Second Injection Of GnRH Research Articles

15 Influence of early progesterone removal on follicular development, estrus expression, and pregnancy rates in presynchronized beef cows

Abstract The objective of this study was to evaluate the impact of early progesterone removal on pregnancy rates to fixed-time artificial insemination (FTAI) in presynchronized beef cows. Postpartum beef cows (n = 922; body condition score = 4.9 ± 0.77; days postpartum = 77.3 ± 20.77 d) from 7 locations were enrolled in a completely randomized design. Within location, cows were stratified by parity and days postpartum before being randomly assigned to 1 of 2 treatments: 1) 7&7 Synch: Cows received a controlled internal drug release insert (CIDR) and a 25-mg injection of prostaglandin F2α (PG1; d 0). Cows received 100 μg of GnRH on d 7 and the CIDR was removed 7 d later, concurrently with a second prostaglandin F2α (PG2) injection (d 14). Cows received a second injection of GnRH and were FTAI 60-66 h after PG2 (d 17); 2) 7&6 Synch: Cows received the same treatment as 7&7 Synch cows; however, CIDR removal and PG2 were performed on d 13, and cows were FTAI 60-66 h after CIDR removal. Ovarian ultrasonography was performed to determine follicle diameter and CL presence at PG2 and FTAI in a subset of cows (n = 40). Estrus detection patches were utilized to evaluate estrus expression between PG2 and FTAI. Pregnancy diagnosis was performed 28-35 d after FTAI. Cows exposed to the 7&7 Synch tended to have larger follicle diameter at PG2 compared with 7&6 Synch cows (P = 0.09); however, there were no differences in follicle diameter at FTAI. Cows that expressed estrus tended to have larger follicle diameter at FTAI compared with cows that failed to express estrus (P = 0.10). Follicular growth between PG2 and FTAI, percentage of cows with a corpus luteum at PG2, and ovulation rate were not impacted by treatment (P ≥ 0.56). No differences were determined between treatments for estrus expression (7&7 Synch: 77.1 ± 5.91; 7&6 Synch: 74.6 ± 6.28; P = 0.50) or pregnancy rates to FTAI (7&7 Synch: 60.1 ± 4.32; 7&6 Synch: 58.2 ± 4.26; P = 0.69). In conclusion, early removal of progesterone did not impact pregnancy rates in presynchronized beef cows. Thus, the 7&6 Synch protocol described herein may be used as an alternative to the conventional 7&7 Synch protocol without compromising fertility.

Methods of artificial regulation of estrous cycle of Aberdeen Angus breeding stock

The research aim is to study the efficiency of using the OvSynch and Co-Synch schemes with subsequent resynchronization on beef cows and heifers of the Aberdeen Angus breed. The hormonal state of animals and the biochemical blood serum parameters were chosen as factors determining reproductive function. The purpose is to study the efficiency of applying the OvSynch and Co-Synch synchronization protocols on cows and heifers of the Aberdeen Angus breed depending on the hormonal state of the inseminated animals and the biochemical blood serum parameters. The rate of fertilization in cows inseminated according to the OvSynch protocol was determined to be 5.0 to 8.5 % higher during the first stage of insemination and 5.5 % higher during the second stage of insemination. In the group of heifers, the best fertilization results were obtained while using the Co-Synch protocol (59.3 %). Giving cows a second injection of GnRH, on day 9 of the OvSynch protocol, 16 hours before insemination, provided an average rate of fertilization of 52.3 %, which is 3.4 % higher compared to the 14-hour interval between GnRH injection and insemination. The concentration of steroid and gonadotropic hormones, including cortisol, estradiol, FSH and LH, in experimental animals during insemination corresponded to the estrus phase. The results of biochemical blood tests indicate a number of metabolic inconsistencies in the animal body. Changes in the biochemical blood serum parameters in animals that did not become pregnant followed the same patterns as in those that became pregnant. However, the level of increase or decrease in parameters was less pronounced. The results obtained can be used in arranging artificial insemination in breeding and commercial agricultural organizations engaged in beef cattle breeding, as well as in teaching process of zootechnical and veterinary disciplines in agricultural higher educational institutions of the Republic of Belarus.

Effect of delayed timing of artificial insemination with sex-sorted semen on pregnancy per artificial insemination in synchronized dairy heifers managed in a seasonal-calving pasture-based system

The objective of this study was to evaluate the timing of artificial insemination (AI) with frozen-thawed sex-sorted semen on pregnancy per AI (P/AI) in dairy heifers. A 6-d progesterone Co-Synch protocol was used for ovulation synchronization of dairy heifers, with timed AI (TAI) coincident with (TAI-0) or 8 h (TAI-8) after the second injection of GnRH, corresponding to either 48 h or 56 h after removal of the progesterone-releasing intravaginal device. Pregnancy diagnosis was conducted by transrectal ultrasound scanning of the uterus 34 d after TAI (n = 816 records available for analysis). Generalized linear mixed models were used to examine the effects of treatment on P/AI. Treatment (n = 2), herd (n = 11), and treatment × herd were included as categorical fixed effects. Heifer body weight and Economic Breeding Index values for milk production, fertility, calving performance, beef carcass, cow maintenance, cow management, and health were included as continuous fixed effects. Heifer ID was included as a random effect. Pregnancy per AI was greater for TAI-8 heifers (59%) compared with TAI-0 heifers (50%). Pregnancy per AI ranged from 38% to 75% between herds but there was no treatment × herd interaction. The fertility subindex (positive) and the cow management subindex (negative) were the only continuous animal variables associated with P/AI. Delaying the timing of AI with frozen-thawed sex-sorted semen by 8 h in dairy heifers enrolled on a 6-d progesterone Co-Synch protocol improved P/AI.

