Influence of starch sources and dietary protein levels on intestinal functionality and intestinal mucosal amino acids catabolism in broiler chickens

Background: There is growing interest in carbohydrate and protein nutrition to enhance the efficiency of animal production.Reduced-crude protein diets depress environmental pollution and feeding cost,but the challenge to their adoption is maintaining digestive function and growth performance of birds.The present study was conducted to evaluate the influence of different dietary starch sources and protein levels on intestinal functionality and mucosal amino acid catabolism.Methods: Six dietary treatments,based on maize and soybean meal,were offered to 360 AA+male chicks from 6 to 35 d post-hatch as a 3 × 2 factorial array.Either waxy rice or amylose was added to a conventional maize-soy diet to provide three sources of starch with different digestion rates and relatively high and low dietary protein levels.Growth performance,parameters of intestinal functionality and concentrations of free amino acid in the portal circulation were determined.Results: In the grower phase,starch source influenced(P < 0.02) weight gain as diets containing amylose supported significantly higher weight gains than waxy rice.Significant increase of ileal ATP concentrations and Na^+/K^+-ATPase activity were found in amylose treatment.Also,amylose decreased BrdU positive cell numbers and down-regulated m RNA expression for CASP-3.GOT activity in the ileum was higher(P < 0.01) in birds offered low protein diets and there was a trend(P = 0.057) for waxy rice as a starch source to increase ileal GOT activities.There was a significant influence on the concentration of seventeen amino acids in the portal circulation with tryptophan the one exception.Waxy rice as a starch source generated 13.6% and 22.4% numerically higher concentrations of non-essential amino acids than maize and amylose,respectively.Conclusions: Amino acid catabolism in the gut mucosa is subject to nutritional regulation.Given that amino acids can be spared from catabolism in the gut mucosa by supplementation of amylose,it follows their post-enteral availability would be improved and intestinal energy would be derived more efficiently from glucose.

Progress towards reduced-crude protein diets for broiler chickens and sustainable chicken-meat production

The prime purpose of this review is to explore the pathways whereby progress towards reduced-crude protein(CP)diets and sustainable chicken-meat production may be best achieved.Reduced-CP broiler diets have the potential to attenuate environmental pollution from nitrogen and ammonia emissions;moreover,they have the capacity to diminish the global chicken-meat industry’s dependence on soybean meal to tangible extents.The variable impacts of reduced-CP broiler diets on apparent amino acid digestibility coefficients are addressed.The more accurate identification of amino acid requirements for broiler chickens offered reduced-CP diets is essential as this would diminish amino acid imbalances and the deamination of surplus amino acids.Deamination of amino acids increases the synthesis and excretion of uric acid for which there is a requirement for glycine,this emphasises the value of so-called“non-essential”amino acids.Starch digestive dynamics and their possible impact of glucose on pancreatic secretions of insulin are discussed,although the functions of insulin in avian species require clarification.Maize is probably a superior feed grain to wheat as the basis of reduced-CP diets;if so,the identification of the underlying reasons for this difference should be instructive.Moderating increases in starch concentrations and condensing dietary starch:protein ratios in reduced-CP diets may prove to be advantageous as expanding ratios appear to be aligned to inferior broiler performance.Threonine is specifically examined because elevated free threonine plasma concentrations in birds offered reduced-CP diets may be indicative of compromised performance.If progress in these directions can be realised,then the prospects of reduced-CP diets contributing to sustainable chicken-meat production are promising.

The influence of phytase, pre-pellet cracked maize and dietary crude protein level on broiler performance via response surface methodology

Background:The reduction of crude protein levels in diets for broiler chickens may generate economic,environmental and flock welfare and health benefits;however,performance is usually compromised.Whole grain feeding and phytase may improve the utilization of reduced crude protein diets.Results:The effects of pre-pellet cracked maize(0,15%and 30%)and phytase(0,750 and 1500 FTU/kg)in isoenergetic maize-soy diets with three levels of crude protein(22%,19.5%and 17%)were evaluated via a BoxBehnken response surface design.Each of 13 dietary treatments were offered to 6 replicate cages(6 birds/cage)of male Ross 308 broiler chicks from 7 to 28 d post-hatch.Model prediction and response surface plots were generated from experimental data via polynomial regression in R and only significant coefficients were included and discussed in the predicted models.Weight gain,feed intake and FCR were all influenced by pre-pellet cracked maize,phytase and crude protein level,where crude protein level had the greatest influence.Consequently,the reduction from 22%to 17%dietary crude protein in non-supplemented diets reduced weight gain,feed intake,relative gizzard weight,relative gizzard content and relative pancreas weight but improved FCR.However,the inclusion of 30%cracked maize to 17%crude protein diets restored gizzard weight and 1500 FTU phytase inclusion to 17%crude protein diets increased relative gizzard contents and pancreas weights.Cracked maize and phytase inclusion in tandem to 17%crude protein diets increased weight gain,feed intake and FCR;however,this FCR was still more efficient than broilers offered the non-supplemented 22%crude protein diet.Broilers offered the prepellet cracked maize and phytase inclusions reduced AME in 22%crude protein diets but improved AME by 2.92 MJ(14.16 versus 11.24 MJ;P<0.001)in diets containing 17%crude protein.Ileal N digestibility was greater in broilers offered diets with 17%crude protein than those offered the 22%crude protein diet;irrespective of phytase and pre-pellet cracked maize.Conclusion:Pre-pellet cracked maize and phytase inclusions will improve the performance of broilers offered reduced crude protein diets.

