To Timed Artificial Insemination Research Articles

Field assessment of a BCS measuring device at timed AI in crossbread dairy cows of Amazonian smallholders

ABSTRACT This study aimed to evaluate the efficiency of a body condition score (BCS) assessment device (BCAD) to identify cows with an adequate BCS and, presumably, a higher fertility when subjected to timed artificial insemination (TAI). We evaluated cows at smallholder dairy farms in the state of Rondonia, Brazil. Crossbred dairy cows (n = 141) were subjected to a TAI protocol and classified according to the BCAD scale as low BCS (red; n = 55) or adequate BCS (green; n = 86). The outcome pregnancy per artificial insemination (P/AI) was analyzed by logistic regression. Cows classified as green by the BCAD had a significantly greater P/AI (41 of 86; 47.7%) than cows classified as red (15 of 55; 27.3%; P = 0.01). In conclusion, the BCS assessment device was an effective tool to detect cows more likely to become pregnant due to their adequate BCS and, consequently, better fertility in TAI.

Effect of increased serum progesterone on luteal morphology and function, pregnancy, and gestational loss in Nelore cows.

The aim of the present study was to determine the impact of different strategies for increasing the level of serum progesterone (P4) on luteal morphology and function in bovine females. The effects of increasing P4 on pregnancy rate and gestational loss (GL) in Nelore cows subjected to timed artificial insemination (TAI) were also evaluated. A total of 939 cows were divided into three groups: P4LA (n=305), 150 mg of long-acting injectable P4 7 days after TAI; GnRH (n=306), 10μg of buserelin acetate 7 days after TAI; and control (n=328), no hormone treatment after TAI. Doppler ultrasound assessments and P4 measurements were performed on days 7 and 16 after TAI. The pregnancy rate and GL as a function of treatment were compared using the SAS GLIMMIX procedure. Corpus luteum (CL) vascular perfusion, volume, and plasma P4 concentration were analysed using the SAS PROC MIXED procedure. No significant difference was found among the treatments in terms of volume, number of pixels, and CL intensity or in the serum P4 concentration at 7 days after ovulation. The CL blood flow at 16 days after ovulation was lower in the P4LA and GnRH groups than that in the control group (p < .01). Serum concentrations of P4 at 16 days after ovulation were higher in the P4LA and GnRH groups than those in the control group (p=.04). A difference in the pregnancy rate (p=.003) and a trend in GL (p=.07) as a function of treatment were found. Overall, long-acting injectable P4 supplementation on day 7 after TAI or GnRH administration affected CL vascularization and increased the serum concentrations of P4 16 days after ovulation, promoting better pregnancy rates than the control.

PSV-B-16 Correlation between Plasma, Uterine, and Vaginal Cytokine Concentrations in Postpartum Beef Cows Prior to Artificial Insemination

Abstract Cytokines have a vital role in reproductive immune environment during the postpartum period. Previous data evaluated uterine and vaginal cytokine concentrations prior to insemination; however, was unable to correlate these data with plasma cytokine concentrations. The objective of this study was to determine relationships between uterine, vaginal, and plasma pro- and anti-inflammatory cytokine concentrations in postpartum beef cows prior to timed artificial insemination (TAI). Bos indicus-influenced beef cows (n=20) free of any physical, health or reproductive-related issues were subjected to the Bee Synch II protocol 8 days prior (d-8) to TAI (d0). Uterine and vaginal flushes and blood were collected on d-3 and d-1. Pregnancy was determined by transrectal ultrasonography on d28 (Pregnant, n=7; Open, n=13). Using the RayBiotech Quantibody Bovine Cytokine Array 1 the following cytokines concentrations were determined: interferon (IFN)-α, IFN-γ, interleukin (IL)-13, IL-1α, IL-1-F5, IL-21, tumor necrosis factor (TNF)-α, chemokine ligand (CXCL)-9, CXCL-10, and chemokine ligand 4 (CCL4). Concentration data were analyzed using PROC GLM and correlations using Pearson correlation in SAS. For plasma samples, 8 pro-inflammatory cytokines (IFN-α, IFN-γ, IL-13, IL-1α, IL-1-F5, IL-21, CXCL-9, and TNF-α) had greater (P&amp;lt; 0.05) concentrations in open cows compared with pregnant cows. For uterine flushes, 3 pro-inflammatory cytokines (IFN-γ, IL-1α, and IL-21) had greater (P&amp;lt; 0.05) concentrations in open cows compared with pregnant cows. For vaginal flushes, IFN-α concentrations were greater (P&amp;lt; 0.05) in open cows, while CXCL-10 concentrations were greater in pregnant cows. There were no significant correlations between plasma and uterine or vaginal samples (P&amp;gt;0.05). Interestingly, for open cows there were correlations for IFN-α (r=0.46; P=0.02), IFN-γ (r=0.58; P=0.002), and IL-21 (r=0.54; P=0.004) between uterine and vaginal samples; however, no correlations were observed for pregnant cows. These results suggest a greater abundance of pro-inflammatory cytokines within the uterus, vagina, and in peripheral circulation for resulting open cows prior to TAI.

