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Use of progesterone releasing intravaginal devices (PRID) in resynchronization of non-pregnant cows

This short review will cover basic aspects to be taken into account when selecting resynchronization programs in high producing dairy herds. The manuscript will show the most important strategies to resynchronize non-pregnant diagnosed cows and will identify the benefits or pitfalls related to timed AI protocols. In addition, some important management aspects related to the implementation of resynchronization protocols with progesterone releasing intravaginal device (PRID) are also discussed. Obviously, the most ideal protocol for a specific herd should be chosen by the herd’s veterinarian according to the herd’s unique management conditions.

Antonio Jimenez, Cattle Technical Manager - SpainCeva Sante Animale

Alessio Valenza, DVM PhDInternational Technical Manager for Ruminants Corporate MarketingCeva Sante Animale

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In the last ten years of research, there have been many advances in how to improve the 1st post-partum AI of dairy cows. Some of these advances include heat detection systems and synchronization protocols with high conception rates at first artificial insemination (AI): intravaginal progesterone devices and protocols like Presynch-Ovsynch®, G6G and Double-Ovsynch®.

However, after the first insemination, more than half of the cows will not become pregnant (“open cows”) and several of them will not be detected in heat in the following oestrus cycle due to limitations related to housing or management and physiological events around the time of ovulation (greater metabolism of steroid hormones in response to greater dry matter intake in high producing dairy cows). Therefore we must focus on the early detection and successful resynchronization of those open cows.

Some important aspects to be taken into account:

1. The most efficient way to re-inseminate a non-pregnant cow is by detecting the following oestrus cycle. Improving estrous detection in cows failing to conceive reduces expenses in hormones and in most cases yields good fertility results. The problem is that many of the cows that failed to conceive will not show estrous behaviors (or will never be detected in estrus) before the pregnancy diagnosis.

2. Generally, the conception rates of the 2nd and consecutive AIs are lower than 1st

postpartum AIs, even in cows bred following estrous behaviors. This might simply be due to statistics: from the population of cows that must be inseminated, as the number of inseminations increases, greater is the proportion of cows which have lower fertility.

3. Early resynchronization of open cows will improve service rates and therefore pregnancy rates. Producers and veterinarians must be aware that conception results following a simple Ovsynch® protocol may not be as good as the ones following natural estrous. But these results can be significantly improved by using latest developments in timed AI programs. Resynchronization results following the Ovsynch® protocol may not be ideal due to the fact that the stage of the estrous cycle in which Ovsynch® is started, can dramatically affect fertility results. The most ideal phase to start Ovsynch® is on days 6 or 7 of the estrous cycle and this is achievable by using presynchronization strategies. Those programs are working very well for 1st postpartum AI, but pre-synchronizing cows at later AIs is a lot more challenging, and most of the time is anti-economic because of the extended breeding intervals.

1. Resynchronization of non-pregnant diagnosed cows

In theory, open cows will come in estrous again approximately 23 days after first postpartum insemination, since the oestrous cycle of lactating dairy cows, is on average 22.9 ± 0.7 days long (Sartori et al., 2004). However, high producing dairy cows will return in estrous anywhere from 18 to 28 days after previous AI (Chebel et al., 2006). The physiological variation in the estrous cycle interval may be explained by different CL lifespan between cows and by early embryonic death. This variable interval to estrous makes it difficult to establish the best day of the cycle in order to start the Ovsynch® protocol.

4. We need to take into account if cows have been synchronized for the 1st AI. Most of the programs for 2nd AI (including estrous detection or other strategies) assume that cows are in a determined day of the estrous cycle following the 1st

postpartum AI. However, it is common to find that some cows did not respond to the first synchronization program or had short cycles due to lack of progesterone pre-exposure before the 1st AI. Therefore, optimizing the 1ª IA with a good synchronization program will improve the results of the following breeding.

5. It is possible to start the resynchronization protocol even before pregnancy diagnosis to decrease the interbreeding interval. In the Ovsynch® protocol, the first GnRH injection has not effect on the pregnancy, and can be given to pregnant cows without any concern. In addition, Chebel et al. (2003) showed that cows starting Ovsynch® protocol before pregnancy diagnosis had similar 1st and 2nd conception results to cows starting Ovsynch® after pregnancy diagnosis. Thus, the first GnRH can be used regardless of whether cows are pregnant or not. Seven days later, cows diagnosed as non-pregnant will receive a PGF2a injection and 56h later, a second GnRH treatment. The AI will be performed 16h after the second GnRH according to the Ovsynch® protocol. Obviously, the advantage is the 7d reduction in the inter-breeding interval from 1st to 2nd AI.