Effect of restricted feeding on hen performance,egg quality and organ characteristics of individual laying hens

This study was to assess the impact of permanent or temporary restricted feeding on laying hen production traits,physiology,and egg quality.Two hundred and forty individually housed ISA Brown hens were monitored across 2 phases,assigned to 3 treatments:ad libitum feeding(ALF),temporary restricted feeding(TRF)and permanent restricted feeding(PRF),n=80 hens per treatment.In Phase 1(P1),22 to40 weeks,the TRF and PRF hens were offered 115 g of feed daily.In Phase 2(P2),41 to 46 weeks,the TRF hens were transitioned to ALF status while the ALF and PRF hens remained as in P1.From 35 to 40 weeks,eggs were collected once weekly from 15 hens per treatment and assessed for differences in albumen,yolk,and shell variables.At 45 weeks,10 hens each from the ALF and PRF groups were euthanized and differences in organ characteristics were assessed.In P1,feed intake,feed to egg conversion ratio and body weight(BW)change were lower(P<0.01),while albumen height and Haugh unit were higher(P<0.01)in both PRF and TRF hen treatments compared to hens allocated the ALF treatment.In P2,TRF and ALF hens had a higher egg production and egg mass than PRF(P<0.01)than ALF.Body weight change in P2 was higher in TRF and similar in both ALF and PRF,while feed intake and feed conversion ratio were higher in TRF followed by ALF and least in the PRF treatment group(P<0.01).At 45 weeks ALF hens had a greater abdominal fat pad weight and fatty liver haemorrhagic syndrome lesion score compared to PRF.Restricting hens to 115 g of feed per day from point of lay restrained BW,improved feed conversion ratio and albumen quality and reduced abdominal fat pad deposition and clinical signs of fatty liver haemorrhagic syndrome in individually housed laying hens.

The influence of dietary crude protein concentrations,grain types and arginine:lysine ratios on the performance of broiler chickens

The objective of this study was to investigate the effects of dietary crude protein(CP)concentrations,grain types and arginine:lysine ratios on performance parameters of broiler chickens.The 2×2×2factorial array of dietary treatments harnessed two CP concentrations(210 and 170 g/kg),two feed grains(wheat and sorghum),and two arginine:lysine ratios(104 and 110).Each dietary treatment was offered to 7 replicates of 14 birds per floor pen,a total of 784 off-sex male,Ross 308 broilers,from 14 to 35 d post-hatch.The dietary CP reduction compromised weight gain by 10.0%(2078 versus 2310 g/bird)as a main effect and FCR by 7.51%(1.474 versus 1.371),subject to an interaction.In a three-way interaction(P=0.008),expanded arginine:lysine ratios improved FCR by 2.30%in 170 g/kg CP,sorghum-based diets but compromised FCR by 2.12%in corresponding wheat-based diets.Sorghum was the more suitable feed grain in reduced-CP diets as sorghum generated significant advantages in weight gain of 7.59%(2154versus 2002 g/kg)and FCR of 6.94%(1.421 versus 1.527)in birds offered 170 g/kg CP diets.Both dietary CP and feed grain generated significant and divergent impacts in apparent ileal digestibility coefficients for the majority of 16 assessed amino acids.Dietary CP reductions increased non-bound amino acid inclusions(NBAA)in wheat-based diets(48.96 versus 9.80 g/kg)to a greater extent than sorghum-based diets(35.3 versus 9.50 g/kg)and increasing dietary NBAA inclusions were linearly associated with compromised weight gain(r=-0.834;P<0.001)and FCR(r=0.862;P<0.001).Increasing ratios of free arginine to lysine plasma concentrations were linearly(r=-0.466;P=0.004)related to improvements in FCR.The implications of the observed outcomes are discussed and possible explanations are advanced.

