الفهرس 
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Abstract
The object of this study was to recognize the extent of changes in the milk production and its composition as the result of rbST administration in the dairy farms under Egyptian conditions. As well as to determine the most suitable lactation stage for its uses as lactogenic agent in dairy cows, through study the changes in the metabolic activity allover the period of study by evaluation of some metabolic hormones and some biochemical blood parameters. In addition to, evaluate the effect of rbST injection on reproductive performance and ovarian activity using ultrasonography and some reproductive efficiency measurement parameters. So, the study was carried out on 70 holstein diary cows in a private farm at Demiatta province during season form September 2002 till February 2003. The study was carried out on 70 holstein dairy cows at the 4th season of lactation conducted as 3 experiments: Experiment I: including 30 cows, divided into control and early treated (15 of each one) strating from one months of lactation and persisted for 18 week (till week 22 of lactation).