The disadvantages of starting Ovsynch® protocol before pregnancy diagnosis are:

6. Lastly, there are many open research lines developing more aggressive resynchronization programs, as for instance, the use of progesterone devices before pregnancy diagnosis or even the use of very early pregnancy diagnosis tests, which could potentially allow vets and producers to resynchronize cows even before the expected natural estrous. The possible effects of these early treatments on the oestrous cycle, and their practical and economical viability, are still under research.

All cows are treated with GnRH before pregnancy diagnosis, which means additional handling and cost of drugs;Most of the non-pregnant cows at the time of GnRH injection will have a dominant follicle (greater than 10mm) and about 50% of them will ovulate that follicle and have a new CL. The new CL will reduce their chances to come into estrus, and more cows will end up the resynchronization program. This may not be economically advantageous in herds with good heat detection systems.

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2. Strategies to resynchronize “open cows”: Nutrition, herd health and transition cow management are key areas for a successful dairy operation. Obviously, there are no reproductive programs that can wholly level out metabolic problems during transition period, uterine diseases (metritis/endometritis), infectious problems, excessive body condition loss, anestrus/anovular condition, etc.

Therefore, several management factors will influence reproductive performance, and even more this must be taken into account for cows undergoing resynchronization programs. We’ll be able to achieve better conception rates for a resynchronization protocol if cows are healthy, have good body condition scores compatible to stage of lactation, and are normally cycling.

1. A single injection of PGF2a (the simple way to induce estrus). The simple shot of PGF2a has probably been one of the first system used to synchronize the estrous cycle in dairy cattle. Non-pregnant diagnosed cows with a Corpus Luteum (CL) receive PGF2a injection and usually estrous behavior should occur from 2 to 7 days later.

LimitationsIt is a straightforward method that tends to work well in some situations; however it has been replaced by alternative approaches mainly because it does not allow timed AI.

First of all, at the time of the pregnancy diagnosis, cows need to be cycling and have a mature CL. Otherwise, cows may not respond to the PGF2a treatment. This may happen in different situations such as anovulatoty condition, or when, at the time of PGF2a treatment, cows are not at the oestrous cycle phase where the corpus luteum is sensitive to prostaglandins (CL <5 days old).

Another limitation is related to possible lack of luteolysis (CL regression) after a single PGF2a dose even in cows carrying mature CLs. Several studies show that almost 20% of cows are not able to regress a mature CL and this poor luteolysis response to a single PGF2a treatment seems to be greater in older cows having two or more lactations.

However the most important variable is related to the phase of the estrous cycle at the time of PGF2a treatment. This results in a great variation on the time of oestrous and ovulation. Cows will come in heat 2 to 5 days later and producers are forced to watch for estrous behavior before breeding cows.

Furthermore, in high producing dairy herds, many cows with positive response to PGF2a treatment might not show estrous behavior and are not inseminated due to high steroids metabolism. In a normal situation, if the heat detection efficiency is not ideal, although the conception results to cows detected in estrous could be good, the number of pregnancies achieved out of the total number of cows treated may not be acceptable. Because of these reasons, many veterinarians do not use anymore the simple PGF2a treatment as a resynchronization method.

2. Ovsynch® protocol.Pursley et al. (1997) showed that Ovsynch® could be successfully used in dairy cows without the need to relay in estrous detection. In his study, cows were either inseminated following natural estrous (control group), or treated with Ovsynch® after a negative pregnancy diagnosis. Overall, cows treated with Ovsynch® conceived sooner than cows in the estrus-detection group. Later, these promising results from Pursley lead to a number of research efforts to develop new resynchronization methods for cows undergoing 2nd and following AIs.