The influence of non-bound amino acid inclusions and starch-protein digestive dynamics on growth performance of broiler chickens offered wheat-based diets with two crude protein concentrations

The primary objective of this study was to investigate the influence of high and low inclusions of nonbound amino acid(NBAA)in standard and reduced-crude protein(CP),wheat-based diets on growth performance in broiler chickens.Dietary treatments were formulated to either 210 or 180 g/kg CP.The210 g/kg CP diets contained either 12.1 or 21.1 g/kg NBAA and 180 g/kg CP diets contained either 44.0 or55.5 g/kg NBAA.The formulations also generated different dietary starch:protein ratios which impacted on starch-protein digestive dynamics.Each of the four dietary treatments were offered to 7 replicates of15 birds housed in floor pens from 14 to 35 days post-hatch or a total of 420 male Ross 308 chickens.Growth performance,relative abdominal fat-pad weights,breast muscle and leg shank yields were determined.Ileal starch and protein(N)digestibility coefficients,disappearance rates and starch:protein disappearance rate ratios were defined.Apparent ileal digestibility coefficients and disappearance rates of 16 amino acids were determined at 35 days post-hatch and free concentrations of 20 amino acids in systemic plasma were determined at 34 days post-hatch.The transition from 210 to 180 g/kg CP diets depressed weight gain by 11.3%(1742 versus 1964 g/bird)and FCR by 10.4%(1.606 versus 1.455),although both parameters were subject to treatment interactions.The treatment interaction(P<0.001)observed for FCR was because high NBAA inclusions significantly improved FCR by 4.17%(1.424 versus1.486)in birds offered 210 g/kg CP diets,but significantly depressed FCR by 3.36%(1.632 versus 1.579)in180 g/kg CP diets.A quadratic relationship(r=0.860;P<0.001)between dietary NBAA inclusions and FCR was detected,which indicated that when NBAA inclusions exceed 18.5 g/kg efficiency of feed conversion deteriorated.However,a multiple linear regression(r=0.913;P<0.001)was detected for FCR where both NBAA inclusions and analysed dietary starch:protein ratios were significantly(P<0.001)related to FCR.This relationship indicates that growth performance of broiler chickens offered wheatbased diets is strongly influenced by dietary NBAA inclusions coupled with dietary starch:protein ratios and consideration is given to the possible underlying mechanisms.

Facilitating the acceptance of tangibly reduced-crude protein diets for chicken-meat production

Inclusions of non-bound amino acids particularly methionine,lysine and threonine,together with the"ideal protein"concept have allowed nutritionists to formulate broiler diets with reduced crude protein(CP)and increased nutrient density of notionally"essential"amino acids and energy content in recent decades,However,chicken-meat production has been projected to double between now and 2050,providing incentives to reduce dietary soybean meal inclusions further by tangibly reducing dietary CP and utilising a larger array of non-bound amino acids.Whilst relatively conservative decreases in dietary CP,in the order of 20 to 30 g/kg,do not negatively impact broiler performance,further decreases in CP typically compromise broiler performance with associated increases in carcass lipid deposition.Increases in carcass lipid deposition suggest changes occur in dietary energy balance,the mechanisms of which are still not fully understood but discourage the acceptance of diets with reductions in CP,Nevertheless,the groundwork has been laid to investigate both amino acid and non-amino acid limitations and propose facilitative strategies for adoption of tangible dietary CP reductions;consequently,these aspects are considered in detail in this review.Unsurprisingly,investigations into reduced dietary CP are epitomised by variability broiler performance due to the wide range of dietary specifications used and the many variables that should,or could,be considered in formulation of experimental diets.Thus,a holistic approach encompassing many factors influencing limitations to the adoption of tangibly reduced CP diets must be considered if they are to be successful in maintaining broiler performance without increasing carcass lipid deposition.

Capping dietary starch:protein ratios in moderately reduced crude protein,wheat-based diets showed promise but further reductions generated inferior growth performance in broiler chickens