Mitigation of low pregnancy rate in excitable Nellore cows by administration of GnRH or P4

This research aimed to determine the effect of temperament on reproductive parameters including cortisol and progesterone (P4) in Nellore cows. Additionally, two methods for increasing plasma progesterone (P4) levels in excitable animals to enhance pregnancy rate (P/AI) and reduce pregnancy loss were investigated. In total, 939 cows were subjected to timed artificial insemination (TAI) and divided into three groups: (P4LA; n = 305) 150 mg of injectable long-acting progestogen 7 days after TAI; (GnRH; n = 306), 10 μg of buserelin acetate on day 7 after TAI; control group (CG; n = 328) without hormonal treatment. In 213 cows, randomly chosen from each group, ultrasound evaluations of the preovulatory follicle (Mode B) were performed on the day of insemination and of the corpus luteum (Color Doppler) 7 and 16 days after TAI. Blood samples were obtained from 20% of the 939 animals, randomly chosen from each group, on the day of insemination and after 7 and 16 days to measure cortisol and progesterone, respectively. At the time of insemination, subjective temperament evaluations were performed with the animals being classified as excitable (EXC) or adequate (ADQ). The SAS GLIMMIX procedure was used to compare the pregnancy rate (P/AI) and gestational loss within each temperament for the three experimental groups. Continuous variables were analyzed utilizing SAS PROC MIXED procedure. Cortisol concentration was higher and POF (preovulatory follicle) and CL (corpus luteum) volumes at the time of insemination and 7 days after AI, respectively, were lower in EXC animals than in ADQ. No significant difference was observed between the number of pixels, CL intensity, and plasma concentration of P4, 7 days after TAI. However, 16 days post-insemination, among the animals classified as EXC, higher concentrations of P4 were observed in the GnRH and P4LA groups than in the control. Regarding P4 concentrations, there was a tendency to be lower in animals classified as EXC than in ADQ within the control group (P = 0.06), while rate of blood flow from the CL was lower in EXC animals than in ADQ animals (P = 0.04). Among the ADQ animals, the GnRH and P4LA groups showed a lower CL flow rate than that observed in the control (P = 0.04), 16 days after the TAI. Among EXC animals, a higher pregnancy rate was observed in the GnRH and P4LA groups than in the control group (P = 0.01). In the control group, the pregnancy rate (P/AI) of the ADQ animals was higher than that of the EXC animals (P = 0.05). No statistically significant differences were observed between gestational losses when the treatments or temperaments were compared. In conclusion, the use of GnRH or P4LA, 7 days after insemination, improves pregnancy rates in excitable animals and is a viable alternative to minimize the negative impact of stress and improve reproductive efficiency in beef cattle.

Taxa de concepção de acordo com o touro, escore de condição corporal e ocorrência de estro em vacas de corte Bos taurus lactantes submetidas à inseminação artificial em tempo fixo

ABSTRACT The objective of this study was to investigate the effect of estrus expression, body condition score (BCS), different sires and semen batches on the conception rate of suckled Bos taurus beef cows submitted to timed artificial insemination (TAI). Data from 7,737 TAI were obtained from five farms in South Brazil. Cows received an estradiol plus progesterone-based estrous synchronization protocol. Only sires (n = 13) with at least two semen batches and 50 AI in two different lots were included in the study. Conception rate was higher for cows in estrus (66.8% vs. 26.3%) or with BCS ≥ 3 (57.2% vs. 51.6%) than in cows without estrus or BCS &lt; 3, respectively (P≤0.001). Conception rate per sire ranged from 42.6% (Sire L) to 74.3% (Sire K). Conception rate in cows with BCS ≥ 3 and estrus occurrence varied from 47.4% (Sire L) to 86.1% (Sire A) among sires. Conception rate differed among semen batches of the same sire (B1 = 58.5%, B2 = 62.5%, and B3 = 83.2%). In conclusion, there was individual variation in conception rate among AI sires and semen batches within sires. The conception rate was increased by estrus occurrence and greater BCS.