In one of the first studies, Fricke et al. (2003) tested the effect of the Ovsynch® protocol (in 711 cows) started at different days of the estrous cycle after the 1st postpartum AI (19, 26 or 33 days). In conclusion, the conception rate to the resynchronization started on day 19 (23%) was much lower than the one at day 26 (34%) and day 33 (38%). Assuming that high producing dairy cows have reproductive cycles of 23 days, these results could be explained in terms of a more favorable stage of oestrous cycle (day 10), for open cows which initiated the resynchronization on day 33 (23 + 10 = 33) compared to the ones that started it on day 19 (23 – 4 = 19) and those of day 26 (23 + 3 = 26). It must be taken into account that cows treated on day 19 had follicles growing under lower progesterone concentration, and the lower level of circulating progesterone has a negative impact on oocyte quality and conception results.

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Sterry et al. (2006), further resynchronized 763 lactating dairy cows on days 26 vs 33, within different parity numbers, using the Cosynch-48h (second GnRH and AI done simultaneously at 48h after the PGF2a treatment). Although it is better to re-inseminate non-pregnant cows as soon as possible, this study showed that, re-synchronizing cows on day 33 yield better conception results than on day 26. First-lactation cows which started re-synch treatment on day 33, had significantly higher fertility compare to multiparous cows.

LimitationsOvsynch® protocol is a very good tool to handle resynchronizations because improves service rates, and hence pregnancy rates. However, Ovsynch® alone does not give the best possible conception results to timed AI. Ovsynch® efficiency depends mainly on: ovulation following the 1st GnRH, successful luteolysis produced by the PGF2a treatment and ovulation to the 2nd GnRH. If any of these three assumptions fail to occur during Ovsynch®, conception results are significantly reduced. In order to increase the efficiency, cows should start the Ovsynch® at days 6-7 of the estrous cycle.

a) Ovulation failure to the 1st GnRH (figure 1). Ovulation of a dominant follicle at the beginning of the Ovsynch® protocol will allow starting a new follicular wave and also will generate an accessory CL that increases circulating P4 during follicle growth. If cows are in an early development of the follicular stage (at any wave during the estrous cycle), the granulosa cells will not have enough LH receptors in order to respond to the GnRH treatment.

Most likely (80% of possibility) this growing follicle will become the new ovulatory follicle at the time of luteolysis induced by the PGF2a shot, and it will be able to respond to the final GnRH injection. However, this follicle might have up to 12 days since its emergence, which in turn will reduce the quality of the ovulating oocyte and conception rate might be lower.

Follicles that will not respond to initial GnRH of Ovsynch® protocol (approximately 20%) may become atresic before the PGF2a treatment. In this case, a new follicular wave starts, generally just before the time of the PGF2a injection. This new emerging follicle may not have enough LH receptors at the time of the 2nd GnRH of the Ovsynch®. In this situation, the cow will probably come in estrous some days after the timed AI. Obviously, conception rate of this cow will be close to 0% after the FTAI.

Figure 2. Spontaneous luteolysis before PGF2a injection (Adapted from Vasconcelos et al. 1999)

Figure 1. Lack of ovulatory response at 1st GnRH (Adapted from Vasconcelos et al. 1999)

b) Spontaneous luteolysis before PGF2a injection if Ovsynch® protocol starts at final stage of estrous cycle (figure 2). If that happens, the cow may show natural estrous and ovulate before the targeted day of the timed AI. If this natural heat is not detected, usually around the time of PGF2a injection, the conception rate might be lower because the timed AI will takes place many hours or days after ovulation when the oocyte is likely no longer viable.

30-40% of the cycle

CL CLFF

Oestrous cycle day-10 210

Ov

GnRH GnRH

GnRH

21

7 days

PGF2a

Ov

-10

P4

Oestrous cycle day

x

50% of the cycle

0

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3.1. Presynchronization with PGF2a:Silva et al. (2007) were one of the first to presynchronize cows before the Ovsynch® treatment. In their study, control cows received the regular Ovsynch®, whereas presynchronized ones were treated 12 days before Ovsynch® protocol with PGF2a.

Presynchronization with PGF2a (Adapted from Silva et al., 2007)

3.2. Presynchronization with GnRH (GGPG):Dewey et al. (2010) compared the simple Ovsynch® resynchronization (Cosynch 72h) started after the negative pregnancy diagnosis, with a presynchronization protocol giving GnRH 7 days before Cosynch 72.

