Studies on Reducing Nitrogen Excretion: Ⅰ. Net Energy Requirement of Finishing Pigs Maximizing Performance and Carcass Quality Fed Low Crude Protein Diets Supplemented with Crystalline Amino Acids

Two experiments were conducted to in- vestigate the effects of net energy （NE） level on the performance and carcass traits of finishing pigs fed low crude protein （CP） diets supplemented with crystalline amino acids （CAA）. A total of 216 （Exp. 1） and 360 （Exp. 2 ） barrows （ Yorkshire × Landrace× Duroc ） were allotted to one of six treatments （n =6）. The experimental diets were based on corn and soybean meal, and consisted of a high-CP diet that contained approximately 16% CP and 2.50 Mcal/kg of NE as well as five low-CP diets in which the CP level of the diet was reduced by approximately four percentage units but was supplemented with crystalline lysine, methionine, threonine, and tryptophan. The low CP diets provided 2.64, 2.58, 2.50, 2.42, or 2.36 Mcal/kg in Exp. 1 as well as 2.45, 2.40, 2.35, 2.30, or 2.25 Mcai/kg in Exp.2. In Exp. 1, a linear （P=0.03） increase in weight gain was observed with decreasing NE level while the ratio of gain to feed was unaffect- ed （P 〉 0.05） by NE level. There was a linear in-crease （P = 0.01 ） in the percentage of fat-free lean and a linear decrease （ P = 0.03 ） in the percentage of total fat with decreasing NE levels. In Exp. 2, a sig- nificant quadratic （ P = 0.03 ） effect of NE level was observed for weight gain. The ratio of gain to feed demonstrated a significant （P 〈0.01 ） quadratic effect with pigs fed 2.35 and 2.40 Mcal/kg of NE, Pigs fed the diet containing 2.40 Mcal/kg of NE had the lowest percentage of total fat （36. 95% ） and the highest percentage of fat-free lean （49.36%）. The overall results of these experiments indicate that feed- ing either a surplus or a deficiency of NE is detrimen- tal to both pig performance and carcass composition when low CP diets supplemented with CAA are fed. Our results indicate that when the CP content of the diet is reduced by four percentage units and the diet is properly supplemented with CAA, maximum per- formance and carcass quality will be obtained if the diet provides approximately 2.42 Mcal/kg of NE.

Effects of Dietary Net Energy Density and Standardized Ileal Digestible Lysine: Net Energy Ratio on the Performance and Carcass Characteristic of Growing-Finishing Pigs Fed Low Crude Protein Supplemented with Crystalline Amino Acids Diets