Expression of genes for transport of water and angiogenesis, as well as biochemical biomarkers in Holstein dairy cows during the ovsynch program

Changes in expression of genes associated with angiogenesis and transport of water by cells, as well as biomarkers of oxidative stress were determined at specific times during the ovsynch protocol to synchronize estrus and breed Holstein dairy cows. Blood samples were taken from 82 lactating Holstein cows at the time of the 1st GnRH injection (G1), 7 days later at the time of the PGF2a (PG) injection, and 48 h after the PGF2a treatment when the second injection of GnRH was administered (G2). The serum was analyzed for malondialdehyde (MDA), reduced glutathione (GSH), glutathione peroxidase (GPX), nitric oxide (NO), catalase (CAT), and total antioxidant capacity (TAC). The expression of vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor 2 (VEGFR2), endothelial nitric oxide synthase (eNOS3), aquaporin 3 (AQP3), and AQP4 mRNAs in peripheral blood mononuclear cells (PBMCs) was analyzed. The number of copies of each of the mRNAs was quantified using qPCR. Pregnancy status was determining at 32 ± 3 days after insemination using an ultrasound “Sonoscape-5V″ model. Receiver operating curves (ROC) were used to assess the sensitivity and specificity of the biochemical parameters in serum to predict establishment of p The expression of MDA, GPX, and Catalase changed (P < 0·05) between G1, PG and G2 phases of the ovsynch protocol with higher levels at PG than at G1 and G2. The highest levels of NO were detected at G2. The ROC analyses identified NO, TAC and CAT as the most sensitive and specific biomarker for pregnancy with areas under the curve being 0.875 (P < 0.0001), 0.843 (P < 0.03), 0.833 (P < 0.017), sensitivity being 75.3, 42.86, and 26.27%, and specificity being 90, 90 and 85% respectively. The expression for VEGF, VEGFR2, eNOS3, AQP3, and AQP4 mRNAs was upregulated at PG compared to G1 and G2 phases of the ovsynch protocol. The results suggest that following the first injection of GnRH, there is an increase in expression of VEGF, VEGFR2, eNOS3, AQP3, and AQP4 mRNAs by the time of the PGF2a injection and then expression decreased. Further, ROC analyses identified increases in NO, TAC and CAT as the most sensitive and specific biomarkers with the greatest potential to predict establishment of pregnancy in Holstein cows.

Resposta do adesivo marcador do estro, inseminação artificial em tempo fixo e protocolo de GnRH em bovinos de corte na Inseminação artificial dividida

Abstract An estrous-detection patch was used to determine the optimum timing for STAI and the necessity of GnRH at STAI on a 7-day CO-Synch+CIDR protocol. Crossbred beef cows (n=216) were stratified into the following treatment groups: CTRL=TAI (n=67) at 72 h post CIDR removal, or TRT=STAI (n=149) at 72 or 84 h post CIDR removal. All females received GnRH (100 mcg) plus a CIDR on d0, PGF2α, CIDR removal, and an Estrotect estrous-detector patch on d7. At 72 h post-CIDR removal, a patch score was assigned (PS1&lt;50% removed; PS2&gt;50% removed) to all females. Cows in the CTRL group were administered a second GnRH (100 mcg) at 72 h TAI. Cows in the TRT group with PS2 were not administered GnRH. At 84 h, the remaining TRT group cows were given a second PS; cows with PS1 received a GnRH (100 mcg), and cows with PS2 were not administered. Results: The TAI pregnancy rates were similar (P=0.81) between the CTRL (45.6%) and TRT (44.8%) groups. Pregnancy rates tended to be higher (P=0.07) for cows with PS2 (50.3%) than for those with PS1 (29.4%). However, by extending TAI to 84 h in unresponsive cows, 82.0% of TRT cows did not receive a second injection of GnRH at TAI. It was concluded that the estrous detector patches reduced the percentage of cows that required GnRH at TAI without compromising pregnancy rates. The estrous detector patches significantly reduced the number of cows that received a second GnRH injection at TAI.

Prostaglandin F2α 7 d prior to initiation of the 7-d CO-synch + CIDR protocol failed to enhance estrus response and pregnancy rates in beef heifers.

To determine the effects of administration of 25 mg of PGF2α 7 d prior to the initiation of the 7-d CO-Synch + controlled internal drug release (CIDR) fixed-time AI (TAI) protocol, 985 Bos taurus beef heifers were enrolled in a completely randomized design at 9 locations from April to July of 2016. Within location, all heifers were randomly assigned to 1 of 2 treatments: 1) CONTROL (n = 496); 100 µg injection of GnRH and a CIDR insert for 7 d [day 7], administration of 25 mg of PGF2α at CIDR removal [day 0], followed by a second injection of GnRH and TAI 54 ± 2 h later; or 2) PRESYNCH (n = 489); same as CONTROL but heifers received an additional injection of 25 mg of PGF2α 7 d prior [day 14] to CIDR insertion. Estrous detection patches were applied to all heifers on day 14 and were evaluated for estrual activity on day 7. Similarly, estrus alert patches were placed on all heifers on day 0 and evaluated for estrual activity at the time of TAI. Pregnancy was diagnosed via transrectal ultrasonography between 35 and 55 d after TAI. The percentage of heifers exhibiting estrus between days 14 and 7 was greater (P < 0.001) for the PRESYNCH (70.1 ± 2.4%) than the CONTROL (41.1 ± 2.3%) treatment, whereas the percentage of heifers exhibiting estrus between day 0 and TAI was greater (P < 0.001) for the CONTROL (55.6 ± 2.4%) than the PRESYNCH (39.7 ± 2.5%) treatment. Estrus response rates differed (P < 0.001) among locations. Pregnancy rates to TAI differed (P = 0.023) among locations; however, they did not differ (P = 0.739) between CONTROL and PRESYNCH treatments (45.4 ± 2.5 vs. 43.2 ± 2.5%, respectively). Final breeding season pregnancy rates did not differ (P = 0.811) between treatments. Therefore, an injection of PGF2α 7 d prior to initiation of the 7-d CO-Synch + CIDR protocol failed to improve pregnancy rates to TAI in replacement beef heifers.

