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.     

Expression of VEGF-receptor system in conceptus during peri-implantation period and endometrial and luteal expression of soluble VEGFR-1 in the pig

In view of the importance of vascular events observed during gestation, it was hypothesized that the VEGF-receptor system plays a critical role during early pregnancy and maternal recognition of pregnancy in pigs. This hypothesis was tested by examining the expression of the VEGF-receptor system in the porcine conceptus. Additionally, the endometrium, corpus luteum (CL) and embryos were studied for the expression of soluble VEGF receptor 1 (sVEGFR-1), the strong endogenous antagonist of VEGF. The expression patterns show that VEGF164 mRNA levels increase gradually in line with conceptus development, whereas VEGF120 and VEGFR-2 remain unchanged during the peri-implantation period. Interestingly, elevated VEGFR-1 expression was observed in conceptuses on days 15-16 of gestation (P < 0.05). Comparison of the endometrial sVEGFR-1 mRNA expression revealed up-regulation on days 12 and 15-16 of pregnancy (P < 0.01 and P < 0.05, respectively). Furthermore, increased sVEGFR-1 levels were observed on day 12 of the estrous cycle in the CL (P < 0.05). Concluding, it seems that conceptus-derived VEGF164 plays crucial role in peri-implantation vascular events in pigs. These results support a potential role of VEGFR-1 in the proper growth and development of porcine conceptus during pregnancy. Moreover, expression patterns of sVEGFR-1 in the endometrium of pregnant pigs suggest that it may participate in vascular remodeling important for successful implantation. Finally, luteal sVEGFR-1 may be involved in the maintenance of CL function whenever pregnancy occurs in pigs.     

Different expression of PGE synthase,PGF receptor,TNF, Fas and oxytocin in the bovine corpus luteum of the estrous cycle and pregnancy

Functional differences between the corpus luteum (CL) of pregnancy and CL of the cycle in cows were examined. Messenger RNA and protein levels of prostaglandin (PG) E synthase (PGES), PGF2α receptor (PGFR), tumor necrosis factor-α (TNF) and Fas were found to be higher in the CL of pregnancy than in CL of the cycle. Oxytocin (OT) mRNA and protein levels were lower in the CL of pregnancy. Messenger RNA levels of progesterone receptor (PR), luteinizing hormone receptor (LHR), PGE2 receptor (PGER), PGF synthase (PGFS), TNF receptor type I (TNFRI) and TNF receptor type II (TNFRII) did not differ between the cycle and pregnancy. PGE2 and PGF2α production by cultured bovine endometrial tissues was decreased by a supernatant derived from the homogenized CL of pregnancy but not by that of the CL of the cycle, suggesting that specific substances in the CL of pregnancy affect endometrial PG production in cows. Collectively, PGES, PGFR, TNF, Fas or OT may contribute to differences between the CL of pregnancy and CL of the estrous cycle in cows.     

Comparison of long- versus short-term CIDR-based protocols to synchronize estrus prior to fixed-time AI in postpartum beef cows

This experiment was conducted to compare pregnancy rates in postpartum beef cows resulting from fixed-time AI (FTAI) after treatment with controlled internal drug release (CIDR)-based protocols to synchronize estrus. Cows assigned to the Show-Me-Synch (n=167) protocol received a CIDR from d 0 to 14, and prostaglandin F(2α) (PGF(2α)) on d 30. Cows assigned to 7-d CO-Synch+CIDR (n=177) received a CIDR and gonadotropin releasing hormone (GnRH) on d 23. On d 30, CIDRs were removed and PGF(2α) was administered. Blood sampling occurred on d -10 and 0 of treatment to determine estrous cyclicity status (progesterone ≥0.5 ng/mL estrous cycling). Treatments were balanced on age, DPP and BCS. Estrous detection was performed using HeatWatch from PGF(2α) to FTAI. Artificial insemination was performed at predetermined fixed times (72 h, Show-Me-Synch; 66h, 7-d CO-Synch+CIDR) and all cows were administered GnRH at FTAI. This experiment was conducted over a two year period; no differences were found between years so the data were pooled for further analysis. Pregnancy rate resulting from FTAI did not differ (P>0.10) between technicians or AI sires. Pregnancy rate resulting from FTAI was similar between treatments (P=0.20); however, cows that exhibited estrus prior to FTAI had a higher pregnancy rate (P<0.01) than for those that did not. Pregnancy rate at the end of the breeding period was similar between treatments (P=0.28). In summary, FTAI pregnancy rates were similar among postpartum beef cows following treatment with either a short- or long-term CIDR-based estrous synchronization protocol.     

