Elements of functional genital asymmetry in the cow

2014 ◽  
Vol 26 (4) ◽  
pp. 493 ◽  
Author(s):  
B. Trigal ◽  
C. Díez ◽  
M. Muñoz ◽  
J. N. Caamaño ◽  
F. Goyache ◽  
...  
Keyword(s):  
Corpus Luteum ◽  
Ovarian Function ◽  
Pregnancy Rates ◽  
Actin Binding ◽  
Complement Factor ◽  
Follicle Diameter ◽  
Ovulatory Follicle ◽  
The Right ◽  
Uterine Proteins

Asymmetry in the cow affects ovarian function and pregnancy. In this work we studied ovarian and uterine asymmetry. Synchronised animals, in which in vitro-produced embryos (n = 30–60) had been transferred on Day 5 to the uterine horn ipsilateral to the corpus luteum (CL), were flushed on Day 8. Ovulatory follicle diameter, oestrus response and total protein flushed did not differ between sides. However, a corpus luteum in the right ovary led to plasma progesterone concentrations that were higher than when it was present in the left ovary. Fewer embryos were recovered from the left than the right horn. Among 60 uterine proteins identified by difference gel electrophoresis, relative abundance of nine (acyl-CoA dehydrogenase, very long chain; twinfilin, actin-binding protein, homologue 1; enolase 1; pyruvate kinase isozymes M1/M2 (rabbit); complement factor B Bb fragment ; albumin; fibrinogen gamma-B chain; and ezrin differed (P < 0.05) between horns. Glucose concentration was higher, and fructose concentration lower, in the left horn. In a subsequent field trial, pregnancy rates after embryo transfer did not differ between horns (51.0 ± 3.6, right vs 53.2 ± 4.7, left). However, Day 7 blood progesterone concentrations differed (P = 0.018) between pregnant and open animals in the left (15.9 ± 1.7 vs 8.3 ± 1.2) but not in the right horn (12.4 ± 1.3 vs 12.4 ± 1.2). Progesterone effects were independent of CL quality (P = 0.55). Bilateral genital tract asymmetry in the cow affects progesterone, proteins and hexoses without altering pregnancy rates.

111 FUNCTIONAL AND MOLECULAR GENITAL ASYMMETRY IN THE COW

2013 ◽  
Vol 25 (1) ◽  
pp. 203
Author(s):  
E. Gómez ◽  
C. Díez ◽  
B. Trigal ◽  
M. Muñoz ◽  
F. Goyache ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Field Experiments ◽  
Ovarian Function ◽  
Early Embryo ◽  
Pregnancy Rates ◽  
Ovulatory Follicle ◽  
Uterine Fluid ◽  
Left And Right ◽  
The Right ◽  
Reproductive Cycles