OvSynch program, its modifications and alternative hormonal programs in cow reproduction

The OvSynch program was formulated over 20 years ago (it consists in administering gonadoliberin on the day of starting the procedure, then injecting prostaglandin 7 days after the GnRH initial injection, and administration of GnRH two days after applying PGF2α. The procedure ends in the insemination of a female 16–20 hours after administering the final dose of the hormone) and it is commonly applied in cow reproduction management protocols. It has evolved into numerous modifications which has boosted its effectiveness. They have consisted in replacing GnRH with hCG or pLH, diversifying the time of the final injection of GnRH, which follows the prostaglandin injection, and postponing insemination after the final GnRH dose, as well as changing the dosage of the aforementioned hormones. To expedite the Ovsynch protocol, so-called PreSynch was used, which involved administering two prostaglandin injections with a 14 day interval before applying the initial GnRH dose in protocol OvSynch. The interval between the second prostaglandin injection in the PreSynch program varied (PreSynch-14, PreSynch-12, PreSynch-11, PreSynch-11 and PreSynch). The pregnancy rate can be also improved by introducing GnRH injection before starting the OvSynch program, administered 7, 6 or 4 days before the initial GnRH injection in OvSynch (G7G, G6G, G4G). Higher pregnancy rates, in comparison to the PreSynch-OvSynch program, can be obtained by applying the DoubleOvsynch protocol. In this protocol two OvSynch programs are administered in a 7-day interval. Lately, alternative programs such as DoubleSynch and EstraDoubleSynch have emerged. The DoubleSynch protocol consists in administering PGF2α in day 0, GnRH on the second day, another PGF application on the 9th day, and the second GnRH dose on the 11th day. Artificial insemination is performed in oriented time (TAI). This solution is used in order to achieve a higher percentage of pregnant cows in comparison to the PreSynch+OvSynch protocol. It also enables synchronisation of heat and ovulation, both after the first and the second hormonal treatment of GnRH. In EstraDoubleSynch protocol the second injection of GnRH at the end of the DoubleSynch program is replaced by estradiol benzoate (BE) administration on the 10th day, in order to acquire a higher level of follicle waves synchronisation and ovulation rate. Those programs applied in cow reproduction management can positively influence fertility and boost cow breeding profitability..

Relationship of follicle size and concentrations of estradiol among cows exhibiting or not exhibiting estrus during a fixed-time AI protocol

Cows exhibiting estrus near fixed-time artificial insemination (AI) had greater pregnancy success than cows not showing estrus. The objective of this study was to determine the relationship between follicle size and peak estradiol concentration between cows that did or did not exhibit estrus during a fixed-time AI protocol. Ovulation was synchronized in beef cows by applying the CO-Synch protocol [GnRH (100 μg) on day-9, prostaglandin F2α (PGF2α; 25 mg) on day-2, and a second injection of GnRH 48 h after PGF2α (day 0)] to both suckled (experiment 1) and nonsuckled (experiment 2) cows. Follicle size (day 0) and ovulation (day 2) was determined by ultrasonography. Blood samples were collected every 3 or 4 h beginning at the time of PGF2α injection (0 h). Estrus was detected by visual observation with the aid of estrus-detection patches, and cows that ovulated were classified as exhibited estrus (n = 46) or did not exhibit estrus (n = 63). In both suckled and nonsuckled cows, there was a positive relationship between all cows (P < 0.05) and among those that exhibited estrus (P < 0.05) between follicle size and peak estradiol concentration, but no linear relationship (P > 0.50) between follicle size and peak estradiol concentration was observed among cows not exhibiting estrus. Cows that exhibited estrus had greater (P < 0.01) peak estradiol concentrations than cows that did not exhibit estrus. Suckled cows exhibiting standing estrus had greater (P < 0.001) preovulatory concentrations of estradiol beginning 6 h (replicate 1) or 4 h (replicate 2) after the injection of PGF2α on day-2 compared with cows not exhibiting standing estrus. Nonsuckled cows exhibiting standing estrus had greater (P < 0.001) preovulatory concentrations of estradiol beginning at the injection of PGF2α on day-2 compared with cows not exhibiting standing estrus. Furthermore, cows that exhibited estrus had an increased (P < 0.01) rate in the rise in concentrations of estradiol following the PGF2α to peak estradiol than cows not exhibiting estrus. In summary, follicle diameter had a positive relationship with peak concentrations of estradiol, but only among cows that exhibited standing estrus, and estradiol increased earlier in cows that exhibited estrus compared with cows that did not.

