A review of mathematical functions for the analysis of growth in poultry

Poultry industries face various decisions in the production cycle that affect the profitability of an operation. Predictions of growth when the birds are ready for sale are important factors that contribute to the economy of poultry operations. Mathematical functions called ‘growth functions’ have been used to relate body weight (W) to age or cumulative feed intake. These can also be used as response functions to predict daily energy and protein dietary requirements for maintenance and growth (France et al., 1989). When describing growth versus age in poultry, a fixed point of inflexion can be a limitation with equations such as the Gompertz and logistic. Inflexion points vary depending on age, sex, breed and type of animal, so equations such as the Richards and López are generally recommended. For describing retention rate against daily intake, which generally does not exhibit an inflexion point, the monomolecular would appear the function of choice

A modelling analysis of growth in poultry

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Application of the law of diminishing returns to estimate maintenance requirement for amino acids and their efficiency of utilization for accretion in young chicks

8 páginas, 3 tablas, 1 figura.Suitability of the monomolecular equation, specifically re-parameterized for analysing energy balance data, has recently been investigated in broilers and turkeys. In the current study, this equation was applied to literature data from growing chicks fed crystalline amino acid (AA) diets, in order to provide estimates for AA requirements for maintenance, body-weight gain and protein accretion. Non-linear regression was used with the data to estimate parameters and combine them to determine other biological indicators. The predictive ability of the model was evaluated with reference to model behaviour when fitting the data, biologically meaningful parameter estimates and statistical performance. The model estimated the maintenance requirements for valine, threonine and lysine to be in the range 80-111, 96-109 and 52-209 mg/kg of liveweight/day, respectively, depending on the response criterion. Requirements for maintenance were in good agreement with values reported previously. Average efficiency of recovering AAs in whole body protein, between maintenance and four x maintenance, was in the reported range of 0.80-1.0 and greatest at low intakes and decreasing as intakes increase.Peer reviewe

Application of the law of diminishing returns to partitioning metabolizable energy and crude protein intake between maintenance and growth in egg-type pullets

Experiments designed to investigate the effect of dietary nutrient concentrations on the growth and development of pullets are relatively long term and expensive to conduct. As the cost of research increases, mathematical models become valuable tools to answer research and development questions. Modeling growth curves allows nutritionists and poultry researchers to predict dynamic or daily nutrient needs more adequately than using fixed requirements. The potential and validity of a specially reparameterized monomolecular model to partition nutrient intakes between requirements for maintenance and growth was previously demonstrated in relation to ruminants, pigs, chickens, turkeys, and broiler breeder pullets. In the current study, the model was evaluated for its ability to estimate ME and CP requirements for maintenance and growth in egg-type pullets. On the basis of the results of this study, along with those previously reported for chickens, turkeys, and broiler breeder pullets, this model is advantageous because it can predict the magnitude and direction of responses of growing poultry to dietary ME and CP intakes without requiring initial assumptions. The model also has the advantage of biological interpretability of the parameter estimates. One of the main consequences of this interpretability is that the results from several experiments can be pooled to obtain the best estimates of the response coefficients. ©2012 Poultry Science Association, Inc

Predicting methionine and lysine contents in soybean meal and fish meal using a group method of data handling-type neural network

8 páginas, 2 figuras, 2 tablas.Artificial neural network models offer an alternative to linear regression analysis for predicting the amino acid content of feeds from their chemical composition. A group method of data handling-type neural network (GMDH-type NN), with an evolutionary method of genetic algorithm, was used to predict methionine (Met) and lysine (Lys) contents of soybean meal (SBM) and fish meal (FM) from their proximate analyses (i.e. crude protein, crude fat, crude fibre, ash and moisture). A data set with 119 data lines for Met and 116 lines for Lys was used to develop GMDH-type NN models with two hidden layers. The data lines were divided into two groups to produce training and validation sets. The data sets were imported into the GEvoM software for training the networks. The predictive capability of the constructed models was evaluated by their abilities to estimate the validation data sets accurately. A quantitative examination of goodness of fit for the predictive models was made using a number of precision, concordance and bias statistics. The statistical performance of the models developed revealed close agreement between observed and predicted Met and Lys contents for SBM and FM. The results of this study clearly illustrate the validity of GMDH-type NN models to estimate accurately the amino acid content of poultry feed ingredients from their chemical composition. © 2015 INIA.Peer Reviewe

