reprodaction Technical Publications Basic guidelines to select the right synchronization protocol for Timed Artificial Insemination in cattle

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1 reprodaction Technical Publications Basic guidelines to select the right synchronization protocol for Timed Artificial Insemination in cattle

2 This short review will cover basic aspects to be taken into account when selecting synchronization programs for beef or dairy herds in countries where estrogens are not allowed. This manuscript obviously does not intend to cover the almost infinite variety of Timed Artifical Insemination protocols used in cattle, but rather will indicate key successful hormonal treatments to synchronize ovulation that may be adapted according to unique management situations with the assistance of the herd s veterinarian. Alexandre Souza, DVM PhD University of California Cooperative Extension Service Alessio Valenza, DVM PhD International Technical Manager for Ruminants Corporate Marketing Ceva Sante Animale

3 TECHNICAL PUBLICATIONS 1. Important aspects to be considered before choosing the synchronization program Understanding the concept of Timed Artificial Insemination The use of synchronization programs for Timed Artificial Insemination (TAI) allows farmers to breed their cattle without relying on estrus detection. In some cases due to prolonged postpartum anoestrus or in herds with high milk production levels, it can be very difficult to detect cows in heat due to different physiological limitations such as lack of Corpus Luteum for 7 to 10 days in the ovaries due to negative energy balance and/or calf presence (in case of beef cows postpartum) or due to high rates of steroid metabolism by the liver (for high producing dairy cows) that may suppress oestrus behavior. Therefore, strategic use of adequate synchronization programs can represent an important tool that helps producers to improve service rates and to treat postpartum anoestrus. However, relying 100% on the TAI programs to breed cows may not be the best option. In most cases, the ideal approach is to combine good heat detection systems with an effective synchronization program, particularly for second and following postpartum breedings. The goal is to breed nearly 100% of the cows for the first time until 100 days in milk (DIM) for mature cows or within 30 days after reproductive age is achieved in case of virgin heifers. A second objective of a good reproductive schedule must be to keep the average interval between breedings less than 35 days in high producing dairy cows and roughly less than 30 days in heifers (dairy and beef) and mature beef cows. Maximum service rate = estrus detection + synchronization protocols Heat detection rate (%) Percentage of AI performed with synch protocols Reference: Souza AH et al, 2013 Thus, some important features of synchronization programs are associated with enhanced heat detection performance and to treatment of anovular/ cows, bringing them back to cyclicity. The number of cows that get pregnant after the

4 use of synchronization programs is normally similar or higher to fertility after natural breedings ranging around 30% to 40% in dairy cows and 45 to 70% in beef cows and heifers (dairy or beef). The decision on how much hormones for synchronization needs to be used in the herd depends largely on the producer s goals in terms of reproduction performance, cattle breed, percentage of anovular/anoestrus cows, price of hormones, labor costs for heat detection (and pregnancy diagnosis), adoption of software to organize the reports of hormones that need to be used, level of milk production, implementation of adequate facilities to handle animals, and most importantly, trained personnel. The importance of good record keeping systems Herds willing to handle larger volumes of breedings through a sequence of hormonal shots, which in some cases can be quite complex, will need to adopt the use of an herd management software. Unfortunately, more than often we come across large herds with sometimes over 2,000 cows in milk that still try to track shots and breeding routines manually. Tracking cows and hormones is unbearable overtime, and decision needs to be made towards start using a consistent herd management software no matter how unfamiliar you are with computers, get adapted to it or you may be out of business in a few years. Most computer programs are not very expensive at all, and they will save enormous amounts of time and headache to producers stop the excuses, stop the hand notes, get started now! Tracking reproductive performance Hopefully you re convinced of the importance of computer programs that will help with the daily routine when using synchronization and TAI. Now, which one should I buy in case I don t have any software? Well, I d pick the one that can handle what I want to do in terms of management routines. It may not be the cheapest one, but as you know, good things are normally not cheap! Before purchasing any software, recheck whether appropriate support is available while setting up the program on your herd - this is probably an important aspect to be considered when choosing your herd management software.