3. Presynchronization strategies in order to improve Ovsynch®

efficiencyCows that initiate Ovsynch® protocol around day 6-7 of the estrous cycle in general have better results. Therefore, there has been plenty of presynchronization strategies using GnRH, PGF2a, GnRH+PGF2a, or hCG in order to have the cows starting the Ovsynch® protocol at day 6-7 of estrous cycle.

Results: Cows presynchronized with PGF2a achieved 9.6 percentage points more in conception rate (35.2% vs 25.6%) compared to simple Ovsynch® ones.Treatment length: 22 days.

Results: Cows presynchronized with GnRH achieved 9.1 percentage points higher conception rate than regular Ovsynch®: 31.2% vs 22.1%.Treatment length: 17 days.

D0 D12

12d

StartOvsynch®PGF2a

D22

Ovsynch®

AI

Presynchronization with GnRH (Adapted from Dewey et al., 2010)

StartOvsynch®GnRH

Ovsynch®

AI

7d

D0 D7 D17

3.4. Presynchronization with hCG:Giordano et al. (2012) studied a re-synch protocol known as HGPG. In this protocol, cows receive an injection of hCG on day 18 after AI, followed by an Ovsynch® 56 treatment starting on day 25. In the first trial, HGPG was compared with Double-Ovsynch® and simple Ovsynch®. In a following experiment, HGPG was compared with GGPG and the simple Ovsynch®. Overall, hCG presynchronization and Double-Ovsynch® treatment produced better conception rate than non-presynchronized cows. In the second trial, hCG replacement by GnRH showed no significant improvement of conception rate.

3.3. Presynchronization with Ovsynch® (Double-Ovsynch®): Giordano et al. (2012) compared, as re-synch for open cows, the regular Ovsynch® with the Double-Ovsynch® protocol (Souza et al., 2008). In both programs the 1st

GnRH was given 7 days before pregnancy diagnosis.

Results: Cows presynchronized with Double-Ovsynch® achieved 8.4 percentage points higher conception rate (32.9% vs 24.5%) compared to simple Ovsynch® ones.Treatment length: 27 days.

Results: hCG presynchronized cows achieved 9.3% percent higher conception rate than simple Ovsynch® ones.Total treatment length: 17 days.

Presynchronization with Ovsynch® (adapted from Giordano et al., 2012)

GnRH PGF2a AIPGF2aGnRHGnRH

D08AM

D78AM

D108AM

D178AM

D248AM

D264PM

GnRH

D278AM

7d 3d 7d 7d 16h56h

Presynch-Ovsynch® Breeding Ovsynch®

Presynchronization with hCG (adapted from Giordano et al., 2012)

StartOvsynch®hCG

Ovsynch®

AI

7d

D0 D7 D17

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3.5. Presynchronization with PGF2a and GnRH (G6G): This protocol was developed by Pursley et al. After a negative pregnancy diagnosis, cows receive a PGF2a injection to regress the existing CL, followed by a GnRH treatment 2 days later in order to induce and synchronize the ovulation. Then, 6 days later, begins the Ovsynch® protocol, when cows are at day 6th of their estrous cycle.

The G6G program aims to increase circulating P4 during the growth of the ovulatory follicle due to induction of an accessory CL, 6 days before the Ovsynch® treatment.

Main aspects:Presynchronizing cows before an Ovsynch®-like program is proven to be a good strategy in terms of basic physiology and field results, that are about 8-9 points greater than the simple Ovsynch® protocol. However, some of the proposed programs may inhibit cows from returning in natural estrous and/or tend to be fairly long and may not be the best strategy in terms of profitability due to increased inter-breeding intervals. For example, these programs may increase inter-breeding intervals anywhere from 7 to 19 days, and although improvements in conception are likely, it may not offset the extra days open that are lost when applying these long programs.

In order to apply these programs (except the G6G), veterinarians and producers need to start the protocol before the pregnancy diagnosis. However, the use of hormones such as GnRH and hCG before the pregnancy diagnosis will suppress estrus behavior. It may not be the very best option particularly for herds having good estrous detection routines.

Treatment length: 18 days.

D08AM

56h 2d 6d 7d 16h

D2 8AM

D8 8AM

D15 8AM

D17 4 PM

D188AM

PGF2a GnRH AIGnRHPGF2aGnRH

Presynchronization with PGF2 and GnRH (adapted from Pursley et al.)a

Presynchronization strategies showed benefits in terms of conception results compare with just the simple Ovsynch® protocol. But may not be the best option in terms of profitability because of the long interval between breedings.

