Anovular or anestrus cows are those females that are not ovulating. Cycling begins within the first few weeks of calving, says Paul Fricke, a dairy reproduction specialist with the University of Wisconsin. However, research by Fricke has shown that 20-30% of cows have not yet reinitiated ovulation after 60 days in milk. “Those are the cows that we are concerned about, these anovular cows,” Fricke says.
BCS Isn’t the Issue
There are several reasons that cows might be anovular. The classical case that people might think about are cows that are in poor body condition and can’t grow follicles that are big enough to ovulate. Fricke notes that body condition problems cover a small percentage of anovular cows.
“The majority of our anovular cows at 60 days in milk are growing follicles big enough to ovulate, but there’s a problem, though, with what we call the hypothalamic pituitary axis,” Fricke says.
It’s a Brain Issue
This brain problem within the cow doesn’t allow enough estrogen to be released from the follicles during the gonadotropin-releasing hormone (GnRH) surge from the hypothalamus and the luteinizing hormone (LH) surge from the pituitary gland.
Because such a high percentage of cows are anovular the first two months after calving it is difficult to breed every female in heat during that first estrus cycle. With more time anovular cows will “resolve that condition on their own,” Fricke says. But with more time there is lost opportunity to get the cow back into milk sooner after the subsequent calving, cutting into a producer’s bottom-line.
Dairies will have to decide how they address anovular cows either through a synchronization protocol at the beginning or with a controlled internal drug release (CIDR) program. Fricke believes both methods are effective at dealing with anovular cows. For instance, Ficke estimates a double Ovsynch program can overcome 85% of anovular problems.
Herds that identify anovular cows through estrus detection might consider an Ovsynch program with progesterone by inserting a CIDR during the GnRH treatment and pulling it after the prostaglandin treatment. “That actually helps to increase conception rate, so the protocols kind of overcome that anovular condition,” Fricke says.
For more information on avoiding anovular cows watch the video above with Fricke.