Effect of Family Size and Genetic Correlation between Purebred and Crossbred Halfsisters on Response in Crossbred and Purebred Chickens under Modified Reciprocal Recurrent Selection원문보기
Response in a modified reciprocal recurrent selection scheme for egg production was evaluated considering variable family sizes and genetic correlation between purebred and crossbred half sisters. The criteria of selection of purebred breeders included pullet's own performance, purebred full and hal...
Response in a modified reciprocal recurrent selection scheme for egg production was evaluated considering variable family sizes and genetic correlation between purebred and crossbred half sisters. The criteria of selection of purebred breeders included pullet's own performance, purebred full and half sisters and crossbred half sister's performance. Heritability of egg production of crossbreds (aggregate genotype) and purebred's was assumed to be 0.2 and genetic correlation between purebred and crossbred half sisters ($r_{pc}$) as 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, -0.1, -0.2, -0.3, -0.4, -0.5 and -1.0. Number of dams per sire to produce purebred and crossbred progenies assumed to be 5, 6, 7, 8, while number of purebred female progeny ($N_p$) and crossbred progeny ($N_c$) per dam were considered to be 3, 4, 5 and 6 in each case. Considering phenotypic variance as unity, selection indices were constructed for different combinations of dams and progeny for each value of $r_{pc}$. Following selection index theory, response in crossbred and purebred for egg production was computed. Results indicated that response in crossbreds depended mainly on crossbred family size and also on magnitude of$r_{pc}$ irrespective of its direction, and response was greater with large crossbred family size than the purebred families. Correlated response in purebreds depends both on magnitude and direction of $r_{pc}$ and was expected to be greater with large purebred family size only. Inclusion of purebred information increased the accuracy of selection for crossbred response for higher magnitude of$r_{pc}$ irrespective of its direction. Present results indicate that desirable response in both crossbred and purebred performance is a function of $r_{pc}$ and family sizes. The ratio of crossbred and purebred family sizes can be optimized depending on the objective of improving the performance of crossbreds and/or of purebreds.
Response in a modified reciprocal recurrent selection scheme for egg production was evaluated considering variable family sizes and genetic correlation between purebred and crossbred half sisters. The criteria of selection of purebred breeders included pullet's own performance, purebred full and half sisters and crossbred half sister's performance. Heritability of egg production of crossbreds (aggregate genotype) and purebred's was assumed to be 0.2 and genetic correlation between purebred and crossbred half sisters ($r_{pc}$) as 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, -0.1, -0.2, -0.3, -0.4, -0.5 and -1.0. Number of dams per sire to produce purebred and crossbred progenies assumed to be 5, 6, 7, 8, while number of purebred female progeny ($N_p$) and crossbred progeny ($N_c$) per dam were considered to be 3, 4, 5 and 6 in each case. Considering phenotypic variance as unity, selection indices were constructed for different combinations of dams and progeny for each value of $r_{pc}$. Following selection index theory, response in crossbred and purebred for egg production was computed. Results indicated that response in crossbreds depended mainly on crossbred family size and also on magnitude of$r_{pc}$ irrespective of its direction, and response was greater with large crossbred family size than the purebred families. Correlated response in purebreds depends both on magnitude and direction of $r_{pc}$ and was expected to be greater with large purebred family size only. Inclusion of purebred information increased the accuracy of selection for crossbred response for higher magnitude of$r_{pc}$ irrespective of its direction. Present results indicate that desirable response in both crossbred and purebred performance is a function of $r_{pc}$ and family sizes. The ratio of crossbred and purebred family sizes can be optimized depending on the objective of improving the performance of crossbreds and/or of purebreds.
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문제 정의
The question that what should be the family structure for producing crossbred and purebred progeny for a particular value of rpc for M-RRS programme? This is necessary in terms of cost of testing the selection programme. So, the objective of this investigation is to study the impact of varying family sizes of purebreds and crossbreds with variable values of rpc on the expected genetic response in crossbreds and correlated response in purebreds.
가설 설정
Following selection index theory, Singh and Kumar (1994) and Wie and van der Werf (1994) have detailed the methodology to combine different sources of informations for a trait considering as two traits for purebreds and crossbreds simultaneously to maximize the genetic response in crossbreds under M-RRS. The question that what should be the family structure for producing crossbred and purebred progeny for a particular value of rpc for M-RRS programme? This is necessary in terms of cost of testing the selection programme. So, the objective of this investigation is to study the impact of varying family sizes of purebreds and crossbreds with variable values of rpc on the expected genetic response in crossbreds and correlated response in purebreds.
성능/효과
From the results, it may be inferred that to improve crossbred performance through M-RRS, magnitude of rpc irrespective of its direction is important while for response in purebreds, both magnitude and direction of rpc is important. Inclusion of purebred informations in the index add to the accuracy of selection if there exist some amount of covariance between purebreds and crossbreds.
5) and equal number of dams in each case (D=6), expected response in crossbreds and purebreds is given in Table 3. The results indicated that response in crossbreds is expected to be more with the increase in number of crossbred progenies than the purebred progenies; however, the gain was expected to be higher with the increase in the number of crossbred and purebred progenies. On the other hand, the correlated response in the purebreds is a function of number of purebred progenies only.
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