TITLE

Genetic aspects of lactation curve traits and persistency indices in Friesian cows

AUTHOR(S)
El-Awady, H. G.
PUB. DATE
January 2013
SOURCE
Archiva Zootechnica;2013, Vol. 16 Issue 1, p15
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
A total of 4769 lactation records of 995 Friesian cows mated by 109 sires during the period from 1988 to 2008 were used to estimate lactation curve and breeding values (BV) for 305day milk yield (305dMY), lactation period (LP), peak yield (PY) and persistency indices (P1, P2 and P3). Data were analyzed using General Linear Model of SAS to determine the significant fixed effects. A Multi-trait animal model with Derivative-Free Restricted Maximum Likelihood procedures was used to estimate genetic and phenotypic parameters and breeding values for different traits studied. Month and year of calving, parity, and farm were considered as fixed effects in the analytical model, while animal, permanent environmental and residuals were included in the model as random effects. Means of 305-dMY, LP, PY, P1, P2 and P3 were 3407 kg, 292 d, 440 kg, 1.17, 5.66 and 10.8, respectively. Heritability estimates for the same traits were 0.30, 0.24, 0.29, 0.55, 0.67 and 0.39, respectively. Genetic correlations between different traits studied were positive and ranged from 0.87 to 0.97 for production traits, from 0.98 to 1.00 for persistency indices and from 0.29 to 0.78 between production traits and persistency indices. Average breeding values were 1678.19 kg for 305-dMY, 146.24 days for LP, 121.40 kg for PY, 1.03 for P1, 8.23 for P2 and 14.15 for P3, respectively. Product moment correlation between BV estimates of different traits studied was positive and ranged from 0.55 to 0.80 for production traits, from 0.33 to 0.71 for persistency indices and production traits and from 0.95 to 0.98 for persistency indices. According to the moderate heritability estimate for milk traits, the high product correlations between BV for persistency indices estimates, it could be concluded that genetic improvement in milk production can be achieved through a selective breeding program. Selecting cows for peak yield will improve persistency and lactation curve traits in Friesian cows.
ACCESSION #
90622698

 

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