A study of broiler breeder eggs differing in eggshell matrix optical density was conducted to determine the association of eggshell structural quality and the risk of disease in broilers.

A total of 10 000 eggs from a broiler breeder flock were examined according to the pre-established criteria, and allocated to groups classified as having a high or low density shell matrix.

The eggs from respective groups were incubated and hatched in a commercial hatchery. Samples of unhatched eggs from each group were subjected to detailed examination to establish the cause of reproductive failure. First, quality chicks from each group were raised as separate flocks in a commercial broiler barn. Group performance, morbidity, and mortality were monitored throughout the growth period. All birds were processed in a commercial plant, and condemnation data were compiled.

There were significantly more unhatched eggs, and fewer quality chicks in the group classified as having a low density eggshell matrix, in comparison to the high-density group.

Embryo pathology accounted for a large proportion of the overall reproductive failure in both groups, with a large proportion of embryos showing anatomical anomalies. The eggs and embryos from the low-density eggshell matrix group were three times more likely to be infected.

Significantly higher production losses associated with mortality/morbidity, and condemnations of carcasses at processing were observed in broilers from the low-density eggshell group compared with the high-density eggshell group.

It is concluded that common metabolic/physiological changes in breeder hens associated with eggshell pathology may be also risk factors linked with predisposition of broiler chicks to some health problems.

In this study, the effect of chlorogenic acid extract from Lonicera japonica Thunb. on Mycoplasma gallisepticum infections and the performance of broiler flocks was investigated.

A total of 360 Ross-308 broiler chicks taken from M. gallisepticum seropositive flocks were divided equally into three groups designated as control (nothing administered), antibiotic (Tylosin tartrate given for the first 3 d and d 20–22) and test group (chlorogenic acid extract given twice a day on d 16 and 22).

Broiler performance analysis, serological tests (slide agglutination), molecular identification (polymerase chain reaction) and histopathological examination were performed to detect M. gallisepticum.

The results show that chlorogenic acid not only increases live body weight but is also an alternative treatment option in M. gallisepticum–infected broiler flocks.

A 4 × 2 factorial experiment was conducted to investigate the effect of inclusion of spray-dried porcine plasma (SDPP), in lieu of meat meal, in the starter diet on performance and digestive physiology of broiler chickens between hatch and 35 d of age. Four levels of SDPP (0, 5, 10 or 20 g/kg) were included in the starter diets in lieu of meat meal on either wheat- or maize-based diets.

Over the first 10 d, and throughout the 35-d experimental period, birds gained more body weight with increasing concentrations of SDPP regardless to the type of grain used. Inclusion of SDPP in the starter diet markedly improved feed per gain in the starter phase and across the 35-d study. There was no significant effect of the type of grain and its interaction with SDPP on the body weight gain and feed per gain for the two assessed periods.

At d 10, the relative weight of the gizzard+proventriculus, spleen and liver increased with increasing concentrations of SDPP.

At 24 d of age, the grain and SDPP inclusion significantly interacted, depressing the weight of bursa and spleen in birds that received the highest concentration of SDPP in the maize-based diet. Birds fed on the maize-based diets had higher relative weight of pancreas than those on the wheat-based diets.

Increasing concentrations of SDPP in the starter diet improved the activities of maltase, sucrase and alkaline phosphatase at 24 d of age. The interaction of grain and SDPP concentration was significant for sucrase activity in birds on the wheat-based diets. Chickens on maize-based diets had higher alkaline phosphatase and maltase activities than those on wheat-based diets.

Chicks that were offered SDPP-containing starter diets had longer villi, deeper crypts and lower villi/crypt than the control at 24 d of age regardless of the grain type used. Furthermore, longer villi and larger villi/crypt were found in chicken groups fed on wheat-based diets than those on maize-based diets.

Chickens on maize-based diets had higher dressing percentage and relative breast weight than those on wheat-based diets at 35 d of age.

It can be concluded that supplementation of starter diets with SDPP would be beneficial to the long-term growth of broiler chickens. The effect of the basal grain used in the diet is minimal.

