The fattening efficiency evaluation in broilers, expressed in the European Efficiency Factor (EEF index) requires the information on mortality rate, body mass and feed conversion ratio reached at the age of their delivery to slaughter. This requirement is met by the use of the deterministic simulation model BIOM N 2001. In contrast to the contemporary widely used models of growth that describe the body mass growth as a function of time, the BIOM N 2001 model is based on the conversion of metabolizable feed energy into the gross energy deposited in the tissues of a growing warm-blooded animal. The results, obtained in an experiment with broiler chickens ROSS 208, demonstrate the formal compatibility of this new methodical approach with the classical growth function of Gompertz. The advantage of this new method is its compatibility with variables, generally used at well performing farms in the course of the fattening period, i.e. good agreement between the calculated values and those measured in an experiment, namely the amount of feed consumed under the measured climatic conditions of the breeding hall, the body mass of broilers (females-2 374 g, males-2 696 g), their age at slaughter maturity, and the feed conversion ratio. Taking into account the actual mortality of the flock it is easy to calculate the EEF index and to use the BIOM N 2001 model for the solution of prognostic or diagnostic tasks. Broiler chickens, deterministic model, body mass, feeding The classical approach to simulation of body mass growth by means of the Gompertz's function frequently used in the growth evaluation of broiler chickens (e.g. Rogers et al. 1987; Hurwitz and Talpaz 1997) describes the experimental growth curve as a function of time. Likewise Emmans (1997) derives the expected feed consumption in the growing organism from the time course of the Gompertz function. The new approach in a simulation of body mass growth based on the conversion of metabolizable energy consumed in the feed, into mass and gross energy of proteins, lipids and carbohydrates deposited in the growing body was published by Novák L. (1996), Novák L. and Zeman (1997). The influence of air temperature, humidity and ventilation rate in the stable on the available net energy for production, compatible with parameters currently found in well performing farms was presented recently (Novák, P. et al. 2000). This knowledge was now incorporated into the series of the growth models BIOM and BIOM N 2001, published by Novák L. (2000, 2003). The aim of this paper is to demonstrate the validity of the BIOM N 2001 model in simulation of body mass growth and feed conversion ratio data, with results of the carefully carried experiment on broiler chickens. Materials and Methods The growth experiment with broiler chickens ROSS 208 was carried out at the Research Institute for Animal Production Praha-Uhfiínûves. The experimental groups were kept separated by sex in pens (1.5•× 3 m) of 50
Novak L.: Self-regulatillg Growth Model in Homoiotherms (SCM). Acta vet. Bmo 1996, 65:107-114.The aim of this contribution was to demonstrate mathematical expression of the growth model which forms the growth curve from objectively measurable values describing the organism. its nutrition. and thermal conditions of the environment where the growth occurs. As presented. the self-regulating growth model (SGM) creates automatically the growth curve of body mass from the input data defined in SI units. In contradiction to currently used formulae of growth curves derived from the logistic curve or polynomials of the nonlinear regression analysis. SGM does not contain the coefficients which should be previously derived from the experimental data of the particular type of the experiment. SGM creates automatically the growth curve values from the following input data: the initial body mass (Go)' the average body mass of the defined adult organism (GLi). specific gross energy content of the body mass increase (SGEG) and a common coefficient (n) which indicates the relation of the rate of the metabolizable energy intake in the feed (MEIF) to the value of the standard metabolic rate (SMR). The physiological limits for the coefticient (n) are between 0 and 5 for most of the homoiotherm species. From the abovementioned set of input data the SGM calculates the growth curve by integration of the body mass increase. The SGM was verified on growth curves of the rat. broilers. pigs. and cattle.GroH·th curve. modellillg. rat. broilers. pig. caule
