Each individual in the population has a distinct maximum growth potential, and the growth curve may vary depending on the response to nutrient intake, growth phase and variability among animals. The present study aimed to (1) model weight gain (WG) response to methionine+cystine (Met+Cys) supply using different mathematical functions, (2) identify functions that better fit the growth responses of pullets, (3) determine the Met+Cys requirements that maximize WG based on breeding standards and (4) partition the Met+Cys requirements for WG and maintenance. Three trials were performed using 1448 laying-type pullets. We adopted a completely randomized design with eight treatments and six replicates. The first trial (2 to 6 weeks, P1) used 15 pullets per experimental unit. The second and third trials (8 to 12 weeks, P2; 14 to 18 weeks, P3) were used eight pullets per replicate. The Met+Cys levels were obtained using a dilution technique. The mathematical functions used to describe WG responses to Met+Cys intake were broken line, broken line with curvilinear ascendancy, Michaelis–Menten, saturation kinetics and three logistic and three exponential models. Models were selected using the Bayesian information criterion and evaluated by residual analysis. It was possible to model the responses using the studied functions. The best functions were obtained by logistic and sigmoidal models in P1 and P2, and with the broken line by the curvilinear ascendancy model in P3. The Met+Cys intake that determined the maximum potential for WG (WGmax) in P1, P2 and P3 were 313, 381 and 318 mg/day, respectively. The Met+Cys requirements for WG were 20, 22 and 27 mg/g, and for maintenance were 214, 53 and 30 mg/kgBW0.75 for P1, P2 and P3, respectively.

Making dairy farming more cost-effective and reducing nitrogen environmental pollution could be reached through a reduced input of dietary protein, provided productivity is not compromised. This could be achieved through balancing dairy rations for essential amino acids (EAA) rather than their aggregate, the metabolizable protein (MP). This review revisits the estimations of the major true protein secretions in dairy cows, milk protein yield (MPY), metabolic fecal protein (MFP), endogenous urinary loss and scurf and associated AA composition. The combined efficiency with which MP (EffMP) or EAA (EffAA) is used to support protein secretions is calculated as the sum of true protein secretions (MPY + MFP + scurf) divided by the net supply (adjusted to remove the endogenous urinary excretion: MPadj and AAadj). Using the proposed protein and AA secretions, EffMP and EffAA were predicted through meta-analyses (807 treatment means) and validated using an independent database (129 treatment means). The effects of MPadj or AAadj, plus digestible energy intake (DEI), days in milk (DIM) and parity (primiparous v. multiparous), were significant in all models. Models using (MPadj, MPadj × MPadj, DEI and DEI × DEI) or (MPadj/DEI and MPadj/DEI × MPadj/DEI) had similar corrected Akaike’s information criterion, but the model using MPadj/DEI performed better in the validation database. A model that also included this ratio was, therefore, used to fitting equations to predict EffAA. These equations predicted well EffAA in the validation database except for Arg which had a strong slope bias. Predictions of MPY from predicted EffMP based on MPadj/DEI, MPadj/DEI × MPadj/DEI, DIM and parity yielded a better fit than direct predictions of MPY based on MPadj, MPadj × MPadj, DEI, DIM and parity. Predictions of MPY based on each EffAA yielded fairly similar results among AA. It is proposed to ponder the mean of MPY predictions obtained from each EffAA by the lowest prediction to retain the potential limitation from AA with the shortest supply. Overall, the revisited estimations of endogenous urinary excretion and MFP, revised AA composition of protein secretions and inclusion of a variable combined EffAA (based on AAadj/DEI, AAadj/DEI × Aadj/DEI, DIM and parity) offer the potential to improve predictions of MPY, identify which AA are potentially in short supply and, therefore, improve the AA balance of dairy rations.

