpleasant odour in fat from boars, but some was also detected in that from gilts and castrates.

Factors affecting voluntary feed intake in pigs. 3. The effect of a period of feed restriction, nutrient density of the diet and sex on intake, performance and carcass characteristics

1. Over the weight range 23–50 kg live weight, pigs were fed either ad libitum or to a restricted scale. From 59 to 91 kg live weight, eight pairs of barrows and eight pairs of gilts were fed on each of two diets varying in nutrient density. The effects of feed restriction, nutrient density of the diet and sex on voluntary feed intake, performance and carcass characteristics were studied.2. Pigs which had been restricted grew more slowly and contained less fat and more lean at 50 kg live weight.3. When restricted pigs were offered feed ad libitum from 59 to 91 kg live weight they ate more and had higher daily intakes of digestible energy than pigs liberally fed in early life.4. There was evidence of compensatory growth in pigs which had received the restricted diet, but there was no significant difference in feed utilization between restricted and ad libitum pigs. It was concluded that the compensatory growth was largely the result of increased appetite.5. Pigs finally fed on a low energy diet, in comparison with those on a high energy diet, ate more feed but less digestible energy indicating that appetite was physically limited. Efficiency of conversion of digestible energy to live weight was similar on both treatments. A higher proportion of acetic acid was produced in the caecum of pigs fed the low energy diet. Pigs receiving the low energy diet had lower killing-out percentages not entirely caused by differences in the weight of the gut and its contents. The carcasses of pigs on the low energy diet were leaner than those on the high energy diet.6. Barrows consumed more digestible energy per day than gilts, required more feed and digestible energy per unit live-weight gain, had lower killing-out percentages, shorter carcasses, larger backfat measurements and smaller eye-muscle areas as estimated by A × B measurements. Barrow carcasses contained less dissected lean and more fat than gilts' carcasses.7. The results are discussed in relation to other work and it is concluded that voluntary feed intake is influenced by the nutrient density of the diet and the level of energy requirement of the pig, which may be affected by previous nutritional history.