Comparison of long-term CIDR-based protocols to synchronize estrus in beef heifers

Two experiments evaluated long-term controlled internal drug release (CIDR) insert-based protocols to synchronize estrus and compare differences in their potential ability to facilitate fixed-time artificial insemination (FTAI) in beef heifers. In Experiment 1 estrous cycling heifers (n = 85) were assigned to one of two treatments by age and body weight (BW). Heifers with T1 received a CIDR from days 0 to 14, gonadotropin releasing hormone (GnRH) on day 23, and prostaglandin F_2α (PG) on day 30. Heifers with T2 received a CIDR from days 2 to 16, GnRH on day 23, and PG on day 30. Ovaries were evaluated by ultrasonography on days 23 and 25 to determine ovulatory response to GnRH. In Experiment 2 heifers (n = 353) were assigned within reproductive tract scores by age and BW to one of four treatments. Heifers in T1 and T2 received the same treatments described in Experiment 1. Heifers in T3 and T4 received the same treatments as T1 and T2, respectively, minus the addition of GnRH. In Experiments 1 and 2, heifers were fitted with HeatWatch transmitters for estrous detection and AI was performed 12 h after estrus. In Experiment 1 heifers assigned to T1 had larger dominant follicles at GnRH compared to T2 (P < 0.01) but response to GnRH, estrous response after PG, mean interval to estrus, and variance for interval to estrus after PG did not differ (P > 0.10). AI conception and final pregnancy rate were similar (P > 0.50). In Experiment 2 estrous response after PG did not differ (P > 0.70). Differences in mean interval to estrus and variance for interval to estrus (P < 0.05) differed based on the three-way interaction of treatment length, GnRH, and estrous cyclicity status. AI conception and final pregnancy rates were similar (P > 0.10). In summary, the greater estrous response following PG and resulting AI conception and final pregnancy rates reported for heifers assigned to the two treatments in Experiment 1 and among the four treatments in Experiment 2 suggest that each of these long-term CIDR-based protocols was effective in synchronizing estrus in prepubertal and estrous cycling beef heifers. However, the three-way interaction involving treatment length, GnRH, and estrous cyclicity status in Experiment 2 clearly suggests that further evaluation of long-term CIDR-based protocols is required with and without the addition of GnRH and on the basis of estrous cyclicity status to determine the efficacy of these protocols for use in facilitating FTAI.     

Expression and localization of progesterone receptor membrane component 1 and 2 and serpine mRNA binding protein 1 in the bovine corpus luteum during the estrous cycle and the first trimester of pregnancy

