The assessment of breeding value in black and white cattle by use of selection index

Abstract

The objective of this study was a construction of selection index on the basis of whose score the cows could be graded during their selection and formation of parent pairs. The most important milk yield traits in standard lactation: milk yield (PM305), milk fat content (%MM305) and protein content (%MP305) were included in the construction of selection index. Variances and covariances deemed necessary for construction of selection index were calculated by use of the mixed model of the Least Squares method. Economic value of the traits was expressed as a relationship of relative cost changes per unit of the traits included in the selection index. The individuals included in the trial on average produced 8261 kg milk with 294.14 kg milk fat and 270.07 kg protein in standard lactation. Equation of selection index used in this study was chosen from a set of selection index equations, as an equation having the highest correlation between the equation and aggregate genotype which amounted to 0.4275.

Cilj istraživanja bila je konstrukcija selekcijskog indeksa, na osnovu čijeg skora bi se mogle rangirati krave prilikom njihovog odabira i formiranja roditeljskih parova. U konstrukciju selekcijskog indeksa uključene su najvažnije osobine mlečnosti posmatrane u standardnoj laktaciji: prinos mleka (PM305), sadržaj mlečne masti (%MM305) i sadržaj proteina (%MP305). Varijanse i kovarijanse neophodne za konstrukciju selekcijskog indeksa izračunate su primenom mešovitog modela metodom najmanjih kvadrata. Ekonomska vrednost osobina je izražena kao odnos relativne promene troškova po jedinici osobina uključenih u selekcijski indeks. Grla obuhvaćena istraživanjem prosečno su proizvela u standardnoj laktaciji 8261 kg mleka sa 294,14 kg mlečne masti i 270,07 kg proteina. Jednačina selekcijskog indeksa prikazana u radu odabrana je iz grupe jednacina selekcijskog indeksa, kao jednacina sa najvećom korelacijom između jednačine i agregatnog genotipa, koja je iznosila 0,4275.