Choosing an estrus synchronization system for use with aritficial insemination can be difficult. Estrus synchronization systems vary in cost, labor requirements, and effectiveness. Following are some key factors to consider when choosing an estrus synchronization system.
1. Available labor and facilities 2. Cost 3. Reproductive state of the females
The first consideration when choosing an estrus synchronization protocol is determining if sufficient labor and facilities are available to successfully implement the protocol and AI. Ask yourself these questions. Do I have adequate facilities (sorting pens, chute, head-catch, etc.)? Do I have enough labor to observe estrus and sort cows two or more times daily or do I need to use timed-insemination? Is a technician available and for how many days? If the facilities are good but labor and technician time is limiting, then chose a system suitable for timed-insemination. If facilities are somewhat limiting but labor and technician are not, then chose an estrus synchronization system that is suitable for insemination after estrus is detected.
The second consideration is cost. Cost for estrus synchronization protocols can vary from as little as $4 per cow to as high as $22 per cow. The cheaper systems typically require more labor and are less effective.
The final consideration for choosing an estrus synchronization protocol is trying to determine the reproductive state of the cow herd. On the first day of the breeding season, cows in most herds are either anestrous or cyclic. An anestrous female is one that has not yet begun to exhibit estrous cycles. Beef females are anestrous prior to puberty and after each calving. Because all cows are anestrous after each calving, it is important to manage the cows such that the length of time that they are anestrous is limited. Normally, cows are anestrus for 45-100 days after calving. Unfortunatley, the length of the anestrous period is variable and difficult to predict. A cyclic female is one that has begun to exhibit estrous cycles. The difficulty with synchronizing estrus in cyclic females is that, on any given day, females are at random stages of the estrous cycle and females at some stages of the estrous cycle are more difficult to synchronize than those at other stages of the estrous cycle.
For a system to effectively control estrus in all cows, it must: 1) induce regression of the corpus luteum or a decline in progesterone, 2) control follicular growth, and 3) induce estrus and ovulation in cows that are anestrus. The goal, then, is to use a system that can be delivered to all cows and result in a synchronous, fertile estrus and greater than 50% pregnant to AI in 1-4 days regardless of their reproductive state.
Etrus synchronization protocols that incorporate timed-insemination are chosen most often because labor is usually the most limiting factor and those protocols are effective in both anestrous and cyclic cows. Visit the learning module on estrus synchronization for more information regarding estrus synchronization protocols.