Effect of presynchronization strategy before Ovsynch on fertility at first service in lactating dairy cows

The aim of this study was to evaluate the effect of presynchronization with or without the detection of estrus on first service pregnancy per artificial insemination (P/AI) and on Ovsynch outcome in lactating dairy cows. A total of 511 cows were divided randomly but unevenly into 3 treatment groups at 44 to 50 days in milk (DIM). Ovsynch was started at the same time (69 to 75 DIM) in all three groups. Cows in the Ovsynch group (CON, N = 126) received no presynchronization before Ovsynch, and all cows were bred by timed AI (TAI). Cows in the presynchronization with estrus detection (PED) and the presynchronization with only TAI (PTAI) groups received two doses of prostaglandin F2α (PGF) 14 days apart, starting at 44 to 50 DIM. Ovsynch was initiated 11 days after the second PGF treatment. Cows in the PED group (N = 267) received AI if estrus was detected after either PGF injection. Cows that were not determined to be in estrus after PGF injection received Ovsynch and TAI. Cows in the PTAI group (N = 118) were not inseminated to estrus, with all cows receiving TAI after Ovsynch. The ovulatory response to the first GnRH injection administered as part of Ovsynch differed (P = 0.002) among treatment groups (83.1% in PTAI, 72.6% in PED, and 62.7% in CON). However, the ovulatory response to the second injection of GnRH during Ovsynch did not differ among treatment groups. Of the 267 PED cows, a total of 132 (49.4%) exhibited estrus and were inseminated. The P/AI at the 31-day pregnancy diagnosis was similar between the cows in the PED group with AI after estrus detection (37.9%; 50/132) and those bred with TAI (34.1%; 46/135). The P/AI in the CON group (46.8%; 59/126) was greater (P < 0.05) than that in the PED group (36.0%; 96/267). In addition, the P/AI in the CON group was greater (P = 0.04) than that in the PED cows receiving TAI (34.1%; 46/135) but less than that in the PED cows bred to estrus (37.9%; 50/132) (P = 0.16). At the 31-day pregnancy diagnosis, the cows in the PTAI group had greater P/AI (55.9%; 66/118) than both those in the PED group (P < 0.01; either estrus or TAI) and those in the CON group (P = 0.08). Thus, presynchronization with PGF (PTAI) increased the ovulatory response to Ovsynch and improved P/AI in dairy cows. Interestingly, the breeding of cows to estrus during presynchronization reduced fertility to the TAI and overall fertility, including cows bred to estrus and TAI. These results indicate that maximal fertility is obtained when all cows receive TAI after the presynchronization protocol.

Effect of timing of artificial insemination after synchronization of ovulation on reproductive performance in Holstein dairy cows

The objective of this study was to determine the effect of timing of artificial insemination on pregnancy rates, calving rates, abortion rates, twinning rates, and calf gender ratio after synchronization of ovulation with Ovsynch protocol in Holstein dairy cows. The ovulation of 219 lactating Holstein dairy cows was synchronized using the Ovsynch protocol. Therefore, cows received an injection of GnRH followed by an injection of prostaglandin F(2α) 7 days later and a second treatment with GnRH 2 days later. Cows were artificially inseminated at 0, 12, or 24 h after the second injection of GnRH. Reproductive performance did not differ between cows inseminated at 0 h (n = 82), 12 h (n = 66), or 24 h (n = 71) after the last injection of GnRH (pregnancy rate: 0 h 48 %, 12 h 47 %, 24 h 52 %; abortion rate: 0 h 5 %, 12 h 0 %, 24 h 11 %; calving rate: 0 h 43 %, 12 h 47 %, 24 h 41 %; twinning rate: 0 h 2 %, 12 h 0 %, 24 h 0 %; calf gender ratio (F/M): 0 h 61:39 %, 12 h 48:52 %, 24 h 39:61 %; P > 0.05). Pregnancy rates for cows inseminated in postpartum times of 50-75, 76-100, and >100 days within the first and ≥ 3 parities were statistically similar (P > 0.05), but pregnancy rates for cows inseminated at different postpartum times of 50-75, 76-100, and >100 days within the second parity were different (P < 0.01). In general, pregnancy rates of cows inseminated at different postpartum times (P < 0.01) and parities (P < 0.001) differed. The findings of the current study showed that rates of pregnancy, abortion, calving, and twinning of Holstein dairy cows subjected to artificial insemination at different times after synchronization were similar. These results also indicate that the timing of artificial insemination after synchronization did not influence calf gender ratio. Furthermore, pregnancy rates of Holstein dairy cows inseminated after synchronization were significantly influenced by postpartum time and parity number.

Corpus luteum development and function and relationship to pregnancy during the breeding season in the Mediterranean buffalo

The aim of this study was to ascertain corpus luteum (CL) development and function in buffaloes synchronized and mated by artificial insemination (AI) during the breeding season. Italian Mediterranean buffalo cows (n = 43) at 86.5 ± 2.7 days postpartum were synchronized by the Ovsynch-TAI Program and inseminated using frozen thawed semen at 20 and 44 h after the second injection of GnRH. The CL dimensions (diameter and area) and blood flow were examined on Days 5, 10, 15, 20, and 25 after AI by realtime B-mode/colour-Doppler ultrasonography. The resistive index (RI), pulsatility index (PI) and time average medium velocity (TAMV) were recorded at each time, together with CL dimensions. Blood samples were taken on the days of ultrasonography for progesterone (P4) assay by RIA. Data were grouped into pregnant or non-pregnant and retrospectively analyzed by repeated measure ANOVA and correlation analyses. Dimensions of the CL on Days 10, 20, and 25 after AI were greater (P < 0.01) in buffaloes pregnant on Day 45 (n = 18) compared with non-pregnant buffaloes (n = 25). The former buffaloes also showed a greater (P < 0.01) rate of CL growth between Days 5 and 10 after AI. Blood flow to the CL on Day 10 after AI showed a higher TAMV (P < 0.01) and lower RI (P < 0.05) in pregnant buffaloes compared with non-pregnant buffaloes. Negative correlations were observed on Day 10 after AI between CL diameter and RI (r = −0.61; P < 0.01) and PI (r = −0.60; P < 0.01); P4 concentrations and RI (r = −0.46; P < 0.02); and RI and pregnancy (r = 0.45; P < 0.02). Positive correlations were observed between pregnancy and CL size (r = 0.54; P < 0.01), ΔCL diameter between Days 5 and 10 (r = 0.52; P < 0.01), ΔCL area between Days 5 and 10 (r = 0.48; P < 0.015), and ΔP4 between Days 5 and 10 (r = 0.50; P < 0.01). Based on these findings it is concluded that the period between Day 5 and 10 is very important for CL growth and crucial in evaluating pregnancy. Accordingly, the assessment of CL parameters during the period from Day 5 to Day 10 after AI might be used to predict the likelihood of an ongoing pregnancy.

