2020 Statistics of embryo production and transfer in domestic farm animals

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Published on: March 30, 2022

IETS 2021 DRC Report (2020 Data)

The impact of the Covid-19 pandemic on the embryo industry: the practitioners’ perspective

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Published on: March 30, 2022

Joao HM Viana1, Daniela Demetrio2

1 Embrapa Recursos Genéticos e Biotecnologia, Brasília, 70770-901 Brazil

2 RuAnn Genetics, Riverdale, CA, United States

Introduction

The numbers presented this year in the Report of the Data Retrieval Committee (DRC) of the International Embryo Technology Society showed that, despite the Pandemic, 2020 was a good year for the embryo transfer industry worldwide. The total number of embryos recorded increased in most countries and for all of the most representative species (cattle, horse, sheep and goats). In cattle, overall embryo production (in vivo and in vitro) increased 7.0% when compared with 2019, with more than 1.5 million embryos recorded [1]. To better understand the apparent contradiction between the positive trends in the embryo transfer industry and the economic and social crises caused by the COVID-19 Pandemic, a survey of practitioners from Brazil, Canada and the United States was conducted. These countries account for 74.6% of all the embryos recorded in cattle. However, their embryo industries are characterized by important differences, which limit extrapolations. Therefore, the current survey aimed to highlight how, in the perception of practitioners, the COVID-19 Pandemic affected the embryo transfer industry in each of their countries, as well as to reveal their expectations for 2021.

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Bovine Early Embryo Development

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Published on: March 30, 2022

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Real-time embryo morphokinetic activity can be measured in short observatory periods to provide objective evaluation of embryo health

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Published on: March 30, 2022

C. Wells1, R. Killingsworth1,2

1EmGenisys, Houston TX 77002

2Shamrock Veterinary Hospital, Shamrock TX 79079

Introduction

Embryo transfer (ET), including in vivo derived (IVD) and in vitro produced (IVP), is a routine breeding strategy in cattle operations as it enables the perpetuation of individuals with high genetic merit, improves herd performance, decreases calving interval, and increases fertility in cows under heat stress and repeat breeder cows (Hasler, 2014; Putney et al., 1989, Ambrose et al., 1999; Drost et al., 1999). ET can also be used to help producers control the sex ratio of their herd, which is often referred to as the “most economical genetic trait” as heifer calves are valued at a premium in a dairy herd due to their ability to produce milk. Additionally, ET is an important tool to enable “beef-on-dairy” strategies to add profitability to the dairy industry as dairy cows giving birth to beef calves keep the milking herd lactating while producing offspring which can be sold into the beef marketing chain. Due to these benefits, ET is becoming an increasingly common breeding strategy for the cattle industry, with some companies reporting a 20% increase year-over-year in number of embryos created and transferred (Genus, 2019). 

Unfortunately, success rates of ET are still low and limits the return on investment. Research from controlled studies report pregnancy rates of 70-80% from embryo transfer, but practitioners and producers in the industry encounter lower rates of these procedures on the farm or ranch (Youngs, 2011). The Canadian Embryo Transfer Association (CETA) reports pregnancy success of conventional fresh ET <57.3% successful with further reduced outcomes with IVF embryos (30%), which is comparable to pregnancy rates achieved in the United States (CETA, 2022). While causes of failed pregnancy are multi-factorial and can stem from embryonic, maternal, environmental stressors, or technician competence it is estimated that 20% of transferred embryos are likely non-viable at time of transfer and will never result in pregnancy (Prien et al., 2015, Vanroose et al., 2000; Diskin and Morris, 2008; Alfieri et al., 2019).

A contributing factor to this problem is the reliance on a subjective grading system dependent on a technician’s ability to grade embryos based on morphological characteristics. While practical and economical, the morphological analysis fails to account for many factors which contribute to an embryo’s health and viability including genetic defects, metabolic activity, acute stress, mitotic activity, and response to environmental factors. Therefore, emerging technologies which are non-invasive and non-subjective to evaluate embryo health can enable ET practitioners to select the healthiest embryos for transfer and subsequently improve pregnancy outcomes of IVF/ET in cattle.

The objective of this study was two-fold. 1.) To determine if embryo morphokinetic activity can be evaluated in short observatory periods and 2.) To determine if embryo morphokinetic activity can be used as an indicator of embryo health and viability.

