Natural Estrus Research Articles

Plasma metabolic differences in cows affected by inactive ovaries or normal ovarian function post partum.

Anestrus is essential to an unsuccessful pregnancy in dairy cows. One of the many factors that influences anestrus is the inactive ovary. To characterize in detail the plasma metabolic pro- file, anestrus cows suffering from inactive ovaries were compared with those with natural estrus. The Holstein cows 60 to 90 day postpartum in an intensive dairy farm were assigned into inactive ovaries groups (IO, n=20) and natural estrus group (CON, n=22) according to estrus signs and rectal palpation of ovaries. Plasma samples from two groups of cows were collected from the tail vein to screen differential metabolites using gas chromatography/mass spectrometry (GC/MS) techniques and multivariate statistical analysis and pathways. The results showed that 106 compounds were screened by GC/MS and 14 compounds in the IO group were decreased by analyzing important variables in the projection values and p values of MSA.Through pathway analysis, 14 compounds, mainly associated with carbohydrate metabolism and amino acid meta- bolism, were identified to results in IO, which may seriously affect follicular growth. Metabolo- mics profiling, together with MSA and pathway analysis, showed that follicular growth and development in dairy cows is related to carbohydrate and amino acid metabolism by a single or multiple pathway(s).

Using Progesterone and Prostaglandin F2α for Ewes Estrus Synchronization during Summer Season in Egypt

This study was carried out to investigate the effect of administration of progesterone (P4) and prostaglandin F2α (PGF2α) hormones on ewe estrus synchronization during summer season in Egypt. The study was performed on thirty four non-pregnant or lactating local ewes, 2 - 4 years old and 42.1 ± 1.8 kg average live body weight. Ewes were randomly divided into three groups as follows: natural estrus (control n = 10), intervaginal progesterone sponges (P4 = 12 ewes) for 12 days and two injections of PGF2α (12 ewes) 12 days apart. Parameters of estrus, conception and body weight of lambs were measured. Results showed that the percentage of estrus signs exhibition in PGF2α group reached 83.3%, while the lowest percentage (60%) was observed in control group (P<0.05). The time of starting estrus was earlier (P<0.05) in PGF2α and P4 groups (44.8 and 46h, respectively) than that in control group (58.4 h). The estrus duration was significantly longer (P<0.05) in PGF2α and P4 groups (44 and 41.6 h, respectively) than control group (31.2 h). The percentages of pregnant and lambing rates were 100% in all animals came to heat in all groups. While pregnancy rates and lambing rates according to initial number used were 83.3, 75% and 60% for PGF2α, P4 and control groups (P<0.05), respectively. The litter size, birth weight and weaning weight of lambs born did not differ significantly among groups. Weaning rate was the highest (P<0.05) in PGF2α group (92.9%) and the lowest in P4 group (85.7%). The percentage of ewes lambed twins was the highest (P<0.05) in P4 group (56%) and the lowest percentage in control group (33%). The percentage of male lambs was the highest (P<0.05) for ewes in PGF2α group (57.1%) and the lowest for ewes in control group (37.5%). In conclusion, PGF2α and P4 protocols could adequately induce estrus synchronization and improve some reproductive and productive traits in local ewes during summer season in Egypt. Further studies are recommended to proof results using more number of ewes.

Changes in blood flow to the umbilicus, placentomes, and uterus in Surti buffaloes during complete gestation

With an objective to record the vascularity changes in the umbilicus, placentomes dimensions, and blood flow to the uterus, Surti buffaloes (n=42) were inseminated during natural estrus during the breeding season and scanned by transrectal B mode and color flow mode ultrasonography every 3-4 days till Day 90 of gestation and then at 15 days interval for the complete gestation in the buffaloes that were pregnant (n=24). The umbilical cord color Doppler wavefronts could first be obtained on Day 46 and became increasingly distinct thereafter. The placentomes could first be identified at Day 76 of gestation. The placentome diameters increased from Day 76 till 8th month with significant increases (P

Recipient Selection to Support The Success Rate of Frozen-Thawed Belgian Blue Embryo Transfer