Today's broiler is characterised by faster-, leaner-growth. A large part of this progress is attributed to the genetic selection that had, and continues to improve growth rate and composition of gain at steady pace. As an illustration of such increases in performance, 2.3 kg live gain (slaughter weight) has been reduced from requiring 52 days in 1995 to 36 days in 2017 - a reduction of 0.73 days per year. In addition, meat yield has increased as a proportion of the carcass, being 12% of body weight in the year 1957 and increasing to 20% in 2001 Recent work in 2017 using high density diets has shown to capacity of birds to attain an FCR of 1.19 at 2500 g live BW. Current research suggests that the optimum level of energy may be well below the recommendation by the primary breeders. For example, reducing energy from 100 to 92.5% (around -200 kcal/kg of diet) resulted in only 2 points loss in body weight corrected FCR. Indeed, very recent work showed that a similar reduction of -200 kcal/kg feed in finisher AME resulted in similar, or higher gains and breast yield while having no effect on FE. Published data regarding the balance between energy and protein in feed suggests an optimum AA density between 100 to 120% of breeder recommendations. It can be therefore suggested that today's broiler needs a higher ratio of essential amino acids to energy. In addition to a net increase in the absolute requirement of amino acids, there is an argument for higher dietary ratio of lysine: essential amino acids which will support increased meat production and may better fit modern broiler genetics.

Reduction of the CP content in the diets of piglets requires supplementation with crystalline essential amino acids (AA). Data on the leucine (Leu) and histidine (His) requirements of young pigs fed low-CP diets are limited and have primarily been obtained from nonlinear models. However, these models do not consider the possible decline in appetite and growth that can occur when pigs are fed excessive amounts of AA such as Leu. Therefore, two dose-response studies were conducted to estimate the standardised ileal digestible (SID) Leu : lysine (Lys) and His : Lys required to optimise the growth performance of young pigs. In both studies, the average daily gain (ADG), average daily feed intake (ADFI) and gain-to-feed ratio (G : F) were determined during a 6-week period. To ensure that the diets had sub-limiting Lys levels, a preliminary Lys dose-response study was conducted. In the Leu study, 60 35-day-old piglets of both sexes were randomly assigned to one of five treatments and fed a low-CP diet (15%) with SID Leu : Lys levels of 83%, 94%, 104%, 115% or 125%. The His study used 120 31-day-old piglets of both sexes, which were allotted to one of five treatments and fed a low-CP diet (14%) with SID His : Lys levels of 22%, 26%, 30%, 34% or 38%. Linear broken-line, curvilinear-plateau and quadratic-function models were used for estimations of SID Leu : Lys and SID His : Lys. The minimum SID Leu : Lys level needed to maximise ADG, ADFI and G : F was, on average, 101% based on the linear broken-line and curvilinear-plateau models. Using the quadratic-function model, the minimum SID Leu : Lys level needed to maximise ADG, ADFI and G : F was 108%. Data obtained from the quadratic-function analysis further showed that a ±10% deviation from the identified Leu requirement was accompanied by a small decline in the ADG (−3%). The minimum SID His : Lys level needed to maximise ADG, ADFI and G : F was 27% and 28% using the linear broken-line and curvilinear-plateau models, respectively, and 33% using the quadratic-function model. The preferred model to estimate the His requirement was the curvilinear-plateau model. However, a 10% reduction in the SID His : Lys level was associated with an 11% reduction in the ADG. In conclusion, the SID Leu : Lys level needed to maximise growth was 108% when using the quadratic-function model as the best-fitting model. The minimum SID His : Lys level required to optimise growth was 28% when using the curvilinear-plateau model as the best-fitting model.

Magnesium has essential functions in cellular metabolism and bone development. Its actions are closely linked to calcium and phosphorus, making the achievement of the right proportion of these elements in diets an important issue in poultry nutrition. The magnesium requirement of poultry has rarely been studied and most studies conducted are more than 35 years old. Despite the fact that magnesium is adequately present in most plant-based diets, supplemental magnesium may positively affect poultry meat quality and body weight at certain developmental stages. However, excessive dietary magnesium could influence calcium and phosphorus availability and metabolism through different mechanisms. Understanding the effects of supplemental magnesium on the availability and metabolism of other dietary constituents and vice versa is important for formulating balanced diets and achieving maximal performance in poultry. Here we review this complex, insufficiently explored issue.

Functions are important in designing. However, several issues hinder progress with the understanding and usage of functions: lack of a clear and overarching definition of function, lack of overall justifications for the inevitability of the multiple views of function, and scarcity of systematic attempts to relate these views with one another. To help resolve these, the objectives of this research are to propose a common definition of function that underlies the multiple views in literature and to identify and validate the views of function that are logically justified to be present in designing. Function is defined as a change intended by designers between two scenarios: before and after the introduction of the design. A framework is proposed that comprises the above definition of function and an empirically validated model of designing, extended generate, evaluate, modify, and select of state-change, and an action, part, phenomenon, input, organ, and effect model of causality (Known as GEMS of SAPPhIRE), comprising the views of activity, outcome, requirement–solution–information, and system–environment. The framework is used to identify the logically possible views of function in the context of designing and is validated by comparing these with the views of function in the literature. Describing the different views of function using the proposed framework should enable comparisons and determine relationships among the various views, leading to better understanding and usage of functions in designing.

