Dietary Metabolizable Energy Concentration Research Articles

Evaluation of dietary metabolizable energy concentrations on meat quality and lipid metabolism-related gene expression in yellow-feathered chickens.

This study evaluated the effects of different dietary metabolizable energy (ME) concentrations on the meat quality, carcass traits, volatile flavourand lipid metabolism-related gene expression levels in yellow-feathered chickens. In total, 600 Huxu female chickens aged 90 days were randomly assigned to six dietary treatments, each with 10 replicates of 10 birds. During the finisher phase, the birds were fed diets containing 2880 (low), 2940, 3000, 3060, 3120and 3180 (high) kcal ME/kg. The results showed that the average daily gain of chickens increased as the dietary ME concentration increased, while the feed to gain improved (p < 0.05), and the intramuscular fat content of breast muscle increased (p < 0.05). The energy concentration had no effect on the breast muscle pH (45 min and 24 h), colour parameter (L*)or percentage of drip loss (p > 0.05), but the shear force values decreased significantly (p < 0.05). The diameter and area of the breast muscle fiber decreased and the muscle fibre density increased as the dietary ME concentration increased (p < 0.05). The highest ME concentration (3180 kcal) increased the percentages of aldehydes (hexanal, heptanal, 2,4-nonadienal, octanal, nonanaland 2-decenal), alcohols (2-nonen-1-ol, trans-2-undecen-1-ol, 7-hexadecenal, 2-hexyl-1-decanoaland n-nonadecanol-1,3,7,11-trimethyl-1-dodecanol), alkanes (2,6-dimethyl-heptadecane)and carboxylic acids (9-hexadecenoic acid), but reduced the percentages of octadecanal, octadecane, heneicosaneand tetradecanal (p < 0.05). In addition, the mRNA gene expression levels of fatty acid-binding protein 3 and apolipoprotein B were significantly upregulated in the liver, whereas that of cholesteryl ester transfer protein was significantly downregulated. In conclusion, increasing the ME diet to 3180 kcal/kg significantly improved the quality and flavour of the meat from yellow-feathered broilers. our finding may help poultry producers to improve the taste of meat by regulating genes related to lipid metabolism, thereby achieving the flavour and taste characteristics preferred by consumers.

93 Predicting Metabolizable Energy from Digestible Energy for Growing and Finishing Beef Cattle and Relationships to Prediction of Methane

Abstract Reliable predictions of metabolizable energy (ME) from digestible energy (DE) are necessary to prescribe nutrient requirements of beef cattle accurately. Our objectives were to add new data to a previously published database and re-evaluate the relationship between DE and ME and to describe and evaluate new methane prediction equations derived from the DE:ME relationship. The previous database, which included 87 treatment means from 23 respiration calorimetry studies was updated to evaluate the efficiency of converting DE to ME by adding 47 treatment means from 11 additional studies. Diets were fed to growing-finishing cattle under individual feeding conditions. A citation-adjusted linear regression equation was developed where dietary ME concentration (Mcal/kg of dry matter [DM]) was the dependent variable and dietary DE concentration (Mcal/kg) was the independent variable: ME = 1.0001 × DE – 0.3926. The slope did not differ from unity; therefore, the intercept defines the value of ME predicted from DE. For practical use, we recommend ME = DE - 0.39. Based on the relationship between DE and ME, the citation-adjusted loss of methane was calculated and yielded a citation-adjusted value of 0.2433 Mcal/kg of DMI. Recognizing that methane production decreases per unit of intake energy as DMI increases above maintenance, we also examined the relationship between multiples of maintenance intake and daily energy lost as methane. This citation-adjusted relationship was: CH4, Mcal/kg = 0.3344 – 0.05639 × multiple of maintenance. Both the 0.2433 value and the result of the intake-adjusted equation can be multiplied by DMI to yield an estimate of methane production. Further research is needed to determine whether coefficients to predict methane from DMI could be developed for specific diet types, levels of DMI relative to body weight, or other variables that affect the emission of methane.

Predicting metabolizable energy from digestible energy for growing and finishing beef cattle and relationships to the prediction of methane.