Frozen-thawed Belgian Blue (BB) Embryo transfer (TE) is an effort of fulfilling meat demand in Indonesia. This research aimed at observing the correlation between estrus expressions of standing heat and the correlation of CL characteristics on the success rate of frozen-thawed BB embryo transfer. The study was conducted on 55 recipient cattle with 62 times of TE application, which were categorized into three groups, namely FTET estrus synchronization (n=14), 24-hour natural estrus detection (n=30) and twice-a-day natural estrus detection (n=18). The implemented synchronization was the combination of estradiol-progesterone and hCG with the modification of 24-hour estrus detection between day-9 and 10. The second method was a natural estrus detection, which was conducted four times for 30 minutes, and the third method was twice-aday estrus detection for 90 minutes. The CL characteristics were observed using ultrasonography (USG) in the TE application day. Pregnancy per ET (P/ET) was determined by ultrasonography on d-20, 30, and 50. This research revealed that expressions of standing heat increased P/ET (p&lt;0.05). The pregnancy loss rate was lower of the recipient which showed the estrus expression of standing heat (18.18%) compared to recipients did not show standing heat (40%). Based on the estrus detection method, there was no significant difference between the FTET modification method and the percentage of pregnancy (p&gt;0.05). The CL characteristics showed there was no correlation between CL diameter with the pregnancy success rate of TE (p&gt;0.05).

11 Invivo-derived embryo pregnancy rates at Maddox Dairy from 2008 to 2018

11 Invivo-derived embryo pregnancy rates at Maddox Dairy from 2008 to 2018

48 Transrectal color Doppler evaluation of umbilicus, placentomes, and uterine vascularity changes throughout pregnancy in Surti buffalo

With an objective to record the appearance, vascularity changes in umbilicus, placentomes, and blood flow to the uterus, adult (age 5-10 yr) Surti buffalo (parity=2-6; n=24) were inseminated during natural oestrus during the breeding season and scanned by transrectal B mode and colour flow mode ultrasonography every 3-4 days till Day 90 of gestation and then at an interval of 15 days for the complete gestation. The umbilical cord was first visible on Day 38; however, colour Doppler wave fronts could first be obtained on Day 46, which became increasingly distinct thereafter. The placentomes could first be identified at Day 76 of gestation. The placentome diameters increased from Day 76 until the month 7 with significant increases (P&amp;lt;0.05) during Day 80, and months 4, 5, and 6 of gestation; thereafter, the increase was not significant. The vascularity of placentomes could also be recognised at Day 76 and this increased with increasing months of gestation. The blood flow to the middle uterine arteries could be identified after month 2 of gestation. The resistive index values of the middle uterine artery ipsilateral to the gravid horn showed an almost linear decline with a significant (P&amp;lt;0.05) drop at months 4 and 9 of gestation. Similarly, resistive index values of the middle uterine artery contra-lateral to the gravid horn revealed a significant (P&amp;lt;0.05) decrease on month 3, 5, and 6. A significant decrease for pulsatility index values of the middle uterine artery ipsilateral to the gravid horn was observed in months 3, 6, and 8 of gestation. However, the pulsatility index values for the middle uterine artery contralateral to the gravid horn showed a nonsignificant decrease. It was concluded that the umbilicus and placentomes are first visible at 38 and 76 days of gestation and the vascularity of the umbilicus, placentomes, and middle uterine artery increases with advancement of gestation in Surti buffalo.

130 Increased antral follicle population at 60 days of gestation in Holstein cows with low antral follicle count

The antral follicle count (AFC) has been pointed out as one of the main factors that influence the efficiency of reproductive biotechniques. Thus, AFC is considered a fertility marker, which has high repeatability in the same animal. The objective of this study was to evaluate AFC in cows at AI (nonpregnant) and at two moments of gestation (30 and 60 days). For this, 35 pregnant cows, aged 23 to 99 months, confined in a freestall system, kept in the same environmental conditions (24°46'28”S, 49°56'42”W) and under the same feeding conditions, were selected for this study. The same technician performed the AI of the females, after detection of natural or induced oestrus, with 25mg of Dinoprost (Lutalyse) intramuscularly (IM). We established AFC (antral follicles ≥3mm diameter) using a convex intravaginal transducer at the time of AI and at 30 and 60 days of pregnancy. Females were distributed in groups of low (≤18 follicles, n=11), intermediate (≥24 and ≤28 follicles, n=11), or high AFC (≥30 follicles, n=13). Data were analysed using a generalized linear mixed model (Minitab version 18.1), with significance declared at P ≤ 0.05. In the low AFC group, there was an increase in the mean number of antral follicles in relation to gestation, presenting 14.82±1.36 at the time of AI and 23.45±2.31 and 35.18±3.17 at 30 and 60 days of pregnancy, respectively (P&amp;lt;0.0001). Similarly, the intermediate group presented an increase in mean AFC, from 24.64±0.76 at the time of AI and 29.27±3.32 at 30 days to 43.36±5.91 at 60 days of gestation (P=0.001). There was no difference in the high AFC group at different moments, as these presented 41.92±3.50 at the time of AI, 38.31±3.96 at 30 days, and 50.92±5.49 at 60 days of pregnancy. Although mean AFCs differed (P&amp;lt;0.0001) between the low, intermediate, and high AFC groups at time of AI and at 30 days of gestation, there were no differences in AFC between the three groups at 60 days of gestation (P=0.329). In conclusion, low AFC females presented an increase in the number of antral follicles at gestation moments 30 and 60 days from AI. This finding reinforces the strategy of using this category more efficiently for ovum pickup at the beginning of gestation.

