الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
This study was carried out to evaluate the breeding plan
implemented on Zaraibi goat flock, raised in El-Serw Experimental Farm
belongs to the Animal Production Research Institute.
Phenotypic selection was practiced since the original flock was
entered to the farm in 1984 and starting from the year 2004 the animal
breeding values were estimated and taken in consideration along the
phenotypic criteria in selecting the animal for breeding.
Data on 13062 Zaraibi kids progeny of 253 sires and 2443 dams
during 1988 to 2018 were used. A total of 1559 Zaraibi does records at
the first lactation during the period from 1990 to 2014 were used to study
total milk yield trait.
Data were analyzed using two statistical models. The first was
used to estimate the non-genetic fixed effects (gender, type of birth, parity
and year –season of birth and some interaction between those effects) on
body weights at 4, 6 and 12 months of age. The fixed effects for total milk
yield were litter size, age of doe and season and year of kidding.
Overall least squares mean of the 4, 6 and 12 months weight of
Zaraibi goat were estimated as 12.14, 15.49 and 24.08 kg, respectively.
Gender and type of birth of kid, parity of dam and year-season of
birth affected (p<0.0001) all studied traits. Interaction between gender
and type of birth and that between gender and season of birth had nonsignificant effect on the studied traits. While the interaction between
parity of dam and season of birth had a significant effect on body weight
at 120 (M4), 180 (M6) and 360 (M12) days of age.
The second model included the fixed effects in the first model in
addition to the random effect of animal that used for estimating, genetic
parameters and the breeding values for estimatly the genetic trend and
year constants for the environmental trend for growth traits. A multi-trait animal model program (MTDFREML) of Boldman et al. (1995) was
utilized to estimate the breeding values with Best Linear Unbiased
Prediction (BLUP) methodology.
Heritability estimates were found to be medium, being 0.28, 0.34
and 0.38 for M4, M6 and M12, respectively.
Positive genetic correlation was found among M4, M6 and M12
ranging from 0.76 to 0.92. Phenotypic correlation was positive and in
general lower in magnitude than the genetic correlation.
Phenotypic trends were estimated by the regression of least
squares means on year of birth. Phenotypic response for M4, M6 and
M12 were positive and significant 0.020, 0.045 and 0.177 kg/year,
respectively.
Genetic trends were estimated by the regression of the predicted
breeding values of animals born in a specific year on the year of birth.
Genetic response for M4, M6 and M12 were 0.091 (p<0.0001), 0.121
(p<0.0001) and 0.158 kg/year (p<0.0001), respectively.
The heritability estimate of total milk yield trait in this study was
0.19. Estimated genetic changes for TMY was 0.215 kg/year (P<0.05).
Estimates of phenotypic response was -1.82 kg/year (P<0.0001) and
environmental response was -2.88 kg/ year (P<0.05).
A total of 14 goats were genotyped for Exon-3 of growth hormone
gene (GH) using direct DNA sequencing of its PCR amplicon. One
nucleotide substitutions SNP at 72 bp (A/G) was detected. This SNP
genotypic dimorphisms (A/G) was found significantly associated with
high breeding value of growth traits in Zaraibi goat (p<0.0001).
The study concluded that
Yearling body weight was the best criterion for improving Zaraibi
kid body weight traits among the studied traits. The genetic response for growth traits indicated that the breeding
program in the flock under study has proved medium efficient.
The decrease in the average breeding values of females compared to
males indicated the importance of changing the selection criteria
used in the selection program.
The phenotypic trend of milk yield trait was declined and this is due
to the deterioration of environment and consideration should be
taken to improve the management in the station.
SNP A72G was detected in exon-3, it is recommended to be
considered as genetic marker in the marker assisted selection
(MAS) breeding programs in goat.