Reliable predictions of metabolizable energy (ME) from digestible energy (DE) are necessary to prescribe nutrient requirements of beef cattle accurately. A previously developed database that included 87 treatment means from 23 respiration calorimetry studies has been updated to evaluate the efficiency of converting DE to ME by adding 47 treatment means from 11 additional studies. Diets were fed to growing-finishing cattle under individual feeding conditions. A citation-adjusted linear regression equation was developed where dietary ME concentration (Mcal/kg of dry matter [DM]) was the dependent variable and dietary DE concentration (Mcal/kg) was the independent variable: ME = 1.0001 × DE – 0.3926; r2 = 0.99, root mean square prediction error [RMSPE] = 0.04, and P < 0.01 for the intercept and slope. The slope did not differ from unity (95% CI = 0.936 to 1.065); therefore, the intercept (95% CI = −0.567 to −0.218) defines the value of ME predicted from DE. For practical use, we recommend ME = DE – 0.39. Based on the relationship between DE and ME, we calculated the citation-adjusted loss of methane, which yielded a value of 0.2433 Mcal/kg of dry matter intake (DMI; SE = 0.0134). This value was also adjusted for the effects of DMI above maintenance, yielding a citation-adjusted relationship: CH4, Mcal/kg = 0.3344 – 0.05639 × multiple of maintenance; r2 = 0.536, RMSPE = 0.0245, and P < 0.01 for the intercept and slope. Both the 0.2433 value and the result of the intake-adjusted equation can be multiplied by DMI to yield an estimate of methane production. These two approaches were evaluated using a second, independent database comprising 129 data points from 29 published studies. Four equations in the literature that used DMI or intake energy to predict methane production also were evaluated with the second database. The mean bias was substantially greater for the two new equations, but slope bias was substantially less than noted for the other DMI-based equations. Our results suggest that ME for growing and finishing cattle can be predicted from DE across a wide range of diets, cattle types, and intake levels by simply subtracting a constant from DE. Mean bias associated with our two new methane emission equations suggests that further research is needed to determine whether coefficients to predict methane from DMI could be developed for specific diet types, levels of DMI relative to body weight, or other variables that affect the emission of methane.

The development of a model to predict BW gain of growing cattle fed grass silage-based diets

The objective of this meta-analysis was to develop and validate empirical equations predicting BW gain (BWG) and carcass traits of growing cattle from intake and diet composition variables. The modelling was based on treatment mean data from feeding trials in growing cattle, in which the nutrient supply was manipulated by wide ranges of forage and concentrate factors. The final dataset comprised 527 diets in 116 studies. The diets were mainly based on grass silage or grass silage partly or completely replaced by whole-crop silages, hay or straw. The concentrate feeds consisted of cereal grains, fibrous by-products and protein supplements. Mixed model regression analysis with a random study effect was used to develop prediction equations for BWG and carcass traits. The best-fit models included linear and quadratic effects of metabolisable energy (ME) intake per metabolic BW (BW0.75), linear effects of BW0.75, and dietary concentrations of NDF, fat and feed metabolisable protein (MP) as significant variables. Although diet variables had significant effects on BWG, their contribution to improve the model predictions compared with ME intake models was small. Feed MP rather than total MP was included in the final model, since it is less correlated to dietary ME concentration than total MP. None of the quadratic terms of feed variables was significant (P>0.10) when included in the final models. Further, additional feed variables (e.g. silage fermentation products, forage digestibility) did not have significant effects on BWG. For carcass traits, increased ME intake (ME/BW0.75) improved both dressing proportion (P<0.01) and carcass conformation (P<0.001) and increased (P<0.001) carcass fat score. Increased dietary CP concentration had no significant (P>0.10) effect on dressing proportion or carcass conformation score, but it increased (P<0.01) carcass fat score. The current study demonstrated that ME intake per BW0.75 was clearly the most important variable explaining the BWG response in growing cattle. The effect of increased ME supply displayed diminishing responses that could be associated with increased energy concentration of BWG, reduced diet metabolisability (proportion of ME of gross energy) and/or decreased efficiency of ME utilisation for growth with increased intake. Negative effects of increased dietary NDF concentration on BWG were smaller compared to responses that energy evaluation systems predict for energy retention. The present results showed only marginal effects of protein supply on BWG in growing cattle.