The hypothesis that capping dietary starch:protein ratios would enhance the performance of broiler chickens offered reduced-crude protein(CP)diets was tested in this experiment.A total of 432 off-sex,male Ross 308 chicks were allocated to 7 dietary treatments from 7 to 35 d post-hatch.The experimental design consisted of a 3×2 factorial array of treatments with the seventh treatment serving as a positive control.Three levels of dietary CP(197.5,180.0 and 162.5 g/kg)with either uncapped or capped dietary starch:protein ratios constituted the factorial array of treatments,whilst the positive control diet contained 215.0 g/kg CP.The positive control diet had an analysed dietary starch:protein ratio of 1.50 as opposed to a ratio of 1.68 in the uncapped 197.5 g/kg CP diet and 1.41 in the corresponding capped diet and the capped 197.5 g/kg CP diet displayed promise.The growth performance this diet matched the positive control but outperformed the uncapped 197.5 g/kg CP diet by 10.4%(2,161 vs.1,958 g/bird;P=0.009)in weight gain,by 3.10%(3,492 vs.3,387 g/bird;P=0.019)in feed intake on the basis of pairwise comparisons and numerically improved FCR by 4.04%(1.616 vs.12684).However,the growth performance of birds offered the 180.0 and 162.5 g/kg CP dietary treatments was remarkably inferior,irrespective of dietary starch:protein ratios.This inferior growth performance was associated with poor feathering and even feather-pecking and significant linear relationships between feather scores and parameters of growth performance were observed.The amino acid profile of feathers was determined where cysteine,glutamic acid,glycine,proline and serine were dominant in a crude protein content of 931 g/kg.Presumably,the feathering issues observed were manifestations of amino acid inadequacies or imbalances in the more reduced-CP diets and consideration is given to the implications of these outcomes.

Performance of broiler chickens offered nutritionally-equivalent diets based on two red grain sorghums with quantified kafirin concentrations as intact pellets or re-ground mash following steam-pelleting at65 or 97℃ conditioning temperatures

The Liverpool Plains is a fertile agricultural region in New South Wales, Australia. Two sorghums from the2009 Liverpool Plains harvest, sorghums #3 and #5, were extensively characterised which included concentrations of kafirin and phenolic compounds plus rapid visco-analysis(RVA) starch pasting profiles. Diets based on these two sorghums were formulated to be iso-nitrogenous and iso-energetic and were offered to male Ross 308 broiler chicks from 7 to 28 days post–hatch as either intact pellets or reground mash following steam-pelleting at conditioning temperatures of either 65 or 97°C. Thus the feeding study consisted of a 2×2×2 factorial array of dietary treatments: two sorghum varieties, two feed forms and two conditioning temperatures. Each of the eight treatments was replicated six times with six birds per replicate cage.Assessed parameters included growth performance, nutrient utilisation, apparent starch and protein(N) digestibility coefficients and disappearance rates from the distal jejunum and distal ileum. Intact pellets supported higher(P <0.001) feed intakes and weight gains by 9.83 and 9.08%, respectively, than reground mash diets. Feed conversion ratios of broilers offered diets steam-conditioned at 97°C were 2.46% inferior(P <0.001) in comparison to 65°C diets and both apparent metabolizable energy(AME) and N-corrected AME(AMEn) were compromised. Broilers offered sorghum #3-based diets significantly(P <0.001) outperformed their sorghum #5 counterparts in terms of weight gain by 3.75%(1,334 versus 1,223 g/bird), FCR by 4.81%(1.524 versus 1.601), AME by 1.06 MJ(13.61 versus 12.55 MJ/kg), ME:GE ratio(ME:GE) by 4.81%(0.806 versus0.769) and AMEn by 1.03 MJ(12.38 versus 11.35 MJ/kg). The inferiority of sorghum #5 appeared to be associated with higher concentrations of kafirin(61.5 versus 50.7 g/kg) and conjugated phenolic acids,including ferulic acid(31.1 versus 25.6 mg/g). There were no significant differences in jejunal and ileal starch and protein(N) digestibility coefficients between the two sorghums. However, starch to protein(N) disappearance rate ratios from the distal jejunum were significantly(P <0.001) correlated with ME:GE and AME. The multiple linear regression equations indicated that energy utilisation was enhanced by coupling rapidly digestible protein with slowly digestible starch, which suggests that bilateral bioavailability of starch and protein is pivotal to efficient energy utilisation.

Protein digestive dynamics of meat and bone meals in broiler chickens

This study determined the variations in protein digestibilities and digestion rates in broiler chickens offered diets containing 7 different meat and bone meals(MBM).A total of 252 male Ross 308 broiler chickens were offered 7 atypical diets largely based on maize and MBM from 24 to 28 d post-hatch.Each experimental diet was offered to 6 replicates with 6 birds per replicate cage.Excreta were collected in their entirety from 25 to 27 d post-hatch and on 28 d post-hatch.Digesta samples were collected from the proximal jejunum,distal jejunum,proximal ileum and distal ileum.Apparent digestibilities of protein were determined in each segment and apparent digestibilities of amino acids were measured in the distal ileum.There were significant differences in apparent protein digestibility coefficients in the proximal jejunum(P=0.006),where broiler chickens offered the high ash beef meal(diet 7)generated the lowest protein digestibility in the proximal jejunum(0.318).Similarly,there were significant differences in apparent digestibility coefficients in the distal jejunum(P<0.001)and distal ileum(P<0.001)but not in the proximal ileum.More pronounced differences were found in the disappearance rate of protein and there were significant differences in all 4 segments of the small intestine(P<0.001).Broiler chickens offered the high ash beef meal had the lowest protein disappearance rate(P<0.001).No difference was observed in the predicted protein digestion rate(P=0.486)but chickens offered the high ash beef meal had the lowest potential digestible protein(0.662,P=0.034)whereas the highest potential digestible protein(0.739)was detected in diet 5(containing a beef meal).This study contributed to the establishment of a preliminary database to include digestion rates of starch and protein into practical diet formulation.