Effect of interval between induction of ovulation and artificial insemination (AI) and supplemental progesterone for resynchronization on fertility of dairy cows subjected to a 5-d timed AI program

Objectives were to investigate 2 intervals from induction of ovulation to artificial insemination (AI) and the effect of supplemental progesterone for resynchronization on fertility of lactating dairy cows subjected to a 5-d timed AI program. In experiment 1, 1,227 Holstein cows had their estrous cycles presynchronized with 2 injections of PGF2α at 46 and 60 d in milk (DIM). The timed AI protocols were initiated with GnRH at 72 DIM, followed by 2 injections of PGF2α at 77 and 78 DIM and a second injection of GnRH at either 56 (OVS56) or 72h (COS72) after the first PGF2α of the timed AI protocols. All cows were time-inseminated at 72h after the first PGF2α injection. Pregnancy was diagnosed on d 32 and 60 after AI. In experiment 2, 675 nonpregnant Holstein cows had their estrous cycles resynchronized starting at 34 d after the first AI. Cows received the OVS56 with (RCIDR) or without (RCON) supplemental progesterone, as an intravaginal insert, from the first GnRH to the first PGF2α. Pregnancy diagnoses were performed on d 32 and 60 after AI. During experiment 2, subsets of cows had their ovaries scanned by ultrasonography at the first GnRH, the first PGF2α, and second GnRH injections of the protocol. Blood was sampled on the day of AI and 7 d later, and concentrations of progesterone were determined in plasma. Cows were considered to have a synchronized ovulation if they had progesterone <1 and >2.26ng/mL on the day of AI and 7 d later, respectively, and if no ovulation was detected between the first PGF2α and second GnRH injections during resynchronization. In experiment 1, the proportion of cows detected in estrus at AI was greater for COS72 than OVS56 (40.6 vs. 32.4%). Pregnancy per AI (P/AI) did not differ between OVS56 (46.4%) and COS72 (45.5%). In experiment 2, cows supplemented with progesterone had greater P/AI compared with unsupplemented cows (51.3 vs. 43.1%). Premature ovulation tended to be greater for RCON than RCIDR cows (7.5 vs. 3.6%), although synchronization of the estrous cycle after timed AI was similar between treatments. Timing of induction of ovulation with GnRH relative to insemination did not affect P/AI of dairy cows enrolled in a 5-d timed AI program. Furthermore, during resynchronization starting on d 34 after the first AI, supplementation with progesterone improved P/AI in cows subjected to the 5-d timed AI protocol.

Fertility of swamp buffalo following the synchronization of ovulation by the sequential administration of GnRH and PGF 2alpha combined with fixed-timed artificial insemination

This study evaluated fertility in swamp buffalo after synchronization of ovulation combined with fixed time artificial insemination. At the start of the study, designated day 0, from a group of 98 female Thai swamp buffalo, 55 buffalo (heifers n° = 20 and cows n° = 35) were selected to be synchronized with GnRH (Day 0) followed by PGF 2alpha (Day 7) and a second treatment with GnRH (Day 9). All buffalo were inseminated at two fixed times 12 h and 24 h after the second injection of GnRH (Ovsynch+TAI group); a second group of 43 buffalo (heifers n° = 19 and cows n° = 24) were not treated and were artificially inseminated (AI) at natural estrus (AI group). Blood samples were taken 22 days after insemination to evaluate progesterone plasma levels. In the Ovsynch+TAI group, overall conception rate (CR; i.e. the number of cows with progesterone >4.0 ng/ml on day 22 after AI divided by the number of animals inseminated), was 38.1% and overall pregnancy rate (PR; i.e. the number of cows that were pregnant at day 50–60 after insemination divided by the number of animals inseminated), was 32.7%. In the AI group overall CR and PR was 34.9%. Within the Ovsynch+TAI group, CR and PR were reduced (P < 0.05) in heifers compared with cows (CR 15.0% vs. 51.4% for heifers and cows, respectively; PR 15.0% vs. 42.9% for heifers and cows, respectively). Within the AI group the efficacy of treatment was similar between heifers and cows (CR and PR 31.6% for heifers and 37.5% for cows). In conclusion, this study indicates that in swamp buffalo it is possible to synchronize ovulation and use timed artificial insemination with the Ovsynch+TAI protocol.

Exogenous Hormonal Manipulation of Ovarian Activity in Dairy Cattle: Impact on reproduction and fertility.

