A Genetic Study on Lifetime Traits for Experimental Herds of Friesian Cattle
Faten Abd El-Rahman | Manal Elsayed | Usama El-Saied | Abdelhaleem Ashmawy | Hussein Mansour
This study analyzed data from 5,518 lactations involving 1,749 Friesian cows raised in two experimental herds between 1992 and 2022. The study aim was to estimate the genetic parameters for longevity traits using a multiple-trait animal model, including age at first calving (AFC), lifetime (LT), lifetime days in milk (LTDIM), total lactations (TL) and lifetime milk yield (LTMY). On average, cows lived for 80.4 months, with 41% of their lifetime spent in milk production. They averaged 3.2 lactations, starting at 32.7 months. Heritability estimates for longevity traits were 0.09 to 0.12 suggesting limited direct selection potential. Strong genetic and phenotypic correlations (0.88–0.96) were observed between lifespan traits and total milk production. Similar correlations were found between partial lifetime milk yield traits for the first three lactations and total lifetime milk yield (0.44 to 0.97). Genetic correlations between lifetime traits were consistently high (0.88 to 0.99), mirroring phenotypic correlations. Notably, heritability estimates for partial performance traits increased with more lactations considered, and correlations between partial and lifetime traits were improved with additional data. These findings suggest the feasibility of early indirect selection for longevity through correlated responses in early performance traits, particularly early lactation milk production, to enhance overall lifetime productivity.
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