Genetic parameter estimation for milk fatty acids in three French dairy cattle breeds
Genetic parameters of milk composition in fatty acids (FA) were estimated in the three French Montbeliarde (MO), Normande (NO) and Holstein (HO) cattle breeds. Data originated from the PhénoFinlait project and from the national genetic database. They contained 101,858 test-day records from 21,947 cows in first lactation. Each test-day was characterized by its profile in FA in milk, as estimated from Mid-Infrared (MIR) spectrometry. Three different models were used to analyze either individual test-day data, or lactation means. Test-day saturated FA (SAT) had higher heritability estimates (from 0.16 to 0.44) than unsaturated FA (UNSAT). FA measurements were highly genetically correlated across different stages of lactation except in the beginning of the lactation. Genetic correlations between FA in milk were positive across SAT, also positive across UNSAT, and negative between SAT and UNSAT. SAT were positively correlated to fat content in milk. The definition of the traits, expressed in percentage of milk or fat, was discussed.
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