High producing dairy cows have low circulating progesterone during follicle growth (Sartori et al., 2004), which in turn causes increased frequency of LH pulses. More frequent LH pulses during follicle growth have been associated with poor oocyte quality and less viable embryos (Inskeep, 2004). Thus, greater concentrations of progesterone during follicle growth seem to be associated with improved fertility in dairy cows (Bisinotto et al., 2010).

Lima et al. (2010) and Cunha et al. (2006) also reported that increased levels of progesterone during timed AI increases conception results and decreases the incidence of double ovulations. In practice, greater circulating progesterone levels during the timed AI program can be achieved either by inducing an accessory CL roughly one week before enrolling cows to the timed AI program, normally through some presynch strategy or simply adding exogenous progesterone through an intravaginal device.

It is important to highlight that during re-synch programs, shorter protocols are generally more profitable because of reduced intervals between inseminations (Cabrera et al., 2011).

Exogenous progesterone supplementation during TAI programs allows producers to reach higher conception results and keep the hormonal treatment period as short as 8 days.

Several studies have shown the positive effects of an intravaginal progesterone device in resynchronization programs for timed AI:

a) Walsh et al. (2007) studied the effect of adding a progesterone device to the Ovsynch® as a resynchronization protocol in 415 cows from 25 different dairy farms. After the negative pregnancy diagnosis, treated cows received a PRID whereas control group cows received a placebo device.

Results: Conception rate was 8.9 percentage points higher for cows treated with progesterone devices compared to control cows (43.8% versus 34.9%).

b) In Dewey et al. (2010) study, a simple Cosynch protocol (control group) was compared with a Cosynch supplemented with a progesterone device. Results: Cows supplemented with progesterone had a conception rate of 7.4 percentage points greater than the non-supplemented ones (29.5% versus 22.1%).

3. Resynchronization protocols with proges-terone releasing intravaginal devices (PRID)

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c) Bisinotto et al. (2010) studied the resynchronization effect on fertility using a 5 days protocol with a progesterone device compared to an Ovsynch® 56 protocol. On days 32 post AI, non-pregnant cows received a progesterone device (n=341) or not (n=334) from the GnRH to the PGF2a shot of the resynchronization protocol. In lactating dairy cows, the 5 days-progesterone protocol requires 2 PGF2a injections 24h apart in order to optimize luteolysis.Results: Conception rate at day 60 post AI was 7.7 percentage points higher for cows enrolled in the 5d-progesterone protocol compare to the cows in the control group (45.5% versus 37.8%).

Furthermore, a follow up experiment of the same study showing results of the 1ª timed AI, indicated that the administration of GnRH simultaneously to AI did not affect fertility in cows receiving the 5 days protocol (Ovsynch® 56 versus Cosynch 72). This may open the door to use Cosynch 72 (with the progesterone device) because facilitates management at farm level.

Adding a progesterone device, conception rate increases by 8% points.Treatment length: 8-10 days.

5d Cosynch + PRID

D0

PRID for 5 days

GnRH PGF2a

D5

GnRH + TAI

D8

24h

D6

48h

PGF2a

7d Ovsynch® + PRID

PGF2a

D0 D7

TAI

D10

PRID for 7 days

GnRH

56h

D9

16h

GnRH

Progesterone supplementation during timed AI programs yields conception results 8% points higher compare to the simple Ovsynch® protocol.

What’s the value of increasing conception rate in 8% points?• We can estimate that the value of a pregnancy (difference in economic value of a pregnant cow compared to an open one) is approximately 400€*.

• Thus, 1% point of increase in conception rate due to a treatment (which produces one extra pregnancy out of 100 AIs) has a value of:

400€/100 = 4€ per treated cow

Therefore, increasing conception rate by 8% points will have an estimated value of:

8X4€ = 32€ per cow

4. Cost-effectiveness of progesterone supplementation

In case of long re-synch protocols, how much do we lose per each additional days of treatment?• In order to assess the contribution of presynchronization protocols in comparison to the simple Ovsynch®, it must be taken into account that each additional day of a whole treatment is equivalent to a day open lost.

