جستجوی مقالات مرتبط با کلیدواژه « selection index » در نشریات گروه « علوم دام »

The aim of this research was to study different economic selection indices to increase body weight in Markhoz goat breed. Body weight (BW) at different ages (birth, weaning, 6-month and 9-month) were categorized as several two- and three-traits selection indices. Genetic parameters were estimated with MTGSAM using the Bayesian statistical method. Selection index analyzes were done using SelAction software. The results of comparing three-trait indices showed that highest total economic gain resuled from I9 which was US$4.86. The total economic response for two-trait index belonged to I4 which was US$3.94 and higher than 5 others. The highest direct genetic gain from three-trait indices was predicted for 9-month weight in I8 and I9 indices to be about 0.63 kg. In addition, the highest direct genetic improvement resulting from two-trait indices was also predicted for the 9-month weight in the I3 to be 0.66 kg. Moreover, the selection and performance criteria revealed decrease in phenotypic variance, heritability, and genetic correlation of traits. These changes differed in alternative selection schemes, which influenced by the initial population parameters, selection intensity, direct or indirect selection, and the number of traits included in the selection index. In conclusion, to maximize the total economic gain, two selection indices I9 and I4 can be suggested for the current condition of the Markhoz goat population. However, to preserve the phenotypic/genetic variance of traits, it is necessary to focus on strategies such as selection intensity, economic coefficients, indirect selection, and increasing the number of traits in selection indices.

The aim of the present study was evaluation of genetic- economic merit for imported Holstein bull semen daughters in different climates of Iran. These progenies were categorized based on different selection indices of their sire semen exporter countries. In this study, data were milk, fat and protein yield, calving age and calving interval in the first lactation of 270566 Holstein cattle that were collected during 1993-2017 at Animal Breeding Center of Iran. The daughters breeding values were predicted under multi-trait animal model by DMU software. The genetic-economic merit of progeny was estimated using the Lifetime Net Income (LNI) index. Estimated least square means of the LNI index for daughters of imported semen under different selection indices were statistically significant in the various climates (p < 0.01). The highest estimated least square mean of LNI index in Iran was related to daughters whose sire semen came from France bulls (2001- 2011). The results obtained in this study showed that the highest estimated least square means of LNI index in cold, semi-cold, moderate and warm climates were related to daughters whose sires were imported from Germany (2008- 2013), France (2001- 2011), France (2012- 2013) and the Netherlands (2012- 2013), respectively. Thus, it could be concluded that the genetic-economic merit of daughters from imported semen in each climate depends on the selection index of bulls in the semen exporter country.

The aim of the present study was to investigate the effect of imported semen under different selection indices on phenotypic changes of production traits in Holstein cattle population in various climates of Iran. In the present research, records of first lactation on milk yield, fat and protein percentage of 269786, 216850 and 270566 Holstein cattle derived from imported semen under different selection indices in cold, semi-cold, moderate and warm climates, were used. The data were collected by the Center of Breeding and Improvement of Livestock Production during 1993 to 2017. The data were analyzed using the General Linear Model (GLM) software SAS 9.2. In cold, semi-cold, moderate and warm climates, the means of milk yield (kg) in the progenies of imported semen were estimated, 9597.92, 9654.46, 9718.34 and 8985.37, the means of fat percentage were estimated, 3.13, 3.07, 3.08 and 3.15 percent, and the means of protein percentage were estimated 3.10, 3.25, 3.14, and 3.16 percent, respectively. In the present study, the highest least square means of the phenotypic value of Holstein cattle derived from imported semen based on different selection indices in cold, semi-cold, moderate and warm climates were according to countries of France 2001-2011, Italy 1993- 2001, Netherlands 2001-2006, France 2001-2011 for milk yield, Netherlands 1999-2000, United States 1987-1988, United States 1992-1993, and Canada 1998-2000 for fat percentage and Canada 1991-1992, France 2012-2013, Sweden 2008-2012 and Germany 2002 -2007 for protein percentage, respectively.

