If you own a female cow, your knowledge of her estrous cycle might be handy for figuring out the reason behind some of her behaviors, whether she's a first-time mother or a mature and experienced bovine. When cows are in heat, the evidence often is visible to onlookers.
How Often Cows Cycle
When female cows are reproductively mature, and not expecting, they go into heat regularly. Their cycles take roughly three weeks or so -- between 18 and 24 days. A cycle represents the period of time that elapses between one heat to the succeeding one. If a female cow is in strong reproductive health, she should experience these cycles smoothly and somewhat predictably. Heat cycles cover all of the hormonal shifts that cows go through from heat to heat.
Duration of Heat
When female cows go into heat or estrus every few weeks, they enter a period of willingness to mate. When they're in heat, they allow intact males, bulls, to mount and mate with them. This period usually has a duration of between 12 and 18 hours. Some cows are in heat for no more than four hours, while others are in heat for as long as a full day. When cows are in the midst of standing heat, they literally stand as a sign that they are open to being mounted by male cows. They plant their four limbs rigidly on the ground in anticipation of being mounted. When they're in standing heat, they don't stand in this position for hours on end nonstop, however. They do so intermittently for bursts of between four and six seconds.
Clues of Heat
A handful of identifying clues can usually help you figure out whether your cow is in heat. Apart from actually observing the cow standing, you can also be attentive to various other key hints. These include attempts to ride fellow cows, redness of the vulva, much more urination than normal and emission of a transparent mucous fluid. Behavioral aspects can also denote heat in cows: If a cow is acting in an uncharacteristic antsy manner, she might be in heat. She might make nonstop crying sounds. She might act abnormally anxiously, moving significant stretches in efforts to track down bulls. She might behave in a much more vigilant way than she normally does.
Timing of Heat Signals
Common signals of heat differ in their intensity and duration. They also differ in when exactly they happen. They can exhibit not only while heat's taking place but also prior to it -- so you can't assume these things necessarily signify that a cow is presently in standing heat. They even happen once standing heat is complete. If a cow shows any of these signals, one way to possibly figure out whether or not she's in standing heat is by bringing another mating cow into her presence in a quiet, distraction-free environment.
- Iowa State University Iowa Beef Center: Beef Cattle Handbook
- University of Hawaii at Manoa Cooperative Extension Service: The Basics of Heat (Estrus) Detection in Cattle
- University of Missouri Extension: The Estrous Cycle in Cattle
- The University of Georgia College of Agricultural & Environmental Sciences: Heat Detection Strategies for Dairy Cattle
- Mississippi State University Extension Service: The Estrous Cycle of Cattle
- Penn State Extension: Signs of Heat
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