I read a lot about cows used in sacrifice , what is the reason that cows were sacrificed and what was the importance of cows for Bani Israel
There are 4 basic categories of animals that are used in Sacrifices.
Goats were used for sacrifices anytime that there is a "Kaparah" or "atonement" related to the sacrifice. I.e. if the purpose of the sacrifice is to correct some wrong, then a goat is used.
Sheep are used for any sacrifices where the focus is on either the individual or family unit. It represents a more intimate and personal sacrifice.
Cows were used for any large or communal offerings. Cows being the largest animal, they were offered only when the entire nation was commanded to take part of the sacrifice.
Birds were used for any sacrifice where the poor were to be represented, either because they were required to bring a sacrifice but could not afford to bring a larger animal or for symbolic purposes.
It is also suggested that which animal to bring for the sacrifice is purely practical. The more people involved the more fatty animal you bring. Goats have the toughest and least amount of meat, then sheep, then cows, and birds were available for the poor.
According to R' Samson Raphael Hirsch, in various places in his commentary on the Torah, the ox, typically used for plowing fields, represents humans' power to do effect change in the world. Thus, any time we sacrifice an ox on God's altar, we're dedicating that power within ourselves to His service.
Cattle, שור, בקר, are animals of work, actively working in the service of their master. ... Hence cattle represent the power of action and active usefulness.
Of the various animal sacrifices, a cow (or more often, a bull) was considered the most expensive and often most choice. (Mind you, a pauper who can afford nothing but grain who brings it with meaning is valued over the mogul who thinks he can pay off G-d with a nice bull.)
Sforno discusses it being of the most utility to us, and also that its gestation period is eerily close to that of a human; hence when placing its blood around the altar, we think "how do I make sure my vitality is centered around the service of G-d."
Maimonides does observe that the mammals sacrificed -- cows, sheep, goats -- were deified by various idolatrous cultures (Indian, Egyptian, Babylonian, respectively), so part of this was a rejection of that.
Although many offerings required specific animals, where there were options the relative value of the offering indicated how special it was. Larger animals, like cows or bulls, were more likely to be brought for communal offerings because of the expense. However, we learn from the Torah that bigger is not necessarily better. In the first chapter of Leviticus, animal offerings are discussed as being brought by a "man" (Hebrew: "adom"). But in Leviticus 2:1-2, we read that a "soul" (Hebrew: "nefesh") brings a meal offering. The Talmud, Menachos 104b, explains that the meal offering is brought by a poor person who can't afford a cow, sheep, goat or even a bird offering. Therefore, by the Torah describing the giver as a "nefesh" it is as if G-d is declaring that He will "consider his act as if he sacrificed his entire soul." Hence, we learn that bigger is not necessarily better; rather an offering is only as good as the intent of the individual bringing it.