Dietary Crude Protein Reduction Research Articles

A multivariate Box-Behnken assessment of elevated branched-chain amino acid concentrations in reduced crude protein diets offered to male broiler chickens.

In a Box-Behnken assessment of elevated branched-chain amino acids (BCAA), 13 nutritionally equivalent maize-based diets were offered to a total of 390 off-sex male Ross 308 broiler chickens from 7 to 28 days post-hatch. The BCAA concentrations investigated in reduced-crude protein diets were 12.5, 15.5, 18.3 g/kg leucine (125, 155, 183); 8.9, 10.2, 12.5 g/kg valine (89, 102, 125) and 7.2, 8.9, 10.8 g/kg isoleucine (72, 89, 109), where their relativity to 11.0 g/kg digestible lysine are shown in parentheses. Determined parameters included growth performance, relative abdominal fat-pad weights, nutrient utilisation, apparent digestibility coefficients, disappearance rates of 16 amino acids and free amino acid systemic plasma concentrations. Increasing dietary leucine linearly depressed weight gain and quadratically influenced FCR where the estimated minimum FCR of 1.418 was with 14.99 g/kg leucine. Polynomial regression analysis and surface response curves of determined parameters were generated for significant (P < 0.05) BCAA variables, based on lack of fit (P > 0.005). Quadratic and cross-product responses were observed for weight gain, FCR, AME, AMEn, N retention and apparent digestibility of 13 amino acids. Relative fat-pad weights declined linearly with increasing isoleucine and valine. The lowest N retention was estimated at a combination of 15.25 and 10.50 g/kg leucine and valine respectively whilst the highest mean digestibility coefficient (0.793) of amino acids was estimated at a combination of 15.74 and 10.47 g/kg of leucine and valine respectively. The remaining parameter minima or maxima responses were not able to be determined since they were outside the extreme BCAA treatment levels. Increasing dietary BCAA significantly increased apparent ileal digestibilities and disappearance rates of BCAA. Systemic plasma concentrations of valine increased (P < 0.001) with increasing dietary valine but leucine was not influenced (P > 0.25). Systemic plasma concentration of isoleucine was maximised (P < 0.001) only when accompanied by elevated dietary leucine. Also, dietary treatments influenced (P < 0.05) apparent disappearance rates of all the essential amino acids analysed, with the exception of methionine. Whilst overall growth performance was not disadvantaged (P > 0.10) by elevated BCAA levels, compared with 2019 Ross 308 performance objectives, polynomial regression analysis suggested both interaction and antagonism between BCAA.

Reduction of dietary crude protein and feed form: Impact on broiler litter quality, ammonia concentrations, excreta composition, performance, welfare, and meat quality.

Nitrogen (N) excreted by poultry is converted to ammonia (NH3), presenting an environmental risk and a health risk to the farmer and animals. A study was performed to investigate the effect of reduced CP and feed form on broiler performance and welfare, meat and litter quality, N utilization, and NH3 concentrations at litter level. A total of 2,232 Ross 308 male broilers was divided into 6 treatments and 6 replicates, which was fed diets in both pellet and mash forms with different CP levels of 205.0 g/kg (H, high), 187.5 g/kg (M, intermediate) and 175.0 g/kg (L, low) in the grower phase and 195.0 g/kg (H), 180.0 g/kg (M) and 165.6 g/kg (L) in the finisher phase. Individual amino acids (AA) were supplemented to maintain digestible AA-to-digestible lysine ratios. Decreasing dietary CP content to 187.5 g/kg in the grower phase and 180.0 g/kg in the finisher phase reduced NH3 concentrations at litter level (P < 0.001), but a further reduction in dietary CP had no additional effect. Mash treatments had better litter qualities and lower incidences of foot and hock lesions than pellet treatments at d 38 (P < 0.001). In addition, treatments with reduced CP had lower incidence of foot lesions at d 38 (P < 0.001). Broilers fed pelleted diets had higher ADFI, ADG, and final BW, improved feed conversion ratio (FCR), and heavier carcasses (P < 0.001) than those fed mash diets over a production period of 39 d. Performance could not be maintained when birds were fed L CP pelleted diets. This study demonstrated that, with the supplementation of AA to meet requirements, the concentration of dietary CP can be reduced to 187.5 and 180.0 g/kg in the grower and finisher phases respectively, without impairing broiler performance, meat yield and quality. Mash diets were favorable when considering the overall litter quality and welfare of the birds. However, they could not maintain the same broiler performance and slaughter yield as pelleted diets. Results from the present study may assist the poultry sector towards a socially acceptable low-emission farming system.