The Performance of Japanese Quail (White Breasted Line) to Dietary Energy and Amino Acid Levels on Growth and Immuno-competence

The response of growing Japanese quails (White Breasted line-CARI UJJWAL, n=900, divided into 36 subgroups) to three dietary levels of essential amino acids (EAA) at three different metabolizable energy (ME) levels (3×3 factorial design) on growth and immunity was investigated. Nine diets including three levels of ME (2700, 2900 and 3100 kcal/kg) each at three levels of EAA (low, medium and high) were formulated. Each diet was offered to 4 replicated groups of 25 Japanese quails up to 5 weeks of age. The ratio of lysine to protein and the level of methionine and threonine to lysine, as specified by NRC (NRC, 1994), remained almost similar in all the diets. Body weight gain, feed intake and feed conversion ratio did not differ statistically due to the treatments i.e. interaction of ME and EAA levels. However, there was linear increase in body weight gain with increased EAA levels during 0-3 or 0-5 weeks of age. Feed intake increased linearly with the decreased ME (P<0.01) and increased EAA (P<0.01) in diets. Feed conversion ratio (FCR) improved (P<0.01) linearly with increase in dietary ME concentration from 0-3, 3-5 or 0-5 weeks of age. Protein efficiency (PE) improved (P<0.01) with decreased EAA levels and also with the increase in dietary ME level during 0-3, 3-5 and 0-5 weeks of growing age, whereas energy efficiency is influenced by EAA levels during 0-3 and 3-5 weeks of age (P<0.01). Maximum performance index during 0-5 weeks of age was observed in diet with 3100 kcal ME/Kg and 115% EAA. Nitrogen retention per unit energy intake was increased (P<0.01) with the increased EAA levels and decreased energy levels. Humoral (SRBC) and cellular (PHA-P) immune response did not differ due to ME, EAA or ME x EAA. Thus, it was concluded that the optimum level of dietary ME is 2700 kcal/kg with CP 25.83%, lysine 1.49%, methionine 0.58% and threonine 1.17% on dry matter basis during 0-5 weeks of age was optimum for gain. However for optimum feed conversion, the growing quails required diet with ME 3100 kcal/kg with CP 23.23%, lysine 1.30%, methionine 0.50% and threonine 1.02% for 0-5 weeks of age.

Influence of different concentrations of metabolisable energy at constant ratio to dietary protein, lysine, methionine, calcium and phosphorus on the performance of White Leghorn layers in the tropics

An experiment was conducted to study the effect of nutrient density on the performance (21–72 weeks of age) of White Leghorn layers reared in an open-sided poultry house in the tropics. Six diets with graded levels (9.62–11.72 MJ/kg) of metabolisable energy (ME) with an increment of 0.42 MJ were formulated. Concentrations of crude protein, lysine, methionine, calcium and non-phytate phosphorus were kept constant to ME in all diets (15.9, 0.73, 0.35, 3.19 and 0.31 g/MJ ME, respectively). At 21 weeks of age, a total of 5280 birds was distributed randomly in 4-bird colony cages and 22 such cages in a row constituted one replicate. Each diet was fed ad libitum to 10 replicates from 21 to 72 weeks of age and performance parameters were recorded at 28-day intervals (period, 1–13). Egg production (EP) increased (P &lt; 0.05) with increasing dietary ME and maximum response in EP was observed when dietary ME levels ranged between 10.93 and 11.69 MJ/kg during the majority of periods, while in periods 6, 7 and 8 (summer, 28−37°C), maximum EP was observed at higher ME levels in diet (11.64–11.69 MJ/kg diet). Feed intake (P &lt; 0.01) decreased, feed efficiency (P &lt; 0.01), egg mass (P &lt; 0.01) and weight gain (P &lt; 0.05) improved quadratically with increase in dietary ME concentration. Maximum feed efficiency was observed at 11.36 MJ ME/kg diet during 21–72 weeks of age. Egg shell defects were not influenced (P &gt; 0.05) by dietary nutrient density. Mortality reduced quadratically with increase in dietary ME concentration and mortality was minimum at 11.64 MJ ME/kg diet. Based on results from the experiment it was concluded that White Leghorn layers (21–72 weeks of age) require 11.36 MJ ME/kg diet for maximum egg production, feed efficiency and egg mass with better liveability. The calculated intake of metabolisable energy, crude protein, lysine, methionine, calcium and non-phytate phosphorus in layers fed 11.30 MJ ME/kg diet was 1.157 MJ, 18.42 g, 865 mg, 409 mg, 3.68 g and 358 mg per bird per day, respectively.

