Optimizing a Co-Synch Repro Plan

Article by Dr. Chet Rawson; Alta Field Fertility Specialist

The best conception rates (CR) from first service OvSynch will be achieved when they are presynchronized with PgF2a and when those services occur at 70 DIM and greater. This is because the cows have additional time for uterine involution and clean-up. It is also because there will be fewer anestrus cows in the population at 70 DIM than at 60 DIM. Increases of 4 to 8% can be achieved by waiting an additional 10 days to start first service OvSynch. This translates to starting the first PgF2a at 32 DIM instead of 22 DIM. Interestingly, Leslie, et al. showed from research in Guelph that cows with endometritis treated with PgF2a at 20 – 25 DIM may suffer a negative effect on subsequent reproductive performance. These are two good reasons to start the program 10 days later.

If pregnancy diagnosis is performed from 32 DSLB (days since last breeding), the OvSynch cows being examined for pregnancy should all be at 32 DSLB. The standard Co-Synch program would have the open cows being started on the next round of OvSynch at 32 DSLB. This is ideal; as cows started on OvSynch between days 5 and 12 of the estrus cycle will perform better than those started at other times in the cycle (with the length of the estrus cycle in Holstein cows being 23 days, the open cows at 32 days would be at day 9 of the cycle). Fricke and others have shown a 3 – 5% increase in CR for cows started in this stage of the cycle. In a controlled trial in Michigan, I observed a 3.5% difference in cows started at day 32 instead of day 26.

I feel that you will not lose performance by removing the CIDRs from normal cycling cows. However, those cows found open at preg check that are cystic or anovular (anestrus) will benefit from the addition of a CIDR to the OvSynch protocol. This would be accomplished by inserting a CIDR at the time of the first GnRH and removing it at the time of the PgF2a injection for those cystic and anovular cows found openat preg check. It is extremely important when dealing with CIDRs that the utmost cleanliness be observed. One should take it to the level of a presurgical prep.

The tail chalking program used to assist in estrus detection can be very useful. When tail chalking, cows should chalked and read daily. This allows the person doing the interpretation to detect daily changes in chalk on individual animals. There always needs to be an emphasis not only on efficiency (finding cows in estrus), but especially on accuracy (finding cows that are truly in estrus). One of the nice things about the Co-Synch plan is that if the operator is not certain that an animal is in estrus, she will be diagnosed within a few days and still be serviced in a timely manner.

I have found that the interval analysis in DC-305 can be helpful in measuring estrus detection accuracy. The command is Bredsum\DI. The “D” allows you to look at a specific date range; the “I” presents the “interval analysis” report.

The key here is to look at the 4-17 day line. The %Conc should be within 5% of the average (here it is 19 vs 24) and the %Tot should be at 10% or less (here it is 12). In herds where the CR is reduced by more than 30% of the average CR and % of services is more than 15-20% of the %Tot, there is a definite Accuracy of Estrus Detection issue.

Not all clients are willing to move from a 50 to a 70 day VWP. I have found that when you implement a program of this nature and overall performance improves, it will be much easier to move that VWP from 60 to 70 some three to six months down the road. I do believe that it is important to tell the whole story on the front end, so that you have planted the seed for further positive change.

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Posted Oct 15th

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