Improving Fertility and Decreasing Twinning
by Dustin Lochner, DVM
Does it feel like your herd’s milk production has improved through the years but your cows’ ability to breed back hasn’t seemed to keep up or that you seem to get more twins than previously? According to researchers, you aren’t the only one to notice. As national averages for milk production have improved throughout the years there has been a coinciding decrease in the national pregnancy rates and twinning rates. Dr. Milo Wiltbank at the University of Wisconsin believes that these are related due to an increase in milk production leading to an increase in dry matter intake. There is also increased blood flow to the liver where hormones are activated and modified which could influence a cow’s reproductive cycle. Dr. Paul Fricke and his team have looked into the role and importance of naturally released reproductive hormones. The one with the greatest effect on fertility is progesterone which is produced by the Corpus Luteum (or CL) after a follicle has ovulated. Dr. Fricke has 4 keys to help achieve a 30% pregnancy rate in herds producing 30,000 lbs of milk and how it may help reduce the amount of twin pregnancies you get.
Key #1: Aggressively inseminate your cows at the end of the voluntary waiting period
Waiting a little bit after a cow freshens before breeding her back gives her body time to return to a normal state and her uterus time to heal after pregnancy. The time that you wait after calving and before breeding is called the voluntary waiting period (VWP). There are two methods to breeding cows after this period has passed: 1) waiting to for that cow to come into a standing estrus on her own and breeding or 2) manipulating her cycle with properly timed shots and breeding. Simply waiting for a cow to come into a standing estrus can leave you waiting to breed some cows for the first time when they are 150+ DIM. This can be extremely costly due to a prolonged dry period and potentially poor metabolic health in the next lactation. Dr. Fricke recommends that if you know what your VWP is, set your cows up using a Pre-synch/Ovsynch protocol to improve fertility at first breeding. Time your protocols so that the timed AI breeding takes place immediately after the VWP has passed.
Key #2: Increase fertility of first breeding
How do you increase fertility of first breeding? Fricke and his team has researched and studied the cow’s reproductive cycle to find the answer. His team looked at Progesterone levels (P4) throughout the Ovsynch protocols and found that ~26% of cows had suboptimal levels of P4 at the first GnRH (G1) injection and ~21% of were suboptimal at the injection of PGF. This led to 26% fewer pregnancies per AI at the first GnRH and 51% fewer at the PGF injection. At the second GnRH shot, ~14% of cows had P4 levels that were too high and had a 66% decrease in pregnancies/AI. They then looked at Pre-synch protocols to help optimize P4 levels. The commonly used 2 injections of PGF two weeks apart 10-14 days prior to Ovsynch has its limitations: 1) anovular cows are not affected and 2) cows are not tightly synched. Pre-synch protocols that help solve these limitations include double ovsynch, GGPG, and G6G. What Dr. Fricke found was that as long as P4 was increased at the time of PGF in Ovsynch, pregnancies per AI increased. As discussed in the March newsletter, adding a second injection of PGF 24 hours after the first PGF in the Ovsynch also increased fertility by getting more complete luteal regression of the CL prior to G2 and breeding.
Key #3 and #4: Identify non-pregnant cows, aggressively re-inseminate and increase fertility to 2nd and greater AI
Identifying non-pregnant cows is important so they can quickly be re-enrolled in a synch protocol and rebred. The use of activity monitors can be beneficial in identifying cows that are likely open to the previous breeding. If you are doing routine preg checks at ~32 days post-AI, preparing these cows ahead of time to be enrolled for breeding right away if they are open can save valuable time. Giving your 32 day preg checks a shot of GnRH 7 days prior to your herd check day has no negative effects on pregnancies and increases the likelihood of a CL being present. Cows that are found open during herd check and have a CL can continue on with resynch and get a PGF injection that day and a second 24 hours later. Those without a CL at an open diagnosis have a low level of P4. Dr. Fricke’s research has shown that cows with a low P4 level have poorer fertility. These cows would then benefit from restarting ovsynch and adding a CIDR to increase P4 and improving fertility at the following breeding.
A recommended Pre-synch/Ovsynch and Resynch protocol to try to maximize fertility are laid out in the diagrams below.
What About Twins?
How does all of this decrease the amount of twins I get? Won’t it actually increase the amount of twins? Again, this was looked at by Dr. Fricke and his team. They found that the primary mechanism for twins is due to double ovulations and that low P4 levels during growth of pre-ovulatory follicles is associated with increased incidences of double ovulation. A few of the associated causes of the low P4 level and double ovulations were anovular cows postpartum, cystic cows in the absence of a CL, and cows producing more than ~90lbs of milk/day prior to estrus. Some farms have tried to get away from Ovsynch and found that they have the same or more twins than when they were using Ovsynch. Cows with high P4 levels at G1 and PGF of Ovsynch as created by Double Ovsynch had significantly fewer double ovulations, more pregnancies/AI, and less pregnancy loss compared to cows with low P4.
While this protocol has proven to increase fertility and decrease twinning rates, it is very labor intensive. We can work with you to develop a protocol that best suits your herd’s management and implement these key points.
Imrestor: A Revolutionary New Tool in Mastitis Prevention
Elanco has just launched a revolutionary product called Imrestor. Imrestor is an antibiotic alternative in the fight against mastitis and yet it is not a vaccine. It works by stimulating the stem cells in bone marrow that create white blood cells, most specifically neutrophils, which increases the cow’s ability to fight infection at a time when their immune system is typically suppressed, i.e. post-calving.
It comes in pre-filled syringes and dosing requires two shots to be given, one 7 days prior to the anticipated calving date and the second within 24 hours post-calving. There are no milk or meat holds required when using this product. Use of this product has not demonstrated any effectiveness in treating clinical cases of mastitis but research has shown it reduces clinical mastitis cases by up to 28%. Imrestor is a protein based product and has the potential to cause allergic reactions. These reactions have shown to resolve within hours of onset without intervention and occurred most often after the first administration. Imrestor will not be available for purchase until June and then by prescription only, so discuss with your veterinarian to see if it is right for your herd.
The Sauk County Dairy Promoters Board is meeting is on April 26th at 7:45pm at the Pizza Hut in Baraboo. The board is looking for new members! Contact Dr. Lochner at the Plain office if you’re interested in getting involved.