Two 3×3 factorial design trials with 1 080 of Yorkshire×Landrace×Duroc barrows were conducted to investigate the effects of dietary net energy （NE） density and standardized ileal digestible （SID） lysine：NE ratio on the performance of growing- finishing pigs and carcass characteristic of finishing pigs fed low crude protein （CP） supplemented with crystalline amino acids （CAA） diets. Low CP corn-soybean meal basal diets （14% for Exp. 1 and 11% for Exp. 2） supplemented with crystalline lysine, methionine, threonine, and tryptophan were formulated. Nine treatments with increasing NE density and SID lysine：NE ratio were used in each trial （Exp. 1： 9.66, 9.87, and 10.08 MJ kg-1 NE, 0.89, 0.96, and 1.03 g MJ-1 SID lysine： NE; Exp. 2： 9.83, 10.04, and 10.25 MJ kg-1 NE, 0.69, 0.76, and 0.83 g MJ-1 SID lysine：NE）. In Exp. 1, we observed that the average daily gain （ADG） for barrows that received the diet containing 9.87 MJ kg-1 NE was significantly higher than that of barrows fed a 9.66 MJ kg-1 NE diet （P0.05）, but no difference was observed when compared with barrows that received a diet containing 10.08 MJ kg-1 NE （P0.05）. The ADG was affected both linearly （P0.05） and quadratically （P0.05） as the SID lysine：NE ratio increased. The NE density or SID lysine：NE ratio and their interaction had no effect on the average daily feed intake （ADFI） and serum urea nitrogen （SUN） （P0.05）. The feed to gain ratio （F：G） decreased （linearly, P0.05; quadratically, P0.05） as the NE density or SID lysine：NE ratio increased, but no interaction of NE density and SID lysine： NE ratio on the F：G. In Exp. 2, the dietary NE density both linearly （P0.05） and quadratically （P0.05） affected the ADG and F：G. Barrows that received a diet containing 10.04 MJ kg-1 NE had a greater ADG （P0.05） than barrows that received a 9.83 MJ kg-1 diet, but there was no difference （P0.05） as compared with barrows that received a diet containing 10.25 MJ kg-1 NE. F：G was significantly higher （P0.05） for barrows that received a 9.83 MJ kg-1 diet when compared with barrows that received the other two diets. The ADG was significantly decreased （P0.05） for pigs that received a diet containing 0.69 g MJ-1 SID lysine：NE ratio when compared with pigs fed a diet containing 0.76 or 0.83 g MJ-1 SID lysine：NE ratio. The NE density or SID lysine：NE ratio and their interaction had no effect on the average daily feed intake, SUN, and carcass characteristic for finishing barrows （P0.05）. The overall results of the two experiments indicated that barrows that received the diet with the dietary CP level reduced 4 percentage units compared the NRC （1998） recommendations. Maximized the best performance with NE density and SID lysine：NE ratio were 9.87 MJ kg-1, 1.03 g MJ-1 NE for 20-50 kg pigs, and 10.04 MJ kg-1, 0.76 g MJ-1 NE for 60-100 kg pigs, respectively.

Net energy yield and carbon footprint of summer corn under different N fertilizer rates in the North China Plain

Excessive use of N fertilizer in intensive agriculture can increase crop yield and at the same time cause high carbon（C） emissions.This study was conducted to determine optimized N fertilizer application for high grain yield and lower C emissions in summer corn（Zea mays L.）.A field experiment, including 0（N0）, 75（N75）, 150（N150）, 225（N225）, and 300（N300） kg N ha–1 treatments, was carried out during 2010–2012 in the North China Plain（NCP）.The results showed that grain yield, input energy, greenhouse gas（GHG） emissions, and carbon footprint（CF） were all increased with the increase of N rate, except net energy yield（NEY）.The treatment of N225 had the highest grain yield（10 364.7 kg ha–1） and NEY（6.8%）, but the CF（0.25） was lower than that of N300, which indicates that a rate of 225 kg N ha–1 can be optimal for summer corn in NCP.Comparing GHG emision compontents, N fertilizer（0–51.1%） was the highest and followed by electricity for irrigation（19.73–49.35%）.We conclude that optimazing N fertilizer application rate and reducing electricity for irrigation are the two key measures to increase crop yield, improve energy efficiency and decrease GHG emissions in corn production.

Oat bran and wheat bran impact net energy by shaping microbial communities and fermentation products in pigs fed diets with or without xylanase

