Digestible Energy Ratio Research Articles

Nutritional values of cottonseed meal from different sources fed to gestating and non-pregnant sows.

This study set out to determine the apparent total tract digestibility (ATTD) of the nutrients and energy in six cottonseed meal (CSM) feedstuffs fed to pregnant and non-pregnant sows. The six types of CSM were: two expelled CSMs with crude protein (CP) levels of 40.67% and 44.64%, and four solvent-extracted CSMs with CP levels of 45.18%, 51.16%, 56.44%, and 59.63%. Fourteen gestating sows (at the 4 th parity with body weights of 220.6 ± 18.4kg at days 30 of gestation) and 14 non-pregnant sows (after the 3 rd parity with body weights of 219 ± 14.6kg) were assigned to a replicated 7 × 3 Youden square design with seven diets and three periods. The seven diets included an entirely corn-based diet and six diets each containing 20.0% of the six CSMs tested. Each period included a 5-day acclimation to the experimental diets, followed by a 5-day period during which urine and feces were collected. Significant differences were found among the six CSM diets, regardless of reproductive stage, regarding: 1) the ATTD of neutral detergent fiber (NDF) (P < 0.05) and 2) the ATTD of dry matter (DM), organic matter (OM), and CP and the gross energy (GE) (P < 0.01). Non-pregnant sows had a greater ATTD of OM and CP (P < 0.01) compared with gestating sows. The digestible energy (DE) and metabolizable energy (ME) of the six CSM samples ranged from 12.48 to 17.15 MJ/kg and 11.35 to 15.88 MJ/kg, respectively, for non-pregnant sows, and from 12.86 to 16.41 MJ/kg and 12.43 to 14.72 MJ/kg, respectively, for gestating sows. However, the DE, ME, and ME:DE ratios of each CSM were similar between gestating and non-pregnant sows. DE and ME were negatively correlated with NDF and ADF, respectively, but were positively corrected with CP level (P < 0.01). Collectively, the DE, ME, and nutrient digestibility of CSM varied greatly according to the chemical compositions, and CSMs with higher protein and lower fiber levels had greater DE and ME levels.

The nutritive value of soybean meal from different sources for sows during mid- and late gestation.

A precise understanding of the nutritive value of soybean meal (SBM) for pregnant sow is required for accurate feeding. Hence, we evaluated the nutritive value of 11 SBM samples from different sources for sows during mid and late gestation. In total, 24 mid-gestating sows (parity three; 230.3 ± 12.0 kg on day 37 of gestation) and 24 late-gestating sows (parity three; 238.8 ± 20.9 kg on day 72 of gestation) were assigned to a replicated 12 × 3 Youden square design with 12 diets and 3 periods. The 12 diets included a corn-based diet and 11 diets containing 25.50% SBMs from different sources. After 5-d adaptation, urine and feces were collected for 5 d. Although the chemical characteristics of SBM varied between samples, no differences were observed in digestible energy (DE), metabolizable energy (ME), apparent total tract digestibility (ATTD) of dry matter, gross energy, crude fiber, and neutral detergent fiber values in SBMs fed to both animal groups. However, de-hulled SBM 4 from Brazil displayed greater ATTD for nitrogen (N) in late-gestating sows (P < 0.05); animals displayed significantly (P < 0.01) greater ME, ME:DE ratio, and N net utilization values when compared with mid-gestating sows. The chemical composition of SBMs can be used to predict DE and ME values. In conclusion, ME, ME:DE ratio, and N net utilization SBM values for late-gestating sows were greater than in mid-gestating sows. Therefore, we should consider differences in ME values for SBMs when formulating diets for sows in mid and late gestation periods.

Influence of dietary fibre on nutrient digestibility and energy utilisation in growing pigs fed diets varying in soluble and insoluble fibres from co-products