Bilateral asymmetry in the cow affects ovarian function, uterine horn morphology, pregnancy, and embryonic sex. However, many aspects and molecular mechanisms of such laterality remain obscure. The objective of this work was identifying new traits of ovarian and uterine asymmetry, as based on oestrus and ovarian monitoring, P4 concentrations, early embryo development, flushing performance, and pregnancy outcomes after embryo transfer (ET). In addition, proteins identified in previous work by difference gel electrophoresis and mass spectrometry (DIGE-MS) in uterine fluid (UF) were reanalyzed in a horn-of-origin basis (n = 16 and n = 14 flushes from left and right horns, respectively; Muñoz et al. 2012 J. Proteome Res. 11, 751–766; Gómez et al. 2011 Reprod. Fert. Dev. 24, 152). Studies were performed in experimental herd and on field. Data were analyzed by Proc GLM of SAS/STAT (Version 9.2; SAS Inst. Inc., Cary, NC) and REGWQ test for means. In experimental herd, we analyzed ovarian and uterine asymmetry within animals (n = 25) monitored through different reproductive cycles (n = 109). Animals synchronised with progestagen + PGF2α were alternatively transferred with IVP embryos (n = 30–60) or vehicle (sham transfer) on Day 5 to ipsilateral horn. On Day 8, embryos and/or diluted UF were recovered by flushing with 30 or 45 mL PBS. Nonsignificant differences (P > 0.7) were obtained in ovulatory follicle diameters 48 h after PGF2α injection, onset oestrus time and recoverable total protein by flushing between animals ovulating in the left or in the right ovary. However, cows bearing the corpus luteum (CL) in the right ovary (i.e. right) had higher (26.3 ± 1.5) Day 8 P4 concentration than those showing a CL in the left ovary (i.e. left) (21.6 ± 1.8) (P = 0.03). Fluid recovery (%) was lower in the left (47.0 ± 6.3) than in the right (64.4 ± 5.0) horn when 30 mL were infused (P = 0.035); in contrast, 45 mL infused did not differ between horns (61.6 ± 4.1 v. 67.9 ± 4.1). Less total embryos were recovered from the left (14.6 ± 4.7) than the right (31.0 ± 3.7) horn (P < 0.02), although the relative proportions of viable embryos were conserved. Among 76 proteins analyzed, concentrations of VLCAD, KPYM, CFB, ALB, FGG, EZR, and ACTB were higher (P ≤ 0.05), while TWF1 and ENO1 were lower in the left horn. On field experiments (n = 184 ET in 286 synchronised animals from 39 farms; ≥3 ET per farm) confirmed on Day 7 the above differences in P4 (right: 8.3 ± 0.43 v. left: 6.1 ± 0.55; P = 0.0058). Pregnancy rates after ET did not differ between horns (51.0 ± 3.6, right v. 53.2 ± 4.7, left). However, P4 concentrations differ (P = 0.018) between pregnant and open animals in the left (15.9 ± 1.7 v. 8.3 ± 1.2) but not in the right horn (12.4 ± 1.3 v. 12.4 ± 1.2), respectively. Genital asymmetry in the cow has physical concerns (flushing and recoveries), while changes in P4 and/or proteins could operate to hold similar pregnancy rates between horns. Project AGL2009-10059 (MICINN). MM, BT and EC are sponsored by RYC08-03454, Cajastur and FPU2009-5265, respectively.

108 FACTORS AFFECTING PREGNANCY RATES IN RECIPIENTS RECEIVING IN VITRO-PRODUCED EMBRYOS BY FIXED TIME EMBRYO TRANSFER

2016 ◽  
Vol 28 (2) ◽  
pp. 184
Author(s):  
M. Pelizzari ◽  
A. Tribulo ◽  
J. Garzon ◽  
B. Bernal ◽  
R. Tribulo ◽  
...  
Keyword(s):  
Corpus Luteum ◽  
Embryo Transfer ◽  
Body Condition Score ◽  
Prostaglandin F2α ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Uterine Horn ◽  
Device Removal ◽  
Embryo Transfer Technique