Background: Dietary fiber can be fermented in gut of pigs and the end products of fermentation were short-chain fatty acids(SCFA). The SCFA had positive effects on gut bacteria and host immune system. In addition, SCFA can provide a part of available energy for pigs. However, there were limited reports on the relationship between dietary fiber, gut bacteria, and energy metabolism. Therefore, this study investigated how dietary fiber and enzyme addition impacted energy metabolism by acting on the microbial community and SCFA.Methods: Wheat bran(WB) was added to the corn-soybean meal-based diet at the levels of 12% and 27%, and oat bran(OB) at 15% and 36%. One of each diet was supplemented with or without 5000 U/kg feed of xylanase, so a total of 10 diets were allotted to 60 growing pigs(initial body weight: 27.2 ± 1.2 kg) using a randomized complete block design. The experiment was conducted in 10 consecutive periods using 6 similar open-circuit respiration chambers. Each pig was used for one 20-day period. During each period, six pigs were allowed 14 d to adapt to the diets in metabolic cages followed by 6 d(from d 15 to d 20) in respiration chambers to measure heat production(HP).Results: Pigs fed 36% OB diets had greater(P < 0.05) nutrient digestibility and net energy(NE) values compared to those fed 27% WB diets. Apparent digestibility coefficients of dry matter(DM) and crude protein(CP) were lower(P < 0.05) in pigs fed 27% WB diets compared with those fed 12% WB diets. Enzyme addition improved(P < 0.05)the NE values(11.37 vs. 12.43 MJ/kg DM) in diets with 27% WB. Supplementation of xylanase did not affect NE values for basal diets, OB diets and 12%WB diets. Compared with diets with 36% OB, pigs fed 27% WB-based diets excreted more total SCFA, acetate and propionate(expressed as g/kg feed DM) in fecal samples of pigs(P < 0.05).Pigs in the WB diets had greater proportion of phylum Bacteroidetes while phylum Firmicutes were greater in pigs fed OB diets(P < 0.05). Pigs fed WB diets had greater(P < 0.05) abundance of Succinivibrio and Prevotella, which were associated with fiber degradation and SCFA production.Conclusion: Our results indicated diets supplied by high level of OB or WB promote the growth of fiber-degrading bacteria. The differences in fiber composition between WB and OB led to differences in nutrient digestibility and bacterial communities, which were ultimately reflected in energy metabolism. Enzyme supplementation improved nutrient digestibility as well as NE values for 27% WB diets but not for other diets, which indicated that effects of enzyme were related to type and level of dietary fiber in diets.

Concerns about the misleading conclusions regarding estimation of the net energy value of soybean meal relative to corn using the caloric efficiency approach in pigs

Apart from energy balance trials such as calorimetry,growth trials could also be used to estimate the energy values of feed ingredients with caloric efficiency as an indicator.Recent work used such methods reported greater net energy(NE)value of soybean meal(SBM)relative to corn in nursery pigs.We theoretically compared the NE values of SBM and corn according to the definition of NE and properties of the major chemical compositions in each ingredient.Meanwhile,we thoroughly examined the diet formulations and related analysis used in this work and compared this study with some peer works.We found that this study may suffer from problems with experimental design,reference citation,and data interpretation.In summary,the conclusion from the recent work that the SBM NE value may be greater than the corn NE value is likely to be erroneous.

Effect of the Standardized Ileal Digestible Lysine to Net Energy Ratio onthe Performance of Weaning Pigs Housed Under Commercial Conditions

Four experiments were conducted to investigate the effects of altering the standardized ileal digestible （SID） lysine to net energy （NE） ratio on the performance of weaned pigs housed under commercial conditions. Exp. 1 and 2 utilized a total of 720 crossbred pigs （Landrace x Yorkshire） weighing an average of 8.41 ± 0.72 kg in Exp. 1 and 6.94 ± 0. 63 kg in Exp. 2. The pigs were allotted to one of three treatments with six pens of 20 pigs per treatment. The treatments consisted of diets with different NE levels （2. 48, 2. 42, or 2. 36 Mcal/kg） and 1.21% SID-lysine. The diets were formulated using corn, soybean meal, wheat middlings, and broken rice. During both 14 day trials, the ADG of the pigs fed the diet providing 2.48 Mcal/kg NE was the highest among the three treatments （P 〈0.01 ）. The ADG of pigs fed diets providing 2.42 and 2.36 Mcal/kg NE did not differ （P 〉 0.05 ）. Exp. 3 and 4 were conducted to study the effects of different SID-lysine levels on the performance of weaned pigs fed diets containing 2.48 Mcal/kg NE. Exp. 3 and 4 utilized 720 crossbred pigs （ Landrace x Yorkshire） weighing 8.48±0.81 kg in Exp. 3 and 6.83 ±0.74 kg in Exp. 4. The pigs Were allotted to three treatments with six pens of 20 pigs per treatment. The treatments consisted of three diets with different SID-lysine levels （1.31%, 1.21%, or 1.11% ） and the same NE level （2.48 Mcal/kg）. Exp. 3 and 4 showed that the ADG of pigs fed the diet with 1.31% SID-lysine was higher than pigs fed the diet with 1.11% SID-lysine （P 〈0.01）. The ADG for pigs fed diets with 1.31% and 1. 21% SID-lysine did not differ （P 〉0. 05）. Based on the results of the present study, to maximize ADG of weaned pigs, the optimal level of NE is 2.48 Mcal/kg and the optimum level of SID-lysine is 1.31%.