Trace minerals are an essential part of poultry diets, even though the trace mineral requirements recommended by the NRC (1994) for poultry are based on very limited research work. For poultry producers, mineral salts are routinely over-formulated to ensure adequate levels are fed and requirements are met. This practice has caused concerns regarding optimising the genetic potential of modern breeds and environmental pollution. In recent years, extensive research work has been carried out to compare organic mineral sources, such as proteinates or amino acid chelates, with inorganic forms in poultry diets. This paper reviewed the research results conducted globally to date with mineral proteinate (Bioplex®, Alltech Inc, USA) including Zn, Cu, Mn and Fe. These replicated trials have used broilers, pullets and laying hens of different ages and in various practical raising conditions such as cages and floor pens. The main findings include: 1) mineral proteinate has a higher retention rate and relative bioavailability value than reagent grade inorganic salts; 2) the antagonism between minerals such as Zn and Cu could be avoided by using organic forms; 3) supplementing high levels of Cu or Zn as inorganic salt in poultry diets negatively affected the efficacy of phytase in the diet, which could be overcome by using mineral proteinate; 4) the replacement of inorganic minerals with lower level organic forms can support the optimal performance of broilers and layers and minimise the impact of minerals on the environment.

Two experiments were conducted to investigate the requirement for dietary crude protein (CP) in growing blue-breasted quail (BBQ). In Experiment 1, 300 1-day-old quails were randomly assigned to 10 groups according to a 2 × 5 factorial arrangement of treatments with two metabolisable energy (ME) levels (12.13 and 13.39 MJ/kg) and five CP concentrations (160, 190, 220, 250 and 280 g/kg) for 8 weeks. In Experiment 2, 300 1-day-old quails were subjected to a different factorial arrangement of treatments with two ME levels (11.51 and 12.13 MJ/kg) and five CP concentrations (210, 220, 230, 240 and 250 g/kg) for 28 days. Experiment 1 revealed that an interaction existed in weight gain between ME and CP levels in weeks 1 to 4. In both ME groups, quails receiving CP of 160 g/kg showed the least weight gains (P < 0.05). No differences (P > 0.05) existed in weight gain between the ME groups in which quails ingested CP of 250 and 280 g/kg, whereas quails consuming CP of 220 g/kg with an ME of 13.39 MJ/kg had smaller weight gain than did those ingesting higher CP concentrations (P < 0.05). Of main effects for weeks 1–4, quails treated with an ME of 12.13 MJ/kg consumed more feed than did those receiving another ME level, whereas quails in both ME treatments showed similar feed efficiencies. For weeks 5 to 8, no difference (P > 0.05) in weight gain, feed intake and feed efficiency was seen regardless of ME levels, and no interaction existed between ME and CP levels. In Experiment 2, the best weight gain and feed efficiency were achieved when the dietary CP concentration was more than 210 g/kg, and quails treated with 11.51 MJ/kg showed better weight gain and feed efficiency (P < 0.05) than did those that received 12.13 MJ/kg. Furthermore, the weight gains and protein intakes on the basis of per MJ from the two experiments were pooled together to estimate the protein intake necessary for the best growth performance by two mathematic models; they were then converted to dietary CP concentrations of 204 (minimum) and 233 g/kg (maximum) when ME was 11.51 MJ/kg. In conclusion, BBQ will achieve good growth performance with dietary CP of more than 204 g/kg on the basis of an ME of 11.51 MJ/kg in weeks 1 to 4.