NOVáK, L., ZEMAN, L., NOVáK, P., MAREŠ, P.: Modeling the pigs body mass growth and the stressing factors impact on the daily feed intake. Acta univ. agric. et silvic. Mendel. Brun., 2005, LIII, No. 5, pp. 105-116 Modeling the body mass growth in fattened pigs by means of the exponential growth function enables to simulate the growth curve from three constants of the gender's, or the hybrid's combination, represented by their body mass phenotype: body mass at birth (G0) genetic limit of body mass (GLi) and the maximum body mass increase reached in the inflexion of the growth curve (dG max). However the expression of animal´s genome to its body mass phenotype depends on the amount and quality of the feed mixture consumed and mainly on the fact how much of the net energy gained remains left for production (NEp), after the mandatory needs of the body maintenance functions are saturated. Only this amount of net energy for production may be deposited into the proteins and fats of the body mass increase (dG/ dt). The net energy for production (NEp) is restricted; if a greater amount of net energy gained (NE) is spend, for compensation of the stressors impact (NE stx). The sum of particular stressor's action is expressed by stressor's index (STX) and indicates the proportional increase of net energy (NE) spend for the maintenance requirement of the animal (NEm). This contribution extends, the classic method of modeling the body mass growth, by the simultaneous modeling of the daily feed mixture intake (DFI) with the content of metabolizable energy (SMEF). The daily feed intake is calculated with respect to the impact of stressors on the net energy consumption. The setting of the model automatically increases the amount of the daily feed intake, so that the adequate amount of net energy for production will not be disturbed. The basic equation for the appropriate daily feed intake sounds as followDetails for calculation, of the net energy for production (NEp) from the input values of the body mass phenotype (G0, GLi, dG max), the content of the metabolizable energy in the feed (SMEF) and of the stressors index value (STX), are described. The validation of the method developed has been approved using the experimental data gained in the fattening of 33 pigs, both sexes, of PIC hybrid combination. Fenotyp hmotnosti prasat je projevem exprese genomu zvoleného plemene nebo hybridní kombinace. V předchozím sdělení (Novák, L. et al., 2004), bylo dokumentováno, že průběh růstu hmotnosti vykrmovaných prasat je charakterizován fenotypem hmotnosti vyjádřeným porodní hmotností, (G0, kg), gene-
New method for evaluation of the ideal growth performance in pigs has been proved in the experimental stable room of MZLU in ŠZP Žabčice. This method is based on the biological interpretation of the exponential growth function of Gompertz. This solution defines the dynamic of the animal’s phenotype by the body mass at the begin of the fattening (G0), by the animal's race standard body mass (Gli) which is equal to the value of the growth curve asymptote and by the value of the daily maximum body mass increase (dGmax) given by the genotype of the animal. This phenotype definition yields the possibility to define the exponential growth curve of the animal from birth until to the body mass maturity by the equation in which (t) represents the age of the animal:Gt = Gli.exp(-ln(Gli/G0).exp(-(e.dGmax/Gli).t)) [kg] (1)The value of the real daily body mass increase is than estimated by the best approximation of the experimental body mass values by the growth curve defined in the equation (1). The distribution of animals in three groups, according to the calculated daily maximum body mass increase: the thin growing animas, by default growing animals and the most growing animals, demonstrated the dynamic of the relation between the value of the daily maximum body mass increase (dGmax) and the body mass of the animals (Gt). In animals aged 37 days the clear correlation between the daily maximum body mass increase and the body mass reached:Y = 21.486x – 14.826 (R2 = 0.69); and Y = 28.609x2 – 45.21x + 23.868 (R2 = 0.70).In animals of the age 150 days the correlation is a little bit looser:Y = 54.316x +39.146 (R2 = 0.31); and Y = 8.203x2 + 35.192x + 50.241 (R2 = 0.31).The presented original methodology for evaluation of the animal’s individuality by means of the biological version of Gompertz exponential growth functions has been proved as a tool for direct evaluation of expression of the genotype body mass into its phenotype values, already during the experiment or the fattening process.
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