Comparative study of apparent metabolizable energy and net energy values of dephenolized cottonseed proteins for laying hens

Optimizing the energy utilization of nutrients and ensuring maximum benefits are continuous goals for livestock producers.The net energy(NE)value of feed reflects its nutritional value in the precision feeding system.An experiment was conducted to determine the apparent metabolizable energy(AME)and NE values of 3 types of dephenolized cottonseed protein(DCP)for Hy Line Brown hens aged 42 to 45 weeks using the reference diet substitution method.A reference diet based on corn soybean meal was used to meet the nutritional needs of Hy Line Brown laying hens.To render the crude protein and energy values of the 3 test diets similar,10.5%,12%,and 16%of the gross energy yielding ingredients from the reference diet were replaced with DCP 1,DCP 2,and DCP 3,respectively.The birds were fed 4 diets during a 7-d adaptation period.After the dietary adaptation period,2 birds per replicate from each treatment group were placed in an individual open circuit respiratory calorimetry chamber for a 3-d experimental period.Daily O_(2)consumption and CO_(2)production were recorded,and excreta samples were collected.The AME values of DCP 1,DCP 2,and DCP 3 were 3,049.05,2,820.13,and 2,982.31 kcal/kg of dry matter(DM),respectively.The NE values of DCP 1,DCP 2,DCP 3 were 1,475.77,1,910.31,and 1,905.37 kcal/kg of DM,respectively,and the NE:AME ratios were 48.40%,67.74%,and 63.89%,respectively.Our data show that the AME value of DCP does not reflect the nutritional value of the feed.The NE value of DCP with a high ME value was not necessarily high.

Wheat bran inclusion level impacts its net energy by shaping gut microbiota and regulating heat production in gestating sows

An accurate estimation of net energy(NE)of wheat bran is essential for precision feeding of sows.However,the effects of inclusion level on NE of wheat bran have not been reported.Inclusion level was hypothesized to impact NE of wheat bran by regulating gut microbiota and partitioning of heat production.Therefore,twelve multiparous sows(Yorkshire×Landrace;2 to 4 parity)were assigned to a replicated 3×6 Youden square with 3 successive periods and 6 diets in each square.The experiment included a corn-soybean meal diet(WB0)and five diets including 9.8%(WB10),19.5%(WB20),29.2%(WB30),39.0%(WB40)and 48.7%wheat bran(WB50),respectively.Each period included 6 d of adaptation to diets followed by 6 d for heat production measurement using open-circuit respiration chambers.Compared with other groups,WB30,WB40,and WB50 enriched different fiber-degrading bacteria genera(P<0.05).Apparent total tract digestibility of neutral detergent fiber and acid detergent fiber of wheat bran were greater in WB30 and WB40(P<0.05).Physical activity(standing and sitting)decreased as inclusion level increased(P=0.04),which tended to decrease related heat production(P=0.07).Thermic effect of feeding(TEF)was higher in WB50 than other treatments(P<0.01).Metabolizable energy of wheat bran was similar among treatment groups(except for WB10).NE of wheat bran conformed to a quadratic regression equation with inclusion level(R^(2)=0.99,P<0.01)and peaked at an inclusion level of 35.3%.In conclusion,increasing inclusion level decreased energy expenditure of sows on physical activity and promoted growth of fiber-degrading bacteria,which improved energy utilization of fiber.Fermentation of wheat bran fiber by Prevotellaceae_UCG-003 and norank_f_Paludibacteraceae might increase TEF.Consequently,sows utilized energy in wheat bran most efficiently at an inclusion level of 35.3%.