Mitigation of enteric methane emissions through improving efficiency of energy utilization and productivity in lactating dairy cows

The data set used in the present study was obtained from 20 energy metabolism studies involving 579 lactating dairy cows (511 Holstein-Friesian, 36 Norwegian Red, and 32 Jersey-Holstein crossbreds) varying in genetic merit, lactation number, stage of lactation, and live weight. These cows were offered diets based on grass silage (n=550) or fresh grass (n=29), and their energy intake and outputs, including methane energy (CH4-E), were measured in indirect open-circuit respiration calorimeter chambers. The objective was to use these data to evaluate relationships between CH4-E output and a range of factors in animal production and energetic efficiency in lactating dairy cows under normal feeding regimens. The CH4-E as a proportion of milk energy output (El), El adjusted to zero energy balance (El(0)), or intakes of gross energy (GE), digestible energy (DE), or metabolizable energy (ME) was significantly related to a wide range of variables associated with milk production (El and El(0)) and energy parameters (energy intake, metabolizability, partitioning, and utilization efficiencies). Three sets of linear relationships were developed with experimental effects removed. The CH4-E/GE intake (r2=0.50–0.62) and CH4-E/El (r2=0.41–0.68) were reduced with increasing feeding level, El/metabolic body weight (MBW; kg0.75), El(0)/MBW, GE intake/MBW, DE intake/MBW, and ME intake/MBW. Increasing dietary ME/DE decreased CH4-E/El (r2=0.46) and CH4-E/GE intake (r2=0.72). Dietary ME concentration and ME/GE were also negatively related to CH4-E/GE intake (r2=0.47). However, increasing heat production/ME intake increased CH4-E as a proportion of El (r2=0.41), El(0) (r2=0.67) and energy intake (GE, DE, and ME; r2=0.62 and 0.70). These proportional CH4-E variables were reduced with increasing ratios of El/ME intake and El(0)/ME intake and efficiency of ME use for lactation (r2=0.49–0.70). Fitting CH4-E/El or CH4-E/El(0) against these energetic efficiencies in quadratic rather than linear relationships significantly increased r2 values (0.49–0.67 vs. 0.59–0.87). In conclusion, CH4-E as a proportion of energy intake (GE, DE, and ME) and milk production (El and El(0)) can be reduced by increasing milk yield and energetic efficiency of milk production or by reducing energy expenditure for maintenance. The selection of dairy cows with high energy utilization efficiencies and milk productivity offers an effective approach to reducing enteric CH4 emission rates.

The prediction of digestible and metabolisable energy concentrations in grass-based diets of producing cattle using data tested with sheep trials at maintenance feeding level

In the UK metabolisable energy (ME) system (AFRC, 1993) it is recommended that dietary ME concentration is reduced by proportionately 0.018 per unit increase in feeding level (FL) above maintenance. This factor was reported by Van Es (1975) two decades ago. At this Institute a total of 33 silages have been offered to sheep as a sole diet at maintenance for measurements of energy intake and outputs in faeces and urine. These silages were also fed to cattle, together with concentrates, at production level for determination of energy metabolism data in calorimetric chambers. The objective of the present study was to use these data to evaluate the combined effects of animal species and level of feeding on ME and digestible energy (DE) concentrations in diets.

Energy and nitrogen balance of lactating dairy cows given mixtures of urea-treated whole-crop wheat and grass silage

AbstractEnergy and nitrogen balances were carried out with four multi-porous Holstein/Friesian cows offered four diets in a Latin-square experiment to evaluate urea-treated whole-crop wheat as a partial grass silage replacement for lactating dairy cows. Grass silage (GS) was produced from the primary growth of a perennial ryegrass sward. Spring wheat (cv. Axona) was harvested at 603 g dry matter (DM) per kg and preserved with 20 (WCW-20) or 40 (WCW-40)kg urea per t DM. The diets were 6 kg DM of a dairy concentrate daily with one of four forage treatments offered ad libitum. The forage treatments were GS alone, a 2:1 DM ratio of GS with WCW-40 (2:1 40), or a 1:2 DM ratio of GS with WCW-20 (1:2 20) or WCW-40 (1:2 40). Each period lasted 4 weeks with energy and nitrogen balances being carried out in respiration chambers over 6 days in the last week. Replacement of GS by diets containing WCW resulted in significant increases in DM intake (P &lt; 0·01). Changes in milk yield and composition were small and non-significant but yields of milk fat and protein were higher on WCW diets than on GS diets (P&lt; 0·05). With increasing proportions of WCW in the diet there were significant linear falls in apparent digestibility of DM (P &lt; 0·001), organic matter (F &lt; 0·001), neutral-detergent fibre (F &lt; 0·01), acid-detergent fibre (F &lt; 0·01), starch (F &lt; 0·001) and nitrogen (P &lt; 0·01). Gross energy intakes (P &lt; 0·01) and faecal (P &lt; 0·001), methane (P &lt; 0·05) and milk (P &lt; 0·05) energy outputs were higher with the WCW diets than with GS but urine energy and heat losses were unaffected. In consequence there were no significant differences among the diets in digestible or metabolizable energy (ME) intakes. However dietary ME concentrations (MJ ME per kg corrected DM) fell with increasing WCW inclusion from 11·54 on GS to a mean of 9·96 on the 1:2 diets (P &lt; 0·001). It was calculated that the ME concentration of the WCW was only 8·1 MJ/kg corrected DM at maintenance intake, considerably lower than values used conventionally. There were no significant diet effects on the partition of ME or on the partial efficiency of ME utilization for milk production (k1). The increasing inclusion of WCW increased N losses in urine (P &lt; 0·05) and faeces (F &lt; 0·01) with no net effect on N digested or retained though there was a small increase in milk N output (P &lt; 0·01). It is concluded that low digestibility is the major cause of the small milk response to the partial substitution of urea-treated WCW for grass silage with no evidence of a reduction in the efficiency of utilization of ME.

