فهرست مطالب saeid ansari-mahyari

Chicken gut microbiota is affected by factors such as diets, environmental ,and bird age. In the current study, the effects of age and region on the ileum bacterial population of broiler chickens were investigated. A total of 2679 chickens in four geographical regions of Iran were sacrificed in the first to eighth week of age. Stool samples were collected and DNA was extracted and analyzed for the detection of Lactobacillus, Enterococcaceae, Clostridiaceae, Streptococcaceae, and Actinobacteria, using specific primers and probes. Purified amplicons were quantified by QuantiFluor® and pooled for sequencing. Findings showed that L. acidophilus was the dominant bacterium during the first four weeks, and was substituted with L. crispatus and L. salivarius in the next four weeks. So, the Lactobacillus family was the most dominant bacteria at all ages showing its essential role in chicken physiology. The age of chickens significantly affected the percentage of L. crispatus, L. acidophilus, L. salivarius, Clostridiaceae, Enterococcaceae, Streptococcaceae, and Actinobacteria. The breeding region influenced Streptococcaceae, with the highest percentage in the hot region. Chicken weight had a significant effect on Enterococcaceae. Broiler breeder age and distance to the nearest farm had no effect on ileum bacterial populations. This study showed there are several factors during the broiler breeding period that have an impact on microbial population changes at different ages.

The recent progress and achievements in the advanced, accurate, and rigorously evaluated algorithms has revolutionized different aspects of the predictive microbiology including bacterial growth.
In this study, attempts were made to develop a more accurate hybrid algorithm for predicting the bacterial growth curve which can also be applicable in predictive microbiology studies.
Sigmoid functions, including Logistic and Gompertz, as well as least square support vector machine (LSSVM) based algorithms were employed to model the bacterial growth of the two important strains comprising Listeria monocytogenes and Escherichia coli. Even though cross-validation is generally used for tuning the parameters in LSSVM, in this study, parameters tuning (i.e.,‘c’ and ‘σ’) of the LSSVM were optimized using non-dominated sorting genetic algorithm-II (NSGA-II), named as NSGA-II-LSSVM. Then, the results of each approach were compared with the mean absolute error (MAE) as well as the mean absolute percentage error (MAPE).
Applying LSSVM, it was resulted in a precise bacterial growth modeling compared to the sigmoid functions. Moreover, our results have indicated that NSGA-II-LSSVM was more accurate in terms of prediction than LSSVM method.
Application of the NSGA-II-LSSVM hybrid algorithm to predict precise values of ‘c’ and ‘σ’ parameters in the bacterial growth modeling resulted in a better growth prediction. In fact, the power of NSGA-II for estimating optimal coefficients led to a better disclosure of the predictive potential of the LSSVM.

One of the important breeding goals in dairy cattle is increasing length of productive life (LPL). In the recent decades, genetic evaluations of dairy cattle longevity have been a major concern for breeders. The trait LPL is defined as the number of days from the first calving to culling, death or censoring. Increasing LPL by reducing the costs of replacement of the heifers and increasing the number of high producing cows plays an important role in increasing the herd incomes and profitability.
This study aimed to evaluate genetic variations for LPL based on the survival analysis models was used to evaluate the impact of environmental and genetic factors on the risk of culling and to estimate the genetic parameters for longevity in Holstein dairy herds. Data included 35,137 records of productive lifetime from the first calving during 1991 and 2012, collected from dairy herds in Isfahan province. Culled and un-culled animals were assigned as uncensored and censored cows, respectively. However, it may be of interest to distinguish between disposal mostly beyond the control of dairy managers such as the sale of profitable but sterile can (involuntary culling) and voluntary disposal of a healthy but not profitable cow. The number of observations was considered with at least 20 records per herd and at least 10 daughters per sire. The last lactation was considered for the animals whose culling date was missed. In this case, cow assigned as culled animal only if the time interval between end of the last lactation and date of recording exceeds 365 days. Three types of cows were excluded in this study: sold, without any records and transferred to other herds. The sires with one daughter in a herd were removed. Genetic parameters were estimated based on a sire model which was implemented in Weibull model in Survival Kit software Survival analysis using proportional hazard model was used to analyze data on LPL. The existence analysis models are the best for the genetic PL evaluation; these models are referred to as the Proportional Risk Models, which are categorized in two semi-parametric Cox and Weibull. Following the designed algorithm in this software, the records with known longevity and low FHL limit were used. Hence, the records were considered uncensored data if the cows were either culled or died for any reason. Therefore, censoring the records represented the cows were sold, exported or leased to other herds. Both Cox and Weibull models were implemented in Survival Kit, and they could be used for continuous and discontinuous (time-dependent) variables.
The average lifetime in uncensored and censored cows were 937.8 and 1002.8 days, respectively. It is obvious that some cows are culled due to calving difficulties on day one, therefore LPL of One day is considered for them. Heritability could change based on the estimates of ρ and scale (λ). Estimates of heritability of LPL according to logarithmic scale and original scale were 0.074 and 0.18, respectively. In many studies on different populations, the heritability evaluated through survival analysis is higher than what is determined through linear models. Regression of phenotypic changes was -0.03±0.01, which showed that the reduction of relative culling risk has occurred slowly across the studied herds. The genetic trends of culling risk showed that regression coefficient was close to zero and therefore, it can be concluded that according to variance of the estimated breeding values in LPL, it would be possible to increase LPL by selecting the high ranked cows. The range of culling risk were calculated from 0.96 to 0.99. An attempt to estimate the genetic trend for sires was made by grouping sires according to their year of birth. Besides, negative phenotypic trends in this study for the proportional culling risk was achieved which demonstrated that LPL was phenotypically improved but based on the genetic trend, an increase in culling risk was observed that indicated a genetically decreasing in productive lifetime in studied dairy herds. More research is needed to analyze more data in other dairy farms in Iran.
Based on the variation of the obtained breeding value, it is possible to increase the lifetime of cows via selecting the higher breeding value cows.

