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Estimation of variance components and correlations of milk yield and type traits for the genetic evaluation of the Mediterranean Italian buffalo population
The objectives of this PhD thesis were to (1) evaluate the impact of parentage misidentification on estimation of genetic parameters for milk yield; and (2) estimate genetic parameters and correlations among type traits and milk yield for the Italian buffalo population. Phenotypic data and pedigree information from the Italian Buffalo Breeders Association (ANASB) database were used to analyse 270d milk yields and 26 partial and linear type traits. Estimates of heritability of milk yield when sires identification were from pedigree file, estimates of heritability were low, which suggests that a large proportion of sires reported from the pedigree are identified incorrectly. Therefore, for genetic evaluation only records of buffalo with sires identified by DNA should be used. Analysis of datasets with both sires and dams identified by pedigree and sires identified by DNA, had the largest estimate of heritability, which was essentially the same as when both sires and dams were identified by DNA. This result suggests that most dams are correctly identified in the pedigree file or dam misidentification has a smaller impact. Implementation of AI programs and DNA testing to identify sires are keys for increasing genetic progress in the Italian buffalo population. Estimates of heritability for type traits were generally less than those found for dairy cows, reflecting the low genetic variability of the traits scored or the heterogeneity of judgments across classifiers. The scoring system for linear type traits with low heritability should not be used for genetic evaluation. Mammary apparatus was positively correlated with most of the udder related traits. Genetic correlations of linear type traits with milk yield were low to moderate. Information provided in this study could be used to produce specific selection indices that would reflect the optimal conformation of dairy buffalo. Further investigations on genetic and environmental correlations between type traits, longevity, and body size are needed to improve the profitable and productive animals.
Parlato, Emanuela, "Estimation of variance components and correlations of milk yield and type traits for the genetic evaluation of the Mediterranean Italian buffalo population" (2013). ETD collection for University of Nebraska - Lincoln. AAI3604776.