The effect of age at first insemination on reproductive, productive, longevity and lifetime production traits in Simmental cows

Abstract

The effect of cow age at first insemination on productive and reproductive traits, as well as on longevity and lifetime production ones was examined in the Simmental cows housed at the 'Zlatiborski Suvati' (Mt. Zlatibor Pastures) Farm. The general linear model was used to calculate linear regression coefficients for the effect of age at first insemination on productive, reproductive traits, longevity traits and lifetime production traits The calculated linear regression coefficients suggested that the age at first insemination had a statistically significant effect (P lt 0.05) on milk, milk fat and 4% fat milk production in whole lactations (bxy=1.508, bxy=0.056 and bxy=1.464), a very high significant effect (P lt 0.001) on the age at culling and cow utilisation index ((bxy=1.386 and bxy=-0.020), and no significant effect (P>0.05) on other longevity traits. The age of cows at first insemination did not significantly affect (P>0.05) fertility and lifetime milk and milk-fat production traits. The presented results suggest that cow age at first insemination should be included in the models used in estimating breeding values of dairy cows.

Uticaj uzrasta krava pri prvoj oplodnji na proizvodne i reproduktivne osobine i osobine dugovečnosti i životne proizvodnje ispitivan je kod krava simentalske rase smeštenih na farmi 'Zlatiborski suvati'. Opštim linearnim modelom izračunati su koeficijenti linearne regresije uticaja uzrasta pri prvoj oplodnji na proizvodne i reproduktivne osobine, kao i osobine dugovečnosti i životne proizvodnje Na osnovu izračunatih koeficijenata linearne regresije uzrast pri prvoj oplodnji statistički je značajno uticao (P lt 0.05) na proizvodnju mleka, mlečne mast i 4% masnog mleka u celim laktacijama (bxy=1.508, bxy=0.056 i bxy=1.464), vrlo visoko značajno (P lt 0.001) na uzrast pri izlučenju i indeks iskorišćavanja krava (bxy=1.386 i bxy=-0.020), dok na ostale osobine dugovečnosti nije imao signifikantan uticaj (P>0.05). Uzrast krava pri prvoj oplodnji nije imao značajnog uticaja (P>0.05) na osobine plodnosti i životne proizvodnje mleka i mlečne masti. Na osnovu prikazanih rezultata uzrast krava pri prvoj oplodnji trebalo bi uvrstiti u modele za procenu odgajivačke vrednosti mlečnih krava.