The co-products from the industry are used to reduce costs in pig diets. However, the co-products used in pig diets are limited because of a high fibre content which is not digested by endogenous enzymes and is resistant to degradation in the small and large intestines. The aim of this study was to investigate digestibility of nutrients and energy, and energy utilisation in pigs fed diets with various soluble and insoluble dietary fibre (DF) from co-products. The experiment was performed as a 4 × 4 Latin square design (four diets and four periods) using four growing pigs (66.2 ± 7.8 kg) surgically fitted with a T-cannula in the end of the small intestine. The pigs were fed four experimental diets: low-fibre control (LF), high-fibre control (HF), high-soluble fibre (HFS) and high-insoluble fibre (HFI) diets. The apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of ash, organic matter, CP, fat, carbohydrates, starch and non-starch polysaccharides (NSP) divided into cellulose and soluble and insoluble non-cellulosic polysaccharide residues were measured using chromic oxide as marker. The recovery of total solid materials, organic matter and total carbohydrates in ileal digesta in pigs fed the HF and HFS diets was higher than in pigs fed LF and HFI, whereas recovery of organic matter and total carbohydrates in faecal materials in the HFS diet was lowest (P < 0.05). AID of organic matter, total carbohydrates and starch was lowest for HFS diet (P < 0.05). ATTD of organic matter and CP was higher for LF diet compared with other diets (P < 0.05), whereas total NSP, cellulose and non-cellulosic polysaccharides residues were highest for HFS diet (P < 0.05). Lactic acid in ileal digesta was influenced by dietary composition (P < 0.05) whereas neither type nor level of DF affected short chain fatty acids. The digestible energy, metabolisable energy, net energy and retained energy intake were similar among diets without influence of DF inclusion (P > 0.05). The metabolisable energy:digestible energy ratio was lower when feeding the HFS diet because of a higher fermentative methane loss. Faecal nitrogen and carbon were positively correlated with DM intake and insoluble DF in the diets (P < 0.05), but nitrogen and carbon (% of intake) were similar among diets. The present findings suggest that high-DF co-products can be used as ingredients of pig diets when features of DF are considered.

543 Late-Breaking: Development of a Model to Predict Dietary Metabolizable Energy from Digestible Energy in Beef Cattle

Abstract We aimed to assess whether predicting the metabolizable energy (ME) to digestible energy (DE) ratio (MDR), rather than a prediction of ME with DE, is feasible and to develop a model equation to predict MDR in beef cattle. For this, we constructed a literature database based on published data. A meta-analysis was conducted with 306 means from 69 studies containing both dietary DE and ME concentrations measured by calorimetry to test whether the exclusion of the y-intercept is adequate in the linear relationship between DE and ME. A random coefficient model with study as the random variable was used to develop equations to predict MDR in growing and finishing beef cattle. The developed equations were evaluated with other published equations. The no-intercept linear equation represented the relationship between DE and ME more appropriately than the equation with a y-intercept. Within our growing and finishing cattle data, the animal’s physiological stage was not a significant variable affecting MDR after accounting for the study effect (P = 0.213). The mean (± SE) of MDR was 0.849 (± 0.0063). Two linear equations with the dry matter intake and content of several dietary nutrients were developed to predict MDR. When using these equations, the observed ME was predicted with high precision (R2 = 0.92). The model accuracy was also high, as shown by the high concordance correlation coefficient (&amp;gt; 0.95) and small root mean square error of prediction (RMSEP), less than 5% of the observed mean. Moreover, a significant portion of the RMSEP was due to random bias (&amp;gt; 93%), without mean or slope bias (P &amp;gt; 0.05). We concluded that dietary ME in beef cattle could be accurately estimated from dietary DE and its conversion factor, MDR, using the two equations developed in this study.

Growth performance and metabolic responses of Nile tilapia fed diets with different protein to energy ratios

The effect of dietary digestible protein to digestible energy (DP/DE) ratio on the growth performance and metabolic responses of Nile tilapia juveniles was evaluated. Five experimental diets were formulated with increasing DP/DE ratio (13.2, 15.5, 18.4, 20.0, and 22.6 mg kJ−1) and fed to eight replicates of Nile tilapia (initial body weight of 9.3 g) for 110 days. The apparent digestibility coefficients of the diets were determined in a parallel trial. Digestibility coefficients of dry matter, crude protein, and crude energy linearly decreased with increasing dietary P/E ratios. A quadratic effect of dietary DP/DE ratio on growth performance was observed, and maximum weight gain (g kg−1 day−1) or daily growth increment was attained with a dietary DP/DE ratio of 16.5 and 17.2 (mg kJ−1), respectively. Feed intake and energy retention (kJ ABW kg−1 day−1) linearly decreased, and feed efficiency linearly increased with increased dietary DP/DE ratio. The increase of dietary DP/DE ratio decreased the whole body, muscle, hepatic, and visceral lipid content and increased the fillet yield. The decrease of dietary DP/DE linearly increased nitrogen retention (% N intake) and whole-body lipid deposition through the reduction of amino acid catabolism (GDH and ALAT) and gluconeogenesis (FBPase) related enzymes and the increase of glycolysis (GK and HK) and lipogenesis- (G6PDH and ME) related enzymes.In conclusion, a dietary DP/DE ratio of 16.5–17.2 mg kJ−1 promoted the maximum growth performance of Nile tilapia juveniles. However, further studies are required to evaluate if a fine-tuning of the protein amino acid profile would allow a further reduction of the optimum dietary DP/DE ratio. Metabolic response to the decrease in dietary DP/DE levels suggested activation of glycolysis and lipogenesis and inhibition of amino acid catabolism and gluconeogenesis, highlighting the high capacity of Nile tilapia for metabolic utilization of dietary carbohydrates.