The effect of reduced CP, synthetic amino acid supplemented diets on growth performance and nutrient excretion in wean to Finish swine.

Mixed sex pigs (n = 720) were placed in 12 rooms (Purdue Swine Environmental Research Building) to measure the effect of reduced crude protein (CP), amino acid (AA)-supplemented diets on growth and the carcass. Pigs were blocked by body weight (BW) and gender and allotted to room and pen (10 mixed-sex pigs/pen). Pigs were fed a nine-phase, wean-finish program. Control pigs consumed corn-soybean meal-distiller's dried grains with solubles (DDGS) diets containing no to minimal (Met) synthetic AA. The 2X diet was formulated to meet the seventh most-limiting AA, and balanced using synthetic AAs to meet all AA needs. The 1X diet was formulated to meet a CP value halfway between the control and 2X diet, and also balanced using synthetic AAs to meet all AA needs. Diets were formulated to identical net energy concentrations and balanced to meet standard ileal digestible NRC 2012 AA requirements. Pit vacuum samples were collected at the end of each growth phase for analyses of nitrogen, C and dry matter (DM). Pigs fed the Control and 1X diet grew faster (P < 0.005), had greater gain:feed (P < 0.001), and were heavier at market (P < 0.001) than animals fed the 2X diet. No consistent effects of diet were observed on average daily feed intake. Carcass data were analyzed for sex, diet and sex*diet effects. Reductions in dietary CP resulted in a linear reduction in ammonium nitrogen excretion per kg of BW gain in Nursery (P < 0.001) and Grow-Finish (P < 0.001) phases. Reductions in dietary CP, with synthetic AA supplementation resulted in a linear reduction in total nitrogen excreted per kg BW gain in the Grow-Finish phase (P < 0.001) and overall (P < 0.001). Total mineral excretion per kg gain was reduced in pigs fed 1X and 2X diets compared with control-fed pigs (P < 0.005). Reductions in dietary CP of ~3 and 5%-units from wean-finish result in reductions of total N excretion of 11.7 and 24.4%, respectively. Reduced performance and carcass characteristics observed in pigs fed the 2X diets indicates an inaccurate estimate of NRC 2012 AA requirements or ratios to lysine in a low CP diet.

Broiler chicken production using dietary crude protein reduction strategy and free amino acid supplementation

Very low self-sufficiency of soybean meal, which is the primary source of protein supplement used by European feed industry, caused great interest in EU to reduce the content of soybean meal in broiler chicken diets. The objective of this study was to evaluate the effect of reduced dietary crude protein (CP) and supplementation with 7 indispensable amino acids on broiler chicken performance and carcass composition. Two experiments (Exp.) were conducted, each with 2,640 fast growing broiler chickens. Grower diets were provided from d 10 to 31 in Exp. 1 and from d 10 to 28 in Exp. 2. In Exp. 1, broiler chickens were assigned to 4 treatments (22, 21, 20, and 18% CP diets supplemented with crystalline amino acids to achieve the same standardized ileal digestible (SID) Lys (10.9 g/kg), SID Met + Cys (8.07 g/kg), SID Thr (7.08 g/kg), SID Ile (7.63 g/kg), and SID Val (8.72 g/kg)) with 6 pens per treatment and 110 broiler chickens per pen. In Exp. 2, broiler chickens were assigned to 3 treatments (20, 19, and 18% CP diets supplemented with crystalline amino acids to have the same SID Lys, Met + Cys, Thr, Ile, and Val plus SID Arg (11.45 g/kg), and SID Trp (10.9 g/kg)) with 8 pens per treatment and 110 broiler chickens per pen. With decreasing CP from 20 to 18%, body weight decreased (P < 0.05). The greatest body weight was achieved at a CP concentration of 20% in both experiments (P < 0.05). In feed conversion ratio, breast meat yield, and an European efficiency factor, there were no differences between CP concentration 20 and 19% in Exp. 2. Based on the European efficiency factor, reducing dietary CP and adding crystalline amino acids seems to be a promising approach to achieve competitive broiler chicken meat production in Europe.