The influence of dietary fibre source and level on the development of the gastrointestinal tract, digestibility and energy metabolism in broiler chickens.

The present study was undertaken to provide detailed information about the effect of fibre source (pea fibre, wheat bran or oat bran) at inclusion levels of 0, 187 and 375 g/kg diet on the development of the digestive tract, nutrient digestibility and energy and protein metabolism in broiler chickens. Heat production was measured using open-air-circuit respiration chambers. Diets with increasing levels of pea fibre decreased the DM in droppings and increased excreta output (2.5-fold) relative to DM intake. Adaptation to increased dietary fibre levels included increases in the size of the digestive system, with pea fibre exerting a stronger impact than wheat bran or oat bran. The length of the intestine, and particularly the length and weight of the caecum, increased with the fibre level. The digestibility of all nutrients also decreased with increasing fibre level. The decrease in the digestibility in relation to NSP for the three fibre sources was bigger for oat bran (0.0020 per g dietary NSP) than for pea fibre and wheat bran (0.0014 and 0.0016 per g dietary NSP) indicating that the cell walls in oat bran (aleurone and subaleurone) had a significant negative effect on the digestibility of cellular nutrients, i.e. protein and fat. The degradation of the NSP constituents was far lower in chickens than found in other animal species such as pigs and rats, thus supporting the view that chickens do not ferment fibre polymers to a great extent. Excretion of organic acids (mainly lactic acid and acetic acid) accounted for up to 2% of metabolizable energy (ME) intake with the highest excretion for the high-fibre diets. H2 excretion was related to the amount of NSP degraded and indicated higher microbial fermentation with increasing fibre levels. The chickens' feed intake responded to a great extent to dietary ME concentration but expressed in terms of metabolic body size (W0.75) ME intake was depressed at the high fibre levels. Dietary NSP was able to explain between 86% (oat bran) and 96% (pea fibre) of the variation in ME concentration. The amount of energy available from fermentation of NSP appears to reach a maximum of 42 kJ/d independent of fibre source and level. Expressed in relation to ME intake the NSP fermentation contributed 3-4%. With increasing fibre intake the partitioning of retained energy between body protein and body fat changed in favour of protein.

The effect of late pregnancy on the diet selections made by ewes

To test the hypothesis that sheep select a diet that meets their physiological needs (imposed by late pregnancy), four foods were formulated of either a high metabolisable energy (ME) concentration (A, B 12 MJ/kg dry matter (DM)) or a low concentration (C, D 9 MJ/kg DM). The crude protein (CP) concentrations of A and C were high (279 and 191 g/kg DM) relative to B and D (105 and 95 g/kg DM); the ratios of metabolisable protein: ME were 12 g/MJ for foods A and C and 4 g/MJ for foods B and D. Twin bearing and non pregnant Greyface ewes of similar body condition were offered ad lib., A, B and C as single foods and paired choices (A with B) and (C with D). Replication was a minimum of four ewes for single foods and six for the choices. Food intakes by pregnant and non pregnant ewes were similar until parturition was imminent, when the intakes by the pregnant ewes declined rapidly. The majority of pregnant ewes carried twin foetuses to term without problems. When the ME concentration of the food choice was high (A/B) pregnant ewes selected a greater proportion (P < 0.05) of the food of high CP concentration than non pregnant ewes: pregnant 0.57 (se 0.074); non pregnant 0.28 (se 0.105). By contrast when ewes were offered a choice between foods of low ME concentration diet selection was unaffected by state: proportion of the higher CP food, C selected were: 0.70 (se 0.070) and 0.79 (se 0.069) for pregnant and non pregnant ewes respectively. These results show that when the dietary ME concentration of foods given as a choice is high, pregnant ewes select a diet that reflects their enhanced demand for protein in contrast with non pregnant contemporaries. However, when the ME of the foods is low priorities other than physiological state may motivate their diet selection. It is suggested that such a priority is the maintenance of a balanced rumen environment.

