In my last article, I talked about the importance of high progesterone and a healthy oocyte to maximize fertility. It is why our first-service timed AI (TAI) programs work so well in properly managed herds. The presynchronization injections in these programs result in a high percentage of enrolled cows having a healthy oocyte that has grown under high progesterone.
But what about after our firstservice breeding? We will still have a significant number of cows that do not conceive, so how do we manage these cows?
Don't Hurt Pregnancy Rate
Obviously, starting the cow on another first-service TAI program is not realistic because it takes so long from initiation of the program to insemination (for the Double Ovsynch it is 27 days). We will not gain enough in conception rate to counter the loss in heat detection rate, and as a result our 21-day pregnancy rate will suffer.
On most dairies, aggressive heat detection with a back stop timed AI program is the most effective way to manage the cows that fail to conceive to our first service breeding. For the cows not found in heat and diagnosed open via palpation, ultrasound or blood test, what do we do with these cows?
Most dairies start these cows immediately or “blindly” a week prior on a synchronization program, such as Ovsynch. Many studies have found that days five through 12 of the estrous cycle tend to be the best days to start Ovsynch, because progesterone is high and a new follicular wave is started. However, without presynchronization, many cows will not be in this ideal stage of their estrous cycle, resulting in much lower conception rates. One especially dangerous time to start cows in Ovsynch is when progesterone is low, such as around an estrus (from proestrus to metestrus) or when cows are not cycling because of negative energy balance or ovarian cysts.
Start with a CIDR
Being able to identify these low progesterone cows and altering the way we manage them can significantly increase overall conception rates. There are a few different management options for these cows. The best strategy, however, is to apply a CIDR (progesterone releasing device) when starting Ovsynch, which will increase progesterone levels for the developing oocyte and improve its fertility.
But how do we identify these low progesterone cows? Measuring blood and milk for lack of progesterone is ideal, but still not yet practical for most dairies. The next best way is ultrasound. Progesterone is made by a structure on the ovary called the corpus luteum, and its presence or absence on the ovary is easy to identify with an ultrasound (palpation is not as reliable). Many dairies are already using this technology to identify open cows, but are not using it to maximize fertility and improve conception rates. If you have an ultrasound being used on your farm to diagnose pregnancy, consider spending a little extra time to look at the ovaries of your open cows and decide if they need additional progesterone when starting the Ovsynch. Placing a CIDR in the ones that do will increase fertility and give you more pregnancies throughout the year.
Kevin McSweeney owns Bovine Reproduction Specialists, a veterinary practice dedicated to training and practicing ultrasound technology on beef and dairy operations.
Note: This story appears in the April 2018 magazine issue of Dairy Herd Management.