Evaluation of three classification methods of antral follicle count and fertility to the timed artificial insemination in cattle.

The controversial data about antral follicle count (AFC) may be partially explained by the different criteria used to determine what is high, intermediate and low AFC. This study evaluated different classification methods for AFC groups, relating them to the conception rate, dominant follicle size and body condition score (BCS) in cows submitted to timed artificial insemination (TAI). Nelore cows (Bos indicus; n = 935), received a reproductive program consisting of TAI and natural breeding. Conception rate, BCS and dominant follicle size during TAI were evaluated by three AFC methodologies: i) mean and standard deviation: low (≤ 15 follicles); intermediate (≥ 16 to ≤ 44 follicles) or high (≥ 45 follicles); ii) quartiles: low (≤ 15 follicles); intermediate (≥ 16 to ≤ 39 follicles), or high (≥ 40 follicles); and iii) AFC score: I (low; ≤ 15 follicles); II (intermediate; ≥ 16 to ≤ 30 follicles); III (high; ≥ 31 to ≤ 44 follicles) or IV (very high; ≥ 45 follicles). Data were analyzed by a GLIMMIX and Tukey test or binary logistic regression model (P ≤ 0.05). The conception rate to TAI was influenced (P < 0.05) by AFC in the three methods classification, being the highest conception rate observed in the low AFC group regardless of method utilized: Mean (low 61.73%a, intermediate 54.02%ab and high 49.48%b), Quartiles (low 61.73%a, intermediate 53.59%ab and 51.46%b) and Score (I 61.73%a, II 54.80%ab, III 53.23%ab and IV 49.48%b). There were variations (P < 0.05) in the conception rate within the 2.50 to 2.75 BCS range for all AFC classification methods, with the low AFC females presenting the best results, regardless of the method used. Also, females with low AFC showed larger (P < 0.05) diameters of dominant follicles at the TAI regardless of method. The different methodologies used (Mean, Quartile and Score) to AFC classification showed a consistency between the main findings, and we believe that this standardization will facilitate the interpretation of data involving AFC.

Vascular perfusion and the volume of the preovulatory follicle are affected by the temperament of Nellore cows

The aim of this study was to evaluate the effect of temperament on vascular perfusion and morphological characteristic (volume) of the preovulatory follicle (POF) and corpus luteum (CL) of Nellore cows submitted to timed artificial insemination (TAI). The effect of temperament on cortisol, P4 concentrations and on ovulation rates was also evaluated. To achieve this, the ovarian cycles of 201 beef cows were synchronized, and temperament assessments were carried out using the chute score and chute exit score at the time of TAI. According to the individual scores, the animals were classified into adequate temperament (ADQ) or excitable (EXC). Blood samples were collected at the time of TAI and 7 days later to measure cortisol and P4, respectively. Color Doppler ultrasound assessments were performed to determine the volume, and blood flow of the POF and CL at the time of TAI (D0) and seven days later (D7), respectively. The ovarian cycle synchronization and ovulation rates were compared between the ADQ and EXC groups using the chi-square test while hormonal concentrations and ultrasound variables were compared using a general linear model. Multiple comparisons between groups were conducted using Tukey's contrasts. The data were expressed as means and standard error. The number of color pixels (p ≤ 0.01), intensity of color pixels (p ≤ 0.01) and volume (p ≤ 0.01) in the POF were all lower for the EXC group. However, cortisol concentrations were higher in the EXC group compared to the ADQ (p ≤ 0.01). This was related to stress during TAI management. The number and intensity of the color pixels in the CL showed no difference between groups, however, the volume was lower (p ≤ 0.01) for the EXC group. There was no difference between groups regarding ovarian cycle synchronization, ovulation rates and P4 concentration. However, the P4/CL volume ratio was higher in the EXC group. The results indicate that the excitable temperament in Nellore cows has important endocrine effects and reflects on the ovarian structures, with less follicular blood flow and a reduction in the volume of the POF and CL, however, without compromising the ovulation rate.