155 Fertility of sexed semen in Holstein heifers and cows

Compared with conventional semen, use of sexed semen decreases the conception rate (CR); therefore, it is important to address the factors that lead to sperm damage. Recently, a novel sexed semen technology was developed for improving dairy cattle fertility (Betthauser et al. 2016 J. Dairy Sci. 99 (E-Suppl. 1), 534). However, there are few reports about the fertility of this novel sexed semen in dairy cattle in Japan. The objective of this study was to compare the CR of traditional sorting semen (S1: flow cytometry/cell sorting) and the novel sexed semen (S2: SexcelTM, ABS Global Inc.) in Holstein heifers and cows in Japan. The CR for the first insemination was obtained from 391 Holstein cows and 148 heifers (10.7-17.8 months old) from 14 dairy farms in Hokkaido from June 2017 to April 2019. Semen used for AI was collected from six bulls and packaged into 0.25-mL straws and frozen. Cows inseminated with conventional frozen semen (S3: unsexed semen in 0.5-mL straws) were used as controls. Calving data were collected from 123 cows and 69 heifers that had calved between January 2018 and May 2019. The diagnosis of pregnancy was confirmed using ultrasonography between 30 and 45 days after insemination. The CR and sex ratio were analysed using chi-square test. The average parity number was 1.9±1.1, and average days open was 84.9±20.4 days. The average interval between calving and the first service was 86.2±20.3 days. The average milk yield (at 305 days) was 12 195±1595 kg. All of the animals were inseminated after the onset of standing heat or removal of the tail chalk of natural heats and oestrus and ovulation synchronisation programmes on the farm. Conception rates of heifers of the first service of S1 (n=54) and S2 (n=94) were 68.5 and 70.2%, respectively. Conception rates of cows of the first service of S1 (n=32), S2 (n=173), and S3 (n=186) were 56.3, 57.8, and 53.8%, respectively. There were no significant differences in CR between these groups (P&amp;gt;0.4). The proportion of female calves produced using S1 (n=61) and S2 (n=57) was 91.8 and 93.0%, respectively, which was significantly more (P&amp;lt;0.01) compared with the 50.0% produced using S3 (n=74). There were no significant differences between S1 and S2 (P&amp;gt;0.8) in terms of the proportion of calves produced. The results of this study demonstrated that the traditional sorting and novel sexed semen (S1 and S2, respectively) did not differ in terms of the first-service CR and produced considerably more female calves than when the conventional semen (S3) was used. Furthermore, these findings indicate that the use of this novel sexed semen could achieve a sex ratio close to 90% female offspring.

Conception Rate of 11 Months Old Dairy Heifer Following Artificial Insemination with Natural Estrus and PGF2α Treatment

