Estimation of Protein and Amino Acid Requirements in Layer Chicks Depending on Dynamic Model

Simple Summary The nutritional requirements of layer hens for protein and amino acids change over time during growth, and traditional feed formulation cannot accurately meet the requirements of the layer hens and tends to waste resources. The use of mathematical models to consider and include the changes in body weight and nutritional requirements of animals at different ages allows appropriate nutrition to be supplied at different stages of animal growth. In this experiment, the Gompertz model was used to consider the growth curve of the layer hens. And the analytical factorization method was used to classify the requirements of the layer hens into growth requirements and maintenance requirements. A dynamic prediction model for protein and amino acid requirements in terms of age was successfully established through a feeding test, slaughter test, nitrogen balance test, and digestive metabolism test. After calculations using the R programming language, it was noticed that the protein requirements of the layer hens decrease with increasing days of age and the amino acid requirements are lower than the recommended values of NRC. The predicted values of the model can provide some reference values for feed formulation in poultry production. Abstract Four trials were conducted to establish a protein and amino acid requirement model for layer chicks over 0–6 weeks by using the analytical factorization method. In trial 1, a total of 90 one-day-old Jing Tint 6 chicks with similar body weight were selected to determine the growth curve, carcass and feather protein deposition, and amino acid patterns of carcass and feather proteins. In trials 2 and 3, 24 seven-day-old and 24 thirty-five-day-old Jing Tint 6 chicks were selected to determine the protein maintenance requirements, amino acid pattern, and net protein utilization rate. In trial 4, 24 ten-day-old and 24 thirty-eight-day-old Jing Tint 6 chicks were selected to determine the standard terminal ileal digestibility of amino acids. The chicks were fed either a corn–soybean basal diet, a low nitrogen diet, or a nitrogen-free diet throughout the different trials. The Gompertz equation showed that there is a functional relationship between body weight and age, described as BWt(g) = 2669.317 × exp(−4.337 × exp(−0.019t)). Integration of the test results gave a comprehensive dynamic model equation that could accurately calculate the weekly protein and amino acid requirements of the layer chicks. By applying the model, it was found that the protein requirements for Jing Tint 6 chicks during the 6-week period were 21.15, 20.54, 18.26, 18.77, 17.79, and 16.51, respectively. The model-predicted amino acid requirements for Jing Tint 6 chicks during the 6-week period were as follows: Aspartic acid (0.992–1.284), Threonine (0.601–0.750), Serine (0.984–1.542), Glutamic acid (1.661–1.925), Glycine (0.992–1.227), Alanine (0.909–0.961), Valine (0.773–1.121), Cystine (0.843–1.347), Methionine (0.210–0.267), Isoleucine (0.590–0.715), Leucine (0.977–1.208), Tyrosine (0.362–0.504), Phenylalanine (0.584–0.786), Histidine (0.169–0.250), Lysine (0.3999–0.500), Arginine (0.824–1.147), Proline (1.114–1.684), and Tryptophan (0.063–0.098). In conclusion, this study constructed a dynamic model for the protein and amino acid requirements of Jing Tint 6 chicks during the brooding period, providing an important insight to improve precise feeding for layer chicks through this dynamic model calculation.