Application of the law of diminishing returns to partitioning metabolizable energy and crude protein intake between maintenance and growth in egg-type pullets

Experiments designed to investigate the effect of dietary nutrient concentrations on the growth and development of pullets are relatively long term and expensive to conduct. As the cost of research increases, mathematical models become valuable tools to answer research and development questions. Modeling growth curves allows nutritionists and poultry researchers to predict dynamic or daily nutrient needs more adequately than using fixed requirements. The potential and validity of a specially reparameterized monomolecular model to partition nutrient intakes between requirements for maintenance and growth was previously demonstrated in relation to ruminants, pigs, chickens, turkeys, and broiler breeder pullets. In the current study, the model was evaluated for its ability to estimate ME and CP requirements for maintenance and growth in egg-type pullets. On the basis of the results of this study, along with those previously reported for chickens, turkeys, and broiler breeder pullets, this model is advantageous because it can predict the magnitude and direction of responses of growing poultry to dietary ME and CP intakes without requiring initial assumptions. The model also has the advantage of biological interpretability of the parameter estimates. One of the main consequences of this interpretability is that the results from several experiments can be pooled to obtain the best estimates of the response coefficients. ©2012 Poultry Science Association, Inc

Effects of dietary fat source and green tea (Camellia sinensis) extract on genes associated with lipid metabolism and inflammatory responses in female broiler chickens

This study was aimed to investigate the effects of dietary fat sources and green tea extract (GTE) on gene expression associated with lipid metabolism and inflammation in broiler chicken. A total of 300 female Ross 308 broiler chicks were allocated to six dietary treatments in a completely randomised design with a factorial arrangement of two levels of GTE (0 and 500 mg/kg diet) × three levels of fat inclusion [without fat (control group), soybean oil (SO) and tallow (Ta)]. Liver fat (LF), liver methallothionin (LMT) content, and lipoprotein lipase (LPL), adipose triglyceride lipase (ATGL), tumour necrosis factor α (TNF-α), and interleukin (IL-6)] genes expression were investigated. Relative expression and statistical analyses of genes expression were assessed using REST software. The effect of added dietary fats was significant and improved performance parameters compared to the control group (p < .05). The highest abdominal fat and blood triglyceride, and the lowest carcase yield, were achieved in chicks fed SO-supplemented diet (p < .05). Chicks fed a diet supplemented with SO showed an overexpression and a decrease of LPL and ATGL compared to the Ta-supplemented and control groups, respectively (p < .05). GTE supplementation was effective on LPL and ATGL expression and ameliorated the effect of SO on abdominal fat percentage. TNF-α expression, LMT content, and relative weight of lymphoid organs were affected neither by GTE nor by the fat sources. There was no detection of IL-6 gene expression in adipose tissue. The results of this study demonstrated that diets rich in SO were capable increase fat deposition by an increase and decrease in LPL and ATGL gene expression, respectively. However inclusion of GTE in broiler diets alleviated the LPL-increasing and ATGL-reducing effects of SO and ameliorated the effect of SO on abdominal fat mass.Highlights Diets supplemented with SO increased abdominal fat mass by changes in LPL and ATGL gene expression. Obesity was not effective in the expression of inflammatory genes (TNF-α and IL-6), indicating a lack of connection between inflammation and obesity in broiler chicken. GTE (500 mg/kg diet) addition to the diets supplemented with SO ameliorated the effect of SO on LPL and ATGL gene expression and abdominal fat mass