الفهرس 
INTRODUCTION
Status of Friesion cattle in the subtropics and tropicsOnly 14 pages are availabe for public view
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Abstract
The present study was carried out on a herd of Friesian cattle raised at the Assiut Governorate to investigate the productive and reproductive performance of successive generations of Friesian cattle under Upper Egypt conditions. Production and repdocution records of 765 Friesian cows having 2815 lacations ranging from the 1st to the 7th lactation during the period of 1983 till 1991, were analyzed. Animals included : 233 Friesian cows having 478 records, which were dams of imported heifers 6o and raised in Holland, 239 imported Dutch Friesian heifers (Gi) having 1259 records, 216 Friesian cows which were locally born in Assiat (62) having 750 records, and 77 Friesian cows, locally born from 62 cows referred to
as 63 with 328 records.
The productive performance studied were: 90, 305 day milk and total milk yield, lactation period, dry period, longevity, productive life, number of calvings and calf birth weight. Reproductive performancesstudied were: age at first calving, service period, calving interval and gestation period. Also, some parameters were taken into consideration such as: abortion, dystocia, weaning weight, age at weaning, mortality rate and weight and age of heifers at first insemination.
Regarding heat regulation mechanism of Friesian cows within generation, some estimates were recorded i.e.,