PSX-B-15 Real-time quantitative PCR versus droplet digital PCR for measurement of peripheral blood leukocytes interferon-tau stimulated genes in beef cattle

Abstract We aimed to compare the abundance of interferon-tau stimulated genes (ISG) transcripts in peripheral blood leukocytes of artificially inseminated beef cows using real-time quantitative PCR (RT-qPCR) versus Droplet Digital PCR (ddPCR). Multiparous Bos taurus beef cows (n = 7) were subjected to timed artificial insemination (TAI) on day 0. Pregnancy was determined by transrectal ultrasonography on days 26 and 30 post-TAI, and cows were classified as: pregnant (n=4; embryo detected on days 26 and 30) or non-pregnant (n = 3; no embryo detected). Coccygeal vein blood samples were collected on days 0, 15, 17, 19, 20 and 24 post-TAI. Leukocyte RNA was extracted from the buffy coat fraction using Trizol associated with the DirectZol-RNA kit and transcribed to cDNA. The abundance of ISG (ISG15 and MX2) was assessed by relative quantification to a reference gene (RPS9) using RT-qPCR and by absolute quantification using the QX100TM Droplet DigitalTM PCR System (Bio-rad Laboratories) according to manufacturer’s recommendations. Data were analyzed using PROC MIXED on SAS 9.4. For the RT-qPCR, pregnant cows had greater (P &amp;lt; 0.05) ISG15 and MX2 abundance compared to non-pregnant cows on days 20 (ISG15:0.11±0.1 vs. 0.01±0.001 and MX2:0.73±0.4 vs. 0.06±0.06) and 24 (ISG15:0.34±0.2 vs. 0.01±0.001 and MX2:0.77±0.2 vs. 0.13±0.04). For ddPCR, a greater ISG15 and MX2 copy numbers in pregnant cows was observed on days 15 (ISG15:129 vs. 44 copies/µl and MX2:33 vs. 10 copies/µl) and 20 (ISG15: 216 vs. 30 copies/µl and MX2: 44 vs. 7 copies/µl), and also on day 24 for ISG15 (32 vs. 7 copies/µl) compared to non-pregnant cows. In conclusion, ddPCR was able to detect an earlier expression of ISG in pregnant cows. Future studies are needed to enroll more animals and establish a suitable cutoff value using ddPCR, which could be less subjective for diagnosis as it does not require the use of a reference gene.

COMPARISON OF PROTOCOLS FOR TIMED ARTIFICIAL INSEMINATION BY ONE OR TWO ARTIFICIAL INSEMINATIONS AND BY RESYNCHRONIZATION OF OVULATION IN BOS TAURUS INDICUS COWS

The goals were to compare the conception rate in cows subjected to timedartificial insemination (TAI) with one AI, two AIs, or resynchronization (RES), and verify the effects of POF (preovulatory follicle) diameter on the CR. Two hundred and seventyfour cows (Bos taurus indicus) were assigned. In the group with one AI (1AIG; n=88), cows were subjected to intravaginal P4 and EB (2mg, IM) on day zero (D0); PGF2α (500μg, IM) on D7; P4 removal on D8; EB on D9; TAI and ultrasonography for POF diameter measurement on D10; PD (pregnancy diagnosis) and natural service on D41; bull removal on D90; and final PD on D110. The same protocol was used in the two AI (2AIG; n=88), except a second AI 20h after the first AI. The resynchronization group (RESG; n=98) was subjected to the same protocol as 1AIG, except a PD was performed on D40, and the non-pregnant cows received the P4 device and EB; PGF2α on D47; P4 removal on D48; EB was administered on D49; TAI was performed on D50; PD was performed, and bulls were introduced on D80; bulls’ removal on D110; final PD on D160. CR of 50, 58, and 73.4% were observed in 1AIG, 2AIG, and RESG, respectively, increasing to 85.2, 88.6, and 87.7% after natural service. The POF diameter at the first TAI was 12.8, 12.1, and 12.7mm in 1AIG, 2AIG, and RESG, respectively, and 12.6mm in RESG and 13.6mm in 2AIG (P=0.031) at the second AI. Groups 1 and 02 inseminations remained with bulls for 49 days and resynchronization for 30 days. In conclusion, RESG yielded a higher CR than TAI with one or two AIs. AI with follicles larger than 12.1mm resulted in a higher CR.

