The objective of this study was to investigate the association between the expression level of the PRLR gene and milk production traits at different parities in pure Holstein-Friesian and Montbeliarde×Holstein crossbred cattle reared under Egyptian conditions, as well as its potential use in future breeding programs. For this purpose, eighteen healthy cows in mid lactation stage belonging to the first, second, and third parities were selected from each breed for sampling, RNA extraction, and quantitative real-time PCR. The results revealed that, the mean relative expression of prolactin receptor gene and its fold change level were significantly higher in pure Holstein-Friesian than Montbeliarde×Holstein crossbred at the level of the first three parities. In addition, there is a significant and strong positive correlation between PRLR1 and PRLR3 in pure Holstein-Friesian cattle. Significant negative correlations between PRLR2 and PRLR3, DMY3 and TMY3, were observed in Montbeliarde×Holstein crossbred cows. In conclusion, this information about the PRLR gene could be a useful indicator for the milk production trait and could be used in crossing programs that depend on genetic selection.
Key words: Holstein-Friesian, Montbeliarde, PRLR gene, Milk yield.
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