The aim of this study was to evaluate the mRNA and protein expression and the localization of progesterone receptor membrane component 1 (PGRMC1), PGRMC2, and the PGRMC1 partner serpine mRNA binding protein 1 (SERBP1) in the bovine CL on Days 2 to 5, 6 to 10, 11 to 16, and 17 to 20 of the estrous cycle as well as during Weeks 3 to 5, 6 to 8, and 9 to 12 of pregnancy (n = 5–6 per each period). The highest levels of PGRMC1 and PGRMC2 mRNA expression were found on Days 6 to 16 (P < 0.05) and 11 to 16, respectively, of the estrous cycle and during pregnancy (P < 0.001). The level of PGRMC1 protein was the highest (P < 0.05) on Days 11 to 16 of the estrous cycle compared with the other stages of the estrous cycle and pregnancy, whereas PGRMC2 protein expression (P < 0.001) was the highest on Days 17 to 20 and also during pregnancy. The mRNA expression of SERBP1 was increased (P < 0.05) on Days 11 to 16, whereas the level of its protein product was decreased (P < 0.05) on Days 6 to 10 of the estrous cycle and was at its lowest (P < 0.001) on Days 17 to 20. In pregnant cows, the patterns of SERBP1 mRNA and protein expression remained constant and were comparable with those observed during the estrous cycle. Progesterone receptor membrane component 1 and PGRMC2 localized to both large and small luteal cells, whereas SERBP1 was observed mainly in small luteal cells and much less frequently in large luteal cells. All proteins were also localized in the endothelial cells of blood vessels. The data obtained indicate the variable expression of PGRMC1, PGRMC2, and SERBP1 mRNA and protein in the bovine CL and suggest that progesterone may regulate CL function via its membrane receptors during both the estrous cycle and pregnancy.     

Fixed-time artificial insemination in red deer (Cervus elaphus) in Argentina

Synchronization of estrous and fixed-time artificial insemination (FTAI) was conducted during the reproductive season of 2008 (March–April) in a local red deer breeding farm in Argentina. Multiparous suckling hinds (n = 38) were artificially inseminated following hormonal treatment (intravaginal sponge containing 100 mg of medroxiprogesterone acetate). At the time of sponge removal (day 12) 250 IU of eCG and 500 μg of PGF2α were given to each hind. The FTAI was performed at 48–55 h after device removal with cryopreserved semen imported from New Zealand. Rectal-transcervical AI method (similar to that in cattle) was performed and semen was deposited within the uterine body (n = 28) or the cervix (n = 10). Pregnancy was diagnosed by means of ultrasonography 44 days after FTAI. The overall pregnancy rate was 36.8% (14/38). Percentage of does that became pregnant with intrauterine seminal deposition was 42.9% (12/28) whereas pregnancy rate in the hinds with intracervical AI was 20% (2/10; P = 0.27).     

Equine chorionic gonadotropin pretreatment 15 days before fixed-time artificial insemination improves the reproductive performance of replacement gilts

Fixed-time artificial insemination (FTAI) technology uses exogenous reproductive hormones to regulate the sexual cycle and ovulation of sows without oestrus identification, which improves the sow breeding utilisation rate, reduces the number of non-productive days, and elevates the efficiency of pig farm management. In this study, we aimed to optimise FTAI procedures. Healthy 190-day-old and about 90 kg Large White × Landrace crossing breed replacement gilts (n = 166) which were of unknown reproductive status were randomly selected and divided into three groups: a control group (n = 62), an eCG-15D group in which the gilts were pretreated with equine chorionic gonadotropin (eCG) injection 15 days before starting FTAI (n = 50), and an eCG-20D group pretreated with eCG injection 20 days before starting FTAI (n = 54). All three groups were then subjected to the same conventional FTAI procedure. Pigs were orally administered Altrenogest (ALT, 20 mg per pig per day) for 18 days and then 42 h after ALT feeding was stopped, they were injected with 1 000 IU eCG followed by 100 μg GnRH 80 h later. The gilts were inseminated for the first time 24 h after gonadotropin-releasing hormone (GnRH) injection and then again 16 h later. After 42 h of ALT feeding, gilts in the eCG-15D group displayed a higher follicular diameter until artificial insemination (AI) than those from the other groups (P < 0.05). In addition, the ovulation times were the most synchronised in the eCG-15D group, with 100% of the gilts ovulating before the second AI on day 25 of FTAI. Furthermore, the gilts in the eCG-15D group achieved the highest pregnancy rate (92%), farrowing rate (90%), total pigs born (11.59), and pigs born alive (11.18). Together, the findings of this study demonstrate that reproductive performance can be optimised by pretreating gilts with eCG 15 days before conventional FTAI.     

