Proceedings
An improved method of computing potential genetic gain per year from selection was developed and applied to selection for milk yield in goats. Genetic progress was defined as the change in the mean breeding value of the milking population, and included changes due to culling among lactating animals for yield. Current U.S. population estimates for the age distribution of does phenotypic means, and heritabilities were used along with assumptions of moderate selection for milk yield. Two phenotypic standard derivations were used: 300 kg to represent the current U.S. population and 200 kg to represent the amount of variation typical of biological traits after several cycles of selection. The proportion of genetic gain expected from female selection is substantially higher for goats than for cows due to reproductive rates which allow for more selection among females. Various levels of usage of progeny tested bucks and young pedigree-selected bucks were examined for their influences on the expected genetic progress. Maximum gain occurred from the use of progeny tested bucks to sire young bucks, but selected young bucks to sire more replacement does. This system has the additional advantage of minimizing the losses due to inbreeding. Expected genetic gains in milk ranged from 3.0 to 3.8 percent per year using a standard deviation of 300 g. Even with a reduced standard deviation of 200 kg, 2.4 percent per year seems possible. These results show that genetic improvement for milk yield in American goats could be quite rapid if effective selection schemes were implemented
| Main Authors: | , , , |
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| Format: | biblioteca |
| Published: |
Scottsdale, AZ (EUA)
1982
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| Subjects: | CAPRINOS, MEJORAMIENTO GENETICO, SELECCION, PRODUCCION DE LECHE, ESTADOS UNIDOS DE AMERICA, |
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