• The value of a single day open for a dairy cow is approximately 2 to 4€*. Therefore, a 10 days length re-synch program will generate a loss of 20 to 40€ due to days open.

2 to 4€ X 10 = 20 to 40€ per cow

Profitability calculation of the protocol with a progesterone device:*Lost of days open in comparison with simple Ovsynch® = 0€*Gross profit obtained due to 8% higher conception rate in comparison with simple Ovsynch®:8x4 = 32€ gross profit per cow (value of 8% increase in conception rate)

*”The dollar value of a pregnancy” Dairy Cattle Reproduction Council.

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Most cows do not conceive following their 1st postpartum AI. Maximizing heat detection rate of open cows is the most ideal strategy. However, in our high producing dairy farms, heat detection rate is not optimal and cows might show estrus for few hours due to high metabolism of steroids.

Therefore having a a good re-synch protocol for cows detected open will likely increase service rate and pregnancy rate results. Resynchronizing cows with the regular Ovsynch® program do not yield the best conception results. In order to improve fertility, it is necessary to increase levels of circulating progesterone during timed AI programs. This can be reached by presynchronizing cows or simply adding a progesterone device during the timed AI protocol.

5. Conclusions

1. Improvement of 8% points in conception rate compare to regular Ovsynch®. This improvement in conception rate has a value of roughly 32€ per treated cow.

2. Shortening the interbreeding interval. Adding PRID to the timed AI program allows cows to be re-inseminated sooner and with good conception outcomes. Also, it saves time (between 7 to 9 days open) and money in comparison with alternative methods.

3. Higher efficacy in problem cows.PRID has been shown to be a good treatment for large follicle-anovular condition (common in modern high producing cows) and deep postpartum anestrous.

Advantages of using PRID for timed AI:

1. The effect of a progesterone releasing intravaginal device (PRID) on pregnancy probability to fixed-time insemination following diagnosis of non-pregnacy in dairy cows. R.B. Walsh, S.J. Leblanc, T.F. Duffield, D.F. Kelton, J.S. Walton, K.E. Leslie. Theriogenology 67 (2007) 948-956.

Summary: The objective was to compare the probability of pregnancy after FTAI in cows diagnosed as non-pregnant and re-inseminated following the Ovsynch® protocol, with or without exogenous progesterone. Cows (n = 415) used in this study originated from 25 farms. Upon a negative pregnancy diagnosis between 30 and 60 days after AI, cows were randomly assigned to receive either a progesterone releasing intravaginal device (PRID; n=208) or a placebo intravaginal device (PID; n=207).

All cows received GnRH at enrolment (D0), PGF2a concurrent with intravaginal device removal 7 days later, GnRH on day 9 and fixed-time insemination 16 h later (D10). Ovaries were examined by transrectal palpation at the time of enrolment and the prominent structures were assessed and recorded. Body condition score, lameness status, interval from previous insemination, and number of AI were recorded.

The probability of pregnancy after fixed-time insemination was 43.8% in PRID-treated versus 34.9% in placebo-treated animals. Exogenous progesterone provided through an intravaginal device to non-pregnant cows that had not displayed oestrous improved the probability of pregnancy after FTAI.