Event Abstract Back to Event Exogenous Hormonal Manipulation of Ovarian Activity in Dairy Cattle: Impact on reproduction and fertility. Mokhtar E. Benhanifia1* 1 Ibn-Khaldoun University, Institute of Veterinary Sciences, Algeria Introduction. Integrated reproductive management in cattle is considered essential to optimise reproductive performance. Oestrus synchronization can facilitate artificial insemination (AI) in cattle by reducing the time and cost of detection but in some AI programs, only 50% of cows are correctly identified when in oestrus. Although estrogens are important veterinary medicinal products used for therapeutic and zootechnical purposes, the use of oestradiol-17β and its related ester derivatives in food-producing cattle for the purposes of oestrous synchronisation is prohibited in the European Union, New Zealand and Australia. So, the aim of the study was to compare the efficiency of new hormonal treatments; Ovsynch (GnRH-PGF2α) with PRID (Progesterone Releasing Intravaginal Device) in lactating dairy cows (n= 154) in central and western Algeria. Methods. Cows were randomly assigned to two experimental groups. Cows in Group 1 (n = 65) were treated with progesterone releasing intravaginal device (PRID) and received AI 56 hours after withdrawal of the device. Cows in Group 2 (n = 89) were treated with GnRH i.m. (Gonadorelin 0.1 mg/ ml Fertagyl-Intervet) without regard to the stage of the estrous cycle (day of treatment, day 0), followed by 25 mg of PGF2α i.m. (Luprostiol–7mg Prosolvin-Intervet) 7 days later. A second-treatment of the same GnRH analogue (Gonadorelin 0.1 mg/ ml i.m.) was given 48 h after PGF2α and the cows received TAI 16-24 h after the second injection of GnRH. The efficacy of treatments was evalued at Day 25 (NRR: non return rate) and Day 90 (PR: Pregnancy rates) after TAI. Results. NRR ranged between 45.7 to 65.5% (mean 57.4%) in central Algeria, while in Western Algeria NRR ranged between 52.3 to 60% (55.7%). No significant difference was observed (P>0.05). Pregnancy rates (PR) were similar in the two groups treatments: PRID, Ovsynch (33.8% versus 33.7%, P>0, 05) Conclusion. As a conclusion, the use of Ovsynch for synchronization in lactating dairy cattle resulted in similar pregnancy rates following synchronized AI compared to a typical PRID device treatment. Further research is necessary to determine the costs and benefits associated with regimens utilising GnRH (reduce treatment length, dose of GnRH), and other alternative treatments protocols should be further investigated in our conditions (Prostaglandin-based regimens, gonadotropins; FSH, LH, PMSG, Gonadotrophin-releasing hormone and prostaglandin combinations). Finally, coordination of management strategies to maximize production and reproductive performance will optimize early return to cyclicity in post-partum cows, and oestrous response and pregnancy rates in heifers and cows, taking into consideration the suitable alternatives to the use of oestradiol 17ß in synchronisation regimens. Keywords: Reproduction, artificial insemination, Estrogens, progestagens, GnRH, PGF2α Conference: 8th Southeast European Congress on Xenobiotic Metabolism and Toxicity - XEMET 2010, Thessaloniki, Greece, 1 Oct - 5 Oct, 2010. Presentation Type: Oral Topic: Xenobiotics and reproduction Citation: Benhanifia ME (2010). Exogenous Hormonal Manipulation of Ovarian Activity in Dairy Cattle: Impact on reproduction and fertility.. Front. Pharmacol. Conference Abstract: 8th Southeast European Congress on Xenobiotic Metabolism and Toxicity - XEMET 2010. doi: 10.3389/conf.fphar.2010.60.00104 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 Mar 2011; Published Online: 04 Nov 2010. * Correspondence: Dr. Mokhtar E Benhanifia, Ibn-Khaldoun University, Institute of Veterinary Sciences, Tiaret, 14000, Algeria, mbenhanifia@yahoo.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Mokhtar E Benhanifia Google Mokhtar E Benhanifia Google Scholar Mokhtar E Benhanifia PubMed Mokhtar E Benhanifia Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

38 APPLICATION OF A FIVE-DAY PROGESTERONE-BASED SYNCHRONIZATION PROTOCOL FOR TIMED AI WITH SEXED SEMEN IN DAIRY HEIFERS

It is expected that pregnancy per AI with sexed semen would be 70 to 75% of that with conventional semen, and the use of sexed semen with timed AI (TAI) protocols is discouraged (DeJarnette et al. 2009 Theriogenology 71, 49-58). It was hypothesized that the 5-day Co-Synch + CIDR (controlled internal drug-release) protocol with 1 injection of PGF2α would be an acceptable reproductive management program for TAI of dairy heifers with sexed semen. The objectives were to compare pregnancy per TAI (P/TAI) using conventional or sexed semen for the first TAI (experiment 1), and to evaluate P/TAI of a reproductive management program with sexed semen for the first TAI and sexed or conventional semen for the second TAI (experiment 2). A total of 1,000 Holstein heifers between 13 to 14 months of age were synchronized with the 5-day Co-Synch + CIDR protocol, that consisted of an administration of GnRH (100 μg i.m. Cystorelin®, Merial Ltd., Iselin, NJ, USA) and a CIDR insert containing 1.38 g of progesterone inserted at Day 0; on Day 5 the CIDR was removed and one injection of PGF2α (25 mg, i.m. Lutalyse®, Pfizer Animal Health, New York, NY, USA) administered; on Day 8 a second injection of GnRH was administered concurrent with TAI. In experiment 1, 198 heifers were assigned randomly to be TAI with conventional (n = 98) or sexed (n = 100) semen for the first TAI. Commercial straws with sexed or conventional semen were obtained from 2 sires. In experiment 2, a total of 802 heifers received TAI to the first service with sexed semen. For the resynchronized TAI, nonpregnant heifers at 32 days after the first TAI were resynchronized with the 5-day Co-Synch + CIDR and were TAI with either sexed semen (n = 114) or with conventional semen (n = 373). Pregnancy per TAI to first and second TAI was analyzed by logistic regression using the GLIMMIX procedure of SAS (SAS Version 9.1 for Windows, SAS Institute, Cary, NC, USA) with heifer treated as a random effect. In experiment 1, P/TAI was 51.0% and 42.0% at 45 days for conventional and sexed semen, respectively (P = 0.1). Pregnancy per TAI with sexed semen was 82.3% of conventional semen. In experiment 2, P/TAI at first service with sexed semen was 35.9% at 45 days after TAI. For the second TAI, P/TAI was 40.4% with sexed semen at 45 days and 59.2% with conventional semen at 60 days (P &lt; 0.001). As expected, P/TAI was lower with sexed compared to conventional semen. Nevertheless, the application of the 5-day Co-Synch + CIDR protocol with one injection of PGF2α, as a reproductive management program for TAI of dairy heifers, achieved an acceptable P/TAI with sexed semen. We conclude that sexed semen can be used with TAI to effectively manage reproduction in dairy heifers by removing the challenges of detection of estrus and increase the number of females born.