5 TECHNICAL PUBLICATIONS Another important point when buying computer programs for herd management is to ask about the features in the software that will allow you and your consultant to track reproduction with modern statistical analysis and ease-to-read graphic tools. For example, try to find out if you can measure the percentage of cows that are bred within 100 DIM, or if you can see the calving distribution from last year s calving season. With this type of tool you and your consulting team will be able to evaluate current status of the herd and make informed management decisions based on accurate numbers. For instance, if less than 90% of the cows are bred before 100 DIM, an action plan needs to be designed in order to fix the problem, and herd management programs need to provide this type of tool to help farmers and consultants to decide to invest and/or modify the current way of managing reproduction. How about herds that may be too small to jump into a wild adventure of buying a software for herd management? This is a rather common picture and the solution is probably to make sure that producers are using well designed paper-cow cards for record keeping. For instance, in these cases heat detection performance can easily be calculated by using the Woods formula. The Woods s calculation simply uses the assumed cow s cycle length divided by the average interval between breedings to estimate heat detection performance. Example of Woods calculation of heat detection rate of a herd: Herd with two cows (n=2) Interval between first and second AI for cow1 (C1 1-2AI )= 46 days Interval between first and second AI for cow2 (C2 1-2AI )= 25 days Standard cow s cycle length (CCL)= 21 days Calculations: Average interval between breedings (IBB) = (C1 1-2AI ) + (C2 1-2AI ) / n = ( ) / 2 = 35.5 days Woods calculation of heat detection rate = CCL / IBB = 21 / 35.5 = 0.59 x 100 = 59% average heat detection rate Type and frequency of pregnancy diagnosis according to herd size Briefly, frequency of pregnancy exams are key part of finding non-pregnant or open cows when relying on TAI protocols. Thus, the correct frequency and type of pregnancy diagnosis approach needs to be well thought during the process of selecting the right synchronization program. Obviously, larger herds will require more frequent and most likely weekly pregnancy exams. Interestingly, in recent years, blood pregnancy tests based on PSPB or PAGs* detection allow smaller producers to re-assign open cows to *PSPB: pregnancy-specific protein B / PAGs: pregnancy-associated glycoproteins.

6 synchronization programs in a weekly basis. In addition to herd size, the importance of frequent pregnancy diagnosis increases a lot as the herd s heat detection efficiency decreases. Therefore, herds using more efficient heat detection strategies such as daily professional tail chalk service, well managed utilization of automated heat detection devices, and/or use of well managed clean up bulls (particularly in beef herds) may in some situations afford having less frequent pregnancy diagnosis. Thus, here is a suggestion of MINIMUM frequency of pregnancy exams according to herd size for dairy herds: Visits for pregnancy diagnosis Montly Biweekly Weekly Minimum number of required veterinary visits according to herd size. (This frequency may need to be increased in herds with poor estrus detection). 100 or less 100 to to 100 Number of lactating cows in the herd Sire selection genetic plan for the herd Having a solid vision on the strengths and potential weaknesses of the herd is essential for genetic advance. Thus, get in touch with your semen provider to come up with a strong genetic plan for your herd based on your market situation. This plan needs to include matings that will reduce inbreeding to less than 6%, use calving-ease sires for virgin heifers, etc while producing animals that are suitable to your management constraints. As far as semen inventory, you may need to plan ahead before start using TAI protocols! This is particularly truth for beef herds make sure the semen provider is ready to keep up with the increased amount of breedings (with sexed or non-sexed semen) after adopting synchronization programs. Photo s courtesy of J. Ruiz del Olmo

7 TECHNICAL PUBLICATIONS 2. Reproductive routine: the concept of Standard Operating Procedure S.O.P. Standard Operating Procedure or S.O.P. is a simple document that explains the weekly routine for any cow-related activities in the herd. Thus, the S.O.P for reproduction can be a written file or just a simple chart that summarizes by day of the week what happens in terms of treatments to postpartum cows, detailed heat detection routine, actions that need to be performed when cows are detected open, people in charge of each task, etc. Sticking to the S.O.P can simplify the overall reproduction management. Before jumping in to the TAI programs, here is a short list of main hormones, its main purpose when used in TAI protocols, and designated short-name that will be used interchangeably throughout this manuscript: Hormone/Device Main function when used in synchronization programs Short-name, will be used interchangeably throughout the manuscript Progesterone Releasing Intravaginal Device Priming of progesterone to induce cyclicity in anovular/ anoestrus cows Avoid premature estrus behavior during the synchronization protocols PRID, P4, P4 device Prostaglandin F2α Induce CL regression in mature CLs (older than 5d) PGF, PGF2α Gonadotropin Releasing Hormone Induce LH surge and ovulation of dominant follicles GnRH Equine Gonadotropin Hormone with FSH/LH-like function used to enhance follicle development at final stages during synchronization protocols Proven to improve ovulation rates and fertility when used in anovular/anoestrus cows ecg (formerly known as PMSG)

