ACE inhibition in goats under fixed‐time artificial insemination protocol increases the pregnancy rate and twin births

To assess the effect of the angiotensin‐converting enzyme (ACE) inhibition on the efficiency of the fixed‐time artificial insemination (TAI), 69 goats were divided randomly into two groups: enalapril (n = 35) and control (n = 34). In the experiment, all animals underwent the protocol of fixed‐time artificial insemination for 12 days. Enalapril group received enalapril maleate dissolved in saline (Enalapril, Lab Teuto Ltda) subcutaneously at the following doses: 0.2 mg/kg/day in D0‐D2; 0.3 mg/kg/day in D3‐D6 and 0.4 mg/kg/day in D7‐D11. The control group received the corresponding volume of 0.9% saline solution. We performed a single insemination 36 hr after sponge removal using frozen semen from two adult male goats with recognized fertility. The ultrasound pregnancy diagnosis was 30 days after the artificial insemination (AI). There was significant increase in pregnancy rates and twinning as well as a decrease in foetal loss in animals receiving enalapril (p < .01). The use of ACE inhibitors during the TAI protocol was shown to be a promising alternative to increase the efficiency of such reproductive biotechnology.     

Comparison of pregnancy per AI of heifers inseminated with sex-sorted or conventional semen after oestrus detection or timed artificial insemination

The objective of the study was to compare the fertility after using sex-sorted or conventional semen either with oestrus detection (EST) or timed artificial insemination (TAI) in Holstein heifers. Holstein heifers were randomly assigned to one of the following treatments in a 2 × 2 factorial design. Heifers in the EST group were inseminated with sex-sorted (n = 114) or conventional semen (n = 100) after spontaneous or induced oestrus. Heifers in the TAI, subjected to the 5-day Cosynch+Progesterone protocol (GnRH+P4 insertion-5d-PGF_2α+P4 removal-1d-PGF_2α-2d-GnRH+TAI), were inseminated with sex-sorted (n = 113) or conventional semen (n = 88). Statistical analyses were performed using PROC GLIMMIX procedure of SAS 9.4 (SAS Institute Inc., Cary, NC). Overall P/AI was 60.7% for EST and 54.2% for TAI regardless of types of semen and 68.1% for conventional and 48.9% for sex-sorted semen regardless of insemination strategies. Fertility of heifers inseminated with either sex-sorted (53.5%; 44.2%) or conventional (69.0%; 67.0%) semen did not differ between EST and TAI respectively. Besides, the interaction between the semen type and the insemination strategy was not significant for P/AI. The embryonic loss was significantly greater with sex-sorted semen (17.1%) compared to conventional semen (1.6%). There was no sire effect with sex-sorted semen on P/AI (52.6% vs. 46.2%) and embryonic loss (16.4% vs. 18.0%). As expected, sex-sorted semen resulted in more female calves (89.8% vs. 51.6%) than conventional semen. Thus, sex-sorted semen can be used with 5-day Cosynch+Progesterone protocol to eliminate the inadequate oestrus detection and to increase female calves born in dairy heifers.     

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 20 mg intramuscular estradiol dipropionate (EDP) 10–11 days after the onset of estrus. Ten additional pigs were inseminated artificially at natural estrus as a control group. Prostaglandin F_2α (PGF_2α) was administered twice with a 24 hr interval beginning 15, 20, or 25 days after EDP‐treatment (n = 10 per group) or between 23 and 39 days after artificial insemination in control pigs. Following this, all pigs were given 1,000 IU equine chorionic gonadotropin and 500 IU human chorionic gonadotropin (hCG) and then inseminated. Embryos were recovered 6 or 7 days after hCG treatment and outcome was recorded. There was no significant difference in the number of normal embryos collected from the pigs with PGF_2α initiated at different time points or from the control group. Embryonic developmental stages 7 days after hCG treatment also did not differ among groups. These results indicate that the use of EDP to induce pseudopregnancy, followed by PGF_2α administration to synchronize estrus for subsequent embryo harvest, is a suitable alternative to the artificial abortion method.     

