Heifers On Pasture

Animal Reproductive Technologies

Estrus detection and signs of "heat"

The main sign of heat is receptivity of the female to advances by the male. There are other signs of heat that help in detecting animals for insemination. In the mare: winking, urination and a bracing posture are common signs when stimulated by a stallion, other mares or even spontaneously.

In cows: standing to be mounted by another cow or calf, excessive walking, swollen vulva and mucous discharge. Cows in heat will also attempt to stimulate sexual activity in other cows by nudging, butting and attempting to mount others. Ewe and doe: same as a cow except that there is less homosexual activity. Teaser rams or bucks are more effective in detecting animals in heat.

Heat detection aids in cattle:

Heat Mount Detectors
There are several methods of detecting mounting behavior have been developed for use in cattle, where mounting behavior is prevalent when a cow is in heat. These are extensively utilized as labor saving devices. Heat detection by observation can be very time consuming and occasional cows will not display estrus due to fear or shyness in the presence of humans. These methods will not only save labor but also increase accuracy of heat detection

The K-Mar heat detection device is a patch, which is glued to the tail head. It contains a capsule of red dye that breaks when the cow is mounted. The dye then stains the detector indicating that the cow has been mounted. The biggest problem is false positive patches due to rubbing or inappropriate of a cow not in heat.

Tail head painting with All Weather Paint Sticks or some other type of paint is the simplest and cheapest method of mount detection. A small amount of paint is applied to the tail head. The cow is then observed for roughing up of the painted hair on the tail head or eventually complete wiping off of the paint. These occurs when the cow is mounted repeatedly by other cows (or a bull in natural service).

Electronic detection devices are also available. "Heat Watch" is a pressure sensitive telemetry device that is glued to the cow's tailhead. The device sends a radio telemetry message to a central computer every time a cow is mounted. The message contains the date, time and animal ID. This system is quite accurate, but may require some interpretation of results. For instance; is a single mount a heat; or is it a false mount heat that can it be ignored.

A pedometer is a radio telemetry device that will count the number of steps that an animal takes. Increased walking and general activity is highly correlated with estrus.

Hormonal assay
Progesterone assays are used in many species. When progesterone drops below 1ng/ml it can be assumed that the animal is not pregnant and may becycling. Animals that are known to be cycling can be assumed to be near estrus. In cattle, progesterone assays are relatively expensive and moderately effective in determining that an animal is not pregnant. Unfortunately they can only be used to determine that an animal is near heat +/- 2 or 3 days.

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