Development of a model to predict dietary metabolizable energy from digestible energy in beef cattle.

Understanding the utilization of feed energy is essential for precision feeding in beef cattle production. We aimed to assess whether predicting the metabolizable energy (ME) to digestible energy (DE) ratio (MDR), rather than a prediction of ME with DE, is feasible and to develop a model equation to predict MDR in beef cattle. We constructed a literature database based on published data. A meta-analysis was conducted with 306 means from 69 studies containing both dietary DE and ME concentrations measured by calorimetry to test whether exclusion of the y-intercept is adequate in the linear relationship between DE and ME. A random coefficient model with study as the random variable was used to develop equations to predict MDR in growing and finishing beef cattle. Routinely measured or calculated variables in the field (body weight, age, daily gain, intake, and dietary nutrient components) were chosen as explanatory variables. The developed equations were evaluated with other published equations. The no-intercept linear equation was found to represent the relationship between DE and ME more appropriately than the equation with a y-intercept. The y-intercept (-0.025 ± 0.0525) was not different from 0 (P = 0.638), and Akaike and Bayesian information criteria of the no-intercept model were smaller than those with the y-intercept. Within our growing and finishing cattle data, the animal's physiological stage was not a significant variable affecting MDR after accounting for the study effect (P = 0.213). The mean (±SE) of MDR was 0.849 (±0.0063). The best equation for predicting MDR (n = 106 from 28 studies) was 0.9410 ( ± 0.02160) +0.0042 ( ± 0.00186) × DMI (kg) - 0.0017 ( ± 0.00024) × NDF(% DM) - 0.0022 ( ± 0.00084) × CP(% DM). We also presented a model with a positive coefficient for the ether extract (n = 80 from 22 studies). When using these equations, the observed ME was predicted with high precision (R2 = 0.92). The model accuracy was also high, as shown by the high concordance correlation coefficient (>0.95) and small root mean square error of prediction (RMSEP), <5% of the observed mean. Moreover, a significant portion of the RMSEP was due to random bias (> 93%), without mean or slope bias (P > 0.05). We concluded that dietary ME in beef cattle could be accurately estimated from dietary DE and its conversion factor, MDR, predicted by the dry matter intake and concentration of several dietary nutrients, using the 2 equations developed in this study.

Animal fat and vitamin E in rabbit diets: Total tract apparent digestibility, growth performance, carcass and meat quality traits

The present study tested the effect of a dietary inclusion with vitamin E and pork lard on the apparent digestibility of the nutrients, the growth performance, the carcass traits, the physical meat quality, and the α-tocopherol content. A total of 60 hybrid rabbits were reared in individual cages from weaning (35 days of age) until slaughter (78 days of age). A control diet with no supplements, one diet supplemented with 2% pork lard, and two diets that used the aforementioned diets supplemented with an additional 200 mg/kg α-tocopheryl acetate were designed. The diets were isoprotein and isoenergy. The fat inclusion increased the crude protein (P &amp;lt; 0.05) and ether extract (P &amp;lt; 0.001) total tract apparent digestibility, and the same was observed for the vitamin E inclusion (P &amp;lt; 0.001 for both variables). This improved the dietary digestible protein content (P &amp;lt; 0.05), which increased the digestible protein to digestible energy ratio (P &amp;lt; 0.001). The fat × vitamin E interaction was observed for the total tract apparent digestibility of the ether extract (P &amp;lt; 0.001), the neutral detergent fibre (P &amp;lt; 0.05) and the acid detergent fibre (P &amp;lt; 0.01). The growth traits were unaffected, with the exception of the feed conversion ratio that improved with the vitamin E addition (P &amp;lt; 0.05). Similarly, the carcass traits remained unaffected, with the exception of the perirenal and total fat incidence that increased with the fat supplement (P &amp;lt; 0.05), and the scapular fat that was reduced with the vitamin E inclusion (P &amp;lt; 0.05). The meat L* (lightness), a* (redness), b* (yellowness) colour values and ultimate pH were unaffected by the experimental treatments, even though a fat × vitamin E interaction was observed for the a* and chroma values of the Longissimus thoracis et lumborum muscle (P &amp;lt; 0.05). Both the fat (P &amp;lt; 0.05) and vitamin E (P &amp;lt; 0.001) dietary inclusion increased the meat α-tocopherol content. Based on the results, it was concluded that the 2% dietary inclusion of animal fat did not provide more benefits for the considered parameters than the sole α-tocopheryl acetate incorporation, but contributed to the increase in the vitamin E content in the meats.

