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Articles by K. Mohammadi
Total Records ( 11 ) for K. Mohammadi
  H. Roshanfekr , M. Mamouei , K. Mohammadi and E. Rahmatnejad
  In this study, the data of Birth Weight (BW), Weaning Weight (WW) and Daily Gain from birth to weaning (DG) of Arabi lambs were used to estimate of environmental effects, heritability, phenotypic and genetic correlations among these traits. The effect of age of dam on BW was highly significant (p<0.01). The BW of lambs born to 2-year-old ewes in comparison to other lambs born to 3-6 year-old was significantly lighter. The male lambs as compared to the female ones had a heavier BW, WW and DG significantly (p<0.01). A comparison between born single (4.12, 26.21 and 0.252 kg, respectively) and twin lambs (3.55, 23.88 and 0.201 kg, respectively) indicated that the BW, WW and DG of born single lambs were significantly higher (p<0.01). Lambing year had a highly significant effect on the pre-weaning traits (p<0.01). Heritability of BW, WW and DG were 0.121±0.073, 0.095±0.072 and 0.096±0.079, respectively. Phenotypic and genetic correlations between BW-WW, BW-DG and WW-DG were (0.229 and 0.489), (0.119 and 0.429) and (0.987 and 0.999), respectively.
  H. Roshanfekr , M. Mamouei , K. Mohammadi and F. Yarinejad
  A total of 136,250 monthly test day milk records collected from 13,625 Iranian Holstein heifers in Yasuj (three times a day milking) calved between 1997 and 2007 and distributed over 264 herds were used to study the effect of some environmental factors influence lactation curve parameters as well as production characteristics. Wilmink's function (Yt = W0 + W1t + W2e-0.05t) was fitted to individual lactation. Least squares analysis of variance indicated that the herd, year and month calving had a significant effect of all traits under consideration. Correlation analysis showed that the parameters W0 had a negative and significant (p≤0.05) relationship with parameters W1 and W2, while it was positively significantly correlated with milk at peak time and 305 days milk yield. Simple linear regression analysis adjusted means of 305 days milk yield, days to reach peak yield as well as peak milk yield in the first year of calving also revealed that there was a phenotypic increase of 137.152, 0.535 and 0.434 kg year-1, respectively.
  H. Roshanfekr , M. Mamouei , F. Yarinejad and K. Mohammadi
  A total of 136,250 monthly test day milk records collected from 13,625 Iranian Holstein heifers (three times a day milking) calved between 1997 and 2007 and distributed over 264 herds were used to study the effect of some environmental factors influence lactation curve parameters as well as production characteristics. Wilmink's function (Yt = W0 + W1t + W2e-0.05t) was fitted to individual lactation. Least squares analysis of variance indicated that the herd, year and month calving had a significant effect of all traits under consideration. Correlation analysis showed that the parameters W0 had a negative and significant (p≤0.05) relationship with parameters W1 and W2, while it was positively significantly correlated with milk at peak time and 305 day milk yield. Simple linear regression analysis adjusted means of a 305 day milk yield days to reach peak yield as well as peak milk yield in the first year of calving also revealed that there was a phenotypic increase of 137.152 kg, 0.535 day and 0.434 kg per year, respectively.
  K. Mohammadi , M.T. Beygi Nassiri , J. Fayazi and H. Roshanfekr
  The study was carried out to investigate the effects of environmental factors on pre-weaning growth traits in Zandi sheep. Data (birth weight, weaning weight and average daily gain from birth to weaning) were collected from lambs that have been born during 1993-2008 in Khojir Research Station (Tehran-Iran) and analyzed using SAS 9.1 software. Birth year, birth type, lamb’s sex and dam’s age were highly significant sources of variation on Birth Weight (BW), Weaning Weight (WW) (p<0.01), whilst lamb’s sex was not significant on Average Daily Gain from birth to weaning (ADG). The interaction effects between birth year and birth type and dam’s age and birth type were significantly affected on these traits (p<0.05). At birth and weaning the male and single lambs were heavier than female and twin lambs. Results that environmental factors have an important role in expressing of genetic potential in the lambs. Average weights were 4.23±0.012, 21.17±0.060 and 0.174±0.00 kg for BW, WW and ADG, respectively.
