Based on a nonlinear N utilization model, 2 N balance experiments with growing broiler chickens were conducted, investigating the ideal amino acid (AA) ratio (IAAR) of the branched-chain AA (BCAA) Leu, Ile, and Val related to Lys. In both of the experiments, the starter (I: 10-20 d of age) and grower periods (II: 25-35 d of age) utilized 36 male Ross 308 chickens each (n = 144). Nitrogen balance periods were divided into an adaptation period (5 d) and 2 consecutive collection periods (2 × 5 d). Diets of experiment 1 were based on a consistent mixture of wheat, soy protein concentrate, wheat gluten, fish meal, and crystalline AA, subsequently diluted by wheat starch to provide 8 graded CP levels (6-34% CP). Results of nonlinear regression between N intake and N deposition yielded the theoretical maximum for N deposition (NDmaxT; I: 4,593 mg of N/BWkg(0.67)/d; II: 4,302 mg of N/BWkg(0.67)/d). Furthermore, the daily N maintenance requirement (NMR) was derived (I: 113 mg of N/BWkg(0.67); II: 215 mg of N/BWkg(0.67)/d). Both the age-dependent data for NMR and NDmaxT were applied to calculate the model parameter b (protein quality, independent of N intake) and bc(-1) (efficiency of limiting AA), respectively. Five diets based on the same ingredients as in experiment 1 were formulated for experiment 2: an AA balanced basal diet and 4 diets of the same composition but lacking in supply of Lys, Leu, Ile, or Val. All experimental diets were isocaloric and isonitrogenous. For calculation of the IAAR, observed bc(-1) data of each AA diluted diet were utilized. The concluded IAAR of Lys:Leu:Ile:Val for the starter and grower period were 100:94:55:65 and 100:106:56:72, respectively. These results indicated a higher demand for Leu and Val during the grower phase and, generally, a lower IAAR for the BCAA than previously reported in comparable experiments.

N balance experiments were conducted to derive age-dependent model parameters for modelling of lysine (Lys) requirements in growing pigs. Modern genotype barrows from 16 litters were utilized (four piglets/litter) at 15, 30, 50, 70, 90 and 110 kg body weight respectively. Six diets provided graded dietary protein supply (40 to 320 g/kg) by a constant mixture of barley, wheat, potato protein, wheat gluten, soybean protein concentrate and crystalline amino acids. Lys was set as the first limiting dietary amino acid. Each age period provided 24 N balance data (n = 4) to derive N maintenance requirement (NMR) and theoretical maximum for daily N retention (NR(max)T) by non-linear regression analysis. At high dietary Lys efficiency, 17-18 g daily Lys intake was required for 170 g daily protein deposition. To achieve similar daily protein deposition, pigs need 21-23 g Lys if the Lys efficiency is 20% lower. For higher daily protein deposition (195-200 g) and varying dietary Lys efficiency, between 22 and 29 g Lys was required. The Lys requirement data yielded by modelling were in line with current recommendations. Further developments of the approach are discussed to improve age-independent applications.

Simple SummaryDietary amino acid concentration should closely meet the quantitative requirement of animals dependent on genotype, gender, age, aimed performance and housing conditions. Both under- and over-supply yield impaired efficacy of individual amino acid utilization and increase the nitrogen excretion. Hence, for optimal feed formulation, a validated knowledge about adequacy of dietary amino acid balance is necessary. Present studies contribute toward ensuring ideal amino acid ratios in diets for growing broiler chicken making use of a new amino acid efficiency-based procedure.AbstractThree consecutive nitrogen balance experiments with fast-growing male broiler chickens (ROSS 308), both during starter and grower periods, were conducted to determine the ideal ratios of several indispensable amino acids relative to lysine. The control diets based on corn, wheat, fishmeal, field peas, wheat gluten and soybean oil were formulated by computer optimizing to meet the assumed ideal amino acid ratios and to fulfill both the energy and nutrient requirements of growing chicken. According to principles of the diet dilution technique, balanced control diets were diluted by wheat starch and refilled by crystalline amino acids and remaining feed ingredients, except the amino acid under study. The lysine, threonine, tryptophan, arginine, isoleucine and valine diluted diets resulted in significantly lower protein quality as compared to control diet, especially following increased dietary lysine supply (experiments II and III) and stronger amino acid dilution (experiment III). Accordingly, the limiting position of individual amino acids was confirmed, and the derived amino acid efficiency data were utilized to derive ideal amino acid ratios for the starter period: Lys (100): Thr (60): Trp (19): Arg (105): Ile (55): Val (63); and the grower period: Lys (100): Thr (62): Trp (17): Arg (105): Ile (65): Val (79).

