Characterization of Friesian Heifer Fertility under Egyptian Conditions

Abstract

Data from 3081 reproductive records of Friesian heifers covering the period from 1979 to 2013 belongs to Sakha and El-Karada experimental farms - Kafr-El-Sheikh Governorate, Animal Production Research Institute, Ministry of Agriculture, Egypt were analyzed. A multitrait animal model was used to estimate genetic parameters, genetic and phenotypic changes for age at first breeding (AFB), age at successful breeding (ASB), age at first calving (AFC), number of services per conception (NSC) and service period (SP). Heritabilities of AFB, ASB, AFC, NSC and SP were 0.15, 0.12, 0.11, 0.02 and 0.01, respectively. Genetic correlations between AFB, ASB and AFC were high and ranged from 0.97 to 0.99, however the phenotypic correlations were ranged from 0.78 to 0.99. Genetic correlations between NSC and both AFB, ASB and AFC were -0.12 to 0.16, however the corresponding phenotypic correlations were ranged from -0.04 to 0.46. The genetic correlations between SP and both AFB, ASB and AFC were ranged from 0.58 to 0.79, however that corresponding estimates of phenotypic correlations were ranged from 0.01 to 0.56. The genetic and phenotypic correlations between NSC and SP were 0.72 and 0.94, respectively. A linear regression analysis of estimated breeding values on year of birth of heifers showed favorable genetic improvement of all fertility traits, however the reverse phenotypic trend was observed for AFB, ASB and AFC.