A retrospective analysis of factors that affect pregnancy rates from 4214 fresh in vitro-produced (IVP) embryos that were transferred at a fixed-time (FTET) in 20 different farms. Recipients were all cycling cows or heifers that were synchronized with 1 of 3 treatments: 1) treatments with progesterone (P4) devices and 2 mg of oestradiol benzoate (EB) on Day 0 (day of insertion) and 24 h after device removal (Day 8); 2) treatments with P4 devices and EB on Day 0, but with 0.5 mg of oestradiol cypionate (ECP) at device removal (Day 8); or 3) treatments with P4 devices and GnRH on Day 0 and a second GnRH 60 h after device removal (Day 5). Cows in all treatment groups also received 500 µg of cloprostenol (prostaglandin F2α) at the time of P4 device removal and 400 IU of eCG either at device removal or 3 days before device removal. All embryos were transferred 7 or 8 days after the expected time of oestrus (24 h after EB, 48 h after ECP or at the time of the second GNRH for each synchronization treatment, respectively). On the day of embryo transfer, recipients were examined by ultrasonography and those with corpus luteum >14 mm in diameter received a fresh, IVP embryo in the uterine horn ipsilateral to the corpus luteum. Pregnancy rates were determined by ultrasonography 35 days after FTET. Data were analysed by logistic regression. Independent variables were classified into the following three categories. 1) Factors related to the recipient and the environment; there were no significant differences in pregnancy rates for corpus luteum diameter (≥14 and <16 mm, ≥16 and <18 mm, or ≥18 mm; P = 0.46), number of corpus luteum (1 or ≥2; P = 0.26), and category of recipient (cow or heifer; P = 0.21). However, there were significant effects of farm (P = 0.01) and body condition score (BCS; P = 0.01). Cows with BCS ≥4.5 (1 to 5 scale) resulted in lower pregnancy rates (4/20, 20.0%) than those with BCS 2 (74/225, 32.9%), 2.5 (502/1434, 35.0%), 3 (570/1467, 38.9%), 3.5 (193/532, 36.3%), and 4 (44/118, 37.3%). 2) Factors related to the synchronization treatment; there were no significant differences between recipients receiving eCG at device removal (84/209, 40.2%) or 3 days before device removal (874/2291, 38.1%; P = 0.35). However, recipients synchronized with P4 devices and ECP had higher (P = 0.01) pregnancy rates (232/483, 48.0%) than those treated with EB (679/1888, 36.0%) or gonadotropin-releasing hormone (47/129, 36.4%). 3) Factors related to the embryo transfer technique; day of the recipient’s oestrous cycle (P = 0.36), stage of embryo transferred (IETS stages 6 or 7; P = 0.62), and operator (P = 0.57) did not affect pregnancy rates. However transfers made in the anterior third of the uterine horn resulted in higher (649/1545, 42.0%) pregnancy rates than those in the mid-third (845/2511, 33.6%) or in the distal third (6/35, 17.1%; P = 0.01). It was concluded that factors related to the recipient and the environment (farm and BCS), the synchronization treatment (ECP), and the embryo transfer technique (site of deposition) affect pregnancy rates in recipients of embryos produced in vitro and transferred at a fixed time.

IN-VITRO STEROIDOGENESIS OF NEWLY FORMED CORPORA LUTEA AND THE NON-LUTEAL OVARY IN THE RAT, RABBIT, HAMSTER AND GUINEA-PIG

1980 ◽  
Vol 84 (1) ◽  
pp. 101-108 ◽  
Author(s):  
P. F. TERRANOVA ◽  
S. K. SAIDAPUR ◽  
G. S. GREENWALD
Keyword(s):  
Guinea Pig ◽  
Corpus Luteum ◽  
Ovarian Function ◽  
Serum Testosterone ◽  
The Other ◽  
Corpora Lutea ◽  
Serum Progesterone ◽  
Antral Follicles ◽  
Baseline Levels

The steroidogenic abilities of the newly formed corpus luteum (8–10 h after ovulation) and the non-luteal ovary were compared in the guinea-pig, hamster, rabbit and rat using an invitro incubation technique. Histologically, newly formed rat corpora lutea (CL) were highly luteinized whereas the CL of the rabbit and guinea-pig were only partially luteinized. The CL of the hamster showed the least amount of luteinization. Serum progesterone was highest in the rat (18 ± 3 (s.e.m.) ng/ml). In the hamster, it was about 8 ng/ml, whereas in the rabbit and guinea-pig it was about 1 ng/ml. Serum androstenedione ranged between 0·5 and 1 ng/ml. Serum testosterone was lowest in the hamster (60 pg/ml) and highest in the rabbit (470 pg/ml), whereas in the rat and guinea-pig, testosterone levels were similar (about 240 pg/ml). Serum oestrogens were at baseline levels in all species. The CL of the rat exhibited considerably greater steroidogenic ability than the CL of the other species, producing 70 ± 6 ng progesterone/mg per h, 215 ± 14 pg androstenedione/mg per h, 49 ± 3 pg testosterone/mg per h, 3 pg oestrone/mg per h and 1 pg oestradiol/mg per h. Rabbit CL produced only progesterone (7 ± 2 ng/mg per h). Newly formed hamster CL produced none of the above steroids. In general, the ability of the CL to produce progesterone in vitro correlated with the degree of luteinization found by histological observation. Guinea-pig CL were embedded deeply in the ovary and could not be obtained without damage. Consequently, a portion of the ovary containing a corpus luteum was incubated. There was no difference in the steroid production by this portion of the ovary compared with the non-luteal ovary. The non-luteal ovary of the rat produced the highest amount of progesterone (10 ± 2 ng/mg per h). The guinea-pig non-luteal ovary produced about 5 ± 2 ng progesterone/mg per h, whereas the non-luteal ovary of the rabbit did not produce any. On the other hand, the hamster non-luteal ovary lost progesterone. Non-luteal ovaries from all species produced androgens. The non-luteal ovary of the guinea-pig contained especially large numbers of atretic antral follicles. The guinea-pig non-luteal ovary produced extremely large amounts of androstenedione (1110 ± 210 pg/mg per h) and testosterone (606 ± 154 pg/mg per h) compared with the amounts produced by the non-luteal ovary of the rat, hamster and rabbit. In the non-luteal ovary, interstitium and atretic antral follicles are the probable source of androgens. Oestrogen production by the non-luteal ovary was at baseline levels in the four species studied correlating with the absence of healthy antral follicles. The results indicate the extreme species differences that exist in ovarian function in the early postovulatory period.