Influence of a controlled internal drug release after fixed-time artificial insemination on pregnancy rates and returns to estrus of nonpregnant cows1

We determined whether an ovulatory estrus could be resynchronized in previously synchronized, AI nonpregnant cows without compromising pregnancy from the previous synchronized ovulation or to those inseminated at the resynchronized estrus. Ovulation was synchronized in 937 suckled beef cows at 6 locations using a CO-Synch + progesterone insert (controlled internal drug release; CIDR) protocol [a 100-microg injection of GnRH at the time of progesterone insert, followed in 7 d by a 25-mg injection of PGF(2alpha) at insert removal; at 60 h after PGF(2alpha), cows received a fixed-time AI (TAI) plus a second injection of GnRH]. After initial TAI, the cows were assigned randomly to 1 of 4 treatments: 1) untreated (control; n = 237); 2) progesterone insert at 5 d after TAI and removed 14 d after TAI (CIDR5-14; n = 234); 3) progesterone insert placed at 14 d after TAI and removed 21 d after TAI (CIDR14-21; n = 232); or 4) progesterone insert at 5 d after TAI and removed 14 d after TAI and then a new CIDR inserted at 14 d and removed 21 d after TAI (CIDR5-21; n = 234). After TAI, cows were observed twice daily until 25 d after TAI for estrus and inseminated according to the AM-PM rule. Pregnancy was determined at 30 and 60 d after TAI to determine conception to the first and second AI. Pregnancy rates to TAI were similar for control (55%), CIDR5-14 (53%), CIDR14-21 (48%), and CIDR5-21 (53%). A greater (P < 0.05) proportion of nonpregnant cows was detected in estrus in the CIDR5-21 (76/110, 69%) and CIDR14-21 (77/120, 64%) treatments than in controls (44/106, 42%) and CIDR5-14 (39/109, 36%) cows. Although overall pregnancy rates after second AI service were similar, combined conception rates of treatments without a CIDR from d 14 to 21 [68.7% (57/83); control and CIDR5-14 treatments] were greater (P = 0.03) than those with a CIDR during that same interval [53.5% (82/153); CIDR5-21 and CIDR14-21 treatments]. We conclude that placement of a progesterone insert 5 d after a TAI did not compromise or enhance pregnancy rates to TAI; however, conception rates of nonpregnant cows inseminated after a detected estrus were compromised when resynchronized with a CIDR from d 5 or 14 until 21 d after TAI.

Effect of preovulatory concentrations of estradiol and initiation of standing estrus on uterine pH in beef cows

Previous studies have indicated that initiation of standing estrus within 24 h of fixed-time AI influenced pregnancy rates. Furthermore, uterine environment at time of insemination can influence sperm transport. We hypothesized that preovulatory concentrations of estradiol would influence uterine pH at time of insemination. The objective of this study was to determine the influence of elevated preovulatory concentrations of estradiol on uterine pH following a fixed-time AI protocol. Cows were synchronized with the CO-Synch ( n = 57) protocol, and 29 cows were treated with an injection of estradiol cypionate (ECP; 1 mg) 36 h before the second injection of GnRH. Cows that exhibited standing estrus or were treated with ECP had increased ( P < 0.05) concentrations of estradiol compared to cows not in estrus and not administered ECP, respectively. There was an ECP by standing estrus interaction on uterine pH ( P = 0.01). Control cows that exhibited estrus had a reduced uterine pH (6.72 ± 0.10; P = 0.05) compared to control cows not exhibiting estrus (7.0 ± 0.06). Cows treated with ECP and detected in standing estrus had a greater uterine pH (7.0 ± 0.07) compared to control cows in estrus ( P = 0.02) and ECP cows not in estrus (6.81 ± 0.09; P = 0.06). The interval between the initiation of standing estrus and when pH was determined also influenced uterine pH. Cows that initiated standing estrus within 4 h of pH determination had a lower uterine pH (6.74 ± 0.12) compared to cows that initiated estrus 4–8 h (7.09 ± 0.08; P = 0.07) or 8–12 h (7.10 ± 0.15; P = 0.03) after pH determination. In summary, elevated concentrations of estradiol influenced standing estrus but only influenced uterine pH when pH was determined within 4 h of the initiation of standing estrus.

