In broiler chickens, the intensive selection for growth rate, feed efficiency, body composition (breast muscle weight) traits in the last decades was successful. To improve economically important characteristics, it is possible to use molecular markers associated with meat production traits. The aim of this study was to examine genotype polymorphisms in ROSS 308 broilers for thyroid hormone responsive Spot14α, insulinlike growth factor 1 (IGF1), IGF-binding protein 2 (IGFBP2), somatostatin (SST) and prolactin (PRL) genes. A further goal of this investigation was to study the relationship between the polymorphisms and phenotypic characteristics.
In the investigated broiler population, the frequency for CC homozygous genotype was 0.77 in Spot14α (AY568628), AA homozygous genotype was 0.80 in IGF1 (M74176), GG homozygous genotype was 0.85 in IGFBP2 (U15086), DD homozygous genotype was 0.60 in PRL (FJ663023 or FJ434669). Only the AA homozygous genotype was found in SST (X60191). Chickens with AC genotype in Spot14α, and with GG genotype in IGFBP2 had higher body weight (BW) and carcass weight (CW), compared to CC and GT genotypes. However, the differences were not significant (P>0.05). There was significant association (P<0.05) between PRL genotypes and body and carcass weight, where chicken with homozygous DD surpassed individuals with homozygous II genotypes.
Models predicting the nutrient partitioning and animal performance have been developed for decades. Nowadays, growth models are used in practical animal nutrition, and they have particular importance in precision livestock farming. The aim of the present study was to introduce a broiler model and to provide examples on model application. The model predicts protein and fat deposition as well as the body weight of an individual broiler chicken from digestible nutrient intake over time. Feed intake (FI) and the digestible nutrient content of the feed are inputs as well as some animal factors like: initial BW, feed intake at 1 and 2 kg of BW, precocity and mean protein deposition. The protein and energy metabolism is represented as in the classical nutrient partitioning models. The protein deposition (PD) is driven by digestible amino acid supply and is under “genetic control”, the so-called potential PD limits the actual PD if protein is oversupplied.
The authors discuss how the model can be used to simulate the animal response upon different scenarios. Examples are given to show that the diet might be limiting if some animal trait is changed. Applicability of the model has shown through running the model by using different feed strategies (three- vs five-phase-feeding) and variations with animal factors. In conclusion, growth models are useful tools to support decision making for defining the most suitable feeds used in a broiler farm. The model presented in this paper shows a high sensibility and flexibility to test different scenarios. By challenging the model with different inputs, the animal response in terms of changes in body weight and feed conversion can be understood more by studying the shift in deposition of chemical constituents. The examples provided in the present paper shows the benefit of using mathematical models and their applicability in precision nutrition. It can be concluded that the growth model helps to apply “from desired feed to desired food” concept.