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.

Assessment of Friesian Cattle Performance Sustainability Through the Evaluation of Phenotypic and Genetic Parameters and Trends of some Economic Traits Under Egyptian Conditions

“…5, the GT of AFC ranged from -0.35 to +0.30 mo/yr and was shorter than the ranges of -2.10 to 2.3 and -5.75 to 5.09 mo/yr reported by Ayied et al (2011) andAbdel-Hamid et al (2017), respectively , showing below-zero fluctuations between 1992 and 2008; then fluctuated irregularly positive or negative until 2019. The regression coefficient of AFC average BVs per year on years of study was close to zero (0.0024 mo/yr), indicating a lack of trend, and close to the values of 0.020 and -0.002 mo/yr, as stated by Abdel-Hamid et al (2017) and Zahed et al(2020), respectively.…”

“…However, being associated with reproductive efficiency traits, reducing AFC might inversely affect MY because of the negative correlation between MY and fertility (Kgari et al 2023). Yet, the regression of the yearly mean of AFC on years of study was generally small (-0.17 mo/yr), but higher than the regression of 0.02 mo/yr, as obtained by Zahed et al (2020). The impact of extended AFC on the herd milk production Fig.…”

“…Moreover, the size and structure of different data sets and the analytical model utilized may influence the estimates.The h 2 estimate of CI was low (0.07 ± 0. 0.001) close to estimates of 0.04 as obtained bySigurdsson and Jonmundsson, (2011), Abdel-Hamid et al (2017), Zahed et al (2019) ,Lopez et al (2019) , Þ´orarinsd´ottir et al (2021) and Refaey et al (2022) , and lower than the range of 0.11 -0.29 as stated by Hammoud et al (2014), Ayalew et al (2017), El-Awady et al (2017), Öztürk et al (2021) and Shalan et al (2022).The h 2 estimate of AFC (0.34±0.002) was higher than the range from 0.11 to 0.27 reported byBuaban et al (2015),Zahed et al (2020) andStefani et al (2021), and lower than a range from 0.36 to 0.47 as obtained byAyied et al (2011), Abdel-Hamid et al (2017 andAyalew et al (2017).…”

Distribution of Nulliparous Fertility Traits

“…A maximum of 5 services per heifer was imposed; services beyond 5 were excluded. Management of the two experimental farms (Saka and El-Karada) was described in more details by Zahed et al, (2020).…”