scholarly journals Evaluation of forage soybean, with and without pearl millet, as an alternative for beef replacement heifers1

2017 ◽  
Vol 1 (2) ◽  
pp. 179-185
Author(s):  
E. G. Taylor ◽  
P. J. Gunn ◽  
L. A. Horstman ◽  
R. L. Atkinson ◽  
K. Herron ◽  
...  
Keyword(s):  
Pearl Millet ◽  
Body Condition Score ◽  
Control Diet ◽  
Latin Square ◽  
Reproductive Function ◽  
Pregnancy Rates ◽  
Beef Heifers ◽  
Estrous Synchronization ◽  
Follicle Diameter ◽  
Ovulatory Follicle

Abstract Apparent ruminal digestibility of forage soybean-based silages, with and without pearl millet, was determined along with evaluation of silages on heifer performance and reproductive function. Fermenters were utilized in a Latin square design and randomly assigned to 1 of the following treatments: 1) control diet of alfalfa haylage (CON), 2) soybean silage (SB) or 3) soybean and pearl millet silage (SB×PM). All diets were formulated to meet or exceed nutrient requirements of replacement beef heifers targeted to gain 0.79 kg/d. These same diets were fed to 90 Angus-Simmental beef replacement heifers [body weight (BW) = 366 kg; body condition score (BCS) = 5.53; age = 377 ± 11 d] 65 d prior to timed artificial insemination (TAI). Heifers were randomly allotted by breed, BCS and BW to 1 of the 3 treatments, with 3 reps/treatment. Diets were terminated 21 d post-TAI and heifers were commingled and placed on a common diet. Pubertal status was determined by progesterone concentrations of 2 blood samples taken 10 d apart prior to both trial initiation as well as initiation of estrous synchronization. Ovulatory follicle diameter was determined at time of breeding by ultrasonography. Pregnancy diagnosis was accomplished 35 and 66 d post-TAI, respectively, to calculate TAI and end of season pregnancy rates. Neither SB nor SB×PM had an effect (P &gt; 0.37) on apparent ruminal digestion of nutrients compared to the CON. Final BW (414 kg; P ≥ 0.10) and BCS (5.28; P ≥ 0.26) for the heifers were similar among treatments. Likewise, there were no differences in TAI (48%; P &gt; 0.43) or overall breeding season (93%; P &gt; 0.99) pregnancy rates. Ovulatory follicle diameters (11.7 mm) was not different (P &gt; 0.19) among treatments. In summary, forage soybean-based silages, with and without pearl millet, was an acceptable alternative forage for developing replacement beef heifers.