In order to studying of genetic variation in Mazandaran and Esfahan native chickens، twenty microsatellite markers were evaluated. These microsatellite markers were MCW0014، MCW0081، MCW0183، MCW0067، MCW0104، MCW0123، MCW0330، MCW0165، MCW0069، MCW0020، MCW0222، LEI0094، MCW0295، MCW0034، MCW0216، ADL0268، ADL0112، ADL0278 and lEI0166. Blood samples of 90 and 150 native chickens of Mazandaran and Esfahan were randomly taken respectively. Genomic DNAs were isolated through optimized and modified salting-out procedure. The number of alleles varied from 1 to 6. In Mazandaran population one locus (MCW0216) and in Esfahan population three loci (MCW0216، MCW67 and MCW222) were monomorphic. The other loci were showed appropriate polymorphism. All the loci except MCW222 and MCW165 in Mazandaran population showed deviations from Hardy-Weinberg equilibrium (p)

This experiment was aimed to study the association between the DGAT1 K232A polymorphism and milk production traits and somatic cell score (SCS) in Iranian Holstein dairy cows. The records of 408 animals from five dairy herds were randomly identified and then genomic DNA was extracted from blood using the modified-salting method described by Miller. RFLP-PCR was performed to obtain all the polymorphisms and two alleles, K and A were observed with frequency of 0.37 and 0.63. Genotypic frequencies of AA, KA and KK were 0.3578, 0.5515 and 0.0907, respectively. The relationship between DGAT1 K232A and milk traits and somatic cell score in the first lactation was studied. The results showed significant difference (p≤0.05) between the genotypes on milk production, fat percent but not for protein percent and SCS. According to this research, the DGAT1 K232A polymorphism can be considered for increasing milk performance traits in Holstein dairy cows in the proximal region of bovine chromosome 14.

For the current research the records of 62 farms in Isfahan province were available. To estimate genetic and phonotypic trends of reproductive traits such as age at first calving, calving interval, days open and number of insemination to conception rate the records of 63,866 cows including 167793 reproductive records were employed. Farms were covered by Vahdat industrial Agriculturists and Dairymen Cooperative of Isfahan during 1986 to 2012. Genetic parameters estimated by linear animal model using Restricted Maximum Likelihood Method (REML). Genetic and phonotype trends were estimated by using regression of average breeding values and phonotype values on calving year. Heritability of age at first calving (0.19±0.007), calving interval (0.06±0.005), days open (0.041±0.004) and number of insemination to conception (0.071±0.004) were estimated. Phonotypic trends of age at first calving, calving interval, days open, number of insemination to conception in first parity and number of insemination to conception in second parity onward were estimated to be -3.48± 1.08, -0.41±0.4, -0.42±0.2, 0.013±0.0025 and 0.031±0.01 respectively. Estimated genetic trends for age at first calving, calving interval, days open, for number of insemination to conception in first parity and number of insemination to conception in second parity onward were estimated to be 0.07±0.06, -0.56±0.5, -0.02±0.06, 0.0015±0.001 and 0.0005±0.005, respectively.

STATs are a family of latent transcription factors that reside in the cytoplasm of resting cells. The STAT1 transcription factor gene located on the chromosome 2 at interval 60 to 63 cM. This factor upon stimulation with INF gamma, dimerizes and translocate to the nucleus where mediates transcriptional regulation. In this study, we estimated the allele and genotype frequencies of STAT1/Pag1 gene polymorphism and examined the association whit milk yield (305-day milk yield) and milk component (fat and protein percentage) traits. DNA was isolated from 317 Holstein cows of five different herds. A 314 bp fragment in STAT1 gene was amplified and the animals were genotyped using RFLP-PCR technique. Seven genotypes including DD (89 animals), BB (25 animals), CC (11 animals), AC (15 animals), BC (9 animals), CD (164 animals) and BD (4 animals) were identified. Frequencies of A, B, C, and D alleles were estimated to be 0.021, 0.101, 0.332 and 0.546, respectively. Association of STAT1/Pag1 genotypes with percentage of fat in the milk was relatively high (P < 0.05); the DD genotype was superior to other groups. But corrected milk production for 305 days and protein percentage of the milk did not differ among all groups (P > 0.01). We concluded that this marker should be considered for milk component (fat percentage) selection in Holstein dairy cows

In this study we estimated the allele and genotype frequencies of SCD1 and DGAT1 gene polymorphism. The analysis was conducted on 408 Holstein cows from five dairy herds in Isfahan province. Genotypes were identified using PCR-RFLP technique. Two genetic variants (A and V) of the SCD1 gene were observed in this experiment. The frequency of A-allele ranged from 0.49 to 0.66, while frequency of V-allele 0.34 to 0.51. Regards with DGAT1 gene, also two genetic variants (A and K) were determined that frequency of A-allele ranged from 0.54 to 0.68 and K-allele 0.32 to 0.46. It was found that these two genes were polymorphic in Isfahan Holstein cows, which suggested that could be associated with composition and production traits