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Single vs. Group In Vitro Culture of Bovine Embryos: Research in Progress

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Published on: March 30, 2022

Austin Byrd and John Gibbons

Texas Tech University, School of Veterinary Medicine

Amarillo, TX 79106

Introduction:

Producing viable embryos and reducing the time between generations is an important, valuable, fast-moving, and trending topic amongst many progressive cattle producers and relies heavily upon effective Assisted Reproductive Techniques (ART’s). In vitro fertilization (IVF) is becoming one of the more popular ARTs as it allows for quicker generation turnover, multiple sires to be used with a single oocyte collection, and more embryos / calves in a given time period. Further, IVF might be chosen over conventional ARTs such as superovulation and embryo transfer because the conventional approaches produce few embryos per collection and the costs are significant. However, the number of oocytes recovered per transvaginal-follicular aspiration session is variable and thus the number of oocytes ultimately placed into culture may be low.  The focus of this preliminary study was to evaluate the percentage of ova that cleave and develop to the blastocyst stage when cultured in single vs. group environments.

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The effects of sire, lactation number, and time of the year on late embryo mortality in dairy cattle

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Published on: December 20, 2021

C. Bailey, J. Gibbons, P. Melendez

Texas Tech University, School of Veterinary Medicine, Amarillo, TX 79106

Introduction

In the dairy industry, there has been considerable drive to maximize birthing rates and profitability by using genetics from beef cattle in both lower performing and lower genetic quality cows. This has allowed cows that are of average quality or aged genetics to provide added value to the operation in the form of crossbred calves for the beef industry.

One measure of infertility in multiparous cows is late embryonic mortality. Although there is likely a higher percentage of embryonic loss during early pregnancy (prior to Day 30; [1]), late embryonic mortality (LEM; defined as pregnancy loss that occurs between 30 and 60 days of gestation) is also a contributor to low profitability. Other research has shown that roughly 12.8% of dairy cows will undergo LEM between 28-42 days post-breeding, averaging a 0.85% loss per day [1].  Some of the factors that cause LEM include genetics, infectious diseases, poor prophylactic management, sanitation, and season of the year.  However, genetic defects of the embryo may also account for up to 20% of early embryonic mortalities [2].

A common method of detecting pregnancy is by measuring Pregnancy Specific Protein B (PSPB) and plasma progesterone (P4) at specific times post insemination. An assay testing PSPB levels indicate a positive pregnancy if PSPB levels are a >10% above non-pregnant cow levels approximately 28 days post artificial insemination [3,4]. Elevated progesterone concentrations (>1 ng/ml) are also useful as a pregnancy detection aid, as they typically begin to taper off around 15 days post estrus in the non-pregnant cow but, are maintained in pregnant cows [5]. Both PSPB and P4 were evaluated and compared between groups in a subset of cows in this study.

The objective of this study was to compare the LEM of Holstein cows bred to Limousin bulls to Holstein cows bred to Holstein bulls. Optical density as a measure of PSPB and P4 concentrations were also evaluated from a blood sample collected at 30 days post breeding for comparison between a subset of 25 cows per group. Further, the LEM was evaluated based upon the time of year that the breeding occurred Summer (April 1 – September 30) and Non-Summer (October 1 – March 31).

Methods

The Limousin X Holstein and Holstein X Holstein breedings in this study were from a large dairy in the southeast US, which consisted of 12,847 Holstein cows. In this herd, 1,166 cows were dry with an average of 171 days open. The cows were milked 3 times a day with a rolling herd average of 14,600 kg of milk per year and were fed a total mixed ration based on corn silage, grass silage, and concentrates. The reproductive program consisted of a 60-day voluntary waiting period and timed artificial insemination using a variety of ovulation synchronization protocols. Cows were diagnosed for pregnancy status by trans-rectal ultrasound between 28 to 35 days post breeding. If the cow was diagnosed open, she was subjected to a resynchronization protocol. If the cow was diagnosed as pregnant, she was rechecked for pregnancy status between 50 to 57 days post breeding by rectal palpation. Blood was collected at random (n = 25 cows per group) at the time of ultrasound pregnancy diagnosis (28-35 days) and tested for PSPB levels expressed as optical densities and P4 concentrations measured by Radio-immuno Assay.

