Modelling broilers’ abdominal fat in response to dietary treatments

Neural networks are capable of modelling any complex function and can be used in poultry production. Dietary crude fibre (CF) and exogenous enzymes (exEn) extensively affected abdominal fat (AF) of broilers. Current methods to study AF and its correlation with dietary CF levels and exEn supplements are costly, laborious and time‐consuming. The purpose of this study was to develop an artificial neural network–genetic algorithm (ANN‐GA) to model data on the response of broiler chickens (AF) to CF and exEn from 0 to 42 days of age. A data set containing eight treatments was divided to the train, validation, and test data set of the ANN models. The information about feeding eight diets at two periods [starter (0–21 days of age) and grower (22–42 days of age)] were used to estimate AF of broilers by ANN‐GA. A multilayer feed‐forward neural network with different structures was developed using matlab software, and optimal values for the ANN weights were obtained using the genetic algorithm (GA). Crude fibre, and exEn were used as input variables and AF of broilers was output variable. The best model of ANN‐GA was determined based on the train root mean square error (RMSE). The best selected ANN‐GA showed desirable results, RMSE, 0.1286% and R² coefficient, 0.876 for test data.     

Phenotypic and genetic parameter estimates for reproductive traits in Zandi sheep

This study reports on the phenotypic and genetic (co)variance components for reproductive traits in Zandi sheep, using between 1,859 and 2,588 records obtained from 577 ewes. The data were collected from the Khojir Breeding Station of Zandi sheep in Tehran, Iran from 1994 to 2008. The basic traits were litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB), and litter mean weight per lamb weaned (LMWLW), and the composite traits were total litter weight at birth (TLWB) and total litter weight at weaning (TLWW). Genetic analyses were carried out using the restricted maximum likelihood method that was explored by fitting the additive direct genetic effects and permanent environmental effects of the ewes as random effects and the ewe age at lambing and lambing year as fixed effects for all of the investigated traits. Akaike’s information criterion was used to choose the most appropriate model. LSB, LSW, LMWLB, LMWLW, TLWB, and TLWW direct heritability estimates were 0.07, 0.05, 0.12, 0.10, 0.08, and 0.14, respectively. The estimated fractions of variance due to the permanent environmental effects of the ewe ranged from 0.03 for LMWLB to 0.08 for LMWLW and TLWW. Corresponding repeatability estimates ranged from 0.10 for LSW to 0.22 for TLWW. Direct genetic correlations varied from ?0.61 for LSB–LMWLB to 0.88 for LSB–LSW and LSB–TLWB. Results indicate that genetic change depends not only on the heritability of traits, but also on the observed phenotypic variation; therefore, improvement of non-genetic factors should be included in the breeding programs.     

Genetic correlations between growth and reproductive traits in Zandi sheep

For the first time, the current study reports the genetic and phenotypic correlations between growth and reproductive traits in Zandi sheep. The data were comprised of 4,309 records of lamb growth traits from 1,378 dams and 273 sires plus 2,588 records of reproductive traits from 577 ewes. These data were extracted from available performance records at Khojir Breeding Station of Zandi sheep in Tehran, Iran, from 1993 to 2008. Correlations were estimated from two animal models in a bivariate analysis using restricted maximum likelihood procedure between lamb growth traits [birth weight (BW), weaning weight at 3 months of age (WW), as well as six-month weight (6 MW)] and ewe reproductive traits [litter size at birth (LSB), litter size at weaning (LSW), total litter weight at birth (TLWB), and total litter weight at weaning (TLWW)]. The genetic correlations between BW and reproductive traits varied from low to high ranges from 0.10 for BW–LSB to 0.86 for BW–TLWB. WW was moderately (0.37) to highly (0.96) correlated with all the reproductive traits. Moreover, the genetic correlations were observed between 6 MW and reproductive traits, varied from 0.19 to 0.95. Relationships between growth and reproductive traits ranged from 0.01 for BW–LSW to 0.28 for BW–TLWB in phenotypic effects. Results indicated that selection to improve WW would have high effect on genetic response in TLWW, and also, these results could be effective for all of the reproductive traits in Zandi sheep.     

Effect of dietary fibres on small intestine histomorphology and lipid metabolism in young broiler chickens

Two experiments were conducted to determine the influence of dietary fibres on small intestine histomorphology and lipid metabolism in broilers from 1 to 21 day of age. In experiment 1, diets containing insoluble [cellulose (CEL); 2% and 4%] or soluble [carboxymethyl cellulose (CMC); 2% and 4%] fibre were fed to broilers from day 1 to 21 post‐hatch and ileal tissue was collected at day 21 of age for histological evaluation. In experiment 2, broilers diet was supplemented with 0%, 1% or 2% insoluble fibre (Arbocel) during day 7 to 21 post‐hatch and plasma and liver lipid metabolism were evaluated at day 21. In experiment 1, inclusion of CMC reduced body weight gain (BWG) and feed intake (FI) and increased feed conversion ratio (FCR) compared with others. Intestinal histomorphology was unaffected by CEL, but CMC led to an increase in crypt depth (CD) and serosa thickness and a decrease in villus height (VH), villus width (VW), VH:CD ratio and villus surface area (VSA), rather than control and CEL groups. Treatment did not affect goblet cell type. Moreover, the CMC‐fed birds had greater total goblet cell count (GCC) as compared with others. In experiment 2, fibre inclusion was associated with increases in BWG from 7 to 14 day of age and an improvement in FCR, whereas FI was not influenced by treatments. Inclusion of fibre in the diet decreased the weight of the abdominal fat and cholesterol concentrations of liver and plasma. No significant effects on fatty acid composition of liver lipid were observed by fibre supplementation. These findings suggest dietary fibre affects performance, intestinal histomorphology and lipid metabolism in young chicks, which may directly affect poultry feeding strategies.