8 3. TAI protocols 5d-Protocol This short P4-based protocol has been developed somewhat recently and most reports are showing very promising results. It seems to work well for mature cows and heifers (beef or dairy). The main advantage of this protocol is its simplicity and length only 3 managements within only 7 days! In addition, this protocol does not use any type of estrogen on day 0 (day of progesterone device insertion), so it can be initiated in pregnant cows with no risk of CL regression, which may save a couple of days when trying to Re-synchronize cows or heifers. This protocol may include a GnRH treatment on Day 0 together with P4 device insertion, and a second PGF treatment given 24h after the first PGF at device removal, mandatory when using GnRH at beginning of the 5d-protocol, otherwise CL will not regress in a good portion of cows (particularly dairy cows) and fertility following TAI will definitely be compromised. Last, more studies are needed to confirm whether ecg can be successfully used at device removal without undesirable increase in double ovulation rates. Previous variations of this protocol included longer periods of P4 device insert also showing fairly good success rates. 5d-Protocol: recommended for dairy or beef cows and heifers PGF GnRH + AI PRID for 5 days 56h to 72h D0 8 AM D5 8 AM D7 4PM Weekly schedule: SU MO TU WE TH : Insert PRID : Remove PRID + PGF 4PM: 56h after PRID removal - GnRH+AI* FR SA : Remove PRID + PGF : Insert PRID 4PM: 56h after PRID removal - GnRH +AI *For best results minimum voluntary waiting period of 60 or more days to AI is strongly recommended HD=strategic heat detection to catch nonpregnant cows returning in heat after 1 st postpartum AI. Pregnancy Diagnosis at 28 days after AI (at the time of P4 insertion) or at 33 days after AI (at the time of P4 removal).

9 { TECHNICAL PUBLICATIONS Pre-synch Ovsynch (2PgF + Ovsynch ) This protocol has been developed more than one decade ago and it is probably the most common TAI protocol used in large dairy herds world-wide. The intervals between PGF and Ovsynch of 14 and 10 days respectively seems to produce somewhat improved results compared to the traditional 14-14d intervals between PGF and Ovsynch. Some disadvantages of this protocol are mainly related to its inability to treat anovular/ anestrus cows and its length and complexity, making it very difficult to use in herds without advanced Standard Operating Procedures (S.O.P.) and computer programs. Therefore, Pre-synch strategies relying exclusively on PGF treatments should be avoided in herds with postpartum cyclicity issues. However, it can be a good option in confined dairy herds that are not undergoing problems related to anovular/anestrus cows. Heat detection and AI after the 2 nd PGF are normally encouraged, but as a rule of thumb only if conception results, out of these estrus-breedings, are >30%. The weekly routine presented below by days of the week shows the sequence of treatment for a Pre-synch Ovsynch for 1 st postpartum AI and the use of the GGPG* protocol (good option when Re-synchronizing open cows for 2 nd and following AIs) for Resynchronizing lactating dairy cows. Heat detection and AI in cows showing estrus behavior PGF2a PGF2a GnRH PGF2a GnRH TAI 14d 10d 7d 56h 16h D0 D14 D24 D31 D33 4PM D34 Adding progesterone devices in Ovsynch -like programs between the 1 st GnRH of Ovsynch until PGF injection increases conception rate of 5 to 8% in both cycling and anovular dairy cows Weekly schedule: SU MO TU WE TH : GnRH : PGF 4PM: GnRH : AI FR : PGF : PGF * SA { Pre-synch Ovsynch 1 st AI : GnRH : GnRH to open cows : PGF 4PM: GnRH : AI *For best results minimum voluntary waiting period of 60 days to AI in high producing cows is strongly recommended HD=strategic heat detection to catch non-pregnant cows returning in heat after 1 st postpartum AI. Pregnancy Diagnosis at 32 days after AI (at the time of the second GnRH). { GGPG for 2 nd + AIs *GGPG (GnRH before Ovsynch )