The aim of this study was to investigate protein requirements for the maintenance and growth of blue-breasted quail (Excalfactoria chinensis) from 7 to 21 days of age. A total of 180 quails, 7 days old, were randomly assigned to 36 cages and for 2 weeks were fed diets with a metabolisable energy concentration of 12.13 MJ/kg and a dietary CP concentration of 125, 150, 175, 200, 225 or 250 g/kg. The average BW per cage and the feed intake per cage were recorded daily. The results showed that quails fed 125 g/kg CP could not maintain their BW and had negative feed efficiency. There were linear and quadratic relationships between CP level and response criteria, including BW, weight gain, feed intake, feed efficiency, final body nitrogen mass and body nitrogen accretion (P < 0.05). The dietary CP requirements, as calculated using a one-slope quadratic broken-line model, were 211 and 202 g/kg according to weight gain and feed efficiency, respectively. The regression equations, on the basis of metabolic BW, of daily weight gain on daily protein intake according to the model were Y = 0.137−2.128(0.113−X) if X < 0.113 and Y = 0.137 if X ⩾ 0.113 (R2 = 0.96, P < 0.001), which meant that the protein requirement for maintenance was 0.049 times the metabolic BW and that to gain 1 g weight quails needed to ingest an extra 0.47 g protein after the maintenance requirement was satisfied. The regression equations, on the basis of metabolic BW, of daily body nitrogen accretion on daily protein intake according to the model were Y = 5.667−76.700(0.119−X) if X < 0.119 and Y = 5.667 if X ⩾ 0.119 (R2 = 0.95, P < 0.001), which meant that quails had to receive an amount of protein equal to their metabolic BW multiplied by 0.045 to satisfy the requirement for maintenance and then ingest an extra 13 g protein to accrete 1 g body nitrogen. In conclusion, growth or protein accretion rates should be regulated according to dietary CP for specific experimental purposes via apportioning protein requirements for maintenance v. growth.

The focus of the review is to show how the Box-Behnken Design (BBD) could be applied in poultry nutrition research. BBD is a multivariate experimental design which uses less treatment combinations and allows researchers to estimate and optimise processes. Box-Behnken design was used in an experiment to estimate growing broiler requirements for total sulphur amino acids (TSAA), lysine (Lys) and threonine (Thr). In the experiment BBD has shown to be a useful tool in estimating and optimizing nutrient requirements in growing broilers.

Determining energy utilization in growing animals enables to adjust the nutritional constraints to nutrient requirements while maximizing the ratio between lean retention and fat retention to improve feed efficiency. In turkey production, the important sexual dimorphism and differences between strains may contribute to differences in basal energy metabolism and the partitioning of energy retention between protein and lipid. The objective of this study was to determine the dynamics of energy utilization in males and females of a heavy strain of turkeys fed ad libitum from 1 to 23 weeks of age. Heat production (HP) was determined by indirect calorimetry and retained energy (RE) was calculated as the difference between metabolizable energy (ME) intake and HP. The RE as protein was determined by a nitrogen balance, while the remaining RE was assumed to be lipid. A modeling procedure allowed partitioning HP between fasting HP (FHP), activity-related HP and thermic effect of feeding. A multiple regression analysis was used to estimate the maintenance energy expenditure (MEm) and the energy efficiencies of protein and lipid retention (kp and kf, respectively). Results were expressed either per day or per kg BW0.75 per day. In comparison with females, males consumed more feed (440 v. 368 g/day), grew faster (163 v. 147 g/day) and retained more protein (38 v. 28 g/day) during the experimental period. Expressed per kg BW0.75 per day, ME intake decreased linearly with increasing age and was not affected by gender. Similarly, RE as protein decreased with increasing age and tended to be greater in males than in females, whereas RE as lipid increased with increasing age and was lower in males than in females. In addition, HP decreased with increasing age and was greater in males than in females, because of greater activity-related HP and FHP (47% and 9% greater in males compared with females). The FHP averaged 417 kJ/(kg BW)0.75 per day during the first 3 weeks of age and decreased to 317 and 277 kJ/(kg BW)0.75 per day in males and females, respectively, from 20 weeks of age onwards. Similar to FHP, MEm was lower in females than in males ((586 to 12 × BW) and (586 to 5 × BW) kJ/(kg BW)0.75 per day, respectively) and the kp and kf were estimated at 0.63 and 0.87, respectively. This study shows that the partitioning of RE and HP differs between genders in growing turkeys, which likely results in differences in nutrient requirements.

