Why should
you be motivated to focus on reproduction?
The ultimate goal of the reproductive program is to achieve a pregnancy
in order to maintain milk production and replacements. Ten Percent of your cows should calve every
month to maintain consistent milk production.
Your greatest return on investment is milk produced during the first 100
days in milk when the return is 3:1!
Additionally, reproduction significantly impacts culling strategy. With
more replacements, culling options increase.
In order to
keep days in milk low, cows need to efficiently conceive in a timely manner
after a clearly defined voluntary waiting period. Optimizing pregnancy risk achieves this
objective. Pregnancy Risk is defined as the probability that an eligible open
cow will become pregnant in the next 21 days, or more simply, the number of
pregnancies over a 21-day period divided by the number of eligible cycles over
the same 21-day period. The average
pregnancy risk in Pennsylvania
Studies have analyzed the value associated with pregnancy risk. A one percentage point increase in pregnancy risk is valued at $15-35 per cow per year. The further you go below the goal pregnancy risk of 22-25% the higher the value of increasing pregnancy risk. Consider this example, a 150-cow herd with an average pregnancy risk of 14% could potentially see an additional profit of $15,750 by increasing pregnancy risk to 17% (3 points*$35/cow/year*150cows). The pregnancy risk value is partially dependent on decreasing days open which has an estimated cost of $2-6 per cow per day open in addition to the cost associated with reproductive culling.
Are you motivated to invest in change? Now let’s discuss getting the most out of your reproductive investment. First, you must start with dairy management basics because all management segments are interdependent. Optimize transitional health and decrease body condition loss post-calving. Promote cow comfort and decrease social stress. Focus on nutrition and work closely with your nutritionist and agronomist to maximize forage quality. Decrease lameness and promote milk quality. Work with your veterinarian to design a vaccination program specific for your dairy. A problem in any of these areas re-partitions nutrients away from reproduction, negatively impacting fertility.
Strict Adherence to Program Compliance is critical to enhancing timed A.I. conception risk. A successful timed insemination program is dependent upon strict protocol compliance. Protocol drift will result in lower conception rates and wasted opportunity. Consider this Ovsynch Compliance Example (based on % compliance per injection) that proves Mistakes Multiply:
90% GnRH1 x 90% PGF2a x 90% GnRH2 = 73% !
With the investment you place in drugs, supplies, and labor
expenses, a 73% compliance rate is not tolerable. Hormones used in your reproductive program
need to be labeled and stored properly. Be
able to control and monitor drug inventory to monitor correct usage rates. Injections must be administered according to
labeled instructions (route of administration and dose) on schedule. Use color-coded bottles and different sized
syringes to make hormone identification easier. Make sure the correct
hormone is administered and the correct cow inseminated at the prescribed times. Timing is extremely critical. Cows enrolled in the program should be easily
identifiable and pregnant cows should be clearly recognized. Give employees
ownership of the program to encourage compliance and accountability. Use the smallest needle allowed, 18 or 20
gauge 1.5 inch needle, so that the injection is placed deep in the muscle with
zero hormone loss from the injection site.
The cow must be inseminated properly by a trained technician. Employees should be retrained annually to prevent protocol drift. Technician conception rates can be monitored through various computer programs. Make sure semen is handled according to the recommendations of the bull stud. Check thermometer accuracy. Timing and maintenance of proper temperature during temperature extremes is critical. Analyze ways to become more efficient by decreasing distance between semen prep and the cow.
An all-encompassing discussion about estrous synchronization protocols is beyond the scope of this article. However, we need to talk about modifications to Presynch and Ovsynch that studies have proven to increase conception risk. Remember this concept - The optimal day of the reproductive cycle to start Ovsynch is 6-7. The first follicular wave is more consistent and 2 CL’s are created which means more progesterone exists to optimize fertility. Using Presynch (Pg-14days-Pg-14days-Ovsynch) to set-up Ovsynch for first service has been shown to increase conception rates by 12%. However, the standard 14 day interval between the second prostaglandin injection and start of Ovsynch is not consistently within the optimal 6-7 day window of the reproductive cycle. Therefore, decreasing the interval between the second Presynch prostaglandin injection and the start of Ovsynch from 14 days to 11-12 days has been shown to further increase conception rates by 6 percentage points.
Now let’s discuss Ovsynch and Cosynch. First, preliminary assumptions are that 56-hour Ovsynch (G-7days-PGF-56hrs-G-16hrs-Breed) has higher conception rates than the typical 48-hour Ovsynch protocol. Unlike Ovsynch where cows are bred 16 hours after the second GnRH injection, Cosynch cows are bred when they are injected with the second GnRH injection eliminating another handling. So, Cosynch is more convenient, but does it pay? Numerous studies have repeatedly shown an 8-10% improvement in conception rates at the optimal time for AI which is 16 hours after a GnRH injection, like 56-hour Ovsynch, compared to a Cosynch protocol. Conception Rate improvements are seen regardless of a Presynch/Ovsynch first service or a Resynch service. Considering the statistically significant difference and investment made into the reproductive program, the decision to use Ovsynch over Cosynch should be clear.
We should
finish up by talking about Resynch conception rates. Resynchronization programs are timed
re-insemination protocols that insure all open cows are re-bred within a
defined interval with the goal of decreasing the interestrous period (time
frame between breedings). In this article,
we will simply discuss Resynch in relation to a standard 56-hour Ovsynch
protocol. Many Resynch protocols exist. The
most common is an Ovsynch protocol initiated a week before pregnancy
check. Resynch conception rates are
typically lower than 1st service conception rates with a Presynch-Ovsynch
protocol. Many studies have analyzed the
optimal time to start Resynch. Conception
rates for Resynchs initiated on days 32-33 (38%) post-A.I have been
consistently higher than Resynchs initiated on days 19 (23%), 21, and 26 (34%)
post-A.I. The difference between d26
cows and d33 cows is likely due to a greater period to allow natural embryonic
death. Studies have shown that 12% of
all pregnancies between 30-42 gestation result in natural early embryonic death. Consequently, you have 2 preg check options
when initiating Resynch on day 32-33 post-A.I.
You could Preg check on day 32 or 33 post-A.I. and give GnRH1 to all open
cows and complete Ovsynch. Or, you could
give GnRH1 on day 32 or 33, preg check on day 39 or 40, and give PGF2a to all
open cows and complete Ovsynch. Consider
using CIDR’s in Resynch-restarts associated with cystic cows and cows without
CL’s. When performing early open tests,
it is very important to recheck pregnancy ~60 days gestation.
As you can
see, many factors impact your reproductive investment. Identify potential risk factors in management
areas that directly and indirectly impact reproduction. Focus on protocol compliance and eliminate
protocol drift. Finally, follow the data
and use proven protocol modifications that enhance conception rates.
14-11day Presynch / 56-hr Ovsynch /
Day 32 Resynch
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Sunday
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Monday
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Tuesday
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Wednesday
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Thursday
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Friday
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Saturday
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Week 1
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PGF (pm)
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Week 2
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Week 3
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PGF (pm)
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Week 4
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Week 5
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GnRH (am)
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Week 6
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PGF (am)
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GnRH (pm)
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Breed (am)
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Week 7
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Week 8
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Week 9
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Week 10
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Week 11
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GnRH (am)
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Week 12
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PGF (am) Preg Check
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GnRH (pm)
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Breed (am)
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