Results

Normal LEM for this herd is approximately 12%. Overall, for all cows bred in the summer the LEM was 15.2 ± 0.6% while those bred in the non-summer had an LEM of 9.9 ± 0.3%, (P<0.0001). Overall, for all Holstein X Holstein embryos the LEM was 15.2 ± 0.6% while the LEM for all Limousin X Holstein embryos was 9.8 ± 0.3%, (P<0.0001).  Differences (P<0.05) in LEM between Holstein x Holstein and Limousin X Holstein were observed during the non-summer months (15.1 ± 0.8% versus 8.3 ± 0.3%, respectively) but not for the summer months (15.1 ± 0.9% and 15.3 ± 0.9%, respectively). summer = 15.23 +/- 0.6%, non-summer = 9.88 +/- 0.3%    P<0.0001

In Figure 1, lactations within breed combination that do not share a common superscript are different (P<0.05). Further, there was a trend (P=0.08) for a difference between Lactation 2 and Lactation 3 for Limousin X Holstein embryos in the non-summer months and there was a breed combination difference (P<0.05) for all lactations during the non-summer months but not for any lactations during the summer months.

Figure 1.  Late embryo mortality (mean ± SEM) percentage over multiple lactation in Holstein cows either bred to Holstein or Limousin bulls that were confirmed pregnant at approximately 30 days post timed artificial insemination either during the summer or non-summer months (see text for more details).

Effects of Season on LEM 

Cows bred in the summer months (Figure 1), regardless of mating, had a higher LEM compared to cows bred in the non-summer months.  A substantial difference in fertility was noted among cows carrying crossbred embryos especially during the non-summer months. Taken together, these data suggest that heat stress during the summer months combined with the stress of milk production, may affect the uterine environment specifically and these stressors cannot be overcome by altering the breed of the sire.  Alternatively, in the non-summer months, the crossbred embryo apparently adapts more readily to the stress of milk production alone than do the Holstein X Holstein embryos.

Protein Specific Protein B and Progesterone

Optical densities of PSPB and P4 concentrations were compared between groups that were diagnosed pregnant at Day 30. The results showed a PSPB optical density of 4.44 in the Holstein X Holstein group and a 3.25 in the Limousin X Holstein group with a pooled standard error of ± 0.27 and a P-Value of 0.023.  Progesterone concentrations were not different (P>0.05) between groups and were 8.66 ng/ml in the Holstein X Holstein group and 8.96 ng/ml in the Limousin X Holstein group with a pooled standard error of ± 0.57.

Conclusion

This field study demonstrated that breeding Holstein cows with Limousin semen reduced LEM by approximately 4% overall and there were seasonal and lactational differences in LEM. During the summer months, the breed combination had a lesser effect on LEM perhaps as all cows exhibited some form of heat stress; however, during the non-summer months, purebred Holstein embryos had a higher LEM than the Limousin X Holstein crossbred embryos, indicating inherent embryo loss dynamics due to factors other than genetics or lactation. These results indicated that breeding beef bulls to lower quality genetic Holstein cows decreased LEM regardless of time of year. However, the lower LEM was especially evident in early lactation cows bred during the non-summer months which likely contains cows that can still contribute genetically to the herd.  The exact components of the “protective mechanism” associated with producing crossbred embryos may be due to hybrid vigor, but has not been fully elucidated; however, it seems to be mostly present during the non-summer months underscoring the ever-present stress of milk production on the females.  The heat induced stress associated with the summer months historically [6] leads to an increase in LEM rates in Holstein embryos and was lactation dependent in both groups in this study. Progesterone concentrations for both groups were similar indicating that corpus luteum function was likely not related to LEM.  Lower optical density which is reflective of the concentration of PSPB was seen in Holstein cows bred to Limousin bulls versus Holstein bulls. More research may be necessary to determine if PSPB plays a role in embryo viability during early pregnancy or if elevated optical density of PSPB is reflective of embryos in distress [7].

References

1)  Wiltbank MC, Baez GM, Garcia-Guerra A, Toledo MZ, Monteiro PLJ, Melo LF, Ochoa JC, Santos JEP, and Sartori R. (2016). Pivotal periods for pregnancy loss during the first trimester of gestation in lactating dairy cows. Theriogenology, 86(1), 239–253. https://doi.org/10.1016/j.theriogenology.2016.04.037 

2)  Alfieri AA, Leme RA, Agnol AMD, and Alfieri AF.  (2019). Sanitary program to reduce embryonic mortality associated with infectious diseases in cattle.  Animal reproduction vol. 16,3 386-393. 22 Oct. 2019, doi:10.21451/1984-3143-AR2019-0073 

3)  Humblot F, Camous S, Martal J, Charlery J, Jeanguyot N, ThibierM, and Sasser RG. (1988).  Pregnancy-specific protein B, progesterone concentrations and embryonic mortality during early pregnancy in dairy cows. J Reprod Fertil. 1988 May;83(1):215-23. doi: 10.1530/jrf.0.0830215. PMID: 3397939.

