جستجوی مقالات مرتبط با کلیدواژه "regression" در نشریات گروه "علوم دام"

The goal of this study was to determine regression equations to predict metabolizable energy of wheat samples given their chemical compositions using meta-analytical approach. A database compromising chemical compositions and apparent metabolizable energy corrected  for the nitrogen (AMEn) of 111 published sources of wheat strains was used. Sample information contains crude protein (CP), ether extract (EE), crude fiber (CF), ash and AMEn. Average values for AMEn was calculated as 2917.46 (kcal/kg), while for the CP, EE, CF, ash was calculated as 12.53, 2.12, 1.61and 1.56 (% dry matter), respectively. Meta-regression equations for predicting AMEn wheat based on chemical composition were developed and evaluated by means of provided database. Best equation obtained as: AMEn (kcal/kg)=1648+45.8 %CP+175.8 %EE+ 185.4 %CF. This equation can be used for predicting energy of wheat variates in feed-factories and poultry farms.

With increasing population, demand for chicken meat has increased and resource constraints have led to increased production with an emphasis on improving the productivity of inputs and energy indices, so studying energy consumption in broiler production is important. One of the important issue in broiler industry is energy consumption. In this study, energy consumption flow and amount of energy production were investigated for broiler farms in Alborz province. Data were collected through interviews and questionnaires. Input energies were consisted of feed, fuel (gas and gas oil), electricity, labor, equipment and chicken. Output energy were the broiler and manure. The total of input and output energies were obtained 125.2, 24.9 GJ/1000Birds, respectively. The highest share of energy consumption belonged to fuel (gas and diesel) with 50.85% and feed with 42.44%, and the machine and labor with 0.16 and 0.07 % were the lowest share among the input energies.  Energy indices, including energy ratio and energy efficiency were obtained 0.199 and 0.019 kg/MJ, respectively. Comparison of energy in three levels of hatching: ˂15000, 15000≤ ˂30000 and ≥30000 chicks showed that total energy inputs were 139.35, 130.55, 105.71, GJ/1000Birds, respectively; the ratio of energy was 0.179, 0.191, 0.236 and energy productivity was 0.017, 0.019 and 0.02 kg.MJ-1, respectively. Econometric model evaluation showed that chicken energy was the most significant input which affects the output in 1% level. If chicken energy increases 1MJ/1000birds, broiler meat production will increase 2.68 kg. Sensitivity analysis results showed that the major Marginal physical productivity (MPP) was obtained for labor energy, followed by chicken energy. The MPP of machine, electricity, fuel and feed were negative indicating that these inputs applied more than the amount required or were not applied properly. Thus, development of broiler farm mechanization and increasing capacity of broiler units is recommended.

The aim of this study was to estimate inbreeding coefficient and its impact on wool performance in Lori-Bakhtiari sheep. In this research, wool weight records of 6234 lambs born from 273 rams and 1924 ewes were used. The data were collected at Shahrekord Sholi station during 1990-2010. In total pedigree, 1764 animals were inbred. Averages of inbreeding coefficient for total and inbred population were estimated at 1.02 and 2.32 respectively. The inbreeding effects reduced wool weight performance approximately 4.2±1 g for each percentage of increase in inbreeding. Increasing 1% of inbreeding coefficient of male and female lambs was respectively accompanied with decreasing 5±1 and 3±1 g in wool weight. This decreasing was 4.6±1 and 2±1 g for single and twine lambs respectively. Annual trend in inbreeding coefficient for total and inbred population were 0.098±0.01 and -0.72±0.1 kg respectively that was statistically significant (P

The aim of this study was to estimate the amount of inbreeding coefficient in Lori-Bakhtiari sheep and its impact on growth performance. In this study pedigree information and body weight at different ages (birth weight, one month weight, weaning weight, 6 month weight, 9 month weight and 12 month weight) of 7697 lambs from 291 rams and 2097 ewes were used. The data were collected at Shahrekord sheep breeding station during 1989-2012. Estimation of inbreeding coefficient was done by CFC program and quantifying the individual inbreeding regression on the traits was applied by Wombat software. Number of inbred animals in the pedigree was 3056 lambs, equal to 39.5% of the total population. The average inbreeding coefficient of the population and inbred population were 0.94 and 2.4%, respectively. The regression coefficients of inbreeding for birth weight, one month weight, weaning weight, 6 month weight, 9 month weight and 12 months weight were estimated as +0.5, -34.4, -109.8, -283.6, -193.1 and -234 g, respectively. The highest inbreeding coefficient was 31.25 % and most inbred animals had inbreeding coefficients lower than 5 %. These results confirmed the low level of inbreeding in the population. Annual trend of the population average of inbreeding coefficient was 0.098 which was statistically significant (P<0.05). Applying a designed mating system like crossbreeding could be a suitable method to avoid inbreeding depression via keeping the level of inbreeding under control.