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Virginia Cooperative Extension - Knowledge for the CommonWealth

Repro Notes:

Dairy Pipeline: April 2007

John Currin
Extension Dairy Veterinarian
(540) 231-5838;


To maximize reproductive efficiency on your dairy farm, it is important to start planning for summer now. Reproductive parameters on Virginia dairy farms decrease significantly due to summer heat (see Table 1 ), with conception rates dropping from 35-37% to 26-29%. It is November before conception rates fully recover (See Graph 1). Maximizing the number of pregnant cows on your dairy by June 30 will minimize the number of cows that have to be bred during summer. There are three ways farmers can accomplish this task:


1) Watch more closely for heats. This system requires no out of pocket costs except the labor required but is difficult to achieve on many farms. Spring is a busy time of year on farms and contributing an extra 30-60 minutes a day to catching cows in heat is hard. Combine this fact with the difficulty in finding the modern dairy cow in heat (see Table 2, next page) and this system alone will not work on most farms.

2) Aggressive use of prostaglandin Another system that farmers can use is prostaglandin shots every two weeks. All cows past the voluntary waiting period and without a current breeding should get a shot of prostaglandin every two weeks until found in heat and inseminated. The positive aspect of this program is that cows will have more opportunity to come into heat. The downside to the program is that cows still have to be found in heat.


3) Use of timed AI Synchronization Protocols The way to ensure the maximum number of breedings in your cows is to make use of one of the timed AI protocols. Timed AI protocols have been used extensively for over 10 years. Numerous research protocols and field trials have demonstrated that they can be used as a tool to help increase the number of pregnant cows.

The two protocols that I would currently recommend are:




One thing is certain—temperatures will increase as we move into summer and this will likely result in fewer cows pregnant on your farm. At your next herd check, discuss any changes you need to make to your reproductive program to better prepare for summer. Your veterinarian can be a valuable resource in helping you adjust your reproductive program as needed

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