4)  Middleton EL, and Pursley JR. (2019).  Short communication: Blood samples before and after embryonic attachment accurately determine non-pregnant lactating dairy cows at 24 d post-artificial insemination using a commercially available assay for pregnancy-specific protein B. J Dairy Sci. 2019 Aug;102(8):7570-7575. doi: 10.3168/jds.2018-15961. Epub2019 Jun 6. PMID: 31178191.

5)  Thirapatsukun T, KW Entwistle, and Gartner, RJW.  (1978). Plasma Progesterone Levels as an Early Pregnancy Test in Beef Cattle.  Theriogenology, Vol. 9, no. 4, pp. 323-332.

https://doi.org/10.1016/0093-691x(78)90125-5.

6)  Morton, JM, Tranter, WP, Mayer, DG, and Jonsson, NN. (2007). Effects of environmental heat on conception rates in lactating dairy cows: Critical periods of exposure. Journal of Dairy Science, 90(5), 2271–2278. https://doi.org/10.3168/jds.2006-574 

7)  Thompson, IM, Tao, S, Branen, J, Ealy, AD, and Dahl, GE. (2013). Environmental regulation of pregnancy-specific protein B concentrations during late pregnancy in dairy cattle1. Journal of Animal Science, 91(1), 168–173. https://doi.org/10.2527/jas.2012-5730 

Dominant Follicle Removal Prior to Superovulation in Ewes

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Published on: December 20, 2021

 T. Mittleider a , C. Holcomba , D. Hobbs a, D. Davis c, L. Miller a , J. Gibbons a, b, d

a College of Veterinary Medicine, b DeBusk College of Osteopathic Medicine, Lincoln Memorial University, Harrogate, TN, 37752, c Laurel Highlands Animal Health, Somerset, PA, 15501, d Texas Tech University – School of Veterinary Medicine, Amarillo, TX, 79106

Link to poster: https://onedrive.live.com/view.aspx?resid=60555781396F53CD!1930&ithint=file%2cpptx&authkey=!AsTpH3b9DzphkGY

The Effects of Melatonin on Ovine Estrus Cyclicity

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Published on: December 20, 2021

C. Holcomb b , D. Hobbs b, J. Gibbons a, b, d, D. Davis c

a College of Veterinary Medicine, b DeBusk College of Osteopathic Medicine, Lincoln Memorial University, Harrogate, TN, 37752, c Laurel Highlands Animal Health, Somerset, PA, 15501, d Texas Tech University – School of Veterinary Medicine, Amarillo, TX, 79106

Link to poster: https://onedrive.live.com/view.aspx?resid=60555781396F53CD!2671&ithint=file%2cpptx&authkey=!AjrXPjYQPdeIIP8

Disappearance and uptake of [125I]FSH in the rat, rabbit, ewe and cow

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Published on: August 18, 2021

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D. B. LasterUSDA

Date of this Version

1972

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Published in J. Reprod. Fert. (1972) 30, 407-415

Abstract

Follicle-stimulating hormone (NIH-FSH-S8) was labelled with 125I to determine its disappearance rate after a single intravenous injection and to determine the level of circulating [125I]fsh in the blood after a single intramuscular or subcutaneous injection in the rat, rabbit, ewe and cow. There was a difference in the disappearance and uptake rates among the four species, but the shape of the curve for rate of loss and uptake of labelled fsh was similar in all species. The disappearance of radioactivity occurred at two rates; the first from 1 to 8 min and the second from 16 to 96 min. The half-life, calculated from the total decay curve in each species was 94±21, 118±16, 334±41 and 301±23 min for the rats, rabbits, ewes and cows, respectively. Intramuscular injections resulted in an average of 56% higher [125I]fsh blood levels than subcutaneous injections for all species.