Chemical composition of carcass soft tissues of serially slaughtered Hereford × Friesian, Friesian and Charolais × Friesian steers finished on two diets differing in energy concentration

ABSTRACTThe chemical composition of the muscle and fatty carcass tissues of Hereford × Friesian (HE), Friesian (FR) and Charolais × Friesian (CH) steers finished on high (H) (12·6 MJ/kg dry matter) and medium (M) (10·4 MJ/kg dry matter) metabolizable energy (ME) concentration diets and slaughtered at low (L), normal (N) and heavy (W) carcass weights was determined in a 3 × 2 × 3 (no. = 9) factorial experiment. There were also pre-finishing slaughter groups of nine animals of each breed type. Target L, N and W carcass weights were 260, 300 and 340 kg, for HE and FR and 260, 320 and 380 kg, for CH, respectively.Main effect side soft tissue weights of the finished groups were 128, 125 and 134 (s.e.d. 1·3) kg for HE, FR and CH, 133 and 125 (s.e.d. 1·1) kg for H and M and 108, 129 and 150 (s.e.d. 1·3) kg for L, N and W, respectively. Soft tissue chemical composition was 540, 562 and 590 (s.e.d. 5·0) g/kg moisture, 162, 174 and 181 (s.e.d. 1·7) g/kg protein and 288, 254 and 220 (s.e.d. 6·6) g/kg lipid for HE, FR and CH and 558 and 570 (s.e.d. 4·1) g/kg moisture, 170 and 175 (s.e.d. 1·4) g/kg protein and 262 and 246 (s.e.d. 5·4) g/kg lipid for H and M, respectively. The allometric regression coefficients for moisture, protein and lipid weights on soft tissue weight were 0·65, 0·69 and 206, respectively. The coefficients for moisture and protein weights on muscle and fat weights were &lt; 1·0, whereas for lipid, they were &gt;1·0. The breed differences in soft tissue chemical composition paralleled differences in physical composition. Dietary ME concentration had little effect on the chemical composition of individual tissues. For the M diet, HE, FR and CH were calculated to have similar soft tissue lipid concentrations (250 g/kg) at side soft tissue weights of 113, 125 and 157 kg, respectively. Corresponding side muscle weights at similar muscle lipid concentration (70 g/kg) would be 77, 90 and 108 kg.

Energy and nitrogen intake, expenditure and retention at 20° in growing fowl given diets with a wide range of energy and protein contents

Heat production (HP) and the intake and retention of energy and nitrogen were measured at 20 degrees in growing female broiler fowl given diets with metabolizable energy (ME) contents ranging from 8 to 15 MJ/kg at each of two crude protein (nitrogen x 6.25; CP) contents (130 and 210 g/kg). ME intake was partially controlled by the birds, but increased by 30% over the range of dietary ME concentration. CP intake varied directly with dietary CP: ME ratio, indicating that control of energy intake took priority and that food intake did not increase in order to enhance amino acid intake on low-CP diets. Maintenance energy requirement and fasting HP were not affected by diet. Although the HP of fed birds was significantly affected by dietary energy source, there was no evidence for regulatory diet-induced thermogenesis as energy intake increased. Total energy retention doubled on the higher-energy diets as a result of increased intake and retention efficiency in the absence of any compensation by diet-induced thermogenesis. The proportion of energy retained as fat was negatively correlated with dietary CP: ME ratio. It was concluded that the growing female broiler fowl responded to large differences in energy intake and dietary CP concentration not by changes in rate of energy dissipation as heat but by changes in the quantity of energy retained and in the partition of retained energy between body protein and body fat.

