Desert cattle breeds

I live in Khartoum, Sudan and am planning on starting a ranch soon God willing. I intend to use holistic planned grazing to restore a desertified savannah with acacia seyal trees spread accross it. What beef breeds would be reselient and hardy to such a climate? We get about 135mm of rain and temperatures vary between 16 ° C in the winter, to 47 ° C in the summer.

In my opinion you might start with the indigenous cattle breeds native to the area.  They would have some inherited abilities to live and produce in your environment and resistance to any parasites and insects of the area.  I hate to be so vague but any of the breeds I'm familiar with in the United States would probably be a wreck waiting to happen in your country.  I was fortunate enough to go to a grazing school featuring Johann Zietzman of Zimbabwe.  In part of his presentation he went over some of the African breeds along their characteristics and benefits.  I purchased his book Man, Cattle, and Veld.  In it there is mention of the Boran and Angoni breeds of the desert, the N'Dama of the tropical area, and Mashona and Nguni of south and central Africa.  That would be a starting point.

You might be better off with the local mutts than anything that has been "improved" with European breeds.  Survival of the fittest has developed some pretty amazing animals.

Good luck to you!