Role of progesterone in embryo development in cattle

2016 ◽  
Vol 28 (2) ◽  
pp. 66 ◽  
Author(s):  
Pat Lonergan ◽  
Niamh Forde ◽  
Thomas Spencer
Keyword(s):  
Corpus Luteum ◽  
Embryo Development ◽  
Early Pregnancy ◽  
Pregnancy Rates ◽  
In Vitro Experiments ◽  
Conceptus Development

Progesterone (P4) from the corpus luteum is critical for the establishment and maintenance of pregnancy and plays a major role in regulating endometrial secretions essential for stimulating and mediating changes in conceptus growth and differentiation throughout early pregnancy in ruminants. Numerous studies have demonstrated an association between elevated systemic P4 and acceleration in conceptus elongation. A combination of in vivo and in vitro experiments found that the effects of P4 on conceptus elongation are indirect and mediated through P4-induced effects in the endometrium. Despite effects on elongation, data on the effects of post-insemination supplementation with P4 on pregnancy rates are conflicting. This review highlights the effects of P4 on conceptus development and examines strategies that have been undertaken to manipulate P4 concentrations to increase fertility.

scholarly journals Myxoma Virus Encodes an α2,3-Sialyltransferase That Enhances Virulence

1999 ◽  
Vol 73 (3) ◽  
pp. 2376-2384 ◽  
Author(s):  
Ronald J. Jackson ◽  
Diana F. Hall ◽  
Peter J. Kerr
Keyword(s):  
Lectin Binding ◽  
Virus Genome ◽  
Myxoma Virus ◽  
Early Gene ◽  
Actin Binding ◽  
Immunoglobulin Superfamily ◽  
Sialyltransferase Activity ◽  
The Right

A 4.7-kb region of DNA sequence contained at the right end of the myxoma virus EcoRI-G2 fragment located 24 kb from the right end of the 163-kb genome has been determined. This region of the myxoma virus genome encodes homologs of the vaccinia virus genes A51R, A52R, A55R, A56R, and B1R; the myxoma virus gene equivalents have been given the prefix M. The MA55 gene encodes a protein belonging to the kelch family of actin-binding proteins, while the MA56 gene encodes a member of the immunoglobulin superfamily related to a variety of cellular receptors and adhesion molecules. A novel myxoma virus early gene, MST3N, is a member of the eukaryotic sialyltransferase gene family located between genes MA51 and MA52. Detergent lysates prepared from myxoma virus-infected cell cultures contained a virally encoded sialyltransferase activity that catalyzed the transfer of sialic acid (Sia) from CMP-Sia to an asialofetuin glycoprotein acceptor. Analysis of the in vitro-sialylated glycoprotein acceptor by digestion withN-glycosidase F and by lectin binding suggested that the MST3N gene encodes an enzyme with Galβ1,3(4)GlcNAc α2,3-sialyltransferase specificity for the N-linked oligosaccharide of glycoprotein. Lectin binding assays demonstrated that α2,3-sialyltransferase activity is expressed by several known leporipoxviruses that naturally infect Sylvilagus rabbits. The sialyltransferase is nonessential for myxoma virus replication in cell culture; however, disruption of the MST3N gene caused attenuation in vivo. The possible implications of the myxoma virus-expressed sialyltransferase in terms of the host’s defenses against infection are discussed.

scholarly journals FSH withdrawal improves developmental competence of oocytes in the bovine model

Reproduction ◽  
2012 ◽  
Vol 143 (2) ◽  
pp. 165-171 ◽  
Author(s):  
Anne-Laure Nivet ◽  
Audrey Bunel ◽  
Rémi Labrecque ◽  
Josée Belanger ◽  
Christian Vigneault ◽  
...  
Keyword(s):  
Developmental Competence ◽  
Success Rates ◽  
Oocyte Competence ◽  
Follicle Diameter ◽  
Follicle Size ◽  
Competence Acquisition ◽  
The Right ◽  
Scheduled Time