10 G-6-G protocol (modified to facilitate weekly routine) This is another GnRH-PGF based protocol but with the advantage of having a GnRH treatment 7 days before the initiation of the Ovsynch protocol. This GnRH treatment should help with cows presenting anovular-large follicle condition postpartum. Can also be a good option for high producing dairy cows. Notice that some of these protocols are quite complex and follow up of treatments need to be through a computer software to avoid mistakes. If computer programs are lacking in the herd you may want to pick a more simple approach to synchronize cows. The weekly schedule below shows the sequence of treatments for the G-6-G protocol that has been slightly modified to facilitate the weekly routine, followed by the GGPG protocol for 2 nd and following breedings. Modified G-6-G protocol: recommended for the 1 st AI postpartum in confined high producing dairy cows PGF GnRH GnRH PGF GnRH AI 3d 7d 7d 56h 16h D0 D3 D10 D17 D19 4 PM D20 Adding progesterone devices in Ovsynch -like programs between the 1 st GnRH of Ovsynch until PGF injection increases conception rate of 5 to 8% in both cycling and anovular dairy cows SU MO TU WE TH : GnRH : GnRH : PGF : GnRH : GnRH to open cows : PGF 4PM: GnRH 4PM: GnRH *For best results minimum voluntary waiting period of 70 or more days to AI in high producing cows is strongly recommended HD=strategic heat detection to catch non-pregnant cows returning in heat after 1 st postpartum AI. Pregnancy Diagnosis at 32 days after AI (at the time of the second GnRH). : AI : AI FR : PGF SA { { Modified G6G 1 st AI GGPG for 2 nd + AIs

11 TECHNICAL PUBLICATIONS Double-Ovsynch protocol This GnRH-PGF protocol has been designed to synchronize 1 st postpartum AI in lactating cows in very high producing dairy herds. It is a fairly long and complex protocol. Thus, it makes the use of computer programs to track cows and treatments mandatory. It is very effective to treat anovular high producing dairy cows that usually present follicles with ovulatory capacity or with diameter > 10mm, but are not cycling (condition now known as large follicle anovular syndrome ). It is not effective in cows undergoing the standard small follicle-postpartum anoestrus, and is not recommended for virgin heifers either. Main advantage is related to high circulating P4 after D17 or at the time of the first GnRH of the breeding Ovsynch (see picture below), which in turn tends to produce oocytes with very high quality even in high producing dairy cows. Seem to reduce double-ovulation rates in lactating cows. Because of its length is normally not recommended during Re-synchronization programs for 2 nd and later AIs. Double-Ovsynch protocol: recommended for the 1 st AI postpartum in confined-high producing dairy cows GnRH PGF GnRH GnRH PGF GnRH AI 7d 3d 7d 7d 56h 16h D0 D7 D10 D17 D24 D26 4PM D27 Pre-synch Ovsynch Breeding Ovsynch SU MO TU WE TH FR SA : GnRH : GnRH : PGF 4PM: GnRH : AI : GnRH : GnRH to open cows : PGF 4PM: GnRH : AI : GnRH : PGF *For best results minimum voluntary waiting period of 70 or more days to AI in high producing cows is strongly recommended HD=strategic heat detection to catch non-pregnant cows returning in heat after 1 st postpartum AI. { { Double-Ovsynch 1 st AI GGPG for 2 nd + AIs Pregnancy Diagnosis at 32 days after AI (at the time of the second GnRH).

12 A few further considerations on Re-synchronization strategies Because dairy herds normally have relatively lower conception results after 1 st AI (~30 to 40%), wide adoption of artificial insemination, and most importantly poor estrus detection efficiency, most herds need to have a precise plan for 2 nd and further breedings in their S.O.P. for reproduction management. Below are a few examples of Re-Synchronization strategies that can be successfully used in dairy herds. Other good option for Re-synchronization in dairy herds may include the 5d-protocol, or even a simple PGF injection to open cows followed by heat detection and Ovsynch to cows not detected in heat 10 days later. GGPG protocol: recommended for the 2 nd+ AIs (Re-synch) postpartum in high producing dairy cows GnRH GnRH PGF2a GnRH AI 7d 7d 56h 16h D21 after AI D28 D35 D37 4PM D38 Pregnancy diagnosis 5d-Protocol: recommended for dairy or beef cows and heifers PGF GnRH + AI D0 PRID for 5 days D5 56h to 72h D7 4PM