Protein sources and starch-protein digestive dynamics manipulate growth performance in broiler chickens defined by an equilateraltriangle response surface design

A total of 360 male,off-sex Ross 308 chicks were offered 10 dietary treatments from 14 to 35 d post ehatch in an equilateral-triangle response surface design feeding study in order to confirm the importance of protein and amino acid digestive dynamics in broiler chickens.The 3 apical diets were nutritionally-equivalent containing either soybean meal,non-bound amino acids or whey protein concentrate as the major source of dietary protein and amino acids.Appropriate blends of the 3 apical diets comprised the balance of 7 diets and each dietary treatment was offered to 6 replicate cages with 6 birds per cage.Growth performance,nutrient utilisation,apparent protein and starch digestibility coefficients were determined in 4 small intestinal segments.The optimal weight gain(2,085 g/bird)and feed conversion ratios(FCR,1.397)were generated by Diet 50S50W which included a 50:50 blend of apical diets rich in whey protein concentrate and soybean meal.Broiler chickens offered Diet 50S50W also had the highest experimental and predicted jejunal digestibility(0.685 in proximal jejunum and 0.823 in distal jejunum).FCR was not correlated with apparent distal ileal digestibility coefficient(P>0.05)of protein but was correlated with apparent protein digestibility in proximal jejunum(r=-0.369,P=0.040)and distal jejunum(r=-0.316,P=0.015).Surplus dietary starch was correlated with increased fat pad weight(r=0.781,P?0.008).The findings confirmed the relevance of protein digestion rate,reflected by jejunal digestibility,on feed conversion of broiler chickens.A balance between protein-bound and non-bound crystalline or synthetic amino acids may be required for optimal growth and protein digestion.

Reducing agent and exogenous protease additions,individually and in combination, to wheat-and sorghum-based diets interactively influence parameters of nutrient utilisation and digestive dynamics in broiler chickens

The objective of the study was to investigate the possibility that tandem inclusions of a reducing agent and a protease may advantage chicken-meat production and to ascertain if the established benefits of including sodium metabisulphite in sorghum-based diets extend to wheat-based diets. The study comprised a 2 x 2 x 2 factorial array of treatments in which either nutritionally iso-nitrogenous and isoenergetic wheat-or sorghum-based diets, without and with sodium metabisulphite(2.75 g/kg), without and with protease(1,000 units/kg) were offered to broiler chickens from 7 to 28 days post-hatch. The effects of dietary treatments on growth performance, nutrient utilisation, protein(N) and starch digestibility coefficients and digestive dynamics were determined. A preliminary investigation into the effects of two treatments on concentrations of free amino acids and glucose in the portal circulation was conducted. There was significant feed grain by sodium metabisulphite interactions(P = 0.03 to 0.005) for parameters of nutrient utilisation(AME, ME:GE ratios, N retention, AMEn). For example, sodium metabisulphite inclusions in sorghum-based diets enhanced AME by 0.18 MJ(12.47 versus 12.29 MJ/kg) but depressed AME by 0.43 MJ(11.88 versus 12.31 MJ/kg) in wheat-based diets. There was a linear relationship between starch:protein disappearance rate ratios in the distal ileum with weight gain(r =-0.484; P = 0.0012) indicating that condensed ratios(or absorption of more protein relative to starch) advantaged growth performance. Concentrations of free amino acids in the portal circulation or the post-enteral availability of certain amino acids, including the branched-chain amino acids, methionine, phenylalanine and threonine, were significantly correlated to FCR. For example, threonine concentrations were negatively correlated to FCR(r =-0.773; P = 0.005). Finally, tandem inclusions of sodium metabisulphite and protease in sorghum-based diets may hold merit but it appears that the established 'energy sparing' effects of sodium metabisulphite inclusions in sorghum-based diets are not duplicated in wheat-based diets.

