Fort Atkinson — The barnyard bull is largely gone, replaced with advances in technology, backed by research, that offers farmers robust and ever-improving ways to manage their cow's reproductive lives.
The techno/repro revolution got rolling in the early 1980s with the introduction of hormones, Dr. Jeffery Stevenson, Kansas State University, said during Hoard's Dairyman's webinar, "A Reproductive Update."
The January event was sponsored by Parnell and hosted by Steve Larson, Hoard's Dairyman, with the help of Jim Baltz, University of Illinois.
"All this technology has come about since 1979, starting when several of the hormones we all use regularly came about," Stevenson said. Timed breeding programs came into use during the mid-90s and continue to be tweaked.
The first pedometer hit the market in 1983; refined in 2005 with the first accelerometer. The progesterone seeders that joined the lineup in 2003 have been a real benefit to breeding programs, he added, as have the advances and opportunities provided by genomics and sexed semen.
Method of heat detection
Stevenson considers heat mount patches to be pretty useful. "The nice thing about them is they really do stay stuck on cows. We've use them a lot and I really have a lot of confidence in them," he said. "They are an added advantage to the market for people who are watching cows, although they are a little more expensive than tail paint and tail chalk.
A tip for those who tail paint or tail chalk their cows: Put the day right on the cow, so you know when she was last inseminated. "It's a real handy thing to have that date right there," Stevenson noted.
Different colors of chalk can also be used, such as green paint when the cow is detected pregnant, red for cows in question and blue for cows found open at preg check day.
The really important bit in heat detection is the onset of estrus. When estrogen peaks in the blood supply, a cow typically stands in estrus for the very first time. She will ovulate about 28 hours after that first standing event.
"What's really important about this whole process is we're really more interested in detecting ovulation than heat detection," Stevenson said. "The whole idea is we're trying to detect that cow properly so we can inseminate her at the proper time."
Activity monitors hinge on the fact that, when a cow comes into heat, her physical activity increases by around 400 percent. Studies have identified a threshold that, when reached, means the cow is usually pretty close to the onset of heat.
There are at least 13 activity monitors available on the U.S. market, including one in the cow's ear tag that also reads ear temperature. "That can give you relative change in temperature of the cow when she may be showing fever, particularly in fresh cows," he noted.
Many of the newer activity monitors have accelerometers, unique devices that can detect movement in all three spatial planes, Stevenson noted, which really increases the accuracy of the data provided.
New activity monitors can measure a cow's eating bouts and rumination, her milk yield and her actual activity on a daily basis. When her rumination drops off, the device provides a health alert.
"It gives you a lot of information that you wouldn't have on an individual cow basis," Stevenson said. "This is one of the blessings you have with these types of monitors that allows you to monitor for estrus."
One study on effectiveness found activity monitoring was almost twofold better at detecting estrus than a timed AI program(42 percent vs. 74 percent).
"That's really important," Stevenson said. "That's one of the things we see with these activity monitors. It helps us detect that very first estrus that occurs after she's been bred, so what we see is actually a shortening of the time between inseminations."
At 150 days in milk, 68 percent of the activity monitored group was pregnant, compared to 52 percent of the study's timed AI cows.
"That's really what we're looking for — getting cows pregnant in a very prompt manner," Stevenson said.
Researchers also compared activity monitors' ability to identify heat mount detectors and heat watch devices. The purpose of the study was to see if all the estrus activity could be detected.
The data showed about 30 percent of the study cows did not show estrus. They were ovulating, Stevenson pointed out, but they had silent heats.
The activity monitors and heat mount detectors picked up only 70 percent of the cows that should have been in estrus, with heat watch devices a bit less.
When making a decision on a heat detection system, Stevenson advises dairy farmers to take cow housing into account. For many herds in dry lot or on pasture, heat detection rates usually exceed 70 percent. "If that's the case, they are probably not going to get a lot of value from an activity monitor in terms of detecting estrus," he suggested.
However, when cows are confined on concrete and heat detection levels are lower because of slippery conditions and, usually, less visual observation due to herd size, there may be some real value because the monitors will pick up estrus by picking up the associated increase in physical activity.
Although most farmers use the seven-day option when using timed AI programs for cows at first service, the five-day option has its merits. Fertility is equal for both ovsynch options, Stevenson noted, and veterinarians may find the shorter programs useful when herd checks are usually scheduled on Monday or Tuesday.
Stevenson believes the new presynch options that use GnRH have some real advantages. Such programs synchronize follicular development and move the cow into a midrange progesterone concentration by the start of ovsynch. "That makes that cow about as fertile as you can get her using timed AI," Stevenson said.
Another advantage of GnRH presynch programs appears to be improved fertility at first service.
"We really think that using the GnRH precinct programs are giving you some added value that you don't have with using the standard presynch program," Stevenson said.
Studies that increased the dose of GnRH found ovulation was clearly increased, but not the pregnancy rate.
Research also shows a second prostaglandin injection results in about 3 percent more second or third lactation cows becoming pregnant . "The pregnancy improvement is really marginal, so it just depends on what an individual herd wants to do," Stevenson observed.
These days, farmers can use transrectal ultrasonography to find out if their cow is pregnant as early as 28-32 days after AI, while manual transrectal palpitation of the uterine contents can be done at 35-40 days after AI.
Test kits for pregnancy specific proteins were developed in 1982 and first became commercially available in 1993. There are now three test kits on the market, including one from DHIA. The best time to take samples for laboratory submission is 32-35 days.
A survey of the dairy farmers in Stevenson's audience found 39 percent checked their herds for pregnancy every week, while 28 percent were every other week and 33 percent were monthly.
Stevenson encouraged dairy producers who check every other week or monthly to consider doing it more frequently. "We pregnancy check to find open cows and, that way, reduce days open," he said. That's really important."