Short communication: Effect of timing of induction of ovulation relative to timed artificial insemination using sexed semen on pregnancy outcomes in primiparous Holstein cows

Our objective was to determine the effect of increasing the interval from induction of ovulation to timed artificial insemination (TAI) on fertility by decreasing the interval from TAI to ovulation using sexed semen within a synchronized breeding program. Our hypothesis was that induction of ovulation earlier relative to TAI would increase pregnancies per artificial insemination (P/AI). Primiparous Holstein cows from 3 commercial dairy farms in the United States were submitted to a Double-Ovsynch protocol for first service as follows: Pre-Ovsynch (GnRH; 7 d, PGF2α; 3 d, GnRH), followed 7 d later by Breeding-Ovsynch [GnRH (G1); 7 d, PGF2α; 24 h, PGF2α], followed by the last GnRH treatment (G2), which varied between treatments, and TAI. To vary the interval between G2 and TAI, cows were randomized to 2 treatments to receive G2 either 16 (G2-16; n = 373) or 24 (G2-24; n = 357) h before TAI, which was fixed at 48 h after the second PGF2α treatment of the Breeding-Ovsynch portion of the protocol. All cows were inseminated with sexed semen, and each herd used sires of their choosing, which were randomly allocated between treatments. Pregnancy diagnosis was conducted by herd veterinarians using transrectal ultrasonography. In disagreement with our hypothesis, G2-24 cows had fewer P/AI than G2-16 cows at 34 ± 3 d (44 vs. 50%) and 80 ± 17 d (41 vs. 48%) after TAI. Pregnancy loss (5 vs. 6%) and fetal sex ratio (92:8 vs. 90:10, female:male) did not differ between treatments for G2-16 and G2-24 cows, respectively. Thus, we reject our hypothesis and conclude that induction of ovulation earlier relative to TAI with sexed semen for first service after a Double-Ovsynch protocol decreased P/AI in primiparous Holstein cows.

Anti-Mullerian hormone and its relationship to ovulation response and fertility in timed AI Bos indicus heifers.

This study evaluated the association between plasma anti-Mullerian hormone (AMH) concentration and fertility in Nelore (Bos indicus) heifers submitted to timed artificial insemination (TAI). At the onset of the synchronization protocol, heifers (n=289) received a subcutaneous P4 ear implant (3mg) and 2mg of oestradiol benzoate. Eight days later, the P4 implant was removed and 0.5mg of oestradiol cypionate, prostaglandin (0.265mg, i.m.) and equine chorionic gonadotropin (300UI, i.m.) was administered, and TAI was performed 48hr after ear implant removal. Ovarian ultrasound evaluations were performed to measure number of ovarian follicles, dominant follicle size and ovulation response. Pregnancy diagnosis was performed by ultrasound 30days after AI. Heifers with greater circulating AMH had more antral follicles, a smaller dominant follicle near timed ovulation and lower ovulation response to the timed AI protocol compared to heifers with lower circulating AMH. Although AMH and pregnancy outcome had a quadratic-shaped pattern, AMH was not significantly associated with fertility. In conclusion, heifers with lower AMH had larger follicles towards the end of the synchronization protocol and greater ovulation responses, whereas greater circulating AMH was unrelated to conception success.

Ultrasonographic evaluation of the reproductive tract as predictors of pregnancy in Girolando heifers submitted to Timed Artificial Insemination

The objective of this study was to evaluate the influence of the degree of uterine and ovarian development on the pregnancy rate of Girolando heifers submitted to Timed Artificial Insemination (TAI). Fifty-six heifers, representing 100% of the category in the herd studied, were evaluated. The heifers were submitted to a gynecological evaluation, prior to hormonal treatment, with ultrasonography, in order to measure the diameter of the uterine horns and ovaries, as well as evaluate the presence of corpus luteum (CL) and antral follicles. According to the values found for the uterine and ovarian diameters, the animals were classified into scores from one to three. After the gynecological evaluation, all animals were submitted to TAI. There was no statistical difference (P>0.05) in pregnancy rates between the different uterine and ovarian scores, as well as in relation to ovarian structures. However, a statistical difference (P<0.05) was observed in the percentage of animals in anestrous within ovarian scores one, two and three (83.3%, 37.5% and 42.8%, respectively). The conclusion was that uterine and ovarian development did not interfere in the pregnancy rate of Girolando heifers in the herd studied.