Interactions of the branched-chain amino acids. 2. Practical adjustments in valine and isoleucine

Reductions in dietary crude protein have potentially allowed for the occurrence of branched chain amino acid antagonism which can negatively influence live performance and carcass traits. Therefore, 2 factorial studies were conducted with the first experiment evaluating valine and leucine interactions during a 32 to 45 d finisher period, while the second experiment evaluated valine and isoleucine interactions during a 39 to 52 d withdrawal period. Valine, leucine, nor their subsequent interaction influenced broiler live performance or carcass traits in Experiment 1. However, a valine × leucine interaction was observed for average woody breast score and occurrence of scores of 1 and 2. This interaction demonstrated that leucine does not increase woody breast in birds fed diets with a valine to lysine ratio of 77, but interaction differences for woody breast severity varied among valine and leucine ratios to lysine. In the second experiment, increasing valine marginally increased feed intake, while isoleucine influenced tender yield. No valine × isoleucine interactions were observed. Within the confines of the levels used in the current study, manipulation of dietary branched-chain amino acid levels had little influence on live performance or carcass traits during the tested growout periods. The occurrence of a valine × leucine interaction on the incidence and severity of woody breast is perplexing and requires more investigation to determine if a successful mitigation strategy could be developed.

Effect of crude protein reduction in blood, performance, immunological, and intestinal histological parameters of broiler chickens.

We aimed to evaluate the effects of the reduction in dietary crude protein (CP) on blood urea, uric acid, performance, immunity, and intestinal histology of broilers. Four diets were formulated with 22.50%, 21.50%, 20.50%, and 19.50% of CP (1 to 21 days) and 19.20%, 18.20%, 17.20%, and 16.20% of CP (22 to 42 days), meeting the requirements of essential amino acids in all diets. A total of 800 male Ross chicks were randomly allocated to 32 pens, with 25 birds each (n = 8). Blood and intestines had been collected for analysis. Uric acid decreased and urea increased with the reduction of CP (p < 0.05). Reduction in performance and intestinal parameters (villus, crypt, and goblet cells) was observed with the reduction of CP (p < 0.05). Lower levels of CP resulted in alteration (p < 0.05) in CD4 and CD8 lineages (21 and 42 days). Broken-line models estimated (p < 0.05) the CP requirement for growth between 21% and 21.3% (1 to 21 days) and between 17.2% and 17.4% (22 to 42 days) and CP requirements between 17.2% and 18.2% for maximum response of immune cells (42 days). Reduction in dietary CP has a negative impact on performance, immune response, and intestinal histology of broilers, even with adequate levels of essential amino acids.

Evaluation of dietary crude protein concentrations, fishmeal, and sorghum inclusions in broiler chickens offered wheat-based diet via Box-Behnken response surface design.

The objective of this study was to investigate the impacts of dietary crude protein (CP), fishmeal and sorghum on nutrient utilisation, digestibility coefficients and disappearance rates of starch and protein, amino acid concentrations in systemic plasma and their relevance to growth performance of broiler chickens using the Box-Behnken response surface design. The design consisted of three factors at three levels including dietary CP (190, 210, 230 g/kg), fishmeal (0, 50, 100 g/kg), and sorghum (0, 150, 300 g/kg). A total of 390 male, off-sex Ross 308 chicks were offered experimental diets from 14 to 35 days post-hatch. Growth performance, nutrient utilisation, starch and protein digestibilities and plasma free amino acids were determined. Dietary CP had a negative linear impact on weight gain where the transition from 230 to 190 g/kg CP increased weight gain by 9.43% (1835 versus 2008 g/bird, P = 0.006). Moreover, dietary CP linearly depressed feed intake (r = -0.486. P < 0.001). Fishmeal inclusions had negative linear impacts on weight gain (r = -0.751, P < 0.001) and feed intake (r = -0.495, P < 0.001). There was an interaction between dietary CP and fishmeal for FCR. However, growth performance was not influenced by dietary inclusions of sorghum. Total plasma amino acid concentrations were negatively related to weight gain (r = -0.519, P < 0.0001). The dietary transition from 0 to 100 g/kg fishmeal increased total amino acid concentrations in systemic plasma by 35% (771 versus 1037 μg/mL, P < 0.001). It may be deduced that optimal weight gain (2157 g/bird), optimal feed intake (3330 g/bird) and minimal FCR (1.544) were found in birds offered 190 g/kg CP diets without fishmeal inclusion, irrespective of sorghum inclusions. Both fishmeal and sorghum inclusions did not alter protein and starch digestion rate in broiler chickens; however, moderate reductions in dietary CP could advantage broiler growth performance.