Embryo Transfer in Cattle

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Published on: August 18, 2021

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Reproductive Physiology Review

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Published on: August 18, 2021

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In Vitro Fertilization in Cattle

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Published on: August 18, 2021

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Articles of Interest

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Published on: August 18, 2021

https://www.animal-reproduction.org/article/5b5a604bf7783717068b46a0

https://www.journalofdairyscience.org/article/S0022-0302(19)30635-6/fulltext

https://www.animal-reproduction.org/article/doi/10.21451/1984-3143-AR1002

https://www.semanticscholar.org/paper/Artificial-Insemination-and-Embryo-Transfer-in-Farin/da20551c1a0fad2bafd1dd931de027691a6bebe0

https://www.sciencedirect.com/science/article/pii/S0022030201746905

https://www.mdpi.com/2076-2615/11/6/1666/htm

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7830735/

https://www.sciencedirect.com/science/article/pii/S0022030208712153

https://rep.bioscientifica.com/view/journals/rep/154/6/REP-17-0357.xml

AETA 2019 Statistics Survey Results Available

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Published on: November 2, 2020

Embryo Evaluation Survey Follow-up

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Published on: November 2, 2020

The link below is a follow-up to the embryo evaluation survey sent out by AETA and conducted by Lincoln Memorial University with the evaluations at the time the images were captured. 

https://lmu.co1.qualtrics.com/jfe/form/SV_cHo9ieqA5iIhqKN

Didactic Assisted Reproductive Techniques Experiences for Veterinary Students at Lincoln Memorial University

Categories: Evidence-Based ET
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Published on: November 2, 2020

J Gibbons, P Gibbons, and L Miller

The faculty and staff at Lincoln Memorial University, College of Veterinary Medicine are committed to education and producing Day 1 ready veterinarians competent in all fields. As a distributive model of education, LMU-CVM students receive real-world training opportunities on sheep, goat, and dairy and beef cattle operations in southwest Virginia and eastern Tennessee during their program. Reproductive physiology, estrous cycle manipulation, and specialized assisted reproductive techniques, such as artificial insemination, embryo transfer, transrectal ultrasonography and palpation, and transvaginal ultrasound-guided follicular aspiration are part of the Theriogenology Core and Elective courses. Material specific to multiple species is delivered by experts in the field (either by faculty or an adjunct) during lecture experiences, with most of the laboratories focusing on cattle. These laboratories consist of breeding soundness examinations, live cow palpation and ultrasound, palpation of pregnant and not pregnant excised reproductive tracts and ovaries, and either commercially available or in-house developed silicone models. LMU-CVM also offers a variety of wet labs focused on bovine embryo evaluation and handling, mock embryo transfer, and recovery experiences using excised reproductive tracts, as well as an Artificial Insemination Certification course. Advanced opportunities include Food Animal procedures and bovine palpation electives (beef and dairy cattle) and a Large Animal specific rotation at the DeBusk Veterinary Teaching Campus. Research opportunities involve in vivo and in vitro approaches to addressing basic and applied reproductive physiology questions. Examples include increasing the efficacy and effectiveness of assisted reproductive techniques, especially embryo transfer in cattle, short term incubation of bovine embryos, evaluation of the role of zinc in in vitro embryo production, dynamics of the bovine maternal to embryonic genome control transition, computer assisted semen analysis, and online and in person bovine embryo evaluation. Students from LMU-CVM have applied and received competitive travel grants to attend the AETA annual conference in 2017, 2018, and 2019 (2020 conference was virtual) and have been very active in recent Society for Theriogenology in-person and virtual conferences.

Effect of Supplemental Trace Minerals on Standard and Novel Measures of Bull Fertility

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Published on: November 2, 2020

T. W. Geary – a2, R. C. Waterman – a, M. L. Van Emon – b, C. R. Ratzburg – c, S. Lake – c, B. A. Eik – a, D. R. Armstrong – a, A. L. Zezeski – a, and J. S. Heldt – d

aUSDA-ARS, Fort Keogh Livestock and Range Research Laboratory, Miles City, MT 59301; bDepartment of Animal and Range Sciences, Montana State University, Bozeman, MT 59717; cDepartment of Animal Sciences, University of Wyoming, Laramie, WY; dMicronutrients USA LLC, 2601 Fortune Circle Drive E. Suite 200C, Indianapolis, IN 46241