6. Relevant studies

30-60 Days conception rate

50

40

30

20

10

0

34,9%

Ovsynch® Ovsynch® + PRID

43,8%

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2. Resynchronization strategies to improve fertility in lactating dairy cows utilizing a presynchronization injection of GnRH or supplemental progesterone: I. Pregnacy rates and ovarian responses. S. T. Dewey, L. G. D. Mendonça, G. Lopes Jr., F. A. Rivera, F. Guagnini, R. C. Chebel and T. R. Bilby. Journal of Dairy Science 93: 4086-4095.Summary: Objectives were to evaluate 3 resynchronization protocols for lactating dairy cows.At 32 ± 3 days after AI, 1 week before pregnancy diagnosis, cows from 2 farms were enrolled and randomly assigned to 1 of 3 resynchronization protocols after balancing for parity, days in milk, and number of previous AI. all cows were examined for pregnancy at 39 ± 3 days after AI. Cows enrolled as controls (n=386) diagnosed not pregnant were submitted to a resynchronization protocol (D0-GnRH, D7-PGF2a, and D10 GnRH and IA). Cows enrolled in the GGPG (GnRH-GnRH-PGF2a-GnRH) treatment (n=357) received a GnRH injection at enrollment (D7) and if diagnosed not pregnant were submitted to the resynchronization protocol for control cows on D0. Cows treated with progesterone (n=316) diagnosed not pregnant, received the resynchronization protocol described for control cows with addition of an intravaginal progesterone device from day 0 to 7. In a subgroup of cows, the ovaries were scanned and blood was sampled for progesterone concentration from day 0 to 7. After AI, cows were diagnosed for pregnancy at 39 ± 3 and 67 ± 3 days (California herds) or 120 ± 3 day (Arizona herds). Cows in the GGPG treatment had more CL than progesterone and control cows on days 0 and 7. A greater percentage of GGPG cows ovulated to GnRH given on day 0 compared with P4 and control cows, but P4 and control group did not differ.At 39 ± 3 days after AI of resynchronization treatment, conception rate was increased for the GGPG (33.6%) and P4 (31.3%) cows compared with the control (24.6%) cows. At days 67 or 120 ± 3 following resynchronization AI, conception rate of the GGPG and P4 group was increased compared with the control cows group (31.2%, 29.5% and 22.1%, respectively).Presynchronizing the oestrous cycle of lactating dairy cows with a GnRH 7 days before the start of the resynchronization protocol or use of an intravaginal progesterone releasing device within the resynchronization protocol resulted in a greater conception rate after resynchronization AI compared with control cows.

67-120 Days conception rate35

30

25

20

15

10

5

0

22,1%

GPG GPG + PRID

29,5%

3. Effect of the interval between induction of ovulation and artificial insemination (AI) and supplemental progesterone for resynchronization on fertility of dairy cows subjected to 5-d timed AI program. R. S. Bisinotto, E. S. Ribeiro, L. T. Martins, R. S. Marsola, L. F. Greco, M. G. Favoreto, C. A. Risco, W. W. Thatcher and J. E. P. Santos. Journal of Dairy Science. 93 :5798–5808.

Summary:Objectives were to investigate 2 intervals from induction to artificial insemination and the effect of supplemental progesterone for resynchronization on fertility of lactating dairy cows subjected to a 5 days FTAI program.

In experiment 1, 1,227 Holstein cows had their oestrous cycles presynchronized with 2 injections of PGF2a at 46 and 60 day in milk (DIM).

The FTAI protocols were initiated with GnRH at 72 DIM, followed by 2 injections of PGF2a at 77 and 78 DIM and a second injection of GnRH at either 56 h (OVS56) or 72 h (COS72) after the first PGF2a of the TFAI protocols.

All cows were inseminated at 72 h after the first PGF2a injection.

Pregnancy was diagnosed on days 32 and 60 after AI.

In experiment 2, 675 non-pregnant Holstein cows had their oestrous cycles resynchronized starting at 34 day after first AI. Cows received the Ovsynch® 56 with or without supplemental progesterone, as an intravaginal insert, from the first GnRH to the first PGF2a. Pregnancy diagnoses were performed on days 32 and 60 after AI.

During experiment 2, subsets of cows had their ovaries scanned by ultrasonography at the 1st GnRH, the 1st PGF2a and the 2nd GnRH injection of the protocol.

Blood was sampled on the day of AI and 7 days later, and concentrations of progesterone were determined in plasma. Cows were considered to have a synchronized ovulation if they had progesterone inferior to 1 ng/mL on the day of AI and superior to 2.26 ng/mL 7 days later, respectively, and if no ovulation was detected between the first PGF2a and second GnRH injections during resynchronization.

In experiment 1, the proportion of cows detected in oestrous at AI was greater for COS72 (40,6%) than OVS56 (32,4%). Pregnancy per AI (P/AI) did not differ between OVS56 (46,4%) and COS72 (45,5%).

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In experiment 2, cows supplemented with progesterone had greater pregnancy rate on day 32 than non supplemented ones (51.3 vs. 43.1). On day 60, the difference was of 45.5% in the progesterone group versus 37.8% in the group with simple Ovsynch®.

Premature ovulation tended to be greater for non supplemented cows compared with cows supplemented with progesterone (7.5% versus 3.6%), although synchronization of the oestrous cycle was similar between treatments.