Outlook:Sorghum as a feed grain for Australian chicken-meat production

This review is an outlook for sorghum as a feed grain for broiler chickens based on a survey of relevant stake-holders and recent research outcomes.Australian grain sorghum production will probably continue to generate a harvest in the order of 2.5×10~6t of which some 7.9×10~5t will be used as a feed grain for poultry and pigs.Feed grains are included primarily to provide energy from starch,but energy utilisation by broiler chickens offered sorghum-based diets is relatively inferior,because of incomplete starch digestion.Kafirin,the dominant protein fraction,‘non-tannin’phenolic compounds and phytate are 3‘starch extrinsic’factors in sorghum that compromise starch digestibility and energy utilisation in broiler chickens offered sorghum-based diets.Kafirin concentrations in 6 sorghum varieties were negatively correlated with metabolizable energy to gross energy(ME:GE)ratios(r=0.891;P<0.02)or the efficiency of energy utilisation in broiler chickens.Importantly,kafirin proportions of sorghum protein may be increasing with time in Australia.If so,this represents a fundamental challenge to sorghum breeders which presumably could be met by the development of sorghum varieties with different characteristics,especially in relation to the g-and b-kafirin fractions.White sorghum varieties contain lower polyphenol concentrations which should be advantageous as concentrations of total phenolic compounds were negatively correlated to ME:GE ratios(r=0.838;P<0.04)in 6 sorghum varieties.It would be desirable if more white varieties were to become available.It is suggested that responses to exogenous phytase in birds offered sorghum-based diets would be more robust if sorghum were to contain lower concentrations of kafirin and phenolic compounds.Paradoxically,while better sorghum varieties almost certainly could be developed,it may not necessarily follow that they will command a price premium from poultry and pig producers.

Starch digestion rates in multiple samples of commonly used feed grains in diets for broiler chickens

In this study the starch digestion rates in broiler chickens from 18 samples of 5 commonly used feed grains(sorghum,wheat,maize,barley,triticale)were determined.The methodology to determine starch digestion rates in poultry is detailed herein.Starch digestion rates were not significantly different(P-0.128)across the 18 feed grains,which reflects the wide variations that were observed within a given feedstuff.Nevertheless,starch digestion rates in broiler chickens offered wheat-based diets were significantly more rapid by 56.0%(0.117 versus 0.075 min-1;p=0.012)than their sorghum-based counterparts on the basis of a pair-wise comparison.In descending order,the following starch diges-tion rates were observed:wheat(0.117 min-1),barley(0.104 min-1),triticale(0.093 min-1),maize(0.086 min-1),sorghum(0.075 min-1).The implications of these findings are discussed as they almost certainly have implications for poultry nutrition and the development of reduced crude protein diets for broiler chickens.

The potential of rapid visco-analysis starch pasting profiles to gauge the quality of sorghum as a feed grain for chicken-meat production

Thirteen extensively characterised grain sorghum varieties were evaluated in a series of 7 broiler bioassays. The efficiency of energy utilisation of broiler chickens offered sorghum-based diets is problematic and the bulk of dietary energy is derived from sorghum starch. For this reason, rapid visco-analysis(RVA)starch pasting profiles were determined as they may have the potential to assess the quality of sorghum as a feed grain for chicken-meat production. In review, it was found that concentrations of kafirin and total phenolic compounds were negatively correlated with peak and holding RVA viscosities to significant extents across 13 sorghums. In a meta-analysis of 5 broiler bioassays it was found that peak, holding,breakdown and final RVA viscosities were positively correlated with ME:GE ratios and peak and breakdown RVA viscosities with apparent metabolizable energy corrected for nitrogen(AMEn) to significant extents. In a sixth study involving 10 sorghum-based diets peak, holding and breakdown RVA viscosities were positively correlated with ME:GE ratios and AMEn. Therefore, it emerged that RVA starch pasting profiles do hold promise as a relatively rapid means to assess sorghum quality as a feed grain for chicken-meat production. This potential appears to be linked to quantities of kafirin and total phenolic compounds present in sorghum and it would seem that both factors depress RVA starch viscosities in vitro and, in turn, also depress energy utilisation in birds offered sorghum-based diets. Given that other feed grains do not contain kafirin and possess considerably lower concentrations of phenolic compounds, their RVA starch pasting profiles may not be equally indicative.