Net energy,energy utilization,and nitrogen and energy balance affected by dietary pea supplementation in broilers

Pea starch consists predominantly of C-type of amylopectin chain which is more resistant to digestive enzymes than A-type of starch thus slowly digested in poultry.It was hypothesized that the presence of slowly digested pea starch in broiler diets will increase net energy and the efficiency of energy utilization in broilers.Two experiments were performed to investigate starch digestibility of pea at different in-cubation times(in vitro study)and the effect of dietary pea on heat increment and net energy in broilers using an open-circuit respiratory calorimetry system(in vivo study).One-day-old Ross 308 male broilers were fed a common starter crumble from d 1 to 10 and standard grower diets thereafter.At d 21,birds were transferred to the chambers each housing 2 birds.Each treatment was replicated 6 times with 2 identical runs of 3 replicates per treatment.A wheat-soybean meal-based diet was used as a control and the treatment diet contained 500 g of pea/kg pea.In vitro study showed that pellet processing increased(P<0.001)starch digestibility,particularly at shorter times for wheat and a much larger response for pea.Birds offered the pea-based diet had lower(P=0.002)feed intake,lower(P=0.020)body weight gain,but a similar(P>0.05)FCR compared to those offered the wheat-based diet.Net energy(NE)and apparent metabolizable energy(AME)values were higher in the pea-based diet than in the wheat-based diet(P-0.037 for NE and P-0.018 for AME).Heat production,respiratory quotient,heat increment of feed,efficiency of utilization of gross energy for AME,and efficiency of utilization of AME for NE did not differ(P>0.05)between the 2 treatments.There was no effect(P>0.05)of pea on the total tract di-gestibilities of dry matter,crude protein and ash,but the total tract digestibility of starch was higher(P-0.022)in the pea-based diet compared to the wheat-based diet.This study provides insight into the energy metabolism of broilers offered a pea-based diet and indicates that dietary pea supplementation increases dietary AME and NE but has no effect on heat increment of feed and the efficiency of energy utilization in broilers.

Effects of different starch structures on energy metabolism in pigs

Background Starch is a major component of carbohydrates and a major energy source for monogastric animals.Starch is composed of amylose and amylopectin and has different physiological functions due to its different structure.It has been shown that the energy supply efficiency of amylose is lower than that of amylopectin.However,there are few studies on the effect of starch structure on the available energy of pigs.The purpose of this study was to measure the effect of different structures of starch in the diet on the net energy(NE)of pigs using a comparative slaughter method and to establish a prediction equation to estimate the NE of starch with different structures.Fifty-six barrows(initial BW 10.18±0.11 kg)were used,and they were housed and fed individually.Pigs were divided into 7 treatments,with 8 replicates for each treatment and 1 pig for each replicate.One of the treatments was randomly selected as the initial slaughter group(ISG).Pigs in the remaining treatments were assigned to 6 diets,fed with basic diet and semi-pure diets with amylose/amylopectin ratio(AR)of 3.09,1.47,0.25,0.15 and 0.12,respectively.The experiment lasted for 28 d.Results Results showed that compared with the high amylose(AM)groups(AR 3.09 and 1.47),the high amylopectin(AP)group(AR 0.15)significantly increased the final BW,average daily weight gain and average daily feed intake of pigs(P<0.05),but the F:G of the AM group was lower(P<0.01).In addition,AR 0.15 and 0.12 groups have higher(P<0.01)nutrient digestibility of dry matter,crude protein,gross energy and crude ash.Meanwhile,compared with other groups,AR 0.15 group has a higher(P<0.05)NE intake and energy retention(RE).The regressive equation for predicting with starch structures was established as RE=1,235.243-48.298AM/AP(R^(2)=0.657,P=0.05).Conclusions In conclusion,NE intake and RE of pigs augmented with the increase of dietary amylopectin content,indicating that diets high in amylopectin were more conducive to promoting the growth of pigs in the late conserva-tion period.

