الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
from the results reported in experiment one, it can be concluded that fat supplementation in term of protected fat during the prepartum period in high producing dairy cows diet could improve some productive and reproductive performances during the postpartum period. This improving was accompanied by a lower incidence of metabolic disorders. Fat supplementation led to positive effect on milk production, 3.5% FCM and some milk components. In addition, cows fed fat treatments have greater concentrations of postpartum plasma NEFA, progesterone and lower concentrations of plasma glucose, leptin, and insulin. At the same time, reproductive performance such as pregnancy rate recorded higher values as a result of protected fat supplementation.
from the present results reported in experiment two, it can be concluded that fat supplementation may play an important role in controlling body thermoregulation and modify heat production and metabolism under stressful condition of high producing dairy cows. Fat supplementation in term of protected fat in the diet of high producing dairy cows during the summer season increased 3.5% FCM and milk fat concentration. Also, cows fed protected fat treatment has greater concentrations of plasma NEF A and lower concentrations of plasma glucose and leptin.
from the present results, it can be recommended that supplementation of protected fat during prepartum and postpartum periods as well as during summer heat stress in high producing dairy cows diet at 2% and 3% of dietary DM led to positive effect on productive and reproductive performances of high producing dairy cows.