EFFECT OF DIFFERENT PROTEIN AND/OR METABOLIZABLE ENERGY LEVELS IN DIETS FORMULATED BASED ON IDEAL PROTEIN CONCEPT ON PERFORMANCE, EGG PRODUCTION, AND EGG QUALITY TRAITS OF LAYERS DURING PHASE 1 OF EGG PRODUCTION

A comparative study was conducted to determine the impacts of crude protein (CP) reductions in laying hen diets. During phase one of egg production, 270 laying hens were randomly assigned into six dietary treatments, which were replicated three times using a 2 × 3 factorial experiment. Reduced CP and metabolizable energy (ME) diets were formulated based on the ideal amino acid profile concept and supplemented with crystalline amino acids. The control treatment received standard commercial diets containing 18.8% CP and 2,725 kcal/kg ME. Average weight gain, hen day egg production percentage, egg weight, egg mass, and other selected egg quality parameters were recorded. Data were statistically analyzed. Feed consumption and the feed conversion ratio were improved in birds fed reduced CP diets supplemented with crystalline amino acids. The dietary CP level significantly influenced shell thickness (ST), while the dietary ME level had no effect. A highly significant interaction was observed between CP percent and the Haugh unit (HU). Results indicate that the “ideal protein concept” may be followed as an economically feasible option for laying hens since it optimizes the dietary amino acid profiles and ME levels, and have a positive effect on hen growth, egg quality and environmental pollution.

A Moderate Reduction of Dietary Crude Protein Provide Comparable Growth Performance and Improve Metabolism via Changing Intestinal Microbiota in Sushan Nursery Pigs.

Simple SummaryDietary protein is an important source of amino acids for livestock, while excess protein consumption and an imbalance of amino acids in the diet result in increased feed costs and an increased risk of diarrhea, caused by the proliferation of pathogenic bacteria. Therefore, we investigated whether a diet with a moderate reduction of crude protein levels, supplemented with crystalline amino acids, could alleviate these problems. The results showed that a moderate reduction in the dietary protein level can provide similar growth performance and improve metabolism, due to the improvement of intestinal microbiota, compared with high protein feed in Sushan nursery pigs. These findings present new insights into the role of microorganisms in metabolism, and point to a potential nutrition strategy for indigenous pig production.In this paper, we investigated the effects of a diet with a moderate reduction of dietary crude protein (CP) level, supplemented with five crystalline amino acids (Lys, Met, Thr, Try, and Val), on the growth, metabolism, and fecal microbiota of Sushan nursery pigs. Seventy Sushan nursery pigs with an average body weight of 19.56 ± 0.24 kg were randomly allocated to two experimental dietary treatments: 18% CP (high protein; group HP), and 15% CP (low protein; group LP). We found that the differences in the two diets had no significant effect on the growth performance of Sushan nursery pigs. Nursery pigs on the 15% CP diet showed significantly improved protein, amino acid, and energy utilization. Furthermore, the LP diet cloud optimized the gut microflora composition to some extent. The functional structure of bacterial communities implied improved metabolic capabilities in group LP. Additionally, correlation analysis between fecal microbiota and metabolic profiles confirmed that the increase of beneficial bacterial in the feces was beneficial to the health and metabolism of the nursery pigs. In conclusion, a moderate reduction in the dietary protein level can improve growth and metabolism due to the improvement of intestinal microbiota in Sushan nursery pigs. This finding could provide useful reference data for the application of a different nutrition strategy in indigenous pig production.