Timed artificial insemination plus heat I: effect of estrus expression scores on pregnancy of cows subjected to progesterone–estradiol-based protocols

Expression of estrus near timed artificial insemination (TAI) is associated with greater fertility, and estrus detection could improve TAI fertility or direct TAI management, although accurate estrus detection can be difficult and time-consuming using traditional methods. The aim of this study is to evaluate influence of estrus on pregnancy (artificial insemination pregnancy rates (P/AI)) and to validate an alternative method to classify estrus/heat expression using tail chalking (HEATSC) in postpartum Bos indicus cows subjected to TAI in progesterone–estrogen-based protocols. In experiment 1 (Exp. 1), cows (5491) were subjected to visual observation of estrus after progesterone device removal, before TAI, and P/AI was evaluated according to estrus and body condition score (BCS). Cows received a progesterone device and 2 mg estradiol benzoate (EB). After 8 days, the device was removed and 150 μg of d-cloprostenol and 300 IU equine chorionic gonadotrophin was given. Later, animals in Exp. 1 received 1 mg EB and TAI 44 to 48 h. In the Exp. 2 – 3830 cows using similar protocol, received different ovulation inducers: 1 mg EB (n=1624) or 1 mg estradiol cypionate (EC; n=2206) on day 8 (D8). Cows were then marked with chalk, and HEATSC evaluated at TAI on D10 (HEATSC1 – no chalk removal=no estrus expression; HEATSC2 – partial chalk removal=low estrus expression; HEATSC3 – near complete/complete chalk removal=high estrus expression). In Exp. 1, cows showing estrus presented greater P/AI (48.4% v. 40.2%, P<0.05). In Exp. 2, P/AI (HEATSC1 – 40.0%; HEATSC2 – 49.7%; HEATSC3 – 60.9%; P<0.001), and larger follicle timed artificial insemination (LFTAI) (<0.001) varied according to HEATSC. There was no difference in P/AI (P=0.41) or LFTAI (P=0.33) according to ovulation inducer. Cows with greater BCS showed greater P/AI in both experiments (P<0.05). Estrus presence and greater HEATSC improved P/AI, and EC v. EB used promoted differential estrus manifestation (cows showing HEATSC2 and HEATSC3: 79.5% with EB v. 69.98% with EC use, P<0.001), however, with similar P/AI. The use of HEATSC in B. indicus cows subjected to TAI is useful to identify cows with greater estrus expression and consequently improved pregnancy rates in TAI, allowing the cows with low HEATSC to be targeted for additional treatments aimed at improving P/AI.     

Buserelin overcomes the effect of the corpus luteum on ovarian follicular development in postpartum cycling cows

Follicular development after treatment with a gonadotropin-releasing hormone agonist (buserelin) was compared in ovaries of postpartum cows bearing (CLO) or not bearing (NCLO) a corpus luteum (CL). In the first experiment, 16 cows on day 7 of the estrous cycle (day 0 of treatment) were treated either with saline or 8 μg of buserelin. Both ovaries were collected on day 3 or day 6 (n = 4 per group per day) and follicles over 1.57 mm in diameter were observed histologically. Compared with day 3 in the saline group, there was a greater decrease in the percentage of Class I total (1.57–3.67 mm; P < 0.08) and Class 1 atretic follicles (P < 0.04) but a greater increase in that of Class 2 total (3.68–8.57 mm; P < 0.06), Class 2 atretic (P < 0.04) and early atretic (P < 0.05) follicles on day 6 in the CLO than in the NCLO. In the buserelin group however, all follicular responses (except for Classes 1 and 2 nonatretic follicles, P < 0.08) were similar (P > 0.1) between CLO and NCLO within 3 days after treatment. In the second experiment, follicular responses in CLO and NCLO were compared by daily ultrasonography in cows that had (n = 6) or did not have (n = 4) a buserelin-induced ovulation. After buserelin treatment, the numbers of medium (5–10 mm) and large (over 10 mm) follicles were not different (P > 0.1) between the CLO and the NCLO whether ovulation occurred or not. Results indicate that treatment with buserelin overcame most of the local effects of the CL on the growth and atresia of ovarian follicles in postpartum cycling cows within a 6 day period and this occurred whether ovulation was induced or not.     