Energy Requirements for Maintenance and Growth of German Mutton Merino Crossbred Lambs

A comparative slaughter trial and a metabolism trial were conducted to determine the requirement of net energy （NE） and metabolizable energy （ME） by the crossbreed of German Mutton Merino×Inner Mongolia Merino for fattening from 35 to 50 kg of body weight （BW）. 49 crossbred female lambs （（33.9＋2.3） （SD） kg BW） of German Mutton Merino×lnner Mongolia Merino were used. 34 lambs were randomly chosen for comparative slaughter, which were offered an identical mixture diet （concentrate：roughage=55：45） at 100, 75 or 55% of ad libitum intake, whereas the remainders were used in the metabolism trial to evaluate the ME of the diet after methane production was measured by open-circuit respirometry. As feed intake decreased from 100 to 75 and 55% of ad libitum intake, the apparent digestibility of dry matter （DM） linearly increased （P=-0.010） from 60.8 to 63.6 and 66.9%, respectively, and methane production decreased from 52.1 to 44.3 and 39.9 L d-l, respectively, but the ratio of methane energy to gross energy intake increased linearly （P=0.010） from 8.20 to 8.96 and 10.97%, respectively. Consequently, the ME values of the diet increased from 9.35 to 9.64 and 9.85 MJ kg-~ DM, respectively. The NE requirement for maintenance （NEro） was 255 kJ kg-1 BW0.75, and the ME requirement for maintenance （MEre） was 352 kJ kg-I BW~.75, with a partial energy efficiency for maintenance （km） of 0.72. The NE requirement for growth （NEg） ranged from 1.26 to 4.66 MJ d-1as average daily gains increased from 100 to 300 g d-1, with a partial energy efficiency for growth （ks） of 0.45. These results indicated that the NEg required by crossbred female lambs of German Mutton Merinoxlnner Mongolia Merino was lower than the recommendation of the American or British nutritional system.

Energy requirements of Dorper×thin-tailed Han crossbred ewes during non-pregnancy and lactation

This experiment was conducted to investigate the energy requirement of Dorper×thin-tailed Han crossbred ewes during non-pregnancy and lactation. Fifteen ewes after parturition were randomly assigned to three treatments： ad libitum（100%） feed intake and 80 or 60% ad libitum intake, and another nine non-pregnant ewes were assigned to a blank control group. Digestibility trials were performed in the non-pregnant ewes and in the lactating ewes on the 20 th, 50 th, and 80 th d of lactation. In parallel with the digestibility trial, a respirometry experiment was conducted to determine the methane and carbon dioxide production with an open-circuit respirometry system that was equipped with respiratory chambers. The net energy（NE） and metabolizable energy（ME） requirements for maintenance and growth were calculated using the carbon and nitrogen balance method. The results revealed that the carbon（C） and nitrogen（N） excretions and energy losses at faeces and urine, as well as the output of methane and CO2, increased significantly with decreasing feed intake（P〈0.01）. The apparent digestibilities of C in th e stages of non-pregnancy and early, middle and late lactation were 55.8–58.3%, 62.5–73.8%, 64.8–71.3%, and 61.7–65.0%, respectively, and the apparent digestibilities of N were 45.2–51.3%, 73.7–82.7%, 72.8–80.5%, and 73.6–76.5%, respectively. The corresponding energy apparent digestibilities were 52.0–56.3%, 60.7–76.6%, 61.0–68.8%, and 61.4–67.7%, respectively. The ME/DE（digestible energy） values were 79.5–85.9%, 79.4–83.5%, 81.0%–85.3% and 78.6–82.9%, respectively. The maintenance requirements of NE, ME, and the efficiencies of ME utilisation for maintenance during the stages of non-pregnancy and early, middle and late lactation were 215.5, 253.1, 247.7, and 244.7 k J kg^（–1） BW0.75 d, and 372.4, 327.1, 320.9, and 362.0 k J kg^（–1） BW0.75 d, and 0.58, 0.77, 0.77, and 0.68, respectively. The ME requirement for the growth of non-pregnant ewes was 31.3 MJ kg^（–1） BW gain.