Effects of broiler chicks fed the low crude protein diet supplemented with Achyranthes japonica Nakai root extract on growth performance and carcass traits

A total of 360 one-day-old broiler chicks were randomly assigned to four treatments with five replicate cages and 18 birds per cage for a 35 d trial to investigate the effects of supplementing Achyranthes japonica Nakai (AJN) root extract in low crude protein (CP) diet on growth performance and carcass traits. Experimental diets were divided as standard CP content diet, low CP content (LCP) diet, and LCP diet supplemented with 0.025% or 0.050% AJN root extract. Dietary CP reduction impaired growth performance and carcass traits, whereas supplementing AJN root extract improved growth performance and carcass traits.

Sustaining live performance in broilers offered reduced crude protein diets based on corn and wheat blend

Previous experimentation has indicated that wheat-based diets are a poor diet type to allow for optimal performance when dietary crude protein (CP) is reduced, while corn-based diets show promise. Potential mitigation of the negative effects associated with reduced CP wheat-based diets could include blending corn and wheat to be used as the cereal grain portion of broiler diets. Therefore, two studies were conducted in order to observe the effects of reduced dietary CP when broilers were fed diets containing a 1:1 blend of wheat and corn. For Experiment 1, 816 Cobb 500 broilers were placed in 24 floor pens to allow for the observation of live performance measurements from 1–41 days of age, and 108 Ross 308 broilers were placed into 18 battery cages for observation of protein and nutrient digestibility from 8–28 days of age in Experiment 2. In the floor pen study, High and Low diets were formulated to contain 235, 215, and 195 and 195, 175, and 155 g/kg CP in the starter, grower, and finisher diets, respectively. The High and Low diets were then blended to produce a Medium diet containing 215, 195, and 175 g/kg CP in the starter, grower, and finisher diets, respectively. Alternately, grower diets were offered to broiler chickens raised in battery cages from day 8–28 in Experiment 2. No effects of reduced CP were found on final body weight (BW), BW gain, or feed intake for any growout period in Experiment 1 but feed conversion ratio (FCR) was significantly increased for broilers fed the Low CP diet compared to broilers fed the High and Medium diets for the 1–27 and 1–41 day periods. In Experiment 2, broilers fed the Low diet achieved lower final BW, BW gain, and feed intake than those fed the High and Medium diets. Feed conversion ratio increased in a stepwise manner as CP was reduced. Nutrient digestibility assays found stepwise increases in nitrogen-corrected apparent metabolisable energy (AMEN) as dietary CP level was reduced and increased nitrogen (N) digestibility for broilers fed the Medium and Low diets compared to those fed the High. These data indicated that including wheat and corn at a 1:1 ratio in reduced CP diets was able to adequately support final BW and BW gain in floor pens.

Cyst(e)ine fortification in low crude protein diet improves growth performance of broilers by modulating serum metabolite profile

This study was aimed to explore the metabolomical mechanisms for the potentially ameliorative effect of cyst(e)ine (Cys) fortification on growth performance of broilers fed low crude protein (CP) diet. A total of 432 1-d-old broilers were randomly divided into 6 groups, each of which received one of the following diets: normal-CP diet (positive control, PC), low-CP diet (negative control, NC), NC diet fortified with 0.05%, 0.1%, 0.15% or 0.2% of Cys. Samples were collected on d 42. Results showed that increasing Cys fortification quadratically elevated (P < 0.05) the accumulative growth performance and leg muscle yield of broilers fed NC diet, with 0.1% being the optimal dose. Thus, samples from PC, NC and NC plus 0.1% Cys (NCC) groups were selected for further analysis. Both dietary CP reduction and fortification of 0.1% Cys in NC diet caused complex changes (P < 0.05) in serum amino acids and some other metabolites primarily involved in lipid metabolism. Multiple lipogenesis-related pathways were regulated (P < 0.05) following Cys fortification in NC diet, which could at least partially interpret the benefit of Cys fortification in NC diet on broiler performance. In conclusion, fortifying low-CP diet with 0.1% Cys promoted the growth performance of broilers probably through modulating serum metabolite profile.

Production performance and plasma metabolite concentrations of broiler chickens fed low crude protein diets differing in Thr and Gly.