Pregnancy patterns during the early fetal period in high producing dairy cows treated with GnRH or progesterone

In order to explore pregnancy patterns in high producing dairy cows treated with GnRH or progesterone at pregnancy diagnosis (Days 28-34), two consecutive experiments were designed. In Experiment 1, cows bearing a single embryo were randomly assigned to a PRID (n = 40; cows fitted with a progesterone releasing intra-vaginal device for 28 days), GnRH (n = 40; cows receiving GnRH) or Control (n = 26; untreated cows) group. PRID treatment led to a rise in plasma progesterone concentrations in the 7 days following the onset of treatment compared to the other two groups. In Experiment 2, in which we also examined twin pregnancies, animals were randomly assigned to PRID (n = 312) or GnRH (n = 294) treatment groups. Treatments were the same as described for Experiment 1. Logistic regression procedures revealed that in cows with a single corpus luteum, the probability of pregnancy loss between the first (Days 28-34) and second (Days 65-62) pregnancy diagnosis decreased by a factor of 0.51 in the PRID group compared to the GnRH group. However, in cows with two or more corpora lutea, PRID treatment increased the likelihood of pregnancy loss by a factor of three, compared to GnRH treatment. In cows carrying twins, the conceptus reduction rate was higher (P = 0.02) for the GnRH (36%) than for the PRID (16.4%) group. Formation of a new corpus luteum was recorded in 17.7% of cows in the GnRH group. Our results indicate that compared to GnRH treatment, progesterone treatment given at pregnancy diagnosis in high producing dairy cows, reduced by a factor of 0.51 and increased by a factor of 3 the probability of pregnancy loss in cows with a single or with two or more corpora lutea, respectively, and reduced the conceptus reduction rate in cows carrying twins. The practical implications of our findings are that in herds with a high incidence of early fetal loss of a non-infectious nature, treatment at the time of pregnancy diagnosis with PRID in cows with one corpus luteum and with GnRH in cows with two or more corpora lutea should offer considerable benefits.     

Timed embryo transfer programs for management of donor and recipient cattle

Currently, timed ovulation induction and fixed-time artificial insemination (FTAI) in superstimulated donors and synchronization protocols for fixed-time embryo transfer (FTET) in recipients can be performed using GnRH or estradiol plus progesterone/progestin (P4)-releasing devices and prostaglandin F_2α (PGF2α). The control of follicular wave emergence and ovulation at predetermined times, without estrus detection, has facilitated donor and recipient management. However, because Bos taurus cows have subtle differences in their reproductive physiology compared with Bos indicus cattle, one cannot assume that similar responses will be achieved. The present review will focus on the importance of orchestrating donor and recipient management to assure better logistics of procedures to achieve more desirable results with embryo collection and transfer. In addition, this will provide clear evidence that the use of FTAI in superstimulated donors and FTET in embryo recipients eliminates the need to detect estrus with satisfactory results. These self-appointed programs reduce labor and animal handling, facilitating the use of embryo transfer in beef and dairy cattle.     

