الفهرس 
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Abstract
In the sub-tropical developing countries, there is a gap between available required animal-feeds. Under these conditions there is always competetion between animals and humans for proteins wtich are krnown to be one of the most limiting nutrients for both humans end farm animals in Egypt as in all developing countries To overcome this problem and to reduce the dependence of livestock on protein sources which can also be used to meet human needs, non protein nitrogen sources (11PN) have been acclaimed by many authors as importent alternative Sources of crude protein - which may be utilized by runinan" ~ "s to replace dietary true protein. Rumnants axe known to depend, entirely, on plant protein to satisfy their N-requirements. Because of the shortage and high price of rich plant protein sources ; roughages were applied to replace a part of plant protein in order to overcome their shortage and to reduce the feeding costa. Therefore, the aim of the present work was to study the effects of feeding rice straw either supplemented or treated with urea (as a source of amnonia) compared with untreated rice straw (all were fed with suitable amount of concentrate feed mixture in approxirrately isonitrogenaus and iso-caloric diets) on productive and reproductive performances of dairy cows. It is an attempt on the of expensive conoentrates as one among the suggested solutiofis of overcoming the feed stortage the hence lowering feeding costs of dairy cattle.