Two experiments were conducted to test the hypothesis that when using similar protein/amino acid diets and environment temperature conditions, the performance and carbon turnover in muscle and liver tissues, as measured by the incorporation of stable isotopes (¹³C/¹²C), must be different between fast-growing Cobb 500® and slow-growing Label Rouge broilers.

For both experiments (Cobb and Label Rouge), 21-d-old birds were distributed in a completely randomised, 3 × 3 factorial design; three environmental temperatures (cyclic heat stress ad libitum, 22°C ad libitum, and 22°C restricted) and three crude protein concentrations (189.1, 210 and 220 g/kg CP) were used.

The Cobb 500® had better performance with higher concentrations of crude protein. Cyclic heat stress (a temperature factor), negatively affected this genetic strain’s performance. For the Label Rouge birds, the crude protein concentrations in the diet presented inconsistent results and cyclic heat stress did not affect the performance.

The carbon turnover rate was affected in the Cobb 500® strain, with a high protein content reducing carbon turnover in the evaluated tissues (liver and muscles). Feed intake had a greater impact on carbon turnover rates than cyclic heat stress. The Label Rouge birds were not affected by the evaluated factors, suggesting that genetic improvement has a leading role on tissue carbon turnover.

There is a genetic influence on carbon turnover in the liver and muscle tissues of broiler chickens. In addition, genetically fast-growing broilers are more susceptible to variations in diet composition and environmental temperature than less rapidly growing animals.

The aim of this study was to investigate the individual and combined effects of rosemary, oregano and fennel volatile oil (FVO) supplementation on the performance and ilio-caecal bacteriological flora of broiler chickens.

A total of 800 male Ross-308 broiler chickens were divided equally into 8 groups; each contained 100 chickens. The study included a control treatment (NC) with no dietary additives that was supplemented with oils according to the following 7 treatments: 200 mg α-tocopherol acetate/kg (PC), 100 mg oregano volatile oil (OVO)/kg, 100 mg rosemary volatile oil (RVO)/kg, 100 mg FVO/kg and an equal mixture of oregano+rosemary+fennel VO (100, 200, 400 mg/kg, VOM-1, VOM-2 and VOM-3, respectively). The experiment lasted for 6 weeks.

At the end of the experiment, dietary supplementation with α-tocopherol, oregano, rosemary and FVO and two different volatile oil mixtures (VOMs) (VOM-2; VOM-3) significantly increased the body weights (BWs) of broilers at 7, 14 and 21 d of age compared to the negative control (NC) (?) and VOM-1 groups. At 0–42 d, birds fed on VOM-3 were considerably heavier and also gained more weight than NC (?) and VOM-1 groups.

The blend of VOs at 400 mg/kg significantly increased Lactobacillus spp. in faeces. The blends of oregano, rosemary and FVOs (VOM-3) at 400 mg/kg concentration and also VOM-3 group exhibited stronger antibacterial activity against coliform bacteria compared to the NC (?) group.

In conclusion, the blend of oregano, rosemary and fennel VOs at higher concentrations (400 mg/kg concentration) in diets can be used to stimulate the growth and can improve the intestinal microbial balance (including a reduction of coliform bacteria and an increase in Lactobacillus spp. counts) of broiler chickens.

A comprehensive study was conducted to analyse the meat quality attributes, composition and carcass traits in Aseel chickens and commercial broilers at market age on the basis of physiological age. A total of 20 Aseel (26 and 56 weeks) and 20 broiler (6 weeks) chickens were divided into two groups on a live weight basis, i.e. large (≥2.5 kg) and small (<2.5 kg) with 10 birds in each subgroup.

The pH of meat did not show any significant variation between Aseel and broiler chickens. The meat from heavier birds had significantly higher pH. Shear force value and hydroxyproline contents were significantly higher in Aseel chickens. Aseel birds had significantly higher red (a*) colouration and lower lightness (L*) than broiler chickens.

The texture and acceptability of Aseel meat were significantly higher.