Minimum length of the adaptation and collection period in digestibility trials with sheep fed ad libitum only forage or forage plus concentrate

Two in vivo digestibility trials with sheep were conducted to identify the minimum period length of feeding a new diet to obtain reproducible values of nutritional variables onward and the minimum length of collection period as to obtain maximal precision for each variable. Trial 1 was conducted with ten Polwarth male sheep (34 ± 5 kg body weight (BW)) throughout three 21‐day periods, in a completely randomized two‐way crossover design. The animals were divided into two groups (Group A and B, n = 5 per group) which were fed ad libitum with a sequence of the following diets throughout the periods: Group A: hay – hay plus concentrate – hay; Group B: hay plus concentrate – hay – hay plus concentrate. The concentrate was included in a proportion of 0.33 of the total diet. The intake, and the faecal and urinary excretion were measured daily throughout the experiment. For evaluating rumen fermentation variables, in Trial 2 four Santa Inês male sheep (65 ± 5 kg BW) fitted with ruminal cannula were used. The animals were randomly divided into two groups (n = 2 per group), and the trial was conducted through four 21 days experimental period, in a three‐way crossover design, using experimental diets and feeding management similar to Trial 1. The results indicated that, even though no clear or consistent steady‐state condition was identified for rumen fermentation or urinary excretion variables, the adaptation period for measuring OM digestibility in in vivo trials with sheep fed ad libitum where the diet shifts from one of only hay to another containing concentrate, or vice‐versa, should be at least 12 days long. Moreover, although no precision improvement was obtained by increasing the collection period above 1 day for measuring OM digestibility, the minimal length of collection period should be 4 days for measuring faecal excretion variables and 7 days for measuring urinary excretion variables.     

Effect of breeding method and season on pregnancy rate and embryonic and fetal losses in lactating Nili-Ravi buffaloes

The aim of this study was to determine the effect of breeding method and season on pregnancy rate and cumulative embryonic and fetal losses in Nili-Ravi buffalo. Estrus detection was performed twice a day by teaser buffalo bull for 1 hour each. A 2?×?2 factorial design was used to address the breeding method and season. Buffaloes (n?=?130) exhibiting estrus were randomly assigned to be bred either in peak breeding season (PBS; n?=?80) or low breeding season (LBS; n?=?50). Within each season, buffaloes were divided to receive either natural service (NS; n?=?65) or artificial insemination (AI; n?=?65). NS buffaloes, in estrus, were allowed to remain with the bull until mating. AI was achieved, using frozen thawed semen of bull of known fertility. PBS comprised of September to December and LBS were from May to July. Serial ultrasonography was performed on days 30, 45, 60, and 90 after breeding (day 0) to monitor pregnancy rate and embryonic and fetal losses. The pregnancy rate on day 30 after breeding was higher in NS as compared to AI group (63 vs. 43%; P?<?0.05) during PBS while it did not differ (48 vs. 32%; P?>?0.05) in LBS. The cumulative embryonic and fetal losses between days 31 and 90 were significantly lower in PBS than LBS (33 vs. 60%; P?<?0.05), ignoring breeding method. Pregnancy rates were better with NS in PBS, and cumulative embryonic fetal losses were higher in LBS in Nili-Ravi buffalo.     

The Effect of Long‐term In Vivo Culture in Bovine Oviduct and Uterus on the Development and Cryo‐tolerance of In Vitro Produced Bovine Embryos

The objective of this study was to compare the embryo production and quality carried out entirely in vitro or partly in vitro combined with short‐ vs long‐term in vivo culture using the homologous cattle oviduct. The IVM oocytes were in vitro fertilized and cultured for 7 and 8 days (IVP‐Group), or after IVF and 2–3 days of IVC, 4–8 cell stage embryos were endoscopically transferred into oviducts of synchronized heifers (In Vivo‐Group) or IVM oocytes were co‐incubated with spermatozoa for 3–4 h and transferred into the oviducts of synchronized heifers (GIFT‐Group). Embryos of the In Vivo‐Group and the GIFT‐Group were recovered on day 7 from the oviducts and uterine horns. Embryos of all groups were either cryopreserved at day 7 (day 7 blastocysts) or cultured in vitro in CR1aa‐medium supplemented with 5% ECS for further 24 h and cryopreserved (day 8 blastocysts). The total blastocyst yield found in the in vivo cultured groups was similar to the results of the IVP‐Group. But the appearance of blastocysts was dependent on the duration of in vivo culture. The more time the embryos spent in the in vivo environment, the more blastocysts appeared at day 8. The quality of produced blastocysts assessed by cryo‐survival was also correlated to the culture conditions; the in vivo cultured embryos showed higher cryo‐tolerance. However, the duration of in vivo culture crucially influenced the cryo‐tolerance of produced blastocysts. It is concluded that tubal access is a promising tool to provide a further basis for studying embryo sensitivity to environmental changes.     

Pregnancy and offspring sex ratio following insemination with SexedULTRA and conventional semen in cows in a commercial beef operation

Pregnancy rate per AI (PR/AI) and breeding season pregnancy rates between insemination with sexed semen (SS; at 18 hr after the onset of oestrus) and conventional semen (CS; at 12 hr after the onset of oestrus,) and offspring gender ratio between two groups were compared. Angus cross cows (n = 686, during 2019 and 2020 breeding seasons) were oestrus-synchronized using Select-Synch + CIDR protocol and were observed thrice daily for oestrus until 72 hr after PGF2α administration. Cows expressed oestrus (n = 513) were inseminated with either SS (n = 246; SexedULTRA 4M™; y chromosome-bearing sperm) or CS (n = 267). Cows (n = 173) that failed to express oestrus at 72 hr after PGF2α received 100 μg of GnRH and CS insemination concomitantly. Two weeks later, cows were penned with natural service sires (bull:cow ratio 1:25) for 45 days. Pregnancy was diagnosed 30 days after bull removal. Calves' gender was determined at birth. For cows that expressed oestrus, PR/AI did not differ (p > .1) between SS (65.0%) and CS (66.7%) groups. The overall PR/AI differed (p < .05) between SS (65.0%) and CS (56.4%) groups. The natural service PR differed (p < .001) but breeding season PR (p > .05) did not differ between SS vs. CS groups. Bull:heifer gender ratio following AI was 88:12 and 52:48 for SS and CS groups, respectively, with an overall 66:34 ratio. Bull:heifer gender ratio for the two breeding seasons was 79:21 and 52:48 for SS and CS groups, respectively, with an overall 62:38 ratio. In conclusion, the fertility of SS insemination at 18 hr after onset of oestrus was 97% of CS insemination at 12 hr after onset of oestrus. Though breeding season pregnancy did not differ between SS and groups, preferred calf gender was 25 percentage points greater for SS over CS application. The gender accuracy was 88%.     

Embryo‐maternal Communication during the First Days of Embryonic Life

The mechanisms of embryo‐maternal communication during the first days of embryonic life are largely unknown. Using the bovine as a model, the aims of our study were to morphologically characterize the interaction between the pre‐implantation embryo and the epithelium of the maternal ampulla, isthmus and uterotubal junction by light and scanning electron microscopy. For this purpose, oviducts were removed from cows revealing a functional corpus luteum on day 3 after insemination. These were compared to oviducts removed on day 3 (metestrus) of the estrous cycle. Three days after insemination, the majority of the epithelial cells in the ampulla were secretory cells distinctly protruding into the oviductal lumen. Contrary the ampulla of cows on day 3 of the cycle predominantly revealed ciliated cells in the oviductal epithelium. As shown by Periodic Acid Schiff reaction (PAS) with and without amylase digestion, the secretory cells of the ampulla synthesized merely glycoproteins during metestrus, but large amounts of glycogen during pregnancy. In the isthmus no morphological differences were seen between pregnant and cyclic cows. The most conspicuous finding during pregnancy was seen in the uterotubal junction: Vital cumulus cells embedded in between epithelial cells had developed short cytoplasmic processes intensely contacting the epithelial uterine cells. The embryos obtained ex vivo were regularly covered with a thick layer of homogenous extracellular matrix. Contrary embryos produced in vitro– both with and without coculture with oviductal cells –revealed a clearly visible zona pellucida with spongy appearance and numerous pores. Our results imply that already during the first days of life there is intense interaction of the pre‐implantation embryo and the maternal genital tract part of which may be mediated by cumulus cells.     

