Association analysis between microsatellite dna markers and milk yield and its components in Egyptian Buffaloes using a random regression model

الملخص EN

Data on 813 lactating Egyptian buffaloes were used to test association between nine microsatellite DNA markers located on buffalo chromosome 7.

Data were recorded from May 2009 until April 2010.

For each buffalo cow the monthly test-day records of milk, fat, protein and lactose yields were available.

A total of 5344 test-day records for each trait were used in the analysis, each cow had at least five test-day records.

Number of genotyped animals ranged from 179 to 471.

Single-trait random regression models were used to analyze daily milk, fat, protein and lactose yields.

The Wilmink’s function was used to fit the random genetic effects associated with marker genotypes and the permanent environmental effects of each cow.

Most of the estimated heritabilities associated with the studied markers were close to zero during almost the whole lactation period.

However, heritability estimates significantly different from zero were found for milk yield associated with markers BM143, BM1329 and ILSTS097 which may be considered as excellent candidates for QTL detection using daughter or grand-daughter designs.

In general, the heritabilities associated with the studied markers increased with the increase of the days in milk for all studied traits.

The models that allow for changing the genetic variances associated with markers over the lactation period seem to be more appropriate than the models that assume constant genetic variances during the lactation period.