GENETIC ANALYSIS FOR SOME PRODUCTIVE TRAITS IN PUREBRED AND GRADED DAIRY CATTLE UNDER THE EGYPTIAN CONDITIONS

Abstract

Data of this study were collected from three dairy herds allocated at El-Gimmiza, • El-Serw and Sids experimental stations. These stations belong to the Animal Production Reseasrch Institute, Agriculture Research Center, Ministry of Agriculture, Egypt. Three up-grading trials were carried out in these stations. Animals of Friesian trial (El-Gimmiza station) involved Friesian, Domiati and their crosses; those of Shorthorn trial (El­ Serw station) included dairy Shorthorn, Domiati and their crosses and those of Jersey trial (Sids station) were Jersy, Domiati and their crosses. These three up-grading trials were used to quantify the heterotic components of direct additive effect (G1 , maternal additive effect (GM), direct heterosis (H1 , maternal heterosis (HM), direct tecombination effect

(R1

and maternal recombiantion effect (RM) for milk production traits and

reproductive intervals in these'trials. Records.were collected over a period of 26 consecutive years started from 1950. Data of each crossbreeding trial were analysed separately using mixed model procedure. The traits included were initial 90-day milk yield (M90), 305-day milk yield (M305), total milk yield (TMY), lactation period (LP), dry period (DP), calving interval (CI), 305-day milk yield divided by calving interval (MCil), total milk yield divided by calving interval (MCI2) and age at first (ACl) and second (AC2) calving. Results obtained could be summarized as follow: