GENETIC ANALYSES OF PROFIT FOR AUSTRALIAN DAIRY-CATTLE

Direct genetic evaluation of profit was investigated as an alternative to a selection index. PROF(k) was defined as (net income)/(food requirement) until the start of the Kth lactation, for k = 2 to 6. Genetic parameters such as heritabilities and genetic correlations were estimated for profit traits for Australian Holstein-Friesian and Jersey dairy cattle. Heritabilities for profit until the start of a given lactation were moderate, ranging from 0.12 (for profit until the start of the lactation in Holsteins) to 0.31 (profit until the start of the third lactation in Jerseys). Genetic correlations between profit traits were very high, and approached unity for most pairs of traits, so that profit early and late in herd life were nearly the same trait. Genetic correlations between profit traits and first lactation milk yield traits were approximately 0.80 for Holsteins and 0.90 for Jerseys. A single analysis was carried our for lifetime profit using all data, including cows that were still in the herd at the time of data collection. Heritabilities were 0.13 for Holsteins and 0.19 for Jerseys. Genetic correlations between lifetime profit and first lactation yields were high. For the selection of dairy bulls, a multivariate analysis on a milk yield fruit (e.g. protein yield) and profit until the last known lactation of bulls' progeny was suggested