Comparison of estradiol benzoate and cypionate in Girolando cows submitted to a timed artificial insemination

The various studies on the manipulation of the estrous cycle culminated in the development of estrous and ovulation synchronization protocols, to the point of defining an optimum moment for artificial insemination. The induction of ovulation is a primordial part for the determination of the moment of the TAI, so to study which hormones and how they behave allows a better understanding of this physiological process and, to manipulate it efficiently. The aim of the present study was to compare the use of estradiol benzoate (EB) and cypionate (ECP) as ovulation inducer in Girolando cows submitted to Timed Artificial Insemination (TAI). Ovulations of 108 Girolando cows were synchronized and the initial day of treatment, recorded as D0, which was when the animals received an intravaginal device containing 1g of progestogen and an intramuscular application (im) of 2mg of EB. After 8 days (D8), the device was removed and 500μg of cloprostenol (im) was administered to all females. Then, the animals were randomly divided into two treatments: BG Group (n = 52) and CG Group (n = 56). The CG animals received 1mg of ECP (im) as the ovulation inducer at the time of device removal, while BG Group cows received 1mg of EB (im) 24 h later (D9). TAI occurred at D10. After device removal, ultrasound evaluations were performed every 12 h up to ovulation. The following reproductive parameters were evaluated: interval from intravaginal device removal to ovulation - IDO (hours); interval from ovulation to TAI-IOT (hours); diameter of the largest follicle at intravaginal device removal (mm); maximum diameter of the DF (mm) at D10; the dominant follicle growth rate (mm/day); synchronization rate - SR (%); ovulation rate - OR (%) and PR - pregnancy rate (%). Only the ovulation rate presented a statistical difference (p&lt;0.05). In conclusion, despite the ovulation rate difference, both estradiol esters administered were effective and presented similar pregnancy rates in Girolando cows submitted to TAI.

Bacterial taxonomic composition of the postpartum cow uterus and vagina prior to artificial insemination1.

The current study characterized the taxonomic composition of the uterine and vaginal bacterial communities during estrous synchronization up to timed artificial insemination (TAI). Postpartum beef cows (n = 68) were subjected to pre-synchronization step 21 d prior to TAI (day -21), followed by an industry standard 7 Day Co-Synch on day -9 and TAI on day 0. Uterine and vaginal flushes were collected on days -21, -9, and -2 of the protocol and pH was immediately recorded. Pregnancy was determined by transrectal ultrasound on day 30. Bacterial DNA was extracted and sequenced targeting the V1 to V3 hypervariable regions of the 16S rRNA bacterial gene. Results indicated 34 different phyla including 792 different genera present between the uterus and vagina. Many differences in the relative abundance of bacterial phyla and genera occurred between resulting pregnancy statuses and among protocol days (P < 0.05). At day -2, multiple genera were present in >1% abundance of nonpregnant cows but <1% abundance in pregnant cows (P < 0.05). Uterine pH increased in nonpregnant cows but decreased in pregnant cows (P > 0.05). Overall, our study indicates bacterial phyla and genera abundances shift over time and may potentially affect fertility by altering the reproductive tract environment.

Timed artificial insemination plus heat II: gonadorelin injection in cows with low estrus expression scores increased pregnancy in progesterone/estradiol-based protocol

The use of tail chalk and estrus/heat expression scores (HEATSC) evaluation is instrumental in identifying cows with greater estrus expression and greater artificial insemination pregnancy rates (P/AI) in cows submitted to timed artificial insemination (TAI), and cows with low or no estrus expression present lower P/AI. It was intended in this study to improve the pregnancy rates in TAI for Bos indicus beef cows, and gonadotrophin-releasing hormone (GnRH) injection was hypothesized to increase pregnancy rates in a TAI program for cows submitted to progesterone–estradiol-based protocols with low or no estrus expression, evaluated by HEATSC. Cows (n= 2284) received a progesterone device and 2 mg estradiol benzoate, after 8 days the device was removed and 1 mg estradiol cypionate, 150 μg of d-cloprostenol and 300 IU equine chorionic gonadotropin was administered. All cows were marked with chalk and HEATSC evaluated (scales 1 to 3) at TAI performed on day 10. Animals with HEATSC1 and HEATSC2 (n= 937) received 100 μg de gonadorelin (GNRH group; n= 470), or 1 ml saline (Control group; n= 467), and cows with HEATSC3 (named HEAT group; n= 1347) received no additional treatment. The larger dominant follicle, evaluated on day 8and at TAI (day 10), was greater in HEAT group (P= 0.0145 and P <0.001, respectively). Corpus luteum (CL) area and progesterone concentration was evaluated on day 17, and CL area was larger in HEAT group, intermediary in Control and lower in GnRH group (Control= 2.68 cm2, GnRH= 2.37 cm2, HEAT group= 3.07 cm2, P <0.001). Greater progesterone concentrations were found in HEAT group than in Control and GnRH groups (Control= 4.74 ng/ml, GnRH= 4.29 ng/ml, HEAT group= 6.08 ng/ml, P<0.001). There was a difference in ovulation rate, greater in HEAT group than GnRH and Control groups (Control= 72.5%; GnRH= 81.25%; HEAT group= 90.71%; P= 0.0024). Artificial insemination pregnancy rates was greater in HEAT group (57.09% (769/1347) than in Control and GNRH groups, with positive effect of GnRH injection at the time of TAI in P/AI (Control= 36.18% (169/467), GnRH= 45.95% (216/470); P<0.0001). In conclusion, GnRH application in cows with low HEATSC (1 and 2) is a simple strategy, requiring no changes in TAI management to increase pregnancy rates in postpartum beef cows submitted to progesterone–estradiol-based TAI protocols, without reaching, however, the pregnancy rates of cows that demonstrate high estrus expression at the TAI.