Digestible energy, protein, and energy–protein ratio requirements of Pseudoplatystoma reticulatum

AbstractThe use of novel aquaculture species depends on the determination of their nutritional requirements. This study aims at determining dietary protein, energy, and protein–energy ratio requirements of juvenile striped surubim, Pseudoplatystoma reticulatum, an economically important carnivorous South American catfish for capture fisheries and highly regarded for fish farming purposes. Juvenile striped surubim (53.6 ± 1.30 g, n = 525) were randomly stocked (n = 7) in 75 test cages (210 L) and hand fed for 60 days, two daily meals, with 25 diets formulated to contain five levels of digestible protein (DP) (320, 360, 400, 440, and 480 g/kg) and five levels of digestible energy (DE) (15.1, 15.6, 16.1, 16.6, and 17.2 MJ/kg) in a completely randomized design, 5 × 5 factorial scheme (n = 3). Dietary energy and protein level affected performance, feed efficiency, and metabolism while the whole‐body composition was not affected by diets. Estimated dietary requirements for the best performance and best nutrient retention were 15.1 MJ/kg DE and 390 g/kg DP, therefore a 25.9 g/MJ of DP:DE ratio.

Effects of varying dietary levels of digestible protein and digestible energy on growth performance in juvenile Yellowstone Cutthroat Trout (Oncorhynchus clarkia bouvieri)

Cutthroat trout (Oncorhynchus clarkii) are widely cultured in state and federal hatcheries and private farms throughout the Western United States for stock supplementation or recreational fisheries. Cutthroat Trout culture techniques often rely on methods borrowed from the culture of closely related Rainbow Trout (Oncorhynchus mykiss). Even though commercial feeds for Rainbow Trout are commonly utilized, these formulations are unlikely to be optimal for Cutthroat Trout growth. Therefore, in an effort to determine an optimal digestible protein to digestible energy ratio for raising Cutthroat Trout more efficiently, eight diets formulated with 4 different levels of digestible protein (DP: 32.5 %, 37 %, 41.7 % and 46 %) and 2 different levels of digestible energy (DE: 4370 kcal/kg and 4770 kcal/kg) were fed to triplicate tanks of Yellowstone Cutthroat Trout and compared with a commercial Rainbow Trout diet over a 12 week study. All test diets performed better on indices of biomass accrual than the commercially available diet. Results suggest commercially available Rainbow Trout diets are less efficient formulations for Yellowstone Cutthroat Trout and new formulations should be considered. Optimizing digestibility, protein retention, minimizing lipid accrual, and maintaining high biomass gain in tanks, leads to the conclusion that a diet representing a DP:DE of 68.4 mg kcal−1 performed best. Moreover, protein retention decreased as DP:DE increased across test diets. Retention of lipids and gross energy did not appear to be significantly altered by dietary DP or DE.

Effect of dietary carbohydrate to lipid ratio on performance of Nile tilapia and enhancement of natural food in pond aquaculture

This study tested the effect of two diets differing in carbohydrate to lipid (CHO:LIP) ratio (4.7 vs. 19.5 g/g) on the contribution of natural food and the total fish production in tilapia ponds. Eight ponds, each divided into three equally sized compartments, were assigned to one of the two diets, which differed in CHO:LIP ratio but had the same digestible protein to digestible energy (DP:DE) ratio (15.5 and 15.6 g/MJ). Ponds were fed equal amounts of crude protein. Three feeding levels (no, low and high) were nested in each pond in a split plot design. Average body weight of fish at stocking was 90 g, and the duration of the experiment was 42 days. Increasing the CHO:LIP ratio had no impact on tilapia production. However, the feeding level influenced both biomass gain, specific growth rate and survival. The apparent digestibility coefficient (ADC) for fat and carbohydrate was influenced by dietary CHO:LIP ratio but ADC for energy was unaffected. Proximate analysis of fish body composition showed no effect of diet except for levels of ash. Diet had no effect on the organic matter composition of the faeces, and the contribution of natural food to fish nitrogen gain. Therefore, we postulate that changing the dietary non-protein energy source from lipid to carbohydrate does not have any impact on tilapia culture in semi-intensive ponds.