Scanning electron microscopy revealed that muscle fibres in Aseels were arranged in a more coiled pattern making the muscle tough. A larger amount of connective tissue was also observed between the muscle fibres compared with the broiler chickens.

The dressing percentage was significantly higher in larger chickens. Commercial broilers recorded significantly higher meat proportion and lower proportion of bone. The meat:bone ratio was 1.07:1.0 in Aseel and 1.31–1.0 in broiler chicken. Breast muscle content was significantly lower in smaller Aseel chickens. Aseel chicken had stronger and heavier backs and shanks. Abdominal fat percentage was significantly lower in Aseel (0.73–0.78%).

The study concluded that the firm texture of Aseel meat was due to the high collagen content and interlocking connective tissue between the muscle fibres. The texture and acceptability of Aseel meat was higher. Aseel cocks had strong legs, lean meat and less abdominal fat, making them a high-value meat bird in addition to their aggressive fighting ability.

The purpose of this paper was to demonstrate the advantages of using a good theory as the basis for designing and conducting research, using personal experience of developing a simulation model to predict food intake in laying hens and broiler breeders.

To develop such a model, research projects were designed to measure, among others, the effect of lighting programmes on age at sexual maturity, changes in internal cycle length, egg and body component weights over time, effects of temperature on performance, and to determine whether these birds would make use of body lipid reserves as an energy source.

Most of the experiments described here were conceived and conducted only because they were seen as a means of collecting information required for the development of empirical and mechanistic models, both of which have contributed to a better understanding of the birds themselves, as well as to the basis for predicting food intake in broiler breeders and laying hens.

For those researchers seeking ideas for further study, there is no better way of generating such ideas than by first developing a theory of the subject to be studied, the greatest benefit from this approach being that such targeted research is bound to be new, innovative and useful.

This study aimed to evaluate the changes in physicochemical, textural and sensory characteristics of broiler (BR) and Taiwan native chicken (TNC) pectoralis muscle heated at temperatures of 50–95°C.

With increasing temperature, cooking loss, collagen solubility, shear force value and hardness, of samples increased in both chicken breeds. Rapid decreases in protein solubility were observed when the meat was heated to 50°C and gradually decreased thereafter.

Meat from BRs and native chickens performed differently upon heating in certain characteristics. TNC meat had longer cooking time and lower myofibrillar fragmentation index than BR meat did. TNC meat had higher collagen content, shear force values and springiness but lower collagen solubility than BR meat did.

BR meat had significantly higher onset and end transition temperatures than TNC meat did. In BR meat, a sensory analysis revealed that moisture release decreased and chicken flavour increased with increasing temperature.

Protein solubility, cooking loss and the texture of heated meat were highly correlated.

This study scientifically assessed the performances of the two breeds of chickens with different thermal treatments; producers could utilise the information to produce poultry products with more desirable qualities.

Sufficient floor space is a fundamental precondition for poultry to perform normal behavioural patterns. To calculate and determine stocking densities, it is essential to know the absolute minimum surface area required by any given animal (body space). Additional space is required for characteristic behaviours (behavioural space) and for adequate inter-individual distances, group sizes and room to perform social interactions have to be taken into account.

To calculate body space, planimetric measurements were carried out by the colour contrast method “KobaPlan” in various poultry species in standing and sitting positions and at a number of different ages. They included laying hens (Lohmann brown (LB), Lohmann selected Leghorn (LSL)), broiler breeders (Ross, both genders), broiler chickens (Ross 308, both genders), turkeys (BUT 6, males), Peking ducks (Cherry Valley, both genders) and Muscovy ducks (Canedins R51, males).

Depending on live weight, age, plumage condition and body position, LB hens occupied an average area between 401 cm² and 542 cm², LSL hens between 353 cm² and 445 cm², broiler breeder females between 440 cm² and 537 cm², broiler breeder males 623 cm² up to 945 cm², broiler chickens up to 434 cm², male fattening turkeys up to 1808 cm², Muscovy drakes up to 873 cm² and Peking ducks up to 627 cm².