The aim of this study was to evaluate the conception rate of 11-months old dairy heifer following artificial insemination with natural estrus or treated with PGF2α at PT. Ultra Peternakan Bandung Selatan. A case study was applied in this study involving all data of 700 records for date of birth, body weight and reproduction status. Sample was selected according the complete records with criteria of age was 11±3 months, body weight >300kg, having normal reproduction organs detected by rectal palpation. The results showed that from observation of selected 300 samples out of 700 heifers, 25 heifers of them were natural estrus (Control), 50 estrus after single PGF2α injection (PG), 95 following single PGF2α and left to normal estrus after 21 days (PG-N), 50 after double PGF2α (2PG), and the rest of 80 heifers showed estrus following double PGF2α – Natural estrus (2PG-N) with the conception rate (CR) of 17/25(68%), 44/50(88%), 42/50(84%), for the respective groups. None of heifers in PG-N and 2PG-N groups became pregnant after first insemination. The body weight (BW) was classified into Low (336-347kg), Medium (348-359kg) and High (360-372kg). The total conception rate was 34%. The CR for Low, Medium and High BW were 41%, 32% and 31%, respectively. The conclusion, the 11-months old heifer was possible to become normal pregnant following insemination without and with PGF2α injection when reached body weight over 300 kg. To ensure the higher number animal exhibiting estrus, double PGF2α injections should be applied.

Exfoliative vaginal cytology of Saanen goat (Capra hircus) during estrus cycle

The exfoliative cytology of the vaginal was evaluated in Saanen goat during the estrus cycle by vaginal smear method. Its a simple technique to determine of estrus cycle stages and a useful tool to determine or identify the estrus phase. The aim of this study was to determine the proportion of exfoliative vaginal cell during the stages of estrus cycle using vaginal smear techniques in Saanen goat. Twenty Saanen goat with weigh 45-55 kg, 3-4 years and had a period of estrus 19-22 days in dry period were observed. All goats were in natural estrus cycle without synchronization. A vaginal smear and vaginal pH were collected from swabbed vaginal epithelium. The result showed the proportion of vaginal cell was significantly different in each phase of estrus cycle. The proportion of superficial cell was dominated in estrus phase. Also, the highest pH values were significantly higher in estrus phase rather than in the other phases. In conclusion, the dominant proportion of superficial cell and a high vaginal pH value which occurred in follicular phase might be used as a marker to determine the optimal time for goat insemination.

Embryo collection from pigs post-pseudopregnancy induced by estradiol dipropionate.

We aimed to define whether embryo collection carried out after pseudopregnancy was of similar outcome and quality as after artificial abortion. To induce pseudopregnancy, 30 gilts or sows were given 20mg intramuscular estradiol dipropionate (EDP) 10-11days after the onset of estrus. Ten additional pigs were inseminated artificially at natural estrus as a control group. Prostaglandin F2α (PGF2α ) was administered twice with a 24hr interval beginning 15, 20, or 25days after EDP-treatment (n=10 per group) or between 23 and 39days after artificial insemination in control pigs. Following this, all pigs were given 1,000IU equine chorionic gonadotropin and 500IU human chorionic gonadotropin (hCG) and then inseminated. Embryos were recovered 6 or 7days after hCG treatment and outcome was recorded. There was no significant difference in the number of normal embryos collected from the pigs with PGF2α initiated at different time points or from the control group. Embryonic developmental stages 7days after hCG treatment also did not differ among groups. These results indicate that the use of EDP to induce pseudopregnancy, followed by PGF2α administration to synchronize estrus for subsequent embryo harvest, is a suitable alternative to the artificial abortion method.

Variations in the body surface temperature of sows during the post weaning period and its relation to subsequent reproductive performance.

ObjectiveA study was made investigate factors affecting body surface temperature changes after weaning in sows, whether these can be used to aid detection of natural estrus and how they relate to subsequent reproductive performance.MethodsA total of 132 sows were selected during summer from a breeding farm, with mean parity of 3.6±2.3 and 28.5±0.9 days lactation length. Four daily measurements (6:00, 8:00, 16:00, and 18:00) of vulva (VST), udder (UST), ear base and central back skin temperatures for individual sows were taken by an infrared thermometer, continuing up to 8 days post weaning.ResultsThe VST obtained from sows showing estrus at 4 days post-weaning (4DPW), 5DPW, and 6DPW showed a peak at the fourth day post-weaning, but then started to decrease. The VST of sows not detected in standing heat (NDPW) remained at a lower level during the experiment, but UST was increased soon after weaning. The VST-UST temperature differences during daytime of sows that were showing behavioural standing heat on 4DPW, 5DPW, 6DPW, and 7DPW were 0.46°C±0.123°C, 0.71°C±0.124°C, 0.66°C ±0.171°C, and 0.58°C±0.223°C, respectively. The NDPW sows had the highest UST observed, but also the lowest VST so that a more negative value of temperature difference (−0.31°C) was seen during first few days post-weaning. A total of 119 sows were observed to show standing heat and were bred. The later the estrus, the smaller the litter size (p = 0.005).ConclusionSows which did not show behavior indicative of stable standing heat after weaning had a VST which remained at a lower level, but the UST increased soon after weaning. Therefore, for sow heat detection under field conditions, the changes of VST and UST and difference between the two should be considered together to increase the accuracy of detection.