Effect of age on the relationship between metabolizable energy and digestible energy for broiler chickens

A total of 960 male Ross 308 chicks (day-old) were used to investigate the effect of age on the relationship between metabolizable energy (ME) and digestible energy (DE) for broiler chickens. Bird growth variables, nitrogen retention (NR), nitrogen digestibility (ND), as well as the relative weight of liver, pancreas, and the gastrointestinal tract were determined. Practical diets that compared 2 cereals (corn and wheat) and exogenous xylanase (0 or 16,000 BXU/kg) were evaluated at 5 ages (7, 14, 21, 28, and 35 D) in a 2 × 2 × 5 factorial arrangement of treatments with 8 replicates per treatment and started with 30 birds per replicate. A randomized block ANOVA analysis of repeated measures was performed, and a 2 × 2 × 5 factorial structure was used to investigate the 2 dietary treatment factors (cereal type and the presence of xylanase) within the 5 bird ages (7, 14, 21, 28, and 35 D), and their interactions. Apparent metabolizable energy (AME) increased linearly from 7 until 28 D of age, but (P < 0.05) decreased at 35 D of age. Digestible energy was high at 7 D of age, then dropped and remained similar (P > 0.05) from 14 to 35 D of age. The AME: DE ratio was lowest (P < 0.05) at 7 D of age but there were no (P > 0.05) differences thereafter. Cereal type and xylanase supplementation did not (P > 0.05) change the ME: DE ratio. The results indicate that determining ME before 14 D of age may give absolute values that are lower than would be obtained with older birds. ME values that are determined on older broiler chickens may overestimate the energy availability of practical feeds used in broiler starter feeds.

Effect of the digestible protein-energy relationship on the growth performance of Nile tilapia (Oreochromis niloticus) fed fishmeal-free diets

This study aimed to determine the best digestible protein: digestible energy (DP:DE) ratio for adult Nile tilapia (Oreochromis niloticus) fed diets formulated with vegetable ingredients (soybean and corn), and without fishmeal. Four hundred and twenty male Nile tilapia (GIFT strain) (initial mean weight 193 ± 12.6 g) were allocated to 60 plastic tanks (1000 L) connected to a water recirculation system, and there were 7 fish in each tank. The experimental design was a 5 × 4 factorial with three replicates for each diet treatment. The fish were fed one of 20 diets containing a combination of five digestible protein levels (140, 190, 240, 290 and 340 g/kg DP) and four digestible energy levels (10.89, 11.72, 12.56 and 13.40 MJ/kg DE) for 96 days. The fish were given three meals each day (8 AM, 1 PM and 6 PM) and feeding was to apparent satiation. At the end of the experimental period, diets presented an interactive effect (P < 0.05) in relation to the productive performance. Final weight (FW = 448.82 g), fillet yield (FY = 32.60 %) and specific growth ratio (SGR = 2.65 %) were increased and a decrease in feed conversion ratio (FCR = 1.20) was observed in diet containing 240 g/kg DP and 12.56 MJ/kg DE. Otherwise, the highest protein efficiency ratio (P < 0.05) was found in diet containing 140 g/kg DP and 12.56 MJ/kg DE. FW, WG, FY and SGR were increased significantly (P < 0.05) up to the 12.56 MJ/kg DE level, independent of digestible protein levels. A quadratic effect was observed for FW, WG and SGR, independent of energy levels. An increase in these variables was observed up to 250.78, 240.70 and 216.70 g/kg DP respectively, and the lowest FCR was 260.58 g/kg DP. A linear increase was observed for FY (P < 0.05) in diets containing higher DP levels. No interaction (P > 0.05) was observed in any treatment for fillet centesimal composition and whole body. However, an increase (P < 0.05) in crude protein of fillet and body moisture was observed in diets containing levels above 240 g/kg DP, independent of DE. The present findings indicate that the optimal DP:DE level was 240 g/kg DP and 12.56 MJ/kg DE in the fishmeal-free diets for males Nile tilapia, promoting adequate growth performance without affecting the proximal tissue composition.