13 TECHNICAL PUBLICATIONS 4. Final thoughts The flow chart below summarizes main synchronization strategies that can be used in different cattle breeds and animal category. Mature beef or dairy cows? Beef or dairy Heifers? lactating Dairy cows Beef cows Beef heifers Dairy heifers Cows housed in confined systems or pasture/mixed? Pasture based Confinement If herd is more than 50 heads: buy herd management software now! If herd is more than 50 heads: buy herd management software now! Is good heat detection system in place? Greater than 60% of estrus detection rates? No Yes Sure? 5d protocol + ecg or calf removal if mature beef cows have low BCS or less than 100 days in milk 1 st AI: Pre-synch + Ovsynch and AIs in cows showing estrus after the 2 nd PgF injection Resynch: simple Ovsynch to non-pregnant cows may work, but adding progesterone device during Ovsynch increases conception results from 5 to 8% in most cases 1 st AI: 5d protocol, Double-Ovsynch, G-6-G protocol Resynch: must have weekly preg checks + GGPG protocol or 5d-protocol Important: - Choose adequate Voluntary Waiting Period (VWP) due to risk of low conception if cows are inseminated too early; - If clean-up bull is necessary: complete breeding soundness exam at least 2x/year and correct bull management including adequate resting time for the bull (particularly dairy herds), correct proportion cows per bull, etc is mandatory.

14 It is important to highlight that synchronization programs can unquestionably help producers to treat anovular/anoestrus cows and increase service rates or heat detection efficiency. Conception results may occasionally be improved with the use of specific protocols in relation to natural estrus breedings, particularly in high producing cows. However, in herds in which cows are inseminated but not getting pregnant very easily, producers and herd consultants need to review other important areas of management such as the transition period, Cow Comfort and nutrition requirements besides trying to solve their fertility issues solely through a fancy TAI protocol. In addition, reproductive performance can be improved through tracking key performance indicators and help producers and consultants to perform management changes based on real evidence. References: Bisinotto, R. S., 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 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. Journal of Dairy Science 93(12): Bisinotto, R. S. and J. E. P. Santos The use of endocrine treatments to improve pregnancy rates in cattle. Reproduction, Fertility and Development 24(1): Bloch, A., Y. Folman, M. Kaim, Z. Roth, R. Braw-Tal, and D. Wolfenson Endocrine Alterations Associated with Extended Time Interval Between Estrus and Ovulation in High-Yield Dairy Cows. Journal of Dairy Science 89(12): Brusveen, D. J., A. P. Cunha, C. D. Silva, P. M. Cunha, R. A. Sterry, E. P. B. Silva, J. N. Guenther, and M. C. Wiltbank Altering the Time of the Second Gonadotropin-Releasing Hormone Injection and Artificial Insemination (AI) During Ovsynch Affects Pregnancies per AI in Lactating Dairy Cows. Journal of Dairy Science 91(3): Brusveen, D. J., A. H. Souza, and M. C. Wiltbank Effects of additional prostaglandin F-2 alpha and estradiol-17 beta during Ovsynch in lactating dairy cows. Journal of Dairy Science 92(4): Chebel, R. C., M. J. Al-Hassan, P. M. Fricke, J. E. P. Santos, J. R. Lima, C. A. Martel, J. S. Stevenson, R. Garcia, and R. L. Ax Supplementation of progesterone via controlled internal drug release inserts during ovulation synchronization protocols in lactating dairy cows. Journal of Dairy Science 93(3): Colazo, M. G., A. Dourey, R. Rajamahendran, and D. J. Ambrose Progesterone supplementation before timed AI increased ovulation synchrony and pregnancy per AI, and supplementation after timed AI reduced pregnancy losses in lactating dairy cows. Theriogenology 79(5): Hernández-Cerón, J., L. Zarco, and V. Lima-Tamayo Incidence of delayed ovulation in Holstein heifers and its effects on fertility and early luteal function. Theriogenology 40(5): Kaim, M., A. Bloch, D. Wolfenson, R. Braw-Tal, M. Rosenberg, H. Voet, and Y. Folman Effects of GnRH Administered to Cows at the Onset of Estrus on Timing of Ovulation, Endocrine Responses, and Conception. Journal of Dairy Science 86(6): Lima, F. S., H. Ayres, M. G. Favoreto, R. S. Bisinotto, L. F. Greco, E. S. Ribeiro, P. S. Baruselli, C. A. Risco, W. W. Thatcher, and J. E. P. Santos Effects of gonadotropin-releasing hormone at initiation of the 5-d timed artificial insemination (AI) program and timing of induction of ovulation relative to AI on ovarian dynamics and fertility of dairy heifers. Journal of Dairy Science 94(10): Moreira, F., C. Orlandi, C. A. Risco, R. Mattos, F. Lopes, and W. W. Thatcher Effects of Presynchronization and Bovine Somatotropin on Pregnancy Rates to a Timed Artificial Insemination Protocol in Lactating Dairy Cows. Journal of Dairy Science 84(7):