It has been about 80 years since Cu was first recognized as being important for maintenance of haemoglobin. Since that time requirement values have been established and signs of deficiency and excess well documented. NRC (1994) provide the most comprehensive list of detailed requirement values for Cu for various classes of poultry, yet these lack extensive detail and are predicated on just five publications, the most recent of which was conducted 30 years ago. Requirement values average 6-8 ppm which traditionally is supplied by inorganic salts and especially copper sulphate. Other inorganic sources vary from 40-115% bioavailability of Cu compared to sulphate. Copper is easily complexed with amino acids or proteins, leading to the development of so-called organic sources of copper which are claimed to have better digestibility and/or less formation of insoluble complexes with other minerals in the digesta. Results on effectiveness of organic vs. inorganic forms of Cu are variable, although this line of research has led to appreciation of the potential to use much lower levels of supplementation. Since at least 80% of dietary copper appears in the excreta, using lower levels of diet supplementation means reduced Cu in the environment. With less supplementation, knowledge about bioavailability of Cu in major feed ingredients becomes important. Copper in cereals is reported to be 80% available to the bird while that in vegetable proteins is closer to 50% available. Availability from animal proteins is very variable, while corn distiller's grains now provides the most concentrated source of Cu within the major ingredients. Copper levels greatly in excess of requirement, at around 125 ppm, have been shown to improve performance of meat birds and egg layers. The mode of action is unknown although likely relates to antibacterial properties of Cu. Likewise high levels of diet Cu have been shown to reduce cholesterol content of eggs and poultry meat, although this is often at the expense of loss in performance and contribution of more Cu to the environment.

Three 8-week growth experiments were conducted to quantify the requirements of the fingerling Cirrhinus mrigala for the dietary branched-chain amino acids valine (experiment 1), isoleucine (experiment 2) and leucine (experiment 3). Six isonitrogenous (400/g) and isoenergetic (17·90k/) test diets were formulated with a gradation of 2·5/g for each test amino acid, valine (7·5–20/g), isoleucine (5·0–17·5/g) and leucine (7·5–20/g), and fed to randomly stocked fish in circular troughs. In experiment 1, the maximum weight gain (312%), best feed conversion ratio (FCR; 1·45) and best protein efficiency ratio (PER; 1·72) were obtained in fish fed 15·0g dietary valin/g. In experiment 2, the highest weight gain (317%), best FCR (1·47) and best PER (1·70) were recorded at 12·5g dietary isoleucin/g, and in experiment 3, the highest weight gain (308%), best FCR (1·46) and best PER (1·71) were noted at 15·0g dietary leucin/g. A quadratic regression analysis of weight gain, FCR and PER data showed an optimum requirement at 15·9, 15·0 and 14·8/g for valine, 13·2, 12·3 and 12·1/g for isoleucine and 15·6, 15·4 and 15·1/g for leucine in dry diets. Low body moisture and higher protein were noted in fish fed diets containing 15·5, 12·5 and 15·0g valine, isoleucine and leucine per kg, respectively. Body fat increased with increasing levels of the branched-chain amino acids. On the basis of a regression analysis of growth data, it is recommended that a diet for C. mrigala should contain valine at 15·2, isoleucine at 12·6 and leucine at 15·4/g dry diet, corresponding to 38·0, 31·5 and 38·5/g dietary protein, respectively.

Besides being an indispensable amino acid for protein synthesis, arginine (Arg) is also involved in a number of other physiological functions. Available data on the quantitative requirement for Arg in different teleosts appear to show much variability. So far, there are very limited data on the maintenance requirements of indispensable amino acids (IAA) in fish. In the present study, we compared N and Arg requirements for maintenance and growth of four finfish species: rainbow trout (Oncorhynchus mykiss), turbot (Psetta maxima), gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax). Groups of fish having an initial body weight close to 5–7 g were fed semi-purified diets containing graded levels of N (0 to 8 % DM) and Arg (0 to 3 % DM) over 4 to 6 weeks. For each species, N and Arg requirements for maintenance and for growth were calculated regressing daily N gain against daily N or Arg intakes. N requirement for maintenance was estimated to be 37·8, 127·3, 84·7 and 45·1 mg/kg metabolic body weight per d and 2·3, 2·2, 2·6 and 2·5 g for 1 g N accretion, in rainbow trout, turbot, gilthead seabream and European seabass respectively. The four species studied appear to have very low or no dietary Arg requirements for maintenance. Arg requirement for g N accretion was calculated to be 0·86 g in rainbow trout and between 1·04–1·11 g in the three marine species. Turbot required more N for maintenance than the other three species, possibly explaining its reputedly high overall dietary protein requirement. Data suggest a small but sufficient endogenous Arg synthesis to maintain whole body N balance and differences between freshwater and marine species as regards Arg requirement. It is worth verifying this tendency with other IAA.