Energy value of dry maize gluten feed in starter, growing or finishing steer diets

ABSTRACTThree experiments were conducted to determine the metabolizable energy (ME) concentration of dry maize gluten feed (DMGF) in starter (experiment 1), growing (experiment 2) or finishing (experiment 3) diets for steers. Seventy-two weanling Holstein-Friesian steer calves (initially 52 kg live weight); 32 Aberdeen Angus and 24 Shorthorn steer calves (initially 250 kg live weight) and 32 Aberdeen Angus, 24 Shorthorn and 68 crossbred steers (initially 367 kg live weight) were used in experiments 1, 2 and 3, respectively. In experiment 1, calves were given one of three total mixed rations in which energy and protein ingredients on a dry matter (DM) basis were (g/kg): (1) 590 ground maize grain (MG), 260 rolled oats (RO) and 150 soya-bean meal (SBM); (2) 210 DMGF, 400 MG, 260 RO and 130 SBM; or (3) 440 DMGF, 210 MG, 250 RO and 100 SBM. Daily live-weight gains (LWG) and food-to-gain (F/G) ratios were similar across dietary treatments (P &gt; 0·05). Calves given the diet containing 440 g DMGF per kg had higher DM intakes (DMI) than those given no DMGF (P &lt; 0·05). ME concentration of the diet without DMGF was greater than ME concentrations of diets containing DMGF (P &lt; 0·05). In experiment 2, calves were given one of four diets containing, on a DM basis (g/kg): (1) 800 maize silage (MS) and 200 MG; (2) 800 MS and 200 DMGF; (3) 500 MS and 500 DMGF; or (4) 200 MS and 800 DMGF. LWG and DMI of calves given 500 or 800 g DMGF per kg diets were higher than those of calves given 0 or 200 g DMGF per kg diets (P &lt; 0·05). F/G ratios tended to increase and dietary ME concentrations tended to decrease with increasing content of DMGF in diets. In experiment 3, steers were given one of four diets, which on a DM basis were (g/kg): (1) 850 MG and 150 MS; (2) 300 DMGF, 150 MS and 550 MG; (3) 500 DMGF and 500 MG; or (4) 750 DMGF and 250 MG. LWG was not altered when DMGF replaced MG only or MG and MS (diet 2 v. 1 or diets 3 and 4 v. 1, respectively (P &gt; 0·05)) in the diet. Steers given the 300 or 750 g DMGF per kg diets had higher DMI and lower F/G ratios than those fed diets without DMGF (P &lt; 0·05). ME concentration of the diet without DMGF was greater (P &lt; 0·05) than the ME concentration of 300 or 750 g DMGF per kg diets. ME concentration of DMGF, calculated by regression, was proportionately about 0·9 of the value of MG in all experiments and averaged 11·46 MJ/kg DM.

Effect of dietary amino acids and metabolisable energy on the performance of broilers kept at high temperatures

Increasing dietary metabolisable energy (ME) at particular amino acid: ME ratios significantly improved growth and food utilisation of broilers kept at moderate (18 to 26 degrees C) and high (25 to 35 degrees C) ambient temperatures during the finishing period from 22 d of age. The optimum amino acid: ME ratio varied with dietary ME concentration in the hot, but not in the moderate environment. Relatively greater increases in food intake and growth rate occurred in the hot environment when dietary ME was increased and the amino acid: ME ratio was reduced. The minimum rate of food intake did not coincide with the period of maximum temperature. Increasing the dietary protein at particular ME concentrations had little or no effect on the food intake and growth rate of birds kept at high temperatures. Supplementation with dietary fat had no beneficial effect on performance at high temperatures. The rectal temperatures of birds in the hot environment increased with age and, towards the end of the finishing period, when higher energy diets were fed.

The effect of slaughter weight upon the growth and carcass characteristics of rabbits fed diets of different dietary metabolizable energy concentrations

ABSTRACTEighteen male and 18 female weaned rabbits were randomly allocated to two diets formulated to give energy concentrations of 8 (LE) and 10 (HE) MJ metabolizable energy per kg dry matter and three target slaughter weights (1·5, 2·25 and 3·0 kg live weight) to give a 2 × 2 × 3 factorial design with three replicates. Voluntary food intake and live-weight gain were monitored and the carcasses chemically analysed. The metabolizable energy concentrations of the diets were determined by balance and found to be 9·87 and 6·84 MJ/kg dry matter for diets HE and LE respectively.Rabbits fed the LE diet consumed more dry matter (P &lt; 0·001) and metabolizable energy (P &lt; 0·01) in total, but grew more slowly than those fed the HE diet (P &lt; 0·001). A diet × slaughter weight interaction occurred (P &lt; 0·01); rabbits of the LE–3 kg treatment took longer to reach target weight as a result of a flattening of their growth curve.Rabbits fed the LE diet had lower killing-out proportions (P &lt; 0·05), heavier gut weights (P &lt; 0·05) and gut contents (P &lt; 0·05), but lighter livers than those fed the HE diet. Killing-out proportion progressively increased with increasing slaughter weight. External offal weight as a proportion of live weight tended to increase while internal offal weight as a proportion of live weight tended to decrease as slaughter weight increased. The carcasses of rabbits slaughtered at 3 kg had lower moisture contents (P &lt; 0·001), greater fat contents (P &lt; 0·001) and lower ash contents (P &lt; 0·05) than other slaughter treatments. A significant diet × slaughter weight interaction occurred in fat content, with rabbits of the LE–3 kg treatment having proportionally more fat. With age at slaughter as a covariate, rabbits fed the HE diet had proportionally more fat (P &lt; 0·05).