353 Starch to fat ratio in piglet nutrition

Abstract Dietary high energy density (HED) and the energy compositions, especially the fat and starch composition could have a variable effect on performance, intestinal health and the profitability of piglet production. The present study evaluated the effects of dietary energy densities and digestible energy ratio of starch to fat on intestinal functions and growth performance of growing pigs. A total of 48 healthy weaners (9.60 ± 0.13 kg) were allocated to two dietary energy densities (14.21 and 15.91MJ/kg) and two digestible energy ratio: high starch: low fat, HSLF (9:1) or low starch: high fat ratio, LSHF (1:3) in a factorial arrangement. It was found that dietary LSHF ratio induced diarrhea in the weaner pigs (P &amp;lt; 0.001). The feed intake of weaners was increased by HED (P &amp;lt; 0.05), however, this did not result in improved body weight gain (P &amp;gt; 0.05). The HED reduced (P = 0.017) energy digestibility, while digestible energy ratio reduced crude protein digestibility and amino acid utilization in the weaners. Fat and dry matter digestibility were not significantly affected (P &amp;gt; 0.05). Dietary LSHF ratio increased intestinal villus height/crypt depth ratio in the duodenum and ileum (P &amp;lt; 0.05). The lymphocyte count was increased by HSLF energy ratio. The highest high-density lipoprotein concentration was exhibited in weaners fed dietary LSHF energy ratio (P &amp;lt; 0.01) and dietary HSLF ratio increased the duodenal sucrase and lactase activities (P &amp;lt; 0.01). The dietary LSHF ratio showed an increased tendency to increase fecal ammonia concentration, but dramatically decreased fecal short-chain fatty acid concentrations (P &amp;lt; 0.01). The HED seems to induced oxidative stress (P &amp;lt; 0.01). The study suggests that dietary high fat, but not dietary starch or HED could decrease the intestinal health of weaner pigs.

Farklı Oranlarda Fındık, Soya Küspesi, Balık Unu ile Birlikte Fitaz İçeren Rasyonların Gökkuşağı Alabalığı (Oncorhynchus mykiss) Yavrularının Gelişimi Üzerine Etkileri

This study aimed to examine the effects of six trial diets (containing different amounts of fish meal, hazelnut, and soybean meal protein, also without the enzyme phytase “0 FTU” and with “1000 FTU”) on the rainbow trout (Oncorhynchus mykiss) juveniles. The study was conducted as three replicates. Live weight gain, feed consumption, feed conversion ratio, specific growth ratio and the protein efficiency ratio of the trial groups were calculated as 52.8-64.3g, 64.1-72.1g/fish, 1.12-1.22, 1.42-1.6% and 1.79-2.0, respectively (P&amp;lt;0.05). The dietary factors did not produce a significant effect on the organ indexes, body chemical composition, digestibility ratios of diets in the fish (P&amp;gt;0.05). But phytase enzyme affected significantly the dietary phosphorus ratio and the digestible energy ratio (P&amp;lt;0.05). Dry matter, crude ash, crude lipid, crude protein and phosphorus components in the fish bodies were found to be 30.7-31.8%, 2.2-2.3%, 11.8-12.8%, 14.5-15.2% and 0.56-0.62%, respectively. In the trial group fishes, values of the total nitrogen and phosphorus consumption, gain and retention were calculated as 1139-1173 mg/kg versus 248-279 mg/kg, 315-350 mg/kg versus 73-82 mg/kg, and 27.2-30.6% versus 26-33%, based on the average daily weight. Generally, the interaction between factors was found to be statistically insignificant (P&amp;gt;0.05).