Two growth experiments with fast growing meat type chickens (Ross 308) were conducted to assess the growth of feathers and feather-free body dependent on age and gender (male:female ratio = 1:1). Birds were reared under uniform management and feeding conditions (floor pens; 15 pens per gender; 5 birds per pen) during the starter (day 1 to 22) and grower period (day 22 to 36). Diets were based on corn, wheat, soybean meal, soybean protein concentrate and balanced with feed amino acids to ensure an equal feed protein quality close to the ideal amino acid ratio by a constant mixture of the feed proteins. At start of the experiment and further on weekly up to the end of the 5 th week, 15 birds per gender (each 3 pens of 5 birds) were selected and 24 h fasted before quantitative de-feathering. Both feather and feather free body fractions were significantly increased with increasing age of the birds (p < 0.001). Feather percentage as related to the empty body weight increased non-linearly from approximately 2% at the end of the first week to about 4% at the end of the experiment. Feather percentage and dry matter content of the feather-free body was significantly higher in female birds (p < 0.001) as compared to males. Further investigations will show how this varying proportions impact on nutrient deposition of modern meat-type chickens dependent on age and gender, respectively.

Simple SummaryCurrently, several alternative protein sources are under investigation for replacing soybean meal in poultry diets. One alternative is larvae meal of the black soldier fly (Hermetia illucens) with a specific sulfur amino acid composition. The larvae meal is limiting in sulfur amino acids supply and provides a wide methionine:cysteine ratio of 61:39. Currently, it is not known whether the insect meal has an impact on the optimal ratio of methionine to cysteine in broiler chicken diets. The methionine:cysteine ratio significantly influences animal growth and welfare. Both methionine and cysteine excess and deficiency can lead to an impaired feed intake, growth, and feed efficiency. Therefore, the aim of this study was to investigate whether the optimal methionine:cysteine ratio is modulated when a high inclusion rate of partly defatted Hermetia illucens meal is applied. The results show that a methionine:cysteine ratio of 50:50 yields superior growth and dietary protein quality. It can be concluded that the insect meal under study is a promising alternative protein source without modulating the optimal methionine:cysteine ratio in broiler chicken diets.AbstractThe dietary methionine:cysteine (Met:Cys) ratio (MCR) is an important factor influencing the optimal growth of chickens. Therefore, this study aimed to contribute to the assessment of the optimal dietary MCR in diets with the complete replacement of soybean meal (SBM) by a partly defatted larvae meal of Hermetia illucens (HM). A growth study with 240 male meat-type chickens (Ross 308) was conducted, also assessing the body nutrient deposition both at the end of the starter (day 21) and the grower (day 35) period. Birds were fed experimental diets based on wheat, maize, and insect meal (23%/21% HM in starter/grower diets). Sulfur amino acids were created as the limiting AA in diets with graded MCR (40:60; 45:55; 50:50; 55:45; 60:40). The control diet contained SBM instead of HM with a MCR of 50:50. The current results based on growth parameters, dietary protein quality, and Met efficiency data gave support to the previous assumption of an ideal MCR of 50:50, which was also valid in diets with a high proportion of insect meal. The lowest MCR of 40:60 led to significantly impaired feed intake and growth of the birds, while the response to the highest MCR (60:40) was moderate.