Phenotypic and genetic variability of milk production traits of the black-and-white dairy cattle breed in the first three complete and standard lactations

Abstract

Improving the genetic capacity for highyielding, highquality and profitable milk production is the priority of countries with cattle production.Due to their marked phenotypic and genetic variability, milk production traits are particularly important in all breeding and improvement programmes. The paper presents the average values and phenotypic variability of major milk production traits examined in the first three complete and standard lactations, as well as the effect of systemic environmental factors on the expression of these traits. The bull-sire, farm, year, calving season and lactation sequence had a highly significant effect on the studiedmilk production parameters (P lt 0.01). The paper also shows the heritability of milk production parameters, calculated with the method of least squares (LS) and the REML method. The coefficients of heritability for milk yield, milk fat content, fat yield and 4% in the standard lactation, calculated with the method of least squares, were 0.109; 0.047; 0.098 and 0.106, respectively. The coefficients of heritability calculated with the REML method were higher for all milk production traits in the standard lactation, being 0.148; 0.086; 0.128, and 0.138, respectively.

U zemljama koje se bave govedarskom proizvodnjom primaran značaj se daje unapređenju genetskih kapaciteta za visoku, kvalitetnu i ekonomski isplativu proizvodnju mleka. Osobine mlečnosti zbog izražene fenotipske i genetske varijabilnosti imaju poseban značaj u svim programima selekcije i oplemenjivanja. U radu su prikazane prosečne vrednosti i fenotipska varijabilnost važnijih osobina mlečnosti ispitivanih u prve tri cele i standardne laktacije, kao i uticaj sistematskih faktora okoline na ispoljenost ovih svojstava. Ustanovljen je visoko značajan uticaj bika-oca, farme, godine, sezone teljenja i redosleda laktacije na ispoljenost posmatranih osobina mlečnosti (P lt 0,01). Prikazana je i naslednost posmatranih osobina mlečnosti, ustanovljena primenom metode najmanjih kvadrata (LS) i REML metodom.Heritabiliteti dobijeni primenom metode najmanjih kvadrata za prinos mleka, sadržaj mlečne masti, prinos mlečne masti i 4% MKM u standardnoj laktaciji bili su 0,109; 0,047; 0,098 i 0,106, respektivno. Koeficijenti naslednosti dobijeni REML metodom imali su veće vrednosti za sve osobine mlečnosti u standardnoj laktaciji: 0,148; 0,086; 0,128 i 0,138, po istom redosledu osobina.