Implications of excreta uric acid concentrations in broilers offered reduced crude protein diets and dietary glycine requirements for uric acid synthesis

In a previous experiment,male Ross 308 broiler chickens were offered dietary treatments with 3 levels of crude protein(222,193,165 g/kg)and 3 feed grains(ground maize,ground wheat,whole wheat)from 7 to 35 d post-hatch.Maize-based diets supported superior growth performance in comparison to wheatbased diets.Uric acid concentrations in excreta were retrospectively determined and related to total nitrogen(N)excreta concentrations.Uric acid concentrations ranged from 28.5 to 69.4 mg/g and proportions of uric acid-N to total excreta-N ranged from 27.4%to 42.6%in broiler chickens offered the 3×3 factorial array of dietary treatments.Proportions of uric acid-N to total N in excreta in birds offered the165 g/kg CP,maize-based diet were significantly lower by 10.6 percentage units(27.4%versus 38.0%;P=0.00057)than their wheat-based counterparts.Total excreta analysed had been collected from 35 to37 d post-hatch when feed intakes and excreta outputs were monitored.There were linear relationships between proportions of uric acid-N to total N in excreta in birds offered the three 165 g/kg CP diets with weight gain(r=-0.587;P=0.010),feed intake(r=-0.526;P=0.025)and feed conversion ratios(r=0.635;P=0.005).The possibility that increasing uric acid-N proportions in excreta is indicative of excessive ammonia accumulations compromising growth performance is discussed.The mean proportion of dietary glycine involved in uric acid excretion was 49.2%across all dietary treatments but ranged from 25.0%to 80.9%.Thus,the appropriate amount of dietary glycine is variable and largely dependent on the volume of uric acid synthesised and excreted.

Assessment of limiting dietary amino acids in broiler chickens offered reduced crude protein diets

As lowering crude protein(CP)in poultry diets continues to minimize amino acid excess,it is important to understand the limiting order of amino acids and the impact of their deficiencies.Therefore,a pair of experiments were conducted to observe the effects of individual amino acid deletions on growth performance,carcass traits,and nutrient utilization.Both experiments involved 3 control diets based on wheat and soybean meal,including a 210.0 g/kg CP industry control(IC),186.7 g/kg CP positive control(PC)supplemented with feed-grade amino acids to match the IC amino acid profile,186.7 g/kg CP negative control(NC)with reducing N corrected apparent metabolizable energy(AMEN)by 0.5 MJ/kg and removing feed-grade amino acids beyond L-Lys-HCl,DL-Met,and L-Thr from PC.Ten deletion diets where the following supplemented amino acids were individually removed from the PC:Val,Ile,Leu,Trp,Arg,His,Phe t Tyr,glycine equivalence(Glyequi),Pro,and Energy(0.5 MJ/kg reduction in AMEN of the PC).All diets were formulated to contain similar concentrations of digestible Lys,total sulfur amino acid(TSAA)and Thr.Experimental diets were offered to broiler chickens from 15 to 22 d postehatch in a cage study(Exp.1)to gain digestibility and nutrient utilization data;whereas they were offered from 15 to 35 d post ehatch in a floor-pen study(Exp.2)to gain performance and carcass yield data.The removal of supplemented Val,Arg,and Ile resulted in reduction on broiler performance(P<0.05),and the removal of Val,Arg,Ile,and Glyequi negatively influenced carcass traits(P<0.05).Results from both experiments indicate that Val and Arg are co-limiting in wheat-soybean meal diets,but that Ile and Glyequi may potentially limit breast and thigh development.

The influence of meat-and-bone meal and exogenous phytase on growth performance, bone mineralisation and digestibility coefficients of protein(N),amino acids and starch in broiler chickens

The objective of this study was to examine the influence of meat-and-bone meal(MBM) and phytase inclusion on growth performance, bone mineralisation and apparent digestibility coefficients of nutrients in broiler chickens offered wheat-based diets. The feeding study comprised 7 dietary treatments: positive control(PC, 9.0% Ca and 4.5% available phosphorous [AvP] in starter, 7.0% Ca and 3.5% AvP in finisher); negative control(NC, 7.2% Ca and 3.0% AvP in starter, 5.2% Ca and 2.0% AvP in finisher) diets incorporating a 3 × 2 factorial array of 3 MBM inclusions(0, 60, 120 g/kg) and 2 levels of phytase supplementation(0 and 1,000 FYT/kg). Each treatment was allocated to 6 replicated pens with 30 birds per pen in an environmentally-controlled deep litter facility. A total of 1,260 one-day-old male Ross 308 chicks were offered starter diets from 1 to 14 days post-hatch and finisher diets from 15 to 36 days posthatch. There were significant(P < 0.05) interactions between MBM inclusions and phytase supplementation on weight gain and feed intake in starter diets. Phytase significantly increased weight gain in diets without MBM and did not influence weight gain in diets with 60 and 120 g/kg MBM. Collectively,increasing MBM inclusion significantly reduced weight gain in starter diets(P < 0.0001). There were dietary interactions(P < 0.01) on toe ash where phytase significantly improved toe ash in diet without MBM and did not influence toe ash in the other two groups of negative control diets. There were no dietary treatment interactions on apparent ileal digestibility coefficients of starch and protein except that diets without MBM had significantly(P < 0.01) lower ileal starch digestibility and diets with 120 g/kg MBM had significantly(P < 0.0001) lower ileal protein digestibility. No dietary influence on ileal fat digestibility was observed. There were dietary interactions on ileal digestibilities of isoleucine, valine and glycine. Phytase significantly increased glycine digestibility in diets with 60 and 120 g/kg MBM but not in diets without MBM, Including 120 g/kg MBM significantly(P < 0.01) depressed apparent digestibility coefficients of 13 ex 16 amino acids in the distal ileum. This study demonstrated the negative impacts of MBM on amino acid digestibility and growth performance. Also, responses to phytase were more pronounced in diets without MBM, which may have been due to their relatively lower available P and higher phytate concentrations in comparison to diets containing MBM.