Corpus luteum function and embryonic mortality in buffaloes treated with a GnRH agonist, hCG and progesterone

The effect of treatment with a GnRH agonist, hCG or progesterone (P 4) on corpus luteum function and embryonic mortality was investigated in buffaloes inseminated during mid-winter. Italian Mediterranean buffaloes ( n = 309) were synchronized using the Ovsynch with timed-AI program and mated by AI at 16 h (Day 0) and 40 h after the second injection of GnRH. On Day 5, buffaloes were randomly assigned to four groups: Control (no treatment, n = 69), GnRH agonist (buserelin acetate, 12.6 μg, n = 73), hCG (1500 IU, n = 75) and P 4 (PRID without E 2 for 10 days, n = 77). Progesterone (pg/ml) was determined in milk whey on Days 5, 10, 15 and 20 and pregnancy diagnosis was undertaken on Day 26 by ultrasound and Day 40 by rectal palpation. Treatment with buserelin and hCG increased ( p < 0.05) P 4 on Day 15 compared with controls (456 ± 27, 451 ± 24 and 346 ± 28 pg/ml, respectively). Buffaloes treated with a PRID had intermediate P 4 concentrations (380 ± 23 pg/ml). Embryonic mortality between Days 26 and 40 (22.9%) and pregnancies at Day 40 (48.9%) did not differ between treatments. A higher ( p < 0.01) P 4 concentration was found on Day 20 in pregnant animals compared with non-pregnant and embryonic mortality buffaloes, which did not differ. In summary, buserelin and hCG increased P 4 concentrations on Day 15 but this was not associated with a reduced incidence of embryonic mortality in buffaloes during mid-winter.

Ovarian Traits After Gonadotropin-Releasing Hormone-Induced Ovulation and Subsequent Delay of Induced Luteolysis in an Ovsynch Protocol

Our objective was to determine whether delaying the PGF2α injection by 24 or 48h after the first GnRH injection in an Ovsynch protocol (from a standard 7 d) altered ovarian characteristics in lactating dairy cows. Beginning 9 d after removal of a progesterone-releasing controlled internal drug release (CIDR) insert and injection of PGF2α (d 6.4 of the estrous cycle), 36 Holsteins (average body weight=707±12kg and body condition score=2.3±0.1) were administered 100μg of GnRH (81±2 d in milk) and assigned randomly to receive a treatment injection of PGF2α 7, 8, or 9 d later. Timed artificial insemination was performed at 48h after PGF2α at which time a second injection of GnRH was administered. Ovarian structures were mapped by ultrasonography on d 0 (first GnRH injection); on d 2 to determine responses to the first GnRH injection; at PGF2α injection; and daily thereafter through 72h after PGF2α to monitor ovulation of preovulatory follicles. Blood was collected on d 0, 2, at PGF2α injection, and at 24 and 48h after PGF2α to monitor serum changes in estradiol-17β (E2-17β) and progesterone (P4). Based on serum P4 and ovarian exams, 2 cows were eliminated because of anestrus and their failure to ovulate a follicle in response to the first GnRH injection. Two other cows in which luteolysis failed to occur after PGF2α treatment also were eliminated. Final numbers of cows per treatment were: 7 d (n=13), 8 d (n=9), and 9 d (n=10). Twenty-nine of 32 cows ovulated (90.6%) in response to the first GnRH injection. Of those cows not ovulating in response to the first GnRH injection, 2 had 1 original corpus luteum and 1 had 2 original corpora lutea. Despite a 24- or 48-h delay between first GnRH and PGF2α injections, the diameter (mm) and volume (mm3) of the ovulatory follicle did not differ among treatments: 14.3±0.6 and 1,526±62 at 7 d; 14.1±0.8 and 1,479±97 at 8 d; and 15.3±0.9 and 1,490±69 at 9 d. In all 32 cows, at least 1 follicle ovulated after treatment, but ovulation rates did not differ: 1.2±0.1, 1.1±0.1, and 1.3±0.2, respectively, for the 7-, 8-, and 9-d treatments. Serum concentrations of E2-17β did not differ among treatments. Four cows in the 7-d treatment were inseminated 24h late and were excluded before assessing conception rates, which were 5/9 (55.6%), 5/9 (55.6%), and 1/10 (10%), respectively. We conclude that delaying PGF2α injection by 24h had no effect on outcomes.

Comparison of the effect of estradiol benzoate plus progesterone and GnRH on the follicular wave emergence and subsequent follicular development in CIDR-treated, lactating dairy cows with follicular cysts

This study examined the effect of estradiol benzoate (EB) plus progesterone (P4) as compared with GnRH on follicular wave emergence and follicular development, and synchrony of ovulation and pregnancy rates following a second injection of GnRH in a controlled internal drug release (CIDR)-based timed AI (TAI) protocol in lactating dairy cows with follicular cysts. Lactating dairy cows diagnosed with follicular cysts received a CIDR device, with an injection of 2 mg EB plus 50 mg P4 (EB + P4 group) or with an injection of 100 μg GnRH (GnRH group) at the beginning of the experiment (day 0). Thereafter, all received PGF 2α at the time of CIDR removal on day 7, GnRH on day 9, and TAI 16 h later. Follicular wave emergence occurred within 7 days in 12/15 EB plus P4-treated and 14/15 GnRH-treated cows ( P > 0.05). The interval to wave emergence was longer in the EB + P4 group (4.8 ± 0.4 days) than in the GnRH group (2.0 ± 0.2 days). The mean diameters of preovulatory follicles and the proportion of cows with preovulatory follicles greater than 12 mm on day 9 did not differ between groups ( P > 0.05). The proportion of cows with synchronized ovulations by 40 h after the GnRH injection on day 11 and pregnancy rates to TAI did not differ between the EB + P4 (13/15 and 36.7%) and the GnRH (14/15 and 53.3%) groups, respectively. Results suggest that a single treatment with EB plus P4 as compared with GnRH simultaneously with CIDR insertion in lactating dairy cows with follicular cysts will result in relatively asynchronous emergence of a new follicular wave, but subsequently similar sizes of preovulatory follicles and synchronous ovulation, resulting in similar pregnancy rates to TAI.