Effect of intrauterine infusion of recombinant bovine interferon αI1 on luteal phase duration and oxytocin-induced release of 13,14-dihydro-15-keto-prostaglandin F2α in postpartum beef cows

The objective of this study was to determine if oxytocin-induced release of prostaglandin F₂α (PGF_2α; measured by the stable metabolite, 13,14-dihydro-15-keto-prostaglandin F₂α (PGFM)) was inhibited following intrauterine infusion of bovine interferon-α_I1 (rboIFNα_I1) into postpartum cows anticipated to have short estrous cycles following first ovulation postpartum. Cows expected to have short estrous cycles were assigned to receive twice daily intrauterine infusions of either placebo (SCP; n = 11) or 2 mg rboIFNα_I1 (SCIFN; n = 14) on Days 1–16 following hCG injection (2500 IU; day 0) on Days 30 or 31 postpartum. On Day 5 following hCG, each cow was injected with 100 IU oxytocin (i.v.) to induce the release of uterine PGF_2α (as measured by PGFM). Other treatment groups consisted of cows expected to have normal estrous cycle lengths following pretreatment with a 9 day norgestomet implant on Days 21 or 22 postpartum followed by hCG injection to induce ovulation. Cows expected to have normal estrous cycle lengths received twice daily intrauterine infusions of either placebo from Days 1 to 16 of the cycle and 100 IU oxytocin (i.v.) on Day 5 (NCPE; n = 11) or twice daily infusions of placebo (NCPL; n = 7) or rboIFNα_I1 (NCIFN; n = 10), from Day 13 post-hCG injection until luteolysis. Oxytocin was injected (100 IU; i.v.) into cows in the NCPL and NCIFN groups on Day 16. The calculated areas under the curve (arbitrary PGFM units) were: 164 ± 18 units, 96 ± 16 units, 93 ± 18 units, 137 ± 27 units and 53 ± 20 units for SCP, SCIFN, NCPE, NCPL and NCIFN, respectively (SCIFN < SCP; NCIFN < NCPL; P < 0.015). Mean luteal phase length was calculated as the number of days from injection of hCG until progesterone declined to below 0.5 ng ml⁻¹ and was: 6.7 ± 1.0 days, 10.5 ± 0.9 days, 12.0 ± 1.0 days, 18.0 ± 1.3 days and 20.7 ± 1.1 days for SCP, SCIFN, NCPE, NCPL and NCIFN, respectively (SCP < SCIFN = NCPE < NCPL = NCIFN; P < 0.01). In summary, luteal phase lengths were increased and oxytocin-induced release of PGFM was reduced by rboIFNα_I1 infusion in cows anticipated to have short luteal phases.     

Effects of kisspeptin-10 on the reproductive performance of sows in a fixed-time artificial insemination programme

Kisspeptin (KP) is a major positive regulator of the hypothalamo–pituitary–gonadal axis and affects female reproductive cyclicity in mammals. It offers an attractive alternative strategy to control reproduction in fixed-time artificial insemination (FTAI) protocols. We aimed to evaluate the effects of different doses of kisspeptin-10 (KP-10) on sow reproductive performance in FTAI protocols. One hundred ninety-eight weaned sows were divided into three groups at random. A FTAI–GnRH group of sows (n = 98) received 100 µg (2 mL) gonadotropin-releasing hormone (GnRH; gonadorelin) by intramuscular injection at 96 h after weaning (t = 0 h); FTAI–KPL (KPL: low-dose KP-10, n = 50), and FTAI–KPH groups of sows (KPH: high-dose KP-10, n = 50) received 0.5 or 1 mg KP-10 (2 mL) respectively at 96 h after weaning. Sows were checked twice daily for oestrus. Ultrasonographic evaluations were performed to determine the follicular diameter and time of ovulation; blood samples were collected immediately before injection (t₀ = 0 min) and at 15, 30, 45, 60, 75, 90 min, 24 and 48 h postinjection. Sows were inseminated at 112 and 132 h after weaning. The oestrus rates (96 vs 92%; 96 vs 88%) and weaning-to-oestrus intervals (98.9 vs 98.6 h; 98.9 vs 97.1 h) were not affected by treatment, but oestrus in the FTAI–KPL group was significantly longer than in the FTAI–GnRH group (38.7 vs 30.0 h; P < 0.05). The peak LH concentrations were 1.29 times greater than at t₀ = 0 in the FTAI–GnRH group, and 1.45 and 1.44 times greater than at t₀ = 0 in the FTAI–KPL and FTAI–KPH groups, respectively. Follicular diameters and pregnancy rates (86 vs 88%, 86 vs 80%, respectively) did not differ between the treatments. Moreover, the total numbers of piglets born and those born alive did not differ among the three groups. These findings suggested that 0.5 mg KP-10 given at 96 h after weaning could be used in FTAI programmes to manage batch farrowing in sows.     