Combinations of genetic, environmental, and management factors are suspected to explain the loss in fertility observed for over 20 years in dairy cows. In some cases, IVF is used. When compared with in vivo embryo production, IVF resulted in low success rates until the FSH coasting process (FSH starvation after superstimulation) was introduced in 2002. Increased competence associated with FSH withdrawal of aspirated oocyte for in vitro maturation and IVF has not been optimized nor explained yet. The goal here was to determine and characterize the optimal oocyte competence acquisition window during the coasting period by determining blastocyst rates and follicular cohort development. Commercial milking cycling cows (n=6) were stimulated with 3 days of FSH (6×40 mg NIH Folltropin-V given at 12 h intervals) followed by a coasting period of 20, 44, 68, or 92 h. Each animal was exposed to the four conditions and served as its own control. At the scheduled time, transvaginal aspirations of immature oocytes were performed followed by IVF of half the oocytes. The outcomes were as follows: i) FSH coasting was optimal at a defined period: between 44 and 68 h of coasting; ii) The best estimated coasting duration was ∼54±7 h; iii) Under these conditions, the best statistical blastocyst rate estimation was ∼70%; iv) Between 44 and 68 h of coasting, follicle size group proportions were similar; v) Follicle diameter was not linearly associated with competence. In conclusion, coasting duration is critical to harvest the oocytes at the right moment of follicular differentiation.

40 TIMING OF INSEMINATION WITH SEXED OR NONSEXED SEMEN ON PREGNANCY RATES OF JERSEY HEIFERS DETECTED IN HEAT BY RADIOTELEMETRY

2010 ◽  
Vol 22 (1) ◽  
pp. 178 ◽  
Author(s):  
J. N. S. Sales ◽  
G. A. Crepaldi ◽  
M. Fosado ◽  
E. P. Campos Filho ◽  
P. S. Baruselli
Keyword(s):  
Pregnancy Rate ◽  
Detection System ◽  
Pregnancy Rates ◽  
Conception Rate ◽  
Follicle Diameter ◽  
Ovulatory Follicle ◽  
Estrus Detection ◽  
Sexed Semen ◽  
Freezing Procedure ◽  
Follicular Dynamics

The objectives of this study were to evaluate the follicular dynamics (experiment 1) and the effects of the timing of insemination with sexed or nonsexed semen on pregnancy rates (experiment 2) of Jersey heifers detected in heat by a radiotelemetric estrus detection system. In experiment 1, 43 Jersey heifers, around 12 mo old and BCS of 2.68 ± 0.11 (1 to 5 scale) were used. The Heat Watch (HW) system was utilized to detect the onset of estrus and mounting behavior associated with estrus. Ultrasound examinations to monitor follicular dynamics occurred every 12 h from estrus onset for 48 h. Statistical analyses were performed using GLM and GLIMMIX procedure of SAS (SAS Institute, Cary, NC, USA). The results of experiment 1 indicated a mean ovulatory follicle diameter of 14.1 ± 0.3 mm, ovulation rate of 86.1% (37/43), and an interval of 31.2 ± 0.9 h from onset of heat to ovulation. In experiment 2, 753 Jersey heifers were allocated in a 2 × 4 factorial with semen (sexed and nonsexed) and AI period (0 to 6, 6 to 12, 12 to 18, and 18 to 24 h after heat onset) as parameters. Semen from 3 bulls was used, with ejaculates divided in 2 fractions: one fraction was submitted to the traditional freezing procedure and the other was submitted to the sexing process and then frozen. The statistical analysis was performed using GLIMMIX procedure of SAS. There was no interaction among the semen, bull, and AI period. There were effects on pregnancy rate by type of semen [sexed 49.5% (189/382) and nonsexed 64.2% (238/371); P = 0.001] and by bull [bull A 53.5% (107/200)b, bull B 50.0% (108/216)b and bull C 63.4% (211/333)a; P = 0.008]. Semen from bull C resulted in a greater pregnancy rate for both sexed and nonsexed semen. Within semen type, there were no differences in pregnancy rates by AI moment [sexed: 0 to 6 h 48.2% (41/85), 6 to 12 h 48.7% (54/111), 12 to 18 h 49.5% (49/99), 18 to 24h 52.4% (44/84) and nonsexed: 0 to 6h 62.8% (49/78), 6 to 12h 60.6% (63/104), 12 to 18h 68.0% (68/100), 18 to 24h 64.8% (57/88); P = 0.77]. We conclude that the use of sexed semen resulted in a lower pregnancy rate than nonsexed semen, and that AI timing does not affect conception rate in Jersey heifers identified in estrus by radiotelemetric estrus detection system. However, there was a bull effect on conception rate. The authors wish to thank Sexing Technologies and Dalhart Jersey Ranch.