The aim of the study was to test the interaction between Thr and Gly in low crude protein (CP) diets in 7 to 28 d broilers on production performance and plasma metabolites. A total of 2,040 broilers were allocated to 17 treatments. A positive control (PC) diet (20.5% CP) was formulated to be adequate in dietary Thr and Gly. A negative control (NC) diet (18.5% CP, deficient in Thr and Gly) was supplemented with crystalline l-Thr and Gly to obtain a 4 Thr × 4 Gly design. Dietary Thr was tested at an apparent faecal digestibility (AFD) Thr-to-Lys ratio, which was 55%, 58%, 61% or 64%, and dietary Gly was tested at an AFD (Gly + Ser)-to-Lys ratio, which was 135%, 142%, 149% or 156%. Plasma samples were collected at 28 d. The low CP diet, formulated at 64% Thr and 156% Gly, resulted in a higher body weight gain (BWG) (P < 0.01) and similar feed conversion ratio (FCR) as the high CP treatment (PC). FCR was improved (P < 0.001) by l-Thr supplementation. Quadratic response to dietary Thr was significant for feed intake (FI), BWG and FCR (P < 0.01). A near-significant interaction for Thr × Gly was observed for FI and BWG (Plinear = 0.091 and P = 0.074, respectively). Gly did not affect production performance. An interaction between Thr × Gly on plasma free AA level was observed (P < 0.05). Free AA concentration in plasma linearly decreased with increase in AFD Thr-to-Lys ratio, and increased with increase in AFD (Gly + Ser)-to-Lys ratio. Plasma uric acid concentration was higher in PC than in all of the other diets, and plasma triglyceride concentration was decreased by l-Thr supplementation, but not by Gly. In conclusion, Gly was not limiting for growth at low dietary CP level unless Thr was deficient, showing that adequate amounts of Thr in broiler diets can overcome marginal supply of Gly and Ser and allow reduction of dietary CP from 20.5% to 18.5% for broilers from 7 to 28 d of age.

Meta-analysis to evaluate the impact of the reduction of dietary crude protein on the gut health of post-weaning pigs

Weaning transition is often associated with the occurrence of the post-weaning diarrhoea syndrome (PWDS). The reduction of dietary crude protein (CP) has been intensively used as a strategy for controlling PWDS. The aim of the present meta-analysis was to report the effect of the reduction of dietary CP on the intestinal parameters related to the gut health, growth and diarrhoea of post-weaning piglets. A literature review of the articles published from 2006 to 2019 produced 48 articles and, of these 26 were selected. Parameters (bacterial metabolites, pH, microbiota diversity, intestinal morphology, inflammation markers, growth, faecal score) were extracted, expressed as a percentage of the control diet and analysed using a general linear model which included the study, reduction in points of dietary CP, and the ratio of digestible Lysine and dietary CP (dLys/CP) as factors. The reduction of dietary CP decreased ammonia (p < .0001), pH (p = .039), total short-chain fatty acids (SCFAs) (p = .027), biogenic amines including cadaverine (p = .034) and putrescine (p = .030) and the expression of TLR4 (p < .0001) in the intestine and also reduced the faecal score (p = .002). The dLys/CP ratio increased the level of Lactobacilli and the expression of TLR4 (p < .05), and tended to increase acetic acid (p < .1). Crypt depth, villus height, microbiota diversity and growth remained unchanged. In conclusion, this study confirmed that a reduction of dietary CP could reduce bacterial protein fermentation and the production of potentially toxic metabolites. In turn, this could result in lower intestinal inflammation and a decreased risk of diarrhoea in weaning piglets. Highlights Reducing the dietary crude protein can decrease the fermentation of undigested dietary protein, especially in the large intestine. Lowering undigested dietary protein results in a reduction of the intestinal pH and potentially toxic metabolites, including ammonia and amines. Diets with lower crude protein reduce inflammation of the intestinal mucosa and the post-weaning diarrhoea of piglets without compromising performance.