Applying the California net energy system to growing goats1

The aim of this review is to describe the main findings of studies carried out during the last decades applying the California net energy system (CNES) in goats. This review also highlights the strengths and pitfalls while using CNES in studies with goats, as well as provides future perspectives on energy requirements of goats. The nonlinear relationship between heat production and metabolizable energy intake was used to estimate net energy requirements for maintenance (NEm). Our studies showed that NEm of intact and castrated male Saanen goats were approximately 15% greater than female Saanen goats. Similarly, NEm of meat goats (i.e., >50% Boer) was 8.5% greater than NEm of dairy and indigenous goats. The first partial derivative of allometric equations using empty body weight (EBW) as independent variable and body energy as dependent variable was used to estimate net energy requirements for gain (NEg). In this matter, female Saanen goats had greater NEg than males; also, castrated males had greater NEg than intact males. This means that females have more body fat than males when evaluated at a given EBW or that degree of maturity affects NEg. Our preliminary results showed that indigenous goats had NEg 14% and 27.5% greater than meat and dairy goats, respectively. Sex and genotype also affect the efficiency of energy use for growth. The present study suggests that losses in urine and methane in goats are lower than previously reported for bovine and sheep, resulting in greater metabolizable energy:digestible energy ratio (i.e., 0.87 to 0.90). It was demonstrated that the CNES successfully works for goats and that the use of comparative slaughter technique enhances the understanding of energy partition in this species, allowing the development of models applied specifically to goat. However, these models require their evaluation in real-world conditions, permitting continuous adjustments.

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.

Muscle growth mechanisms in response to isoenergetic changes in dietary non-protein energy source at low and high protein levels in juvenile rainbow trout

This study investigates muscle growth mechanisms in juvenile rainbow trout in response to isoenergetic changes in dietary non-protein energy (NPE) source (F, fat vs. C, carbohydrates) at two levels of digestible protein to digestible energy (DP/DE) ratio. Fish (initial weight 32.4 g) were fed four diets having similar DE levels (~18 kJ g−1) with a high (HP/E~26 mg kJ−1) vs. low (LP/E~14 mg kJ−1) DP/DE ratio using F or C as major NPE source (7 week-experiment). The lowering of dietary DP/DE ratio increased myoblast determination protein 1a (myod1a) and decreased myostatin 1b (mstn1b) and cathepsin D (ctsd) muscle mRNA levels. The isoenergetic change in dietary NPE from F to C decreased myod1a and proliferative cell nuclear antigen (pcna) muscle mRNA levels. An interaction between DP/DE ratio and NPE source was observed in muscle transcript levels of myogenic factor 6 (mrf4/myf6), fast myosin heavy chain (fmhc) and fast myosin light chain 2 (fmlc2). White muscle total cross-sectional area decreased at low dietary DP/DE ratio and also when NPE source changed from F to C, linked i) to a decreased total number of white muscle fibres, indicating that low dietary DP/DE restricted muscle hyperplasia and that dietary carbohydrate were less efficiently used than fat to sustain muscle hyperplasia, and ii) to decreased percentage of large muscle fibres, indicating limited fibre hypertrophy. Not only the DP level or the DP/DE ratio, but also the isoenergetic change in dietary NPE source (fat vs carbohydrates) thus appears as a potent regulator of muscle hyperplasia and hypertrophy.

Effect of constant digestible protein intake and varying digestible energy levels on energy and protein utilization in Nile tilapia

In literature, the variability in the estimated optimal digestible protein to digestible energy ratio (DP/DE) is high. The present study aimed to estimate the optimal DP/DE ratio in Nile tilapia (Oreochromis niloticus) using different criteria (performance, energy and nitrogen balances parameters). Duplicate aquaria were randomly assigned to one of 16 diets. These diets covered a wide range of dietary DP/DE ratio (from 16.7 to 27 g MJ−1). DP levels ranged between 36 and 50% and DE levels between 17.5 and 22 MJ kg−1. Fish were fed restrictively based on a similar digestible protein amount at all 16 diets. Initial fish weight was 6.7 g. Broken line analysis showed that no optimal DP/DE ratio was present for Nile tilapia within the DP/DE ratio range studied. Regression analysis showed that growth declined as DP/DE ratio increased and seemed to level off at high DP/DE ratio (25 g MJ−1). FCR ranged between 0.8 and 1.1 and increased linearly with increasing DP/DE ratio. Decreasing the DP/DE ratio resulted in a linear increase in protein efficiency to a highest value of 53%. However, protein efficiency did not show a plateau or a maximum value. Moreover, decreasing the DP/DE ratio resulted in a very high fat content of the fish (over 16%). In conclusion, an optimal DP/DE ratio in Nile tilapia being fed restrictively seems to be absent or to be below 16 g MJ−1. A maximum protein deposition level is not present in 5–40 g Nile tilapia.

Effect of level of soluble fiber and n-6/n-3 fatty acid ratio on performance of rabbit does and their litters.