83 Pregnancy losses after transfer of bovine embryos produced by assisted reproductive technologies

2019 ◽  
Vol 31 (1) ◽  
pp. 167
Author(s):  
L. F. Feres ◽  
M. P. Palhao ◽  
L. G. B. Siqueira ◽  
J. H. M. Viana
Keyword(s):  
Risk Factors ◽  
Developmental Stage ◽  
Corpus Luteum ◽  
Pregnancy Loss ◽  
Assisted Reproductive Technologies ◽  
Reproductive Technologies ◽  
Quality Score ◽  
Pregnancy Rates ◽  
Embryo Production

The aim of this study was to evaluate risk factors for pregnancy loss in embryo recipients. We evaluated data from 31,792 embryo transfers (ET), including 859 embryos derived in vivo (IVD), 28,814 produced in vitro (IVP), and 2,119 produced by somatic cell nuclear transfer (SCNT), recorded from 2008 to 2012 on a single commercial farm. Embryos were produced by different in vitro embryo production laboratories, but ET was performed by the same team and within the same herd. Recipients were checked for pregnancy (PR) by ultrasonography 23 days after ET and re-examined on Days 60, 90, and 120 of gestation to identify pregnancy losses (PL). Data were analysed for the main effect of embryo production technique upon PL. For IVD and IVP embryos only, additional risk factors were included in the statistical model, including cryopreservation, type of semen (conventional, sex-sorted, reverse sex-sorted), embryo developmental stage, recipient corpus luteum quality score, use of natural oestrus or synchronization protocol, embryo-recipient synchrony, embryo genetics (taurine v. zebu, dairy v. beef), season (summer v. winter), and fetal sex. Data were analysed using the GLIMMIX procedure of the SAS Software (v 9.3, SAS Institute Inc., Cary, NC, USA). Overall PR was 42.1% (13,395 of 31,792) and PL between days 30 and 60, 60 and 90, and &gt;90 were 8.7, 5.3, and 3.5%, respectively (cumulative PL=17.4%). The SCNT embryos had lower PR compared to IVP and IVD embryos (36.6, 42.5, and 44.2%, respectively; P&lt;0.001) as well as a greater PL in all periods (30-60=45.2, 6.4, and 8.2%; 60-90=3.5, 1.4, and 1.8%; and &gt;90=21.4, 6.3, and 7.1%, respectively; P&lt;0.0001). The PR was similar between fresh and frozen embryos, but lower for vitrified ones (42.9, 43.1, and 39.1%, respectively, P&lt;0.05). Slow freezing resulted in a greater total PL compared to fresh embryos (18.0v. 13.9%, respectively; P&lt;0.05). We observed an interaction between embryo genetics and season. The taurine dairy subgroup had the lowest PR during summer (37.7v. &gt;41.7% in all other groups; P&lt;0.01), but within this group PR increased during winter (37.7v. 44.6%, P&lt;0.05). The PL was greater for taurine than zebu during summer (17.8v. 14.0%; P&lt;0.001), but did not differ during winter (P&gt;0.05). The type of semen, embryo developmental stage, corpus luteum quality score, and embryo recipient synchrony affected pregnancy rates (P&lt;0.05) but not pregnancy losses (P&gt;0.05). Interestingly, the use of ovulation synchronization protocols resulted in similar pregnancy rates but greater pregnancy losses compared to natural oestrus (41.8v. 43.2%, P&gt;0.05; and 15.9v. 22.1%, P&lt;0.05, respectively). Pregnancy loss after 60 days was similar between female and male fetuses (5.0v. 4.9%, respectively; P&gt;0.05). In summary, the assisted technology used to produce and freeze embryos was the main cause of variation in pregnancy losses, which were also affected by the interplay of season by genetic background and by the use of synchronization protocols. Conversely, factors known to affect pregnancy rates, such as embryo developmental stage, corpus luteum quality, and embryo-recipient synchrony, had no effect upon pregnancy loss. Research was supported by Mineirembryo, CAPES, and FAPDF.

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