A review of physical supply and EROI of fossil fuels in China

This paper reviews China’s future fossil fuel supply from the perspectives of physical output and net energy output. Comprehensive analyses of physical output of fossil fuels suggest that China’s total oil production will likely reach its peak, at about 230 Mt/year(or 9.6 EJ/year),in 2018; its total gas production will peak at around350 Bcm/year(or 13.6 EJ/year) in 2040, while coal production will peak at about 4400 Mt/year(or 91.9 EJ/year)around 2020 or so. In terms of the forecast production of these fuels, there are significant differences among current studies. These differences can be mainly explained by different ultimately recoverable resources assumptions, the nature of the models used, and differences in the historical production data. Due to the future constraints on fossil fuels production, a large gap is projected to grow between domestic supply and demand, which will need to be met by increasing imports. Net energy analyses show that both coal and oil and gas production show a steady declining trend of EROI(energy return on investment) due to the depletion of shallow-buried coal resources and conventional oil and gas resources, which is generally consistent with the approaching peaks of physical production of fossil fuels. The peaks of fossil fuels production, coupled with the decline in EROI ratios, are likely to challenge the sustainable development of Chinese society unless new abundant energy resources with high EROI values can be found.

Energy Expenditure of Adolescents During Overground Walking and Running

This study aimed to determine the net energy expenditure(EENET)required for overground walking and running 1200 m in a sample of healthy adolescent boys and girls.A secondary purpose was to describe the effect of body composition on energy expenditure(EE)of walking versus running.Twenty healthy adolescents(9 boys,11 girls)aged 15.85±2.80 years performed 2 field tests in regular outdoor conditions:overground walking(1.64±0.17 m/s)and submaximal running(3.13±0.42 m/s),at a self-selected steady pace.EE was measured via indirect calorimetry.Paired sample t-tests were used to determine if there were differences between walking and running conditions and mean percentage differences were estimated for various physiological parameters.Differences in EENET between conditions were performed for both genders using a two(condition)by two(gender)analysis of variance repeated measures design,with fat free mass as a covariate.Speed increased by 90.43%between the 2 conditions,while the different components of EE increased by almost 20%.Running elicited a significantly greater EENET than walking for both genders;however,boys’and girls’EE did not differ significantly.When EENET was adjusted for fat free mass,there was a statistically significant condition×fat free mass effect.The findings in this study indicate that both adolescent boys and girls expend more energy during running than walking,without being affected by body composition.Body mass and fat free mass significantly correlated with EE only during running.In addition,the trained participants of the study optimized locomotion to minimize EE.

Protease supplementation reduced the heat increment of feed and improved energy and nitrogen partitioning in broilers fed maize-based diets with supplemental phytase and xylanase