Implications of elevated threonine plasma concentrations in the development of reduced-crude protein diets for broiler chickens

There is a real quest to develop reduced-crude protein diets to facilitate sustainable chicken-meat production. However, pronounced elevations in threonine plasma concentrations in systemic plasma have consistently been observed pursuant to crude protein reductions in diets for broiler chickens. The aim of the present Perspective was to consider the genesis and consequences of these elevated threonine concentrations. A series of five reduced-crude protein feeding studies with maize-based diets completed on the Camden Campus of Sydney University was the basis of the present Perspective. Collectively, an average reduction in dietary crude protein from 212 to 167 g/kg generated a mean increase of 64.8% (867 versus 526 μmol/L) in threonine plasma concentrations. This was attributed to the downregulation of hepatic threonine dehydrogenase activity, which catalyses threonine to acetyl-CoA and glycine and a mechanism for this inhibition is proposed. Tangible reductions in dietary crude protein usually impair feed conversion efficiency and increase fat deposition. Threonine plasma concentrations are elevated by these reductions and the likelihood is that threonine concentrations may be an indicative biomarker of the precision with which efficient reduced-CP broiler diets are formulated and, if so, would facilitate their successful development.

Determining the 4th limiting amino acid in low crude protein diets for male and female Cobb MV × 500 broilers

ABSTRACT 1. Four experiments were conducted to determine the 4th limiting amino acid (AA) in maize–soybean meal-based diets. 2. Deletion assay methodology was used to quantify performance and carcase trait responses to potential deficiencies in essential and conditionally essential AA caused by reductions in dietary crude protein of maize–soybean meal-based diets from 202.9 to 186.5 g/kg. 3. The deletion of Val, Phe and Gly + Pro resulted in negative effects on live performance and carcase traits for male broilers, whereas AA deletion only affected wing weights for females with no response on live performance. 4. Further experimentation could not duplicate a response to Phe or Pro in male broilers. 5. Valine was identified as the potential 4th limiting AA in maize–soybean meal-based diets and was not found to be co-limiting with Ile.

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.

Effect of high concentration of phytase supplementation on energy and nutrient digestibility of growing pigs fed with reduced dietary crude protein balanced with limiting amino acids

There is a need to improve pig production at least cost through various dietary manipulations and nutrient management strategies that will foster reduced environmental wastes of N, amino acids (AA), P, and Ca. This experiment was designed to estimate the effect of phytase supplementation on energy and nutrient digestibility of growing pigs fed with reduced dietary crude protein (CP) balanced with limiting AA. Experimental diets were formulated in a 3 × 2 factorial arrangement of 6 dietary treatments containing 3 CP concentrations (14, 16, and 18%) supplemented with or without 5,000 units phytase/g. Limiting AA of the diets were balanced using crystalline Lys, Met, Thr, and Trp. The 6 experimental diets were fed to 6 cannulated growing pigs (30.00 ± 2.10 kg) in a 6 × 6 Latin square arrangement of 6 diets and 6 periods. Fecal and ileal samples were collected to estimate the apparent and ileal digestibility of nutrients and energy. Apparent total tract digestibility (ATTD) of dry matter (DM), N, crude fibre, ether extract, and energy decreased (P< 0.05) linearly as CP concentration increased in the diets. Apparent ileal digestibility (AID) and ATTD of N linearly decreased (P = 0.000) by increasing CP concentration in the diets from 14 to 18%. Increasing CP concentration linearly increased ATTD (P = 0.002) and AID (P = 0.003) of P. Greater ATTD and (AID) (P< 0.001) of nutrients and energy were observed with pigs fed diets supplemented with phytase. Apparent ileal digestibility of Lys, Met, Thr, Trp, and Glu decreased linearly and quadratically (P< 0.005) while, AID of Arg, His, Iso, Leu, Phe, Val, Ala, Asp, Cys, Gly, Pro, Ser and Tyr improved (P = 0.000) linearly and quadratically as dietary CP increased from 14 to 18% CP. Dietary supplementation with phytase improved (P< 0.001) AID of all the essential amino acids. Arg, His, Ile, Leu, Asp, and Pro were not affected by CP and phytase interaction. Greater (P< 0.001) AID values were observed for all AA following phytase supplementation. It was concluded from the present study that 2 and 4% reduction in dietary CP balanced with Lys. Met, Thr, and Trp resulted in improved ATTD and AID of DM, N and AID of the supplemented AA in growing pigs. Pigs fed diets supplemented with phytase had better ATTD and AID of nutrients and energy than those fed without phytase supplementation.