Non-surgical artificial insemination using a GnRH analogue for ovulation induction during natural oestrus in African lions (Panthera leo)

Despite postulated potential for wildlife conservation, success of assisted reproduction techniques (ART) in ex-situ feline breeding remains <25%. The aim of this project was to develop a simplified, non-surgical artificial insemination (AI) protocol for African lions (Panthera leo), using an exogenous GnRH analogue to induce ovulation in females presenting natural oestrus, and minimizing manipulation of the animals. Four protocols were tested in five trained lionesses (3.5–8 years), for a total of 14 inseminations (2–4 per lioness). These protocols differed in the time lapse between GnRH injection and insemination, on days 4, 5, or 6 from onset of natural oestrus, determined by daily behavioural observation and vaginal cytology. Semen was collected from 8 different males by urethral catheterization and electro-ejaculation, during full anaesthesia. Females were immediately immobilized for AI after semen collection. After transrectal ultrasound examination of the reproductive tract, insemination was performed either intravaginal or transcervical using a commercial dog urinary catheter (2.0 × 500 mm, Buster®, Krusse, South Africa) with a metal stylet. A single intramuscular dose of exogenous GnRH (20 μg burserelin-acetate, Receptal®, MSD, Intervet, South Africa) administered 30 or 48 h before AI or during the AI procedure induced ovulation successfully, as all females entered either a non-pregnant luteal phase of 59.6 ± 0.95 days (n = 10) or a pregnant luteal phase of 111.7 ± 0.33 days (n = 3). However, the timespan between GnRH injection and end of behavioural and/or cytological oestrus differed widely (range: 0–120 h). The final pregnancy success rate was 33.3%.

English

The present study was conducted to analyse the factors influencing the success of artificial insemination (AI) in pigs using extended fresh semen in rural smallholder pig farms. One hundred female pigs from Rulindo and Gicumbi districts in Northern Region of Rwanda were artificially inseminated using locally collected and extended fresh semen. The pregnancy was confirmed by using both no returns to estrus and abdomen palpation at 21 and two and half months post insemination, respectively. The factors influencing the success of AI were analysed using one way analysis of variance (ANOVA) test. The results showed that the number of inseminations per conception (IC) and litter size were 1.89 &plusmn; 0.83 and 7.94 &plusmn; 2.24, respectively. The number of AI per conception was significantly influenced (p &lt; 0.05) by intrinsic factors (age and parity of the female pig) and extrinsic factors (sex, age and education of household head, time of AI and distance between the farm and semen collection center). The litter size was significantly influenced (p &lt; 0.05) by parity. From the results, we recommend establishing more semen production centers and providing more training on pig management and AI. Key words: Inseminations per conception, litter size, swine, fresh semen, smallholder farms, natural oestrus. &nbsp

Combined effect of heat and nutritional stress on superovulation of Malpura ewes in a semi-arid region

Sheep reared in hot semi-arid environments are generally exposed to heat and nutritional stress in some seasons of the year, which affects both production and reproduction. To assess the effect of high ambient temperature and feed scarcity on superovulation, 16 adult Malpura ewes were randomly divided into two groups of 8 animals each. G1 (control) was kept under a shed and offered a maintenance diet, and G2 (combined stress) was subjected to both nutritional (30% less of maintenance diet) and heat (38–44 °C for 6 h/day) stress. Ewes were superovulated without estrus synchronization by a combination of single injection of 200 IU eCG and 8 injections of FSH (Folltropin-V) at 12-h intervals in tapering doses of 5 mg/kg body weight, starting from the day 7 of natural estrus. eCG was given with the first injection and PGF2α (10 mg) was given with the second last FSH injection. G2 increased respiration rate and rectal temperature (P < 0.01), and blood urea level (P < 0.05), whereas it decreased average daily gain, plasma T4 concentration (P < 0.01) and body weight (P < 0.05). Plasma estradiol level was lower (P < 0.05) in G2 ewes as compared to control (G1) ewes. However, the number of ewes showed a superovulatory response (88 vs 66% ewes ≥ 3 corpus luteum), ovulation rate (8.75 vs 5.88) and embryo production (5.5 vs 3.9) decreased, and the number of large follicles (anovulation) increased (1.0 vs 2.14) in G2 ewes. G2 had a comparable effect on the superovulatory response compared to control ewes although physiological changes occurred as an adaptive mechanism to stress. Therefore, the well-adapted cyclic sheep of the semi-arid region may be used for superovulation despite the stressful condition of heat exposure and nutritional insufficiency.

