Anywhere from a few weeks to a couple days.
It depends on the cow. Heifers sometimes will bag up (udder fills with milk) for weeks before they calve, other times they will bag up after the calf is born. Most cows will bag up a few days before a calf is born, so it can be either or.
Females (heifers and cows) have four teats: one for each quarter of the udder.
No. When bred, cows or heifers will begin to develop an udder during the last stages of pregnancy.
Are you meaning fetal development, or in a heifer? In the heifer, the udder starts to form as her unborn-calf develops, although this development can vary dramatically from heifer to heifer. Some fully bag-up (are full of milk) weeks before the calf is born; some do not get a full udder right before or right after the birth. The breed of cow also influences the size and development of the udder. Udder development continues during lactation. The udder stretching by being full of milk, and the calf nursing on the teats, helps to increase the size of the udder in the young cow. By the second birth, the udder will often be larger and really show the cow (goat, sheep's) potential as a milk-producer.
By their teeth. Depending on the age of the heifers, they would still have most of their milk teeth. However, as long yearlings (14-18 months of age) the central pair of temporary incisor teeth or pinchers would be replaced by the permanent pinchers. At 2 years of age, the central permanent incisors attain full development (having been replaced by permanent teeth). From birth to yearling age (short or long) they would have 8 temporary incisors that have appeared. You can also tell the age of the heifers by their size in comparison to the rest of the mature beef cow herd. They are smaller and younger-looking than the older cows, with not as broad a muzzle nor as developed an udder. All heifers prior to having a calf do not have a defined udder; it is still quite small and neatly tucked up between their rear legs. After they have had their calf, the udder is still smaller than the older cows.
The teats on the udder.
The Udder.
The floor of the udder is just that- The floor of the udder. The shape of the udder is determined by the medial and lateral suspensatory ligaments. Poor ligaments mean a saggy, mastitis prone, misshapen udder.
When they are either no longer fertile (or cannot come back into heat on time), when they have terrible udder structure or have coke-bottle teats that a calf cannot suckle from, when they are culled for certain reasons like temperament, health issues or maternal characteristics, or when they are dead.
A complex system of ligaments holds the udder to the abdomen.
When the cow's udder is full and heavy, it needs to be milked.
Cows only have one "breast," and that is the udder.