Impact of supplementation with long-acting progesterone on gestational loss in Nelore females submitted to TAI

The goal of this study was to evaluate the effect of long-acting progesterone supplementation on pregnancy rates and gestational losses in Nelore females (Bos taurus indicus) submitted to Timed Artificial Insemination (TAI). Ovulations of multiparous (n = 534), primiparous (n = 117) and nulliparous (n = 81) Nelore females were synchronized for TAI and the day of insemination was considered D0. After TAI, the animals were allocated into three groups. Two groups received 150 mg of long acting injectable progesterone (P4) in a single dose, 5 (D = 5) or 11 (D = 11) days after TAI, resulting in the following treatments: 1) Group P4 - D5 (n = 235); 2) Group P4 - D11 (n = 245); and 3) Control Group (n = 252). The animals in the control group did not receive any supplementation. Pregnancy was checked by ultrasonography, 30 days after the TAI. The gestational losses were evaluated at two different periods: 1) from 30 to 60 days, and 2) from 60 to 90 days. The pregnancy rate and the gestational losses as a function of the treatments were tested by the non-parametric binomial test with 5% significance level. The pregnancy rates were different between the groups P4 - D5 and Control (47 and 39%, respectively) (P < 0.05), but no difference was observed in relation to the P4 - D11 group. There was a difference in gestational losses from 30 to 60 days and total losses between the groups treated with P4 on the fifth day and eleventh day after TAI in relation to the control group (P = 0.0173; P = 0.0454), but no difference was observed between the treatments in relation to the losses between 60 and 90 days (P ≥ 0.0578). Among the animals that were cycling at the beginning of the protocol, the groups supplemented with progesterone at day 5 or 11 after insemination had gestational losses significantly lower (P = 0.04) than the control group (P4 - D5 = 2%; P4 - D11 = 2%, control = 14%). The animals in anestrous that received supplementation 5 days after TAI had lower gestational losses (P = 0.049) compared with the other groups (P4 - D5 = 3%, P4 - D11 = 7% Control = 10%). Under the conditions of this study, the use of long-acting injectable progesterone 5 days after TAI in Nelore females increased the pregnancy rates, but when supplemented 11 days after TAI, it did not have the same effect. Also, when used 5 days after TAI, it significantly decreased gestational losses on both anestrous and cycling animals. Therefore, it may be an interesting alternative to increase reproductive and productive efficiencies.

Short communication: Effect of adding a second prostaglandin F2α injection during the Ovsynch protocol on luteal regression and fertility in lactating dairy cows: A meta-analysis

Incomplete luteal regression after treatment with a single dose of prostaglandin F2α during an Ovsynch protocol decreases fertility to timed artificial insemination (TAI). To increase the proportion of cows with complete luteal regression and subsequently pregnancy per artificial insemination (P/AI), an additional treatment with PGF2α 24 h after the first has been recommended. A systematic review of the literature and meta-analytical assessment were performed with the objective of evaluating the effects of adding a second PGF2α treatment during the Ovsynch protocol on luteal regression and reproductive performance in lactating dairy cows. Based on the heterogeneity among the experimental treatments, a fixed or a random effects meta-analysis was conducted. Reproductive outcomes of interest were luteal regression at the end of the Ovsynch protocol, and P/AI measured 32 to 39 d after TAI. Seven randomized controlled experiments from 6 published manuscripts including 5,356 cows with the primary objective to evaluate the effect of an additional treatment with PGF2α during the Ovsynch protocol on P/AI were used. Information regarding luteal regression at the end of the Ovsynch protocol was available for 1,856 cows. Adding a second PGF2α treatment on d 8 during the Ovsynch protocol increased the relative risk (RR) of complete luteal regression at the end of the Ovsynch protocol (RR = 1.14; 95% confidence interval = 1.10 to 1.17) using a fixed effects model and the RR for pregnancy (RR = 1.14; 95% confidence interval = 1.06 to 1.22) 32 d after TAI using a fixed effects model. No heterogeneity was observed among the 6 manuscripts regarding complete luteal regression and P/AI. In summary, there was a clear benefit of an additional PGF2α treatment during the Ovsynch protocol on luteal regression (+11.6 percentage units) and on P/AI (+4.6 percentage units).