Vaginal biota number is smaller in tailed than docked hair ewes (Ovis aries), but is not affected by copulation.

A greater accumulation of feces could facilitate the entrance of bacteria or inert particles into the vagina, particularly while mating tailed ewes. Two experiments were performed to determine if the tail has an active role in the growth of bacterial flora and the entrance of inert material in the vagina after mating, during induced or natural estrus. Twenty ewes were used, 10 tailed and 10 docked. All ewes displayed estrus after CIDR treatment, and half of them; 5 tailed and 5 docked were exposed to rams during the first experiment. For the second experiment, the rest of the animals were mated 15-17 d later at spontaneous estrus. In the induced estrus, no differences in the number of CFU/mL in docked or tailed ewes were observed before mating, but after mating, CFU values tended to be greater in docked than tailed ewes, and the number of inert particles was greater in docked than tailed ewes (5.8 ± 1.3 vs 1.6 ± 0.6, P = 0.024). During natural estrus, docked ewes had less CFU/mL than tailed ewes (19.6 × 103 ± 0.4 vs 80.0 × 103 ± 0.0, P = 0.006) before mating, and a similar tendency was maintained after mating, when the number of inert particles was similar in docked and tailed ewes. Staphylococcus and Escherichia were observed in the induced estrus, while in the natural estrus, even though these were the more frequent, five other genera of bacteria were observed. It was concluded that the presence of the tail protects the vaginal environment against increases of the biota load.

Perbaikan Manajemen Reproduksi Kambing Peranakan Etawah Melalui Sosialisasi dan Pelatihan kepada Kelompok Ternak Subur Kokap Kulon Progo DIY

Reproduction management Socialiszation to “Subur” Perananakan Etawah (PE) Goat Farmer Comunitee in Hargo Tirto, Kokap, Kulon Progo, Yogyakarta was focused on reproduction problems in PE Goat. The main issue that should be priority is Goat Reproduction. Good Dairy goat management reproduction will give positive effect to success of milk production. The back ground of animal husbandary comunitee is located in mountain range of Kulon Progo, their main job activity are as a coconut sugar farmer. The Subur Animal Husbandary Comunitee is grouped as a new dairy goat farmer. They still trying to learn how to develop their husbandary, do not have adequate knowledge of good management farming and good information about reproduction. That condition are the reasons to choose Subur Animal Husbandary Comunitee as a target for Socialiszation in presentation and discussion to farmers. Specific explanation and direct practice in field and does oestrus observation. Distribution of feed, medicine, vitamin and mineral were given to Subur Animal Husbandary Comunitee. The results of this program give many positive impact to the farmers and dairy goats such as; the farmers understand and be able to detect signs of oestrus which is very important to them, the farmers have apply detection of oestrus by visual and buck as a natural oestrus detector, natural mating and pregnant occurrence increased after the farmers have applied oestrus detection in does of PE Goat.