  K. Mohammadi , M.T. Beygi Nassiri , J. Fayazi and H. Roshanfekr
  The present study was carried out to investigate the effects of environmental factors on pre-weaning growth traits in Zandi sheep. Data (birth weight, weaning weight and average daily gain from birth to weaning) were collected from lambs that have been born during 1993-2008 in Khojir Research Station (Tehran-Iran) and analyzed using SAS 9.1 software. Birth year, birth type, lamb’s sex and dam’s age were highly significant sources of variation on Birth Weight (BW), Weaning Weight (WW) (p<0.01), whilst lamb’s sex was not significant on Average Daily Gain from birth to weaning (ADG). The interaction effects between birth year and birth type and dam’s age and birth type were significantly affected on these traits (p<0.05). At birth and weaning, the male and single lambs were heavier than female and twin lambs. Results showed that environmental factors have an important role in expressing of genetic potential in the lambs. Average weights were 4.23±0.012, 21.17±0.060 and 0.174±0.00 kg for BW, WW and ADG, respectively.
  K. Mohammadi , M.T. Beygi Nassiri , J. Fayazi and H. Roshanfekr
  The present study was carried out to investigate the effects of environmental factors on pre-weaning growth traits in Zandi sheep. Data (birth weight, weaning weight and average daily gain from birth to weaning) were collected from lambs that have been born during 1993-2008 in Khojir Research Station (Tehran-Iran) and analyzed using SAS 9.1 software. Birth year, birth type, lamb ’s sex and dam ’s age were highly significant sources of variation on Birth Weight (BW), Weaning Weight (WW) and Average Daily Gain from birth to weaning (ADG) (p<0.001). The interaction effects between birth year and birth type and dam ’s age and birth type were significantly affected on these traits (p<0.001). At birth and weaning, the male and single lambs were heavier than female and twin lambs. Results showed that environmental factors have an important role in expressing of genetic potential in the lambs. Average weights were 4.23 ±0.012, 21.17 ±0.060 and 0.174 ±0.00 kg for BW, WW and ADG, respectively.
  K. Mohammadi , A. Aghaei , M. Bojarpour , Kh. Mirzadeh and Gh. Motaghinia
  The aims of this study were to investigate the importance of maternal effects and to determine the most appropriate model of analyses for early growth traits of Arabi lambs. Records of 2445 lambs from 139 rams and 804 ewes for Birth Weight (BWT) on 2237 lambs from 127 rams and 784 ewes for Weaning Weight (WWT) and on 2098 lambs from 115 rams and 739 ewes for Average Daily Gain from birth to weaning (ADG) were used in this research. The data collected from Animal Science Research Station of Agricultural and Natural Resources Ramin (Khuzestan) University during 2001-2008. Genetic parameters were estimated by derivative free restricted maximum likelihood method. Six different animal models were fitted by including or excluding maternal genetic effect, maternal permanent environmental effect and covariance between direct-maternal genetic effects. On the basis of log likelihood ratio test results, Model 3 which included direct genetic and maternal genetic effects was determined to be the most appropriate model for all traits. The maternal genetic effects contributed about 74, 69 and 64% to the direct genetic effects and 15, 11 and 10% to the phenotypic variance for BWT, WWT and ADG, respectively. Depending on the model, the estimates of maternal heritability ranged from 0.074-0.146 for early growth traits of Arabi lambs. Results showed that maternal genetic effects were important for pre-weaning growth traits and should not be neglected from the model; therefore inclusion of maternal effects into the model for mentioned traits is necessary.