The effect of dietary metabolizable energy concentration upon the pre- and post-weaning performance of growing rabbits

ABSTRACTTwenty-five Californian does were mated and given pelleted diets of either 8(LE) or 10(HE) MJ/kg dry matter (ruminant metabolizable energy values) throughout gestation and lactation. Litter sizes were adjusted to six offspring per doe. Milk yield was estimated from the weight differences of the litters before and after suckling, when the opportunity for nursing was confined to once daily. The young rabbits were allowed access to either the LE or HE diets from 18 days of age. Weaning took place at 32 days of age when four rabbits from each doe grouP × pre-weaning diet were slaughtered. Diet had no effect on litter size or birth weight, but does on the LE diet had lower live weights post partum (P &lt; 0·05). Dry-matter consumption by the does on the LE diet was greater than for the HE diet (P &lt; 0·05) both during gestation and lactation, but calculated metabolizable energy intakes were lower during lactation. There were no statistically significant differences between treatments for milk yield or live-weight gain to weaning and dry-matter intakes of the young at weaning, but daily live-weight gain from fostering to 18 days of age was greater for litters of does fed the HE rather than the LE diet (P &lt; 0·05). There were no statistically significant differences between diets for carcass traits at weaning.After weaning, 32 rabbits were given either the LE or HE diet until 2 kg live weight when they were slaughtered. A post-weaning × pre-weaning diet interaction (P &lt; 0·05) occurred for live weights of the rabbits at the start of the post-weaning trial (i.e. after a 10-day adaptation period) with LE: LE rabbits being lighter than other rabbits as a results of poor live-weight gains during the adaptation period. Live-weight gains to slaughter were greater for the pre-weaning LE diet (P &lt; 0·05) and the post-weaning HE diet (P &lt; 0·01), although dry-matter intakes of the HE diet were less (P &lt; 0·05). Rabbits on the LE diet had greater empty gut weights (P &lt; 0·05) and lighter livers (P &lt; 0·05) at slaughter.

Effects of dietary energy concentration on production of broiler chickens

Eight least-cost diets with a determined range of metabolizable energy (ME) concentrations from 9.3 to 14.3 MJ kg-1 were formulated. Each diet was offered for about 12 weeks to two pens of about 100 broilers of each sex. Observations on feed consumption, liveweight and mortality were made weekly for each pen. Dressing percentages were recorded for samples of ten birds from each pen at two different Iiveweights. As ME concentration of the diets increased, birds grew faster and required less food, in terms of both total weight and total energy, to reach specified liveweights, although these effects were not marked when the dietary ME concentration was above 13.5 MJ kg-1. Feed conversion was less efficient at the same ME concentration when birds of each sex were taken to higher liveweights. Dressing percentage increased with increases in dietary ME concentration for males, but for females it tended to decline at the highest energy concentrations. Mortality was the same (2 per cent) on all diets.

Dietary energy content and floor space relationships for optimal growth and efficiency of broilers

Commercial broilers, kept in small, fixed-size pens, were allowed 310, 370, or 460 cm2 of floor space per bird started at one day of age, in a windowless controlled environment house. At each stocking density birds were offered diets with 12.5, 12.9, or 13.4 MJ kg-1 of metabolizable energy from 41 to 64 days of age. Male and female broilers grew more slowly (P &lt; 0.05) when offered the lowest energy diet. They were heavier (P &lt; 0.05) when allowed 460cm2 of floor space per bird. Total output on the basis of liveweight produced per unit of floor space over 64 days of age was largest in the most densely stocked pens. Optimal dietary metabolizable energy concentration was approximately 12.9 MJ kg-1; however, reasons for varying this recommendation are discussed.