11 Conception rate of high-producing dairy cows at first service using prostaglandin F2α and oestradiol benzoate

We have shown that a simplified oestrus synchronization protocol using prostaglandin F2α (PG) and oestradiol benzoate (EB) resulted in a satisfactory conception rate, similar to that obtained in high-producing dairy cows with natural oestrus (Yamaguchi et al. 2018 Reprod. Fertil. Dev. 30, 147 abstr). However, we found no significant effect of PG+EB protocols on the first-service conception rates (CR) of dairy cows. This study investigated the effect of the first-service CR by using PG+EB protocols in the high-producing dairy cows that had not exhibited oestrus expression after calving. Data concerning the first-service CR were obtained for 481 Holstein cows from 4 commercial dairy herds in Hokkaido and Ibaraki, Japan, from 2014 to 2017. The average number of parity, average interval between calving and the first service, and average milk yield (at 305 days) of the cows were 2.2±1.3, 89.7±26.1 days, and 10314±1994kg, respectively. We carried out the PG+EB protocols on cows not showing evident standing heat from Days 50 to 150 postpartum regardless of the presence of a corpus luteum in the ovary. The statuses of ovaries of cows were confirmed using ultrasonography before starting the treatment. Prostaglandin F2α (25 mg; Lutalyse, Pfizer, New York, NY, USA) was injected into cows with a &amp;gt;20mm cutoff for functional corpus luteum diameter at a random stage of oestrus, and EB (1 mg; Ovahormon®, Aska Animal Health Co., Tokyo, Japan) was injected 24h later, and AI was carried out 24 to 48h after EB injection. Cows with a natural oestrus service from Days 50 to 150 postpartum were used as control. All the cows were inseminated after the onset of standing heat or removal of the tail chalk. Pregnancy diagnoses were performed using ultrasonography 30 to 45 days after AI. The CR and intervals of partum to conception were analysed using a chi-square test and ANOVA. The first-service CR (i.e. the number of pregnant cows/total number of cows in the treatment group) of the natural oestrus (n=330) and PG+EB (n=151) groups were 42.7 and 41.1%, respectively, and there were no significant differences between these 2 groups (P=0.7). The average interval between calving and the first service of the PG+EB groups was significantly longer than that of the natural oestrus groups (86.4±1.5 days v. 96.9±1.9 days; P&amp;lt;0.01). The average days open of the natural oestrus and PG+EB groups were 88.5±3.2 days and 98.1±2.3 days, respectively (P&amp;lt;0.05). These results confirmed that the first-service CR in the PG+EB and natural oestrus groups of high-producing dairy cows were similar. We suggest that conducting PG+EB protocols was effective in the high-producing dairy cows that had not exhibited oestrus expression after calving. Moreover, using PG+EB protocols could prevent the further increase in the number of days open.

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

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

Extended lactation in high-yielding dairy cows. I. Effects on reproductive measurements

The objective of this prospective field study was to evaluate the effects of extending the lactation period on various reproductive measurements of high-yielding Holstein cows. On 40 d in milk (DIM), cows were gynecologically examined (transrectal palpation, sonography, vaginoscopy). Cows without signs of clinical endometritis were blocked by parity and were randomly allocated to 1 of 3 experimental groups with a voluntary waiting period (VWP) of 40, 120, and 180 d, respectively (G40, n = 135; G120, n = 141; G180, n = 139). Cows of G120 and G180 were reexamined at the end of the VWP. If natural estrus was detected within 46 d after the end of the VWP, an artificial insemination was performed. If no estrus was detected, the respective cows were synchronized by applying the classical Ovsynch protocol. We found no difference in the proportion of cows in which estrus was detected between 40 to 86 DIM or in the days to first estrus between the 3 groups. Estrus detection in this period was lower in cows with body condition score <3 on 90 DIM compared with body condition score ≥3 (61.5 vs. 76.0%) and in cows with high energy-corrected milk production (ECM) on 92 DIM [58.6 vs. 70.1%, for cows with higher and lower than the median (39.9 kg) ECM, respectively]. The proportion of cows that estrus was detected within 46 d after the VWP was greater in G120 (88.9%) and G180 (90.8%) compared with G40 (70.4%). These effects were more apparent in cows with high ECM. The rate of estrus detection and of becoming pregnant in this period was greater for G120 (hazard ratio = 2.2 and 1.6, respectively) and for G180 (hazard ratio = 2.4 and 1.8) compared with G40. Cows in both groups with extended lactation had greater overall first service conception rates (G120 = 48.9%; G180 = 49.6%) and a lower number of services per pregnant cow (G120 = 1.56 ± 0.1; G180 = 1.51 ± 0.1) compared with G40 (36.6%; 1.77 ± 0.1). We observed no difference in pregnancy loss or in the proportion of cows culled up to 305 d of lactation between the 3 groups. The number of Ovsynch protocols per 1,000,000 kg of ECM was reduced by 75% in G180 and by 74% in G120 compared with G40 (5.9 vs. 7.1 vs. 25.1). In conclusion, extending the lactation of dairy cows can improve main reproductive measurements in high-yielding cows.