The values can be regarded as necessary minimum spatial requirements for the measured poultry species and genotype.

The current method offers the potential to record the area occupied by animals exhibiting species-specific behavioural patterns.

Two experiments were carried out in parallel with male Ross 308 broilers over 37 d. An experiment with a total of 736 broilers was performed to study the effect of dietary inclusion of crimped kernel maize silage (CKMS) on broiler production and meat quality. Another study with 32 broilers was carried out from 21 to 25 d to investigate the inclusion of CKMS on nutrient digestibility.

In both trials, 4 dietary treatments were used: wheat-based feed (WBF), maize-based feed (MBF), maize-based feed supplemented with 15% CKMS (CKMS-15) and maize-based feed supplemented with 30% CKMS (CKMS-30).

Compared with MBF, the dry matter (DM) intakes of broilers receiving CKMS-15 and CKMS-30, respectively, were numerically 7.5 and 6.2% higher and feed conversion ratio 6 and 12% poorer (significant for 30% CKMS), although there were no significant differences in AME content between the three diets. At 37 d, the body weight of birds receiving 15% CKMS was similar to birds fed with MBF. However, the inclusion of 30% CKMS decreased broiler growth. Dietary supplementation with CKMS significantly reduced the apparent digestibility of phosphorus. The fat digestibility was significantly lower for CKMS-30 than for the other three diets.

Broiler mortality decreased significantly when CKMS was added to the diet.

The consumption of drinking water was significantly lower in all maize-based diets as compared to WBF and was lowest in broilers fed with CKMS-30.

An improved litter quality in terms of DM content and a lower frequency of foot pad lesions was observed with broilers supplemented with both dietary levels of CKMS.

The addition of CKMS to maize-based diets increased juiciness, tenderness and crumbliness of the meat.

In conclusion, the dietary supplementation of 15% CKMS had no negative effect on broiler growth and positively influenced bird welfare in terms of mortality and foot pad health. Therefore, the addition of 15% CKMS to maize-based diets is considered an advantageous feeding strategy in broiler production.

The present study was conducted to evaluate the role of extruded flaxseed (EFS) and α-tocopherol acetate (ATA) for the enhancement of polyunsaturated fatty acids ratio (PUFA) over saturated fatty acids (SFA) in broiler meat as a source of healthier meat.

A total of 96 one-d-old Cobb 550 broilers were randomly divided into 8 treatments with three replicates having 4 birds in each. EFS (extruded at 155°C) at 100, 150 and 200 g/kg alone and in combination with ATA at 200 mg/kg were supplemented through normal feed from the third week onward.

During the 6-week growth period, body weight gain (BWG), feed intake (FI), feed conversion ratio (FCR) and mortality were recorded. At slaughter, weight of liver, heart and kidney and fat content in breast and leg meat were measured. Fatty acid profiles in breast and leg meat were developed to estimate the PUFA to SFA ratio.

The results revealed that FI and FCR changed significantly in all groups and BWG increased in all the supplemented groups. The weight of liver, kidney and heart increased more in the supplemented group containing the maximum level of EFS with ATA compared with single supplementation of EFS.

The fat content in breast and leg meat decreased as the inclusion level of EFS increased. The level was low in leg meat compared with breast meat. Mortality decreased in all supplemented groups.

The PUFA to SFA ratio was significantly higher in leg meat (3.23) compared with breast meat (1.81) and the study therefore indicates that ATA and EFS supplementation could be used to improve the PUFA to SFA ratio in broiler meat.

The purpose of this study was to determine the effect of limestone particle size and calcium (Ca) to non-phytate phosphorus (P) ratio on the true ileal Ca digestibility of limestone for broiler chickens. A limestone sample was passed through a set of sieves and separated into fine (<0.5 mm) and coarse (1–2 mm) particles. The analysed Ca concentration of both particle sizes was similar (420 g/kg).

