In The literature, most of the studies dealing with the effects of heat stress and its amelioration on dairy cattle were achived in climatic chambers, while information are avaliable in this respect, under the natural hot condiditions in the field. The objectives of the Present investigation were the effect of heat stressful conditions of summer season and amelioration of these conditions by some new techniques, on lactating friesian and holstein cows, under natural field conditions in Egypt. The effect of protection of the lactating Friesian and Holstien cows from winter cold conditions using jute sheats on milk production, thyriod, liver and kidny functions, blood metabolites and blood haematology, were also studied.