Comparison of PGF2α-induced luteolysis in early pregnant and estrogen-treated ‘pseudopregnant’ gilts

Conceptus estrogen clearly plays a major role in luteal maintenance in the pig; however, other conceptus-derived substances or conceptus-induced uterine secretory products appear to have a local luteotrophic/anti-luteolytic effect on the corpora lutea (CL) and likely may play a key role in maternal recognition of pregnancy in the pig. The objective of these studies was to compare PGF₂α-induced luteolysis in estrogen-treated ‘pseudopregnant’ gilts versus pregnant gilts during the period of maternal recognition of pregnancy. In Experiment 1, doses of PGF₂α ranging from 1 to 100 μg were administered via intraluteal silastic implants to pseudopregnant gilts to determine the dose necessary to cause functional (progesterone) and structural (weight) luteal regression similar to that observed during the natural estrous cycle. Luteal sensitivity to this minimally effective luteolytic dose of PGF₂α was then determined for both pseudopregnant and pregnant gilts in Experiment 2. Experiment 3 investigated whether Day 13 porcine conceptus tissue could directly prevent PGF₂α-induced luteolysis at the level of the CL. The minimally effective luteolytic dose of PGF₂α (100 μg) determined in the pseudopregnant pig caused a similar decline in progesterone concentration and weight of CL in pregnant gilts, suggesting that the susceptibility of CL of pregnant and pseudopregnant pigs to PGF₂α is similar. However, luteal weight was greater (P<0.05) for the pregnant gilts than for pseudopregnant gilts, suggesting that estrogen treatment alone cannot mimic the conceptus effects on CL growth and development. Experiment 3 demonstrated that lyophilized Day 13 conceptus tissue implanted directly into individual CL could partially inhibit PGF₂α-induced luteolysis, providing for the first time direct evidence that porcine conceptuses as early as Day 13 contain factors which can directly (i. e. at the level of the CL) prevent luteal regression.     

Effects of using vasectomized bulls in artificial insemination practice on the reproductive efficiency of Italian buffalo cows

The effects of the presence or absence of vasectomized male buffaloes on the reproductive efficiency of buffalo cows (n = 396) undergoing artificial insemination (AI) was studied on six farms owned and operated by a single consortium. Lactating animals were separated into two groups of various sizes on each farm and kept under semi-range conditions. Vasectomized bulls were present in one group at a bull/empty-cow ratio of 1:30. No bulls were present in the other group. Reproductive efficiency between the two groups over a period of 3.5 months was compared and evaluated on the basis of: 1) the number of spontaneous overt estruses associated with either feeble or intense signs of estrous behaviour; 2) the number of functional estrous cycles, i.e. estrous cycles with luteal phases defined as normal, based on specified progesterone concentrations in milk or blood plasma 8–10 days after estrus; 3) the number of consecutive functional estrous cycles in cases of induced estrus; and 4) pregnancy rate.Groups with bulls present demonstrated a significantly higher reproductive efficiency than groups without them. There was a higher incidence of spontaneous estrus (92 versus 69%; P < 0.01); spontaneous estrus of high intensity (62.2 versus 31.1%; P < 0.01); and higher incidence of functional estrous cycles following both spontaneous (65.8 versus 57.1%) and induced (77.0 versus 59.5%; P < 0.05) estrus. Exposure to vasectomised bulls also increased the incidence of consecutive functional estrous cycles (90.5 versus 68.1%; P < 0.01), and the pregnancy rate in cows inseminated at spontaneous (42.5 versus 18.9%; P < 0.01) or induced (51.1 versus 33.3%; P < 0.05) estrus. Overall pregnancy rate did not differ significantly between cows inseminated at induced or spontaneous estrus, although in the absence of bulls, pregnancy rate per AI was higher in cows inseminated at induced than at spontaneous estrus (33.3 versus 18.9%).     

