Aggressive reproductive management programs for dairy cows that maximize 21-day pregnancy rates integrate technologies for submission of cows for artificial insemination and for non-pregnancy diagnosis.
Dr. Paul Fricke, professor of Dairy Science at the University of Wisconsin-Madison, says two factors that determine the 21-day pregnancy rate in a dairy herd are the AI service rate and the resulting fertility of the inseminated cows.
Speaking to a large crowd at World Dairy Expo Dr. Fricke points out those cows are in estrus a shorter time than heifers and pregnancy losses are greater with cows than heifers. Conception rates are less than fifty percent in cows and greater in heifers.
That’s why the role of progesterone is extremely important. Two things regulate progesterone and that is metabolism and production.
“Cows make milk out of feed and the highest producing cow will eat more than others,” he points out. “When high producing dairy cows eat a lot of feed they increase their blood flow to the gut. The first place it goes is to the liver resulting in lower levels of estrogen and circulatory metabolism.”
He said as milk production continues to go up, so do the issues with reproductive performance.
Dr. Fricke pointed out that the development of the Ovsynch protocol and timed AI over the last 20 years provided dairy managers with a tool to dramatically increase the AI service rate and yielded fertility similar to that of cows submitted for AI after a detected estrus.
“Modifications of the original Ovsnch protocol can now yield high fertility to timed AI in high-producing dairy cows,” Fricke said.
He added, “The key factor affecting fertility to an Ovsynch protocol is the response to each of the three sequential hormonal treatments which we have defined using progesterone profiles.”
According to Fricke, cows with the greatest fertility to timed AI have mid-level progesterone concentrations at the first GnRH treatment, high progesterone concentrations at the PGF2a treatment, and low progesterone concentrations at the last GnRH treatment of the Ovsynch protocol.
In a traditional Double-Ovsynch protocol, a protaglandin shot is given on Monday, a GnRH shot is given Wednesday and timed A.I. is done on Thursday. Under the revised protocol, an additional prostaglandin shot is also given on Tuesday, 24 hours after the first.
He noted that the biggest effect seems to be in second-calf and older cows.
Early identification of non-pregnant cows after AI coupled with a strategy to resynchronize non-pregnant cows for second and greater timed AI further increases the 21-day pregnancy rate by decreasing the interval between AI services, thereby increasing the AI service rate, he said.
Fricke said heat watch, tail chalk and other technologies are tools that help with dealing with the issue of getting cows pregnant. “Those tools are to address the people problem of catching cows in heat," he said. "They do not deal with the cow problem.
“It doesn’t matter how much you watch for heat, you will never ever catch all of your cows in heat at the end of their rest period. Even a bull will not catch her.”
Fricke pointed out that activity monitors and technology identifies the cycling cows but just as important, it identifies that cows are not cycling and those are the ones you need to do something with, utilizing an Ovsynch and timed AI program.
He predicts that in the future technology utilizing milk samples to know progesterone levels will be perfected and will be an important tool for helping with this issue.
Finally, Fricke noted that none of these results are possible without good nutrition, adequate body condition score, low rates of mastitis and good uterine health.