  K. Mohammadi , M.T. Beigi Nassiri , J. Fayazi , H. Roshanfekr and A. Aghaei
  Genetic parameters and (co) variance components were estimated on 2445 lambs from 139 sires and 804 dams for Birth Weight (BW) on 2237 lambs from 127 sires and 784 dams for Weaning Weight (WW) and on 2098 lambs from 115 sires and 739 dams for Average Daily Gain (ADG). The data collected from Animal Science Research Station of Agricultural and Natural Resources Ramin (Khuzestan) University during 2001-2008. Analyses were carried out by Restricted Maximum Likelihood (REML) method. Six different animal models including or ignoring maternal genetic or permanent environmental effects were fitted for traits. The Model 3 with only maternal additive effects seemed most suitable. Influencing factors such as birth year, birth type, lamb’s sex and dam’s age were investigated as the fixed effects for the models. Estimates of direct heritability from model 3 were 0.194 for birth weight, 0.163 and 0.149 for weaning weight and average daily gain, respectively. Maternal heritability estimates for birth weight, weaning weights and average daily gain were 0.15, 0.11 and 0.09, respectively. For these traits, correlation estimates between direct additive and maternal genetic (ram) effects were high and negative ranging from -0.57 to 0.93. Bivariate analysis by Model 3 was also used to estimate genetic correlations between traits. The estimates of genetic, phenotypic and environmental correlations among traits were positive and intermediate to high in value. The results indicate that in addition to additive direct effect, additive maternal effect for all traits was important.
  K. Mohammadi , M. Mamouei , M. Bojarpour , Kh. Mirzadeh and A. Aghaei
  The aim of the present study was to estimate variance components and genetic parameters for post-weaning growth traits of 2634 Zandi lambs from 202 sires and 1093 dams for 6 Month Weight (6MW) of 1893 lambs from 188 sires and 816 dams for 9 Month Weight (9MW) and of 1115 lambs from 156 sires and 514 dams for Yearling Weight (YW). Data and pedigree information used in this study were collected from Khojir Research Station (Tehran-Iran) during 1993-2008. Genetic parameters were carried out by Restricted Maximum Likelihood (REML) method, under six different single-trait animal models. Log likelihood ratio test indicated the most appropriate model for 6MW should included direct additive genetic effects as well as maternal permanent environmental effects whilst the most appropriate model for 9MW and YW had only the direct additive genetic effects. The effects of lamb’s sex, dam’s age and birth year were highly significant on all three traits (p<0.01) but birth type was only significant effect on 6 MW (p<0.05) and was no significant effect on 9MW and YW (p>0.05). Average weights were 27.55±0.09, 32.67±0.11 and 34.92±0.16 kg for 6MW, 9MW and YW, respectively. Estimates of direct heritability (h2) were 0.132, 0.134 and 0.133 for 6MW, 9MW and YW, respectively. The estimate of maternal permanent environmental variance as a proportion of phenotypic variance (c2) was 0.056 for 6MW.
  K. Mohammadi , M.T. Beigi Nassiri , H. Roshanfekr , K. Mirzadeh and A. Aghaei
  Data from body weights at post-weaning were used to genetic trend for Zandi sheep reared in Khojir breeding station of Tehran-Iran over a 16 years period (1993-2008) using animal model for lambs, rams and ewes. Genetic trends were estimated for 6 Months Weight (6MW), 9 Months Weight (9MW) and Yearling Weight (YW) traits. For investigation of each trait appropriate models using 3-trait analysis were applied. Breeding values of animals were predicted by Best Linear Unbiased Prediction (BLUP) methodology under three-trait animal models. Genetic trends of studied traits were estimated by regressing mean of breeding values on birth year. The genetic trends were positive and significant for 6MW, 9MW and YW and were 21, 72 and 65 g year-1, respectively.
  H. Roshanfekr , M. Mamouei , K. Mohammadi and E. Rahmatnejad
  In this study, the data of Birth Weight (BW), Weaning Weight (WW) and Average Daily Gain from birth to weaning (ADG) of Arabi lambs were used to estimate of environmental effects, heritability, phenotypic and genetic correlations among these traits. The parameters were estimated using derivative free restricted maximum likelihood methods by excluding or including maternal genetic or maternal permanent environmental effects to optimize the model for each trait. Influencing factors such as type of birth, year of birth, lamb’s sex and age of dam were investigated as the fixed effects for models. The results showed that year of birth, type of birth, lamb’s sex and age of dam were highly significant sources of variation on mentioned traits (p<0.001). On the basis of log likelihood ratio test results, model 1 which included direct genetic effects only was determined to be the most appropriate model for above traits. Direct genetic heritability of BW, WW and DG were 0.12±0.07, 0.10±0.07 and 0.10±0.08, respectively. Phenotypic and genetic correlations between BW-WW, BW-ADG and WW-ADG were 0.23 and 0.49, 0.12 and 0.43 and 0.67 and 0.89, respectively.
 
 
 
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