Factors affecting pregnancy loss for single and twin pregnancies in a high-producing dairy herd

Our objective was to determine the magnitude of, and factors affecting, pregnancy loss for lactating Holstein cows on a commercial dairy farm when diagnosed with twin (n = 98) or single (n = 518) pregnancies using transrectal ultrasonography. Pregnancy losses were assessed with records of non-viable embryos at first pregnancy examination and embryo losses between the first (25-40 d after AI) and second (48 and 82 d after AI) post-breeding pregnancy examinations. Among cows diagnosed with single pregnancies, 3.7% were diagnosed with a non-viable embryo at first pregnancy examination, and 4.6% of those diagnosed with a viable embryo underwent pregnancy loss by the second examination. A total of 11.2% of cows diagnosed with twins experienced a single embryo reduction, whereas 13.3% lost both embryos. Overall, the total proportion of cows experiencing pregnancy loss or experiencing embryo reduction was greater for cows diagnosed with twin than single pregnancies (odds ratio; OR = 3.6), resulting in an embryo survival rate of 91.9% for cows diagnosed with single compared to 75.5% for cows diagnosed with twin pregnancies. Season of breeding and milk production were associated with pregnancy loss for single pregnancies, whereas CL number was associated negatively with embryo reduction and pregnancy loss for twin pregnancies. The risk of twinning and double ovulation among pregnant cows increased with days in milk (DIM), and the risk of double ovulation was greater for cows diagnosed with ovarian cysts and lacking a CL at initiation of an Ovsynch protocol. We concluded that in this herd, embryo reduction and pregnancy loss during early gestation was greater for lactating Holstein cows diagnosed with twin compared to single pregnancies. In addition, cows diagnosed with ovarian cysts and lacking a CL had an increased risk for double ovulation.     

Swine leukocyte antigen-DQ expression and its regulation by interferon-gamma at the maternal-fetal interface in pigs

Successful pregnancy requires an appropriate intrauterine immune response to the conceptus, which is a semiallograft within the uterus. We reported that swine leukocyte antigen-DQA (SLA-DQA), a major histocompatibility complex (MHC) class II gene, is expressed in the uterine endometrium at the time of conceptus implantation in pigs. Because MHC molecules play critical roles in the immune system, SLA-DQ was hypothesized to be involved in immune regulation during pregnancy. Therefore, we examined expression of SLA-DQ in uterine endometrial tissues obtained during the estrous cycle and pregnancy. SLA-DQA and SLA-DQB mRNAs were detected as 1.3-kb and 1.2-kb bands, respectively. Real-time RT-PCR analysis indicated that SLA-DQA and SLA-DQB mRNA expression was affected by day and pregnancy status, with the highest expression on Day 15 of pregnancy. SLA-DQ was localized primarily to subepithelial stromal cells and endothelial cells of the uterus. Using endometrial explant cultures from Day 12 of the estrous cycle, we determined that expression of SLA-DQA and SLA-DQB mRNAs increased in response to interferon-gamma (IFNG), which is produced by pig conceptus trophectoderm between Days 14 and 18 of pregnancy. The abundance of SLA-DQ protein was less in endometria from gilts with conceptuses resulting from somatic cell nuclear transfer compared with endometria from gilts with conceptuses resulting from natural mating. These results support our hypothesis that SLA-DQ is expressed in response to IFNG from the conceptus, and likely regulates immune response at the maternal-fetal interface to support the maintenance of pregnancy in pigs.