The aim of this study was to compare three selection strategies and two properties of breeding value estimations using computer simulation. Simulated traits were weights at birth (BW1), eight weeks (BW8), twelve weeks (BW12), maturation (BWM) and also age at first laying (AFL), weight of first egg (EWM), average egg weight (EW) and egg number (EN). The first strategy was to select cockerels based on breeding value of BW12 and selection of hens based on a selection index with four traits including BW12, AFL, EW and EN. In the second strategy, cockerels and hens were selected using a selection index, as already said. But in the third strategy, cockerels were selected based on breeding value of BW12 and hens based on breeding value of EN. The individual's breeding values for three schemes were estimated by BLUP and ssGBLUP. Matings were performed based on the optimal genetic contribution. The results showed that the total economic values of the first and second programs using ssGBLUP estimations were 450, 460 and 421, and using BLUP were 434, 349 and 418, respectively. The rate of true inbreeding coefficient for ssGBLUP estimations were more than BLUP estimations (0.083, 0.287 and 0.046 vs. 0.072, 0.116 and 0.024, respectively). The results showed that the first strategy for a breeding flock of broiler production, the second strategy for a dual-purpose flock for producing egg and meat and the third strategy for a flock to achieve the highest total economic value with the lowest possible rate of true inbreeding were desirable.

The aim of the study was to compare two strategies in Mazandaran native fowls using computer simulation.  Simulated traits included body weight at birth (BW1), at eight weeks of age (BW8), at twelve weeks of age (BW12), at maturation (BWM), age at sexual maturity (AFE), weight of first egg (EWM), mean egg weight from 28 to 32 weeks of age (EW28-32) and egg number (EN). The first strategy was to select cockerels based on breeding value of BW12 and hens based on a selection index with 4-traits including BW12, AFE, EW28-32 and EN. The second strategy was to select cockerels and hens using a selection index based on a 4-traits including BW12, AFE, EW28-32 and EN. After 10 generations, the first strategy improved BW1, BW12, BWM, EW28-32 and EWM to 1.49, 573.81, 397.58, 3.96, and 3.75 grams and AFE and EN to -3.51 days and 2.09 eggs, respectively. After 10 generations, the gain for traits in the second strategy for BW12, BWM, AFE and EN was 415.78, 218.74 grams and -9.77 days and 9.45 eggs, respectively. At the end of the tenth generation increase of inbreeding in the first and second strategies was 0.048 and 0.070, respectively.  The results showed that the first strategy was suitable for a breeder flocks with the aim of chickens suitable for broiler production and the second strategy was suitable for a dual-purpose flocks with the aim of producing egg and meat.

This study was achieved to evaluation of some strategies and determination the best suitable selection index for Afshari sheep using simulated data. The relative importance of traits was determined based on the estimated economic values and consequently، the most benefit traits were applied to selection indexes construction. The interest indexes were different combination of traits including ewe body weight (EBW)، annual wools weight (AWW) and total weaning weight for each exposed ewe (TWWEE). The index 1 were included all three mentioned traits. The indexes 2، 3 and 4 were included (AWW، TWWEE)، (EBW، TWWEE) and (TWWEE)، respectively. The results indicated that the aggregate genotype، selection index and economic progress increased by increasing in the population size and decreasing in ram ratio، but made reduction in inbreeding average، in all indexes. In more cases، the aggregate genotype decreased by removing a trait in the index. The comparisons among indexes indicated that the most suitable selection index for this breed is index 1 which included EBW، AWW and TWWEE. This index had a maximum selection index average، aggregate genotype and economic progress.

The aim followed in the present study was to investigate the economic aspects of, and to derive Economic Weights (EWs) for Mature Body Weight (MBW) as well as for age at First Calving (AFC) in Holstein dairy cattle of Iran. Economic values (EVs) for traits were estimated using trait-by-trait bio-economic models. Absolute EVs were RLs -16400 and -17900 per cow per year for MBW and AFC, respectively. Because of the negative effects of these traits on profitability, EWs of -7540 for MBW and -3760 for AFC are suggested for a national selection index. A one day increase in AFC increased production costs by Rls 39600 per cow per year. Sensitivity analysis revealed that the EV for MBW was more sensitive to changes in live weight price than to feed costs. Results obtained in this study can be used in the development of breeding objectives and in the cost- benefit analysis of management programs which aim at changing the attitudes of farmers and of their consultants towards decreasing costs and therefore increasing profitability.