15 TECHNICAL PUBLICATIONS Pursley, J. R., M. O. Mee, and M. C. Wiltbank Synchronization of ovulation in dairy cows using PGF2α and GnRH. Theriogenology 44(7): Ribeiro, E. S., R. S. Bisinotto, M. G. Favoreto, L. T. Martins, R. L. A. Cerri, F. T. Silvestre, L. F. Greco, W. W. Thatcher, and J. E. P. Santos Fertility in dairy cows following presynchronization and administering twice the luteolytic dose of prostaglandin F2α as one or two injections in the 5-day timed artificial insemination protocol. Theriogenology 78(2): Santos, J. E. P., C. D. Narciso, F. Rivera, W. W. Thatcher, and R. C. Chebel Effect of reducing the period of follicle dominance in a timed artificial insemination protocol on reproduction of dairy cows. Journal of Dairy Science 93(7): Sartori, R., J. M. Haughian, R. D. Shaver, G. J. M. Rosa, and M. C. Wiltbank Comparison of Ovarian Function and Circulating Steroids in Estrous Cycles of Holstein Heifers and Lactating Cows. Journal of Dairy Science 87(4): Souza, A. H., H. Ayres, R. M. Ferreira, and M. C. Wiltbank A new presynchronization system (Double- Ovsynch) increases fertility at first postpartum timed AI in lactating dairy cows. Theriogenology 70(2): Souza, A. H., A. Gumen, E. P. B. Silva, A. P. Cunha, J. N. Guenther, C. M. Peto, D. Z. Caraviello, and M. C. Wiltbank Supplementation with estradiol-17 beta before the last gonadotropin-releasing hormone injection of the ovsynch protocol in lactating dairy cows. Journal of Dairy Science 90(10): Valenza, A., J. O. Giordano, G. Lopes Jr, L. Vincenti, M. C. Amundson, and P. M. Fricke Assessment of an accelerometer system for detection of estrus and treatment with gonadotropin-releasing hormone at the time of insemination in lactating dairy cows. Journal of Dairy Science 95(12): Walker, W. L., R. L. Nebel, and M. L. McGilliard Time of Ovulation Relative to Mounting Activity in Dairy Cattle. Journal of Dairy Science 79(9): Walsh, R. B., S. J. LeBlanc, T. F. Duffield, D. F. Kelton, J. S. Walton, and K. E. Leslie 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 67(5): Wiltbank, M. C., P. D. Carvalho, K. Abdulkadir, K. S. Hackbart, M. A. Meschiatti, M. R. Bastos, J. N. Guenther, A. B. Nascimento, M. M. Herlihy, M. C. Amundson, and A. H. Souza Effect of Progesterone Concentration During Follicle Development on Subsequent Ovulation, Fertilization, and Early Embryo Development in Lactating Dairy Cows. SSR, 161 (Abstract). Wiltbank, M. C., A. H. Souza, J. O. Giordano, A. B. Nascimento, J. L. M. Vasconcelos, M. H. C. Pereira, P. M. Fricke, R. S. Surjus, F. C. S. Zinsly, P. D. Carvalho, R. W. Bender, and R. Sartori Positive and negative effects of progesterone during timed AI protocols in lactating dairy cattle. Page 10 in Animal Reproduction. Vol. 9. reprodaction Reproductive management in Action Ask your Ceva representative for ReprodAction advice

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