الفهرس 
Introduction
Effect of breedOnly 14 pages are availabe for public view
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Abstract
This study was carried out by the cooperation between the animal production institute and animal production department faculty of agriculture, Mansoura university. Data used in the present study were collected during the period from 1990 to 2002. Rahmani (RA) flock was raised in the ElSerw station (north Delta), while Romanov (RO) and their crosses with Rahmani were raised in MehalletMousa station (Mid Delta). The total number of 12258 lambs and 6552 ewes used in this for RA, RO, (<U+00BD> RO. <U+00BD> RA), (<U+00BC> RO. <U+00BE> RA), F1 (<U+00BC> RO. <U+00BE> RA), F2 (<U+00BC> RO. <U+00BE> RA) and (3/8 RO.5/8 RA). Ewes in Rahmani flocks and their crosses were bred under an accelerated lambing system (3 mating /2 years), while Romanov was bred under one lambing system per year. The body weights for Rahmani, Romanov and crossbred lambs were weighted at birth and monthly until twelve month. Average daily gains (ADG) were calculated bimonthly for the stages of growth of Romanov, Rahmani and crossbred lambs at the periods from birth to 8 and 12 months. The results showed that, the conception rate and Both the number lambs and the number of kilograms lambs born and weaned of Rahmani ewes and their crosses were affected (P<0.01) by year, lambing season, breed, parity and the interactions between breed with parity and /or lambing season. Year had non significant effect on number of lambs born and weaned per Romanov ewe. The results showed total number and total kilograms (life time production) of lambs born and weaned per Romanov ewe were significant affected (P<0.01) by year, but the same traits were not affect by parity. Although pure Romanov are seasonal sheep their crossbreeds with Rahmani Egyption sheep breed are able to breed all the year round. In general, the performance of the Rahmani ewes was much closer to the performance of its <U+00BC> Ro Crosses. Grading up towards Romanov showed cause an increase number of lambs born and weaned by 20.80 % and12.19 %, respectively. Half Romanov ewes showed lower conception rate and litter weights than did Rahmani ewes. However, productivity of Romanov crosses can be increased in system in which the management can be altered to allow more of extra lambs to be reared by the ewes.