Abstract

Two studies were conducted to evaluate the effects of trace mineral supplementation on traditional and novel measures of bull fertility. In experiment 1, 37 mature bulls received one of three dietary supplements daily for 71 d: 1) Supplement without Cu, Zn, and Mn (CON); 2) Supplement with Cu, Zn, and Mn sulfate (SULF); and 3) Supplement with basic Cu chloride, and Zn and Mn hydroxychloride (CHLR). In experiment 2, 128 Angus or Angus-Hereford calves were maintained on a growing diet for 75 d (year 1) or 119 d (year 2) in Calan gate equipped pens without mineral supplementation. Bulls (n = 32 head/treatment) received one of four trace mineral supplements daily for 84 d: 1) Zn with no Cu (ZN), 2) Cu with no Zn (CU), 3) Cu and Zn (ZNCU), or 4) no Cu or Zn (CON). Fertility measures included a breeding soundness examination (BSE) and novel fertility measures conducted using flow cytometry. In mature bulls, final liver Zn concentration was positively correlated (P = 0.02) with sperm concentration (r = 0.31) and tended (P = 0.06) to be negatively correlated with acrosome damage (r = -0.39). Peripubertal bulls receiving ZNCU had greater ADG than CU bulls (P = 0.05). Each BSE and novel fertility component improved from d 0 to 84 in peripubertal bulls and were not affected (P > 0.10) by mineral supplementation. Bulls that received no supplement (CON) had greater (P < 0.01) percentage of sperm with distal midpiece reflex and Dag defect in their ejaculates. Sperm viability after 30 min of incubation were not affected by trace mineral supplementation, but after 3 h incubation, sperm viability tended to differ (P = 0.06) between treatments and tended to be less for CON bulls compared to ZNCU bulls. Among contrast comparisons, trace mineral supplemented bulls had greater (P < 0.05) percentage of viable sperm at 3 h post collection and reactive oxygen resistant sperm than CON bulls. Addition of Zn to trace mineral containing Cu (ZNCU) improved (P < 0.05) percentage of sperm in the ejaculate with high mitochondrial energy potential and viable sperm with intact acrosome membrane. In summary, it appears the homeostasis mechanisms for bull trace mineral maintenance are extremely efficient and mineral supplementation of mature and peripubertal bulls did not have major improvements in any laboratory or chute-side measures of bull fertility, however bulls exposed to breeding or in environments with diet antagonists might respond differently.

Out of Season Artificial Insemination and Embryo Transfer Results in Ewes: A Field Trial

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Published on: November 2, 2020

B Price, T Mittleider, S Collins, P Gibbons, and J Gibbons

College of Veterinary Medicine, Lincoln Memorial University, Harrogate, TN

Introduction: 

Ewes are seasonally polyestrous short-day breeders with an estrous cycle of approximately 16 – 17 days.  In the northern hemisphere ewes have active estrous cycles and are naturally receptive to rams from late September to late December when there is less than 12 hours of daylength.  However, progressive sheep breeders often prefer to breed sheep earlier in the year, during periods where there is more than twelve hours of daylength, (July and August) in order to have lambs that are appropriate to target specific show markets.  In order to facilitate this out of season breeding and accelerate genetic gain, producers rely on Assisted Reproductive Techniques such as Laparoscopic Artificial Insemination (LAI), ovarian hyper-stimulation, embryo collection from valuable embryo donors, and embryo transfer (ET) into synchronized recipients (1,2,3.)  This field trial was conducted during late July through early August in southwest Virginia (latitude 36-38’12” N), during a daylight period of about 14 hours. Pregnancy rates of ewes bred by means of AI were compared to those that underwent ET.

Ovine Embryos

Categories: Evidence-Based ET
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Published on: November 2, 2020

In vivo (flush) produced ovine embryos

By Dr Tad Thompson and Dr Leonardo Fernandes – Reproduction Specialty Group Inc. – Lebanon, IN

7 & 7 Synch: An Estrus Synchronization Protocol for Postpartum Beef Cows

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Published on: November 2, 2020

Overview


Researchers at the University of Missouri recently
evaluated a new protocol for synchronization of estrus
among postpartum beef cows. This protocol was found
to be highly effective both for cows receiving embryo
transfer (ET) and cows receiving fixed-time artificial
insemination (AI). Extensive field trials with 7 & 7
Synch observed improvements in the proportion of
cows expressing estrus and in the proportion of cows
becoming pregnant to embryo transfer or to AI.

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