The aim of this work was to study whether the dietary supplementation with soluble fiber (SF) and the reduction of the n-6/n-3 fatty acid ratio or the combination of both influences the survival, body and milk composition, and reproductive performance of rabbit does during the first four parturitions. Four diets in a 2 × 2 factorial arrangement were used with two levels of SF (7.8 vs. 13.0, on dry matter [DM] basis; high soluble fiber [HSF] and low soluble fiber [LSF]) and two different n-6/n-3 fatty acid ratios (13.4/1 vs. 3.5/1). Nulliparous does (24/diet) were inseminated 11 d after parturition. Body chemical composition and energy content of rabbit does and their performance, litter growth, and milk production were measured between birth and weaning (25 d) along four parturitions, and milk composition and fecal digestibility were also recorded. The proportion of total removed does decreased in HSF respect to LSF groups (22.9 vs. 50.0%; P = 0.005), and it tended to decrease in LSF groups when the n-6/n-3 ratio increased and in HSF groups when the n-6/n-3 ratio decreased (P = 0.059). The increase of the level of SF reduced the digestible crude protein (CP)/digestible energy ratio (by 4%; P < 0.001) and improved the digestibility of all fibrous fractions (P < 0.001). The reduction of the n-6/n-3 ratio reduced the total dietary fiber digestibility in rabbit does fed LSF diets, but it had no effect in those fed HSF diets (P = 0.043). Treatments had no effect on average daily feed intake among parturitions (P = 0.16), but the digestible CP intake among parturitions was lower in HSF than in LSF groups (P = 0.003). Treatments had no effect on the total number of kits born, litter or average kit weight at birth, or litter size at weaning, fertility, feed efficiency, total milk production, and body chemical composition and energy content of rabbit does (P ≥ 0.29). The average weight of kits at weaning of LSF_Hn-6/n-3 and HSF_Ln-6/n-3 groups decreased by 6% compared with those from the other two groups (P = 0.030). The reduction of the dietary n-6/n-3 ratio increased the milk fat content by 12% with no effect on protein and DM content (P = 0.031). The proportion of milk odd fatty acids and saturated fatty acid increased in rabbit does fed the HSF diets compared with those fed LSF diets (P ≤ 0.037) with no effect of the n-6/n-3 fatty acid ratio. In conclusion, SF reduced the replacement rate of rabbit does with no effect of the n-6/n-3 ratio, while both dietary factors modified milk composition and fatty acid profile with minor influence on litter productivity.

Effect of different forage types and concentrate levels on energy conversion, enteric methane production, and animal performance of Holstein × Zebu heifers

The aim of this study was to evaluate the effect of diets containing corn silage (CS) or sugarcane (SC) with 300 or 500 g/kg of concentrate (on a DM basis) on energy conversion, enteric methane (CH4) production, and the animal performance of Holstein × Zebu heifers. An experiment was conducted while using comparative slaughter. Twenty Holstein × Zebu heifers with an average age of 12 ± 1.0 months and an average bodyweight of 218 ± 36.5 kg were used. Four heifers were assigned to a baseline group, whereas the remaining 16 heifers were distributed in a completely randomised design using a 2 × 2 factorial scheme (n = 4), with two types of roughage (CS or SC) and two levels of concentrate (300 or 500 g/kg) on a DM basis of the diet over the course of 112 days. For the evaluation of the apparent total-tract digestibility of diets and energy losses, a digestibility assay was performed by using the total collection of faeces and urine over three consecutive days. The enteric CH4 production was quantified by continuous analysis of regular samples of air excreted by the animals throughout the day. The greatest (P &lt; 0.05) average daily gain was observed for heifers that were fed CS-based diets or with 500 g/kg of concentrate. Greater (P &lt; 0.05) daily CH4 emissions were observed for heifers that were fed 500 g/kg of concentrate; CH4 production as a function of DM intake was greater (P &lt; 0.05) for heifers that were fed SC-based diets. The efficiency of the conversion from digestible energy (DE) to metabolisable energy (ME) was not influenced (P &gt; 0.05) by variables that were analysed in this study. However, the mean value that was observed in the present study was above those values proposed by the main evaluation systems of feedstuffs and nutrient requirements of ruminants. Therefore, we concluded that CS-based diets allow for better animal performance of Holstein × Zebu heifers in relation to SC-based diets. Also, the increased concentrate improves the performance of growing heifers. A greater inclusion of concentrate in SC-based diets can allow for a reduction of CH4 emissions per consumed unit and per gain unit. The mean suggested value for the ME : DE ratio based on this study is 0.86. However, more studies are necessary to validate this result.