Identifying the shortfalls of crude protein-reduced,wheat-based broiler diets

The objective of this review is to identify the shortfalls of wheat-based,crude protein(CP)-reduced diets for broiler chickens as wheat is inferior to maize in this context but to inconsistent extents.Inherent factors in wheat may be compromising gut integrity;these include soluble non-starch polysaccharides(NSP),amylase trypsin inhibitors(ATI)and gluten.Soluble NSP in wheat induce increased gut viscosities,which can lead to compromised gut integrity,which is not entirely ameliorated by NSP-degrading feed enzymes.Wheat ATI probably compromise gut integrity and may also have the capacity to increase endogenous amino acid flows and decrease apparent starch and protein digestibilities.Gluten inclusions of 20 g/kg in a maize-soy diet depressed weight gain and feed intake and higher gluten inclusions have been shown to activate inflammatory cytokine-related genes in broiler chickens.Further research is required,perhaps particularly in relation to wheat ATI.The protein content of wheat is typically higher than maize;importantly,this results in higher inclusions of non-bound amino acids in CP-reduced broiler diets.These higher inclusions could trigger post-enteral amino acid imbalances,leading to the deamination of surplus amino acids and the generation of ammonia(NH3)which,if not adequately detoxified,results in compromised growth performance from NH3overload.Thus,alternatives to nonbound amino acids to meet amino acid requirements in birds offered CP-reduced,wheat-based diets merit evaluation.The digestion of wheat starch is more rapid than that of maize starch which may be a disadvantage as the provision of some slowly digestible starch in broiler diets may enhance performance.Alternatively,slowly digestible starch may result in more de novo lipogenesis.Therefore,it may prove instructive to evaluate CP-reduced diets based on maize-wheat and/or sorghum-wheat blends rather than entirely wheat.This would reduce non-bound amino acid inclusions by lowering dietary CP derived from feed grains and may enhance starch digestive dynamics by retarding starch digestion rates.Also,the use of biomarkers to monitor gut integrity in broiler chickens is examined where calprotectin,ovotransferrin and possibly citrulline appear to hold promise,but their validation requires further research.

Graded methionine dietary inclusions influence growth performance and apparent ileal amino acid digestibility coefficients and disappearance rates in broiler chickens

Graded quantities of 1.38,2.76 and 4.14 g/kg L-methionine were included in a control diet formulated to contain 3.07 g/kg digestible methionine.Each of the 4 dietary treatments was offered to 6 replicate cages(initially 8 birds per cage)from 1 to 21 d postehatch.The parameters assessed included growth performance,nutrient utilisation(apparent metabolisable energy[AME],AME:GE ratios,N retention,Ncorrected apparent metabolisable energy[AMEn]),apparent digestibility coefficients and disappearance rates of amino acids in the distal ileum.They also included free amino concentrations in systemic plasma(brachial vein)at 20 d postehatch and in hepatic tissue at 14 and 21 d postehatch.Graded L-methionine inclusions quadratically influenced weight gain(r=0.688;P=0.001)and FCR(r=0.780;P<0.001).It may be deduced from the quadratic regressions that 3.43 g/kg L-methionine supported maximum weight gain of 1,036 g/kg and 3.50 g/kg L-methionine minimum FCR of 1.193,from 1 to 21 d postehatch.The control diet contained specified levels of 3.07 g/kg digestible methionine and 13.0 g/kg digestible lysine.Thus,an inclusion of 3.465 g/kg L-methionine corresponded to a total of 6.535 g/kg methionine or a methionine-to-lysine ratio of 50.3,which is higher than standard recommendations.The implications of this and other outcomes of the present study are reported and discussed.