Six experimental diets were developed using each particle size with Ca:non-phytate P ratios of 1.5:1, 2.0:1 and 2.5:1, with ratios being adjusted by manipulating the dietary Ca concentrations. A Ca-free diet was also developed to determine the basal ileal endogenous Ca losses. Titanium dioxide (3 g/kg) was incorporated in all diets as an indigestible marker.

Each experimental diet was randomly allotted to 6 replicate cages (8 birds per cage) and fed from d 21 to 24 post hatch. Apparent ileal digestibility of Ca was calculated using the indicator method and corrected for basal endogenous losses to determine the true Ca digestibility.

The basal ileal endogenous Ca losses were determined to be 127 mg/kg of dry matter intake.

Increasing Ca:non-phytate P ratios reduced the true Ca digestibility of limestone. The true Ca digestibility coefficients of limestone with Ca:non-phytate P ratios of 1.5, 2.0 and 2.5 were 0.65, 0.57 and 0.49, respectively.

Particle size of limestone had a marked effect on the Ca digestibility, with the digestibility being higher in coarse particles (0.71 vs. 0.43).

The aim of this study was to analyse the morphological lesion pattern of the heart of broiler chickens (Cobb 500, Hubbard F15 and Ross 308) during fattening with no clinical signs of disease and to determine the most susceptible period for the occurrence of morphological lesions.

The most frequently diagnosed lesions in each genetic line were degeneration of the fibres with vacuolation, congestion of cardiac muscle, oedema and vacuolisation of the Purkinje cells.

The highest numbers of morphological lesions were observed on d 38, 31 and 10 of life. The lesions were most numerous in the septum, followed by the left and right ventricles.

Ischaemic cardiomyocytes were also most numerous on d 38 of life and in the left ventricle.

Overload of cardiac muscle, prolonged hypoxia and increasing body weight on d 38 are the likely reasons for the largest number of lesions and ischaemic fibres, which may lead to heart failure.

The objective of this study was to investigate and compare the effects of α-tocopherol acetate (vitamin E (VE)) and microencapsulated VE (MVE) on growth performance, meat quality and antioxidant capacity in broiler chickens.

A total of 360 d-old broiler chicks were procured and randomly allocated into three groups with 6 replicates. Each replicate had 20 chickens. Chickens were fed with basal diets (CON group) or experimental diets supplemented with 20 mg/kg VE (VE group) or 20 mg/kg MVE (MVE group) for 42 d.

The results showed that the MVE group had higher body weight gain (BWG) than the CON and VE groups, and higher gain/feed ratio (G/F ratio) than the CON group during the period of 22–42 d. During the whole experiment, a higher increase in BWG was found in the MVE group than the CON group.

Chickens fed on diets supplemented with the VE or MVE had lower abdominal fat percentage, higher pH and antioxidant enzyme activity than the CON group in the breast meat.

There was an increased tendency in the hepatic glutathione peroxidase (GSH-Px) enzyme activity of the VE and MVE groups than the CON group. The hepatic mitochondrial total antioxidant capacity and GSH-Px enzyme activity in the MVE group were higher than the CON group. Hepatic 2,2-dipheny-?-picrylhydrazyl scavenging activity of the MVE group was higher than the CON group.

These results suggested that the dietary addition of VE or MVE could improve breast meat quality in broilers. MVE supplementation may improve growth performance, hepatic mitochondrial antioxidant capacity and free radical scavenging capacity in chickens. In addition, dietary supplementation of MVE gave better broiler growth performance than VE.

An experiment was conducted to determine the effects of dietary supplementation of thymol, synbiotic (Biomin, IMBO) and their combination in laying hen diets on laying performance, egg quality and serum metabolic profile from 24 to 36 weeks of age.

Treatment groups were fed on a control diet, the control diet supplemented with thymol (250 mg/kg), the control diet supplemented with synbiotic (250 mg/kg) or the control diet supplemented with a combination of thymol (250 mg/kg) and synbiotic (250 mg/kg).