The effect of reduced dietary glycine and serine and supplemental threonine on growth performance, protein deposition in carcass and viscera, and skin collagen abundance of nursery pigs fed low crude protein diets.

Thirty five barrows (initial body weight [BW]: 15.1 ± 1.0 kg) were used to determine the effect of partially replacing Gly + Ser with Thr in reduced crude protein (CP) diets on growth performance, protein deposition in carcass and viscera, and skin collagen abundance during the late nursery phase to 25 kg BW. Pigs were individually fed one of five iso-nitrogenous diets (n = 7) for 21 d. The basal diet met estimated essential amino acids (AA) requirements by using all essential AA plus Gly and Ser in free form (CON; 12.1% CP; as-fed, analyzed contents). The remaining four diets were formulated by reducing total Gly and Ser concentrations to 60% or 20% of the CON diet. The N removed with Gly and Ser was replaced with either crystalline Thr or Glu. Total analyzed Thr made up either 1.59% (T1; 12.5% CP) or 2.34% (T2; 12.2% CP) of the Thr-supplemented diets, and total analyzed Glu made up either 3.47% (G1; 12.7% CP) or 4.64% (G2; 12.9% CP) of the Glu-supplemented diets. Pigs were slaughtered on day 21 to determine body composition and skin collagen abundance via bright field microscopy. Overall, average daily gain (ADG) and G:F and final carcass weights were greater for pigs fed diets supplemented with Glu (G1 + G2) vs. those fed diets supplemented with Thr (T1 + T2; P < 0.05, P = 0.060, and P = 0.050 for ADG, G:F, and final carcass weight, respectively); intermediate values were observed for CON. Nitrogen retention in carcass plus viscera and the AA profile of deposited protein in the carcass were not influenced by dietary treatment. Pigs fed the T2 and G2 diets had greater retention of Thr (vs. CON and G2) and Glu (vs. CON and T2) in the viscera protein, respectively (P < 0.05). The apparent utilization efficiency of standardized ileal digestible Thr for protein deposition in carcass plus viscera was less for pigs fed T2 (15.1%) vs. those fed CON (56.7%) or G2 (58.6% ± 2.9%) diets (P < 0.001). Only pigs fed T1 had skin collagen abundance not different from CON; pigs fed G1, G2, and T2 had reduced skin collagen abundance compared with CON and T1 (P < 0.01). Using Glu as an N source when Gly and Ser were reduced to 60% and 20% of CON in reduced CP diets maintained ADG for pigs between 15 and 25 kg BW, whereas supplying Thr as a N source reduced ADG and carcass weight. When dietary Gly and Ser were supplied at 60% of CON, only Thr supplementation rescued skin collagen abundance. Therefore, supplemental Thr at excess levels is not sufficient to replace N from Gly and Ser in reduced CP diets fed to late nursery pigs, despite supporting skin collagen abundance as a secondary indicator of Gly status.

Synthetic and Crystalline Amino Acids: Alternatives to Soybean Meal in Chicken-Meat Production.

: This review explores the premise that non-bound (synthetic and crystalline) amino acids are alternatives to soybean meal, the dominant source of protein, in diets for broiler chickens. Non-bound essential and non-essential amino acids can partially replace soybean meal so that requirements are still met but dietary crude protein levels are reduced. This review considers the production of non-bound amino acids, soybeans, and soybean meal and discusses the concept of reduced-crude protein diets. There is a focus on specific amino acids, including glycine, serine, threonine, and branched-chain amino acids, because they may be pivotal to the successful development of reduced-crude protein diets. Presently, moderate dietary crude protein reductions of approximately 30 g/kg are feasible, but more radical reductions compromise broiler performance. In theory, an 'ideal' amino acid profile would prevent this, but this is not necessarily the case in practice. The dependence of the chicken-meat industry on soybean meal will be halved if crude protein reductions in the order of 50 g/kg are attained without compromising the growth performance of broiler chickens. In this event, synthetic and crystalline, or non-bound, amino acids will become viable alternatives to soybean meal in chicken-meat production.