Milk production of first lactation records of Fleckvien cows in Austria were used to construct different selection indices and subindices. Data on 19215 daughters from 933 sires were used to estimate the genetic and phenotypic variation and covariation of )00-day and 305-day milk, carrier (= milk minus fat and protein), fat and protein yield traits. Ten indices of selection for improving yield traits of cows were Constructed involving the combinations of two or three traits. Subindices were derived as if the three or two sources of information were used to select for just one trait, viz. yield of milk or carrier or fat or protein or fat-plus-protein as a composite trait. Large differences in index coefficients (b's} for fat yield against yields of milk or carrier or protein were observed. Rate of genetic progress in aggregate genotype decreased when fat yield was dropped and consequently, a considerable genetic improvement for cow productivity might be achieved through selection for fat yield. Milk and fat yields contributed about 90% of the total economic-genetic gain while yield of protein contributed the remainder, 10%, i.e. an index including milk and fat yields in selection programmes of Fleckvieh cattle offers more economic-genetic gain over an index including milk and protein only. Index including carrier yield would contribute about 1B% of the total economic-genetic gain, while yields of fat and protein would contribute the remaining 82%. Percentages of expected gain in traits of 305-day lactation were higher than traits Of 100-day lactation. The expected genetic gain per generation in yield traits was large in all of the indices and subindioes constructed; estimates averaged 4% of the respective overall mean of the trait. correlations between the index or Subindex constructed and Animal Production. |