Supplementation of thymol and synbiotic, separately as well as combined, improved egg weight, egg production, egg mass and feed conversion ratio from 24 to 36 weeks of age. The eggs obtained from thymol, synbiotic or their combination treatments displayed higher values of shell thickness, Haugh unit and shell percentage compared to the control.

Serum cholesterol significantly decreased in the single or combined form of thymol and synbiotic supplementation treatments.

The aim of this study was to investigate the effect of white lupin (Lupinus albus) meal (WLM) addition on the intestinal viscosity, bird performance, nutrient utilisation and villi morphology of growing broiler chicks.

The experiment was conducted with 480 broiler chicks divided into 6 dietary treatments, including a maize-soybean meal control diet (CON) and 5 experimental diets containing 100, 150, 200, 250 and 300 g/kg WLM.

During the period from d 0 to 35, birds fed on 200 or higher WLM/kg were characterised by lower body weight gain and feed intake than CON. The use of 150 g of WLM/kg increased feed conversion ratio (FCR) compared to CON treatment. Apparent metabolisable energy corrected to zero N balance (AME_N) and apparent ileal digestibility of dry matter, ether extract, crude protein and starch, linearly decreased as WLM increased from 0 to 300 g/kg.

There was a quadratic effect of WLM dose on sialic acid excretion. A strong negative linear correlation was found between the excretion of sialic acid and AME_N. The viscosity of ileal digesta was linearly increased as WLM increased. The effect of WLM dose on ileum villus height (VH) was linear, while that on ileum villus area (VA) was quadratic. Both parameters decreased as WLM increased from 0 to 300 g/kg.

In conclusion, the use of over 150 g/kg of WLM in broiler diets depressed performance results. However, depression of nutrient utilisation was only observed when 250 or 300 g/kg of WLM was used.

The diet of broiler chickens supplemented with increasing concentrations of copper (Cu) was assessed for the effect of Cu on liver mitochondrial function.

A total of 160, 1-d-old Cobb 500 broilers (Gallus domesticus) were randomly assigned in equal numbers into 4 groups, which differed in the concentration of copper supplements in the diet; 11 (control), 110, 220 and 330 mg of Cu/kg dry matter. Liver mitochondrial function was recorded at 12, 24, 36, 48 and 60 d of age.

Supplementation with 110 mg Cu/kg dry matter enhanced mitochondrial function and activities of complexes I–V, and this was significant at 36 d of age compared with the other diets (P < 0.05). Supplementation with 220 mg Cu/kg dry matter and 330 mg Cu/kg dry matter enhanced mitochondrial function and activities of complexes I–V at 12, 24 and 36 d of age, but displayed reduced function (P < 0.05) at 48 and 60 d of age except in complex IV (P > 0.05). Mitochondrial hydrogen peroxide (H₂O₂) production was also increased (P < 0.05) with an increase of copper supplementation in the diet.

The results indicate that appropriate dietary copper supplements are sufficient for improving mitochondrial function and activities of the respiratory complexes. Higher concentrations of copper, on the other hand, lead to copper toxicity by affecting certain respiratory complexes.

A growth experiment was conducted to determine the effectiveness of liquid analogue, DL-2-hydroxy-4-(methylthio) butanoic acid (HMTBA), compared to powder DL-methionine (DLM), in commercial maize–soybean-meal broiler diets similar to those commonly used in China, on feed conversion ratio (FCR), growth performance and European Production Index (EPI) of broilers.

A 4 × 2 + 1 factorial arrangement of treatments was used in which HMTBA or DLM was fed at 4 concentrations (low, medium, high and very-high inclusion rates) of supplementation at 100% equivalence on an equimolar basis. Negative control diets were commercial starter, grower and finisher feeds with no added methionine. A total of 1008 commercial-type Arbor Acres 1-d-old chicks were randomly distributed into 9 groups, with 8 replicates of 14 (7 male + 7 female) birds per treatment.

The body weight gain of the control group was significantly lower than that of the others in the starter period but did not show any differences during the other periods. The FCR of the control group was higher than that of the others except for those with HMTBA in the grower period. It was also observed that the FCR dropped as the supplemented concentration of methionine was increased regardless of the source. Some of the treatment groups produced a better breast yield than the control. The EPI between the two products did not show any significant difference.