An experiment was conducted to explore the effects of digestible amino acid(dAA)concentrations and supplemental protease on live performance and energy partitioning in broilers.Ross 308 male broilers(n?288)were distributed into 24 floor pens and offered 1 of 4 dietary treatments with 6 replicates from 1 to 35 d of age.Dietary treatments consisted of a 2×2 factorial arrangement with dAA concentrations(standard and reduced[34 g/kg below standard])and supplemental protease(without or with)as the main factors.At 1,15,28,and 35 d of age,feed and broilerswereweighed to determine live performance.From20 to 23 d of age,a total of 32 birds(2 birds/chamber,4 replicates)were placed in closed-calorimeter chambers to determine respiratory exchange(heat production,HP),apparent metabolisable energy(AME),retained energy(RE),and net energy(NE).From 29 to 35 d of age,supplemental protease in the reduced-dAA diet decreased broiler feed conversion ratio(FCR)by 5.6 points,whereas protease supplementation in the standard-dAA diet increased FCR by 5.8 points.The indirect calorimetry assay revealed that supplemental protease decreased(P<0.05)the heat increment of feed(HIF)by 0.22 MJ/kg.Also,from 20 to 23 d of age,broilers offered the reduced-dAA diet with supplemental protease had a higher daily body weight gain(BWG)(t10.4%),N intake(t7.1%),and N retention(t8.2%)than those offered the standard-dAA with supplemental protease.Broilers offered the reduced-dAA without supplemental protease exhibited a 3.6%higher AME-to-crude protein(CP)ratio than those offered other treatments.Protease supplementation in the standard-and reduced-dAA diets resulted in 2.7%and 5.6%lower AME intake-to-N retention ratios,respectively,compared with the unsupplemented controls.Reduced-dAA increased(P<0.05)AME intake(t4.8%),RE(t9.8%),NE intake(t5.8%),NE intake-to-CP ratio(t3.0%),and RE fat-to-RE ratio(t8.6%).Protease supplementation increased(P<0.05)respiratory quotient(t1.2%)and N retention-to-N intake ratio(t2.2%),NE-to-AME ratio(t1.9%),and reduced HP(3.6%),heat increment(7.4%),and NE intake-to-N retention(2.5%).In conclusion,protease positively affected FCR and energy partitioning in broilers;responses were most apparent in diets with reduced-dAA concentrations.

Multi-carbohydrase enzymes improve feed energy in broiler diets containing standard or low crude protein

This study evaluated the effect of multi-carbohydrase(MC)on energy and nitrogen(N)balance and gene expression in broilers fed diets with different crude protein(CP)contents.The study employed a 2×2 factorial arrangement of treatments.The factors were presence or absence of MC,and standard(SCP)or low(LCP)dietary CP concentration.A 3-phase feeding program was used,including starter(0 to 7 d),grower(8 to 17 d)and finisher(18 to 28 d)phases.The study was undertaken in closed calorimetry chambers.Each of the 4 dietary treatments was replicated 8 times in total across 2 runs,with 2 birds per replicate(n=64).Data for energy partitioning and N balance were collected from d 25 to 28.On d 28,birds were euthanized to collect muscle and intestinal tissue samples for gene expression.The results showed that the MC increased apparent metabolizable energy(AME,P<0.01)and net energy(NE,P<0.05),and reduced the feed conversion ratio(FCR,P<0.01)in all diets.The proportion of energy retained as fat per total energy retention(REf/RE)was positively correlated with feed AME and NE(r=0.541,P<0.01 and r=0.665,P<0.001,respectively),suggesting that feed energy augmented with increased fat gain.Muscle ATP synthase subunit alpha(ATPSA1W)gene expression had a positive cor-relation with REf/RE and feed NE(r=0.587,P<0.001 and r=0.430,P<0.05,respectively).Similarly,muscle peroxisome proliferator-activated receptor gamma coactivator 1 alpha(PGC-1A)expression was negatively correlated with weight gain and positively correlated with FCR(r-0.451,P<0.05 and r-0.359,P<0.05,respectively).These correlations show that over-expressions of muscle genes related to energy production reduce bird performance.This study demonstrated that MC increase dietary energy utilization,regardless of dietary CP concentration.However,the energy released by the enzymes in-creases feed energy-to-CP ratio,meaning there is excess energy that is then deposited as body fat.This suggests that supplemental MC in broiler feeds is beneficial if diets are formulated to contain marginal energy levels.