Timing of induction of ovulation with GnRH relative to insemination did not affect conception rates of dairy cows enrolled in a 5 day timed AI program.

Furthermore, during resynchronization starting on day 34 after the first AI, supplementation with progesterone improved conception rates in cows subjected to the 5 days timed AI protocol.

60 Days conception rate

50

40

30

20

10

0

37,8%

5d protocol 5d protocol + PRID

45,5%

Pursley JR, Wiltbank MC, Stevenson JS, Ottobre JS, Garverick HA, Anderson LL. Pregnancy rates per artificial insemination for cows and heifers inseminated at a synchronized ovulation or synchronized oestrous . J. Dairy Sci. 1997 Feb; 80(2):295-300.

Fricke PM, Caraviello DZ, Weigel KA, Welle ML. Fertility of dairy cows after resynchronization of ovulation at three intervals following first timed insemination. J. Dairy Sci. 2003 Dec; 86(12):3941-50.

Sterry RA, Welle ML, Fricke PM. Effect of interval from timed artificial insemination to initiation of resynchronization of ovulation on fertility of lactating dairy cows. J. Dairy Sci. 2006 Jun; 89(6):2099-109.

J. Richard Pursley & Joao Paulo N. Martins. Control farmacológico de la función del folículo y del cuerpo lúteo para mejorar la fertilidad en las vacas lecheras en lactación. XVI Congreso internacional ANEMBE de medicina bovina. Avila, 2011.

Silva E, Sterry RA, Kolb D, Wiltbank MC, Fricke PM. Effect of pretreatment with prostaglandin F2alpha before resynchronization of ovulation on fertility of lactating dairy cows. J. Dairy Sci. 2007 Dec;90(12):5509-17.

Dewey ST, Mendonça LG, Lopes G Jr, Rivera FA, Guagnini F, Chebel RC, Bilby TR. Resynchronization strategies to improve fertility in lactating dairy cows utilizing a presynchronization injection of GnRH or supplemental progesterone: I. Pregnancy rates and ovarian responses. J. Dairy Sci. 2010 Sep;93(9):4086-95. doi: 10.3168/jds.2010-3233.

Mendonça LG, Dewey ST, Lopes G Jr, Rivera FA, Guagnini FS, Fetrow JP, Bilby TR, Chebel RC. Effects of resynchronization strategies for lactating Holstein cows on pattern of reinsemination, fertility, and economic outcome. Theriogenology. 2012 Apr 1;77(6):1151-8. doi: 10.1016/j.theriogenology.2011.10.021. Epub 2012 Jan 26.

Giordano JO, Wiltbank MC, Guenther JN, Ares MS, Lopes G Jr, Herlihy MM, Fricke PM. Effect of presynchronization with human chorionic gonadotropin or gonadotropin-releasing hormone 7 days before resynchronization of ovulation on fertility in lactating dairy cows. J. Dairy Sci. 2012 Oct;95(10):5612-25. doi: 10.3168/jds.2011-5035. Epub 2012 Aug 9.

Giordano JO, Wiltbank MC, Guenther JN, Pawlisch R, Bas S, Cunha AP, Fricke PM. Increased fertility in lactating dairy cows resynchronized with Double-Ovsynch® compared with Ovsynch® initiated 32 d after timed artificial insemination. J Dairy Sci. 2012 Feb;95(2):639-53. doi: 10.3168/jds.2011-4418.

Walsh RB, Leblanc SJ, Duffield TF, Kelton DF, Walton JS, Leslie KE. The effect of a progesterone releasing intravaginal device (PRID) on pregnancy risk to fixed-time insemination following diagnosis of non-pregnancy in dairy cows. Theriogenology. 2007 Mar 15;67(5):948-56. Epub 2006 Dec 18.

References:

TECHNICAL PUBLICATIONS

Bisinotto RS, Ribeiro ES, Martins LT, Marsola RS, Greco LF, Favoreto MG, Risco CA, Thatcher WW, Santos JE. Effect of interval between induction of ovulation and artificial insemination (AI) and supplemental progesterone for resynchronization on fertility of dairy cows subjected to a 5-d timed AI program. J Dairy Sci. 2010 Dec;93(12):5798-808. doi: 10.3168/jds.2010-3516.

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RTP

14

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