In conclusion, both of the methionine sources were equally effective in ameliorating the effects of a dietary deficiency of total sulphur amino acids.

Micronutrients, especially zinc, have an important role in normal metabolism and growth of broilers. Using novel technologies helps to synthesise novel zinc complexes to deliver this micronutrient more efficiently.

In the present study, the effects of different zinc complexes and nano complexes on broiler performance were compared. Broilers in 6 groups were given basal diet (without zinc) and basal diet supplemented with zinc-sulphate, zinc-methionine, zinc-nano-sulphate, zinc-nano-methionine and zinc-nano-max (that was synthesised based on nanochelating technology) at a concentration of 80 mg/kg of diet.

At 1–42 d of age, dietary zinc-nano-sulphate supplementation decreased weight gain and feed intake. However, feed conversion ratio was not influenced by treatments. Carcass yield (%) of birds in the zinc-nano-sulphate and control groups were dramatically reduced at 42 d of age and abdominal fat (%) increased in these groups.

Relative to the control group, the antibody titre, spleen and bursa of Fabricius (%) were significantly higher in groups supplemented with zinc. Heterophil (%) was also significantly higher in the zinc-nano-methionine group in blood on d 42 compared to the control, zinc-sulphate and zinc-nano-sulphate.

Compared to the controls, the mean malondialdehyde content in thigh tissue was significantly reduced in groups supplemented with zinc at the time 0, 50, 100 and 150 min after oxidation.

Tibia zinc concentration in nanoparticle zinc samples was significantly higher relative to the control and zinc-sulphate groups.

Taken together, our data indicate that delivery of zinc in the structure of zinc-nano-methionine and zinc-nano-max at concentrations of 80 mg/kg of diet improves growth performance. However, dietary zinc-nano-sulphate decreased growth performance in broilers.

Three experiments were conducted to evaluate the applicability of the Taguchi method (TM) and optimisation algorithms to optimise the branch chain amino acids (BCAA) requirements in 0 to 7 d broiler chicks.

In the first experiment, the standardised digestible (SID) amino acids and apparent metabolisable energy (AME) values of maize, wheat and soya bean meal were evaluated.

In the second experiment, three factors including leucine (Leu), isoleucine (Ile) and valine (Val), each at 4 levels, were selected, and an orthogonal array layout of L16 (4³) using TM was performed. After data collection, optimisation of average daily gain (ADG) and feed conversion ratio (FCR) were obtained using TM. The multiobjective genetic algorithm (MOGA) and random search algorithm (RSA) were also applied to predict the optimal combination of BCAA for broiler performance.

In the third experiment, a growth study was conducted to evaluate the applicability of obtained optimum BCAA requirements data by TM, MOGA and RSA, and results were compared with those of birds fed with a diet formulated according to Ross 308 recommendations.

In the second experiment, the TM resulted in 13.45 g/kg SID Leu, 8.5 g/kg SID Ile and 10.45 g/kg SID Val as optimum level for maximum ADG (21.57 g/bird/d) and minimum FCR (1.11 g feed/g gain) in 0- to 7-d-old broiler chickens. MOGA predicted the following combinations: SID Leu = 14.8, SID Ile = 9.1 and SID Val = 10.3 for maximum ADG (22.05) and minimum FCR (1.11). The optimisation using RSA predicted Leu = 16.0, Ile = 9.5 and Val = 10.2 for maximum ADG (22.67), and Leu = 15.5, Ile = 9.0 and Val = 10.4 to achieve minimum FCR (1.08).

The validation experiment confirmed that TM, MOGA and RSA yielded optimum determination of dietary amino acid requirements and improved ADG and FCR as compared to Aviagen recommendations. However, based on the live animal validation trial, MOGA and RSA overpredicted the optimum requirement as compared to TM. In general, the results of these studies showed that the TM may be used to optimise nutrient requirements for poultry.