Effect of Parity and Milk Production on Conception Rate After Two Synchronization Protocols in Dairy Cows

Presynchronization strategies, such as Presynch- Ovsynch and Double- Ovsynch, increase fertility to timed artificial insemination (TAI) compared with Ovsynch alone; however, simpler presynchronization strategies could reduce costs and simplify reproductive management. Our objective in this study the effect of parity and average milk production on the conception rate after resynchronization with G6G protocol or Ovsynch protocol. Lactating Holstein cows (n = 100) divided into two groups (Ovsynch and G6G) cows in this group1 (n = 50) were received the following treatment sequence, 12 µg Buserelin on day zero, 500 µg IM of Cloprostenol on day seven, 12 µg Buserelin IM on day nine and received timed artificial insemination (TAI) 16 hours later. Group II (G6G): were received 500 µg IM Cloprostenol on day zero, 12 µg Buserelin on day two and six days later these cows received the Ovsynch as previously explained in the first group. Conception rate was (40 vs. 30 %) for G6G and Ovsynch protocol respectively primiparous cows, conception rate to G6G program was 46.15%, compared to 28.57% in cows synchronized with Ovsynch program. In Multiparous cows, the similar trend was observed but the difference was smaller (conception rate 37.8 vs. 30.55% in cows synchronized with G6G and with Ovsynch, respectively). In high producers, conception rate was numerically higher in the Ovsynch group (40%) compared to the G6G group (36%). While, in low producers, conception rate to G6G protocol (48%) tended (P = 0.07) to be higher than that to Ovsynch protocol (20%) in conclusion Administration of PGF2α 8 d before initiation of Ovsynch did not improve conception rate compared with the standard Ovsynch protocol

Ovarian follicular dynamics and conception rate in Bos indicus cows with different antral follicle counts subjected to timed artificial insemination

Two experiments in Nelore cows subjected to timed artificial insemination (TAI) were designed to compare the influence of the antral follicle count (AFC/AFCs) on (1) ovarian follicular dynamics and (2) conception rates. First, multiparous cows with high (≥45 follicles; n=43) or low (≤15 follicles; n=32) AFCs were selected to undergo a TAI protocol to monitor ovarian follicular dynamics. Second, the AFCs of 962 cows also subjected to TAI were determined and classified as groups of high (G-high; ≥45 follicles; n=194), intermediate (G-intermediate; ≥20≤40 follicles, n=397) or low (G-low; ≤15 follicles; n=243) AFCs. In study I, the ovarian measurements (diameter, perimeter and area) were greater (P≤0.05) and there was a greater consistency in number of antral follicles during the period of synchronization for TAI in the high than low group. Effects of the AFC and ultrasonic evaluation interval on the follicular diameter were observed (P≤0.05); however, there was no interaction (P>0.05). Dominant follicles had greater diameters (P≤0.05) in the G-low than in the G-high at D4 (7.3±2.2 vs. 6.2±1.4mm, respectively, P=0.06), D8 (11.2±1.8 vs. 9.5±1.8mm, respectively), D9 (12.3±1.7 vs. 10.6±1.7mm, respectively), and D10 (13.4±1.3 vs. 12.2±1.8mm, respectively), as well as greater estimated diameters of ovulatory follicles (14.4±1.5 vs. 13.4±2.1mm, respectively, P=0.08). In study II, the cows with fewer AFCs had greater (P≤0.05) conception rates (61.7%) than the cows with the intermediate (52.9%) and greater (49.5%) AFCs. Nelore cows with fewer AFCs subjected to synchronization of time of ovulation had a larger follicular diameter and a greater conception rate than the groups with intermediate and a greater AFCs.

Evaluation of forage soybean, with and without pearl millet, as an alternative for beef replacement heifers.

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 > 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 > 0.43) or overall breeding season (93%; P > 0.99) pregnancy rates. Ovulatory follicle diameters (11.7 mm) was not different (P > 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.