Timed artificial insemination in crossbred mares: Reproductive efficiency and costs

Timed artificial insemination (TAI) has boosted the use of conventional artificial insemination (CAI) by employing hormonal protocols to synchronize oestrus and ovulation. This study aimed to evaluate the efficiency of a hormonal protocol for TAI in mares, based on a combination of progesterone releasing intravaginal device (PRID), prostaglandin (PGF_2α) and human chorionic gonadotropin (hCG); and compare financial costs between CAI and TAI. Twenty-one mares were divided into two groups: CAI group (CAIG; n = 6 mares; 17 oestrous cycles) and TAI group (TAIG; n = 15 mares; 15 oestrous cycles). The CAIG was subjected to CAI, involving follicular dynamics and uterine oedema monitoring with ultrasound examinations (US), and administration of hCG (1,600 IU) when the dominant follicle (DF) diameter's ≥35 mm + uterine oedema + cervix opening. The AI was performed with fresh semen (500 × 10⁶ cells), and embryo was recovered on day 8 (D8) after ovulation. In TAI, mares received 1.9 g PRID on D0. On D10, PRID was removed and 6.71 mg dinoprost tromethamine was administered. Ovulation was induced on D14 (1,600 IU of hCG) regardless of the DF diameter's, and AI was performed with fresh semen (500 × 10⁶ cells). On D30 after AI, pregnancy was confirmed by US. The pregnancy rate was 80.0% in TAIG and 82.3% in CAIG (p > .05). The TAI protocol resulted in 65% reduction in professional transport costs, and 40% reduction in material costs. The TAI was as efficient as CAI, provided reduction in costs and handlings, and is recommended in mares.     

Comparative efficiency of novel laparoscopic and routine vaginal inseminations with cryopreserved semen in rabbits

Laparoscopic artificial insemination technique (LAI) is described to overcome reduced fertility problems in sheep artificial insemination (AI) programmes with frozen semen. Later on, this technology was modified for endangered non-domestic cats to deposit low quality or reduced number of sperm cells hardly obtained by electro-ejaculation into the oviduct. This technique by passes the complex structure of cervix and efficiently transfers the sperm cells to the point of fertilization. In recent years, rabbits are becoming popular transgenic animal models producing various therapeutic and commercial products, as well as being experimental animals for disease models. The worldwide transportation of frozen semen and re-establishment of transgenic lines using AI technology has become a common practice. Therefore, this study was designed to describe a laparoscopic intrauterine insemination technique, which might assist in conceiving the animals with limited number of sperm cells. The female rabbits were laparoscopically (n = 22) or vaginally (n = 13) inseminated with frozen–thawed semen samples containing approximately 10 × 10⁶ motile sperm. The laparoscopic insemination technique provided higher pregnancy rate (45.5%) than vaginal insemination technique (7.7%) (p < .05). In conclusion, the described laparoscopic AI might be a new alternative technique, thus enabling limited or low-quality frozen sperm samples to establish pregnancy in rabbits.     

Urine levels of luteinizing hormone as predictor of the period of ovulation for advantage of timed‐artificial insemination in murrah buffalo (Bubalus bubalis)

Assessment of urine levels of luteinizing hormone (LH) for predicting the reproductive status of animals is in practice. The aim of this study was to predict the period of ovulation based on the urine levels of LH for timed‐artificial insemination to increase the conception rate in buffaloes, which are naturally silent‐oestrous animals. Level of LH in urine was assessed using ELISA, and a cut‐off LH concentration for prediction of ovulation period was obtained using receiver operating characteristic analysis. Artificial insemination was performed before‐ and after ‐positive prediction of ovulation period adopting this method, and the rates of conception were assessed. Urine LH level of 105 mIU/ml (n = 14) was derived as a cut‐off concentration which predicts the ovulation period. The buffaloes in the positively predicted group (day 1 or 2) inseminated via intracervical route had an increase in the conception rate (83.33%); however, the insemination in the before‐positive‐prediction group resulted in poor conception rates (day 0; 16.66%) compared to that of the naturally inseminated group (day 0; 75.0%). In conclusion, the urinary LH would possibly be a fairly reliable predictor of the ovulation period. The day when cut‐off LH concentration is obtained may be taken as the most favourable time for artificial insemination, so as to attain a much better rate of conception in the buffalo.     

Aldosterone breakthrough with benazepril in furosemide‐activated renin‐angiotensin‐aldosterone system in normal dogs

Pilot studies in our laboratory revealed that furosemide‐induced renin‐angiotensin‐aldosterone system (RAAS) activation was not attenuated by the subsequent co‐administration of benazepril. This study was designed to evaluate the effect of benazepril on angiotensin‐converting enzyme (ACE) activity and furosemide‐induced circulating RAAS activation. Our hypothesis was that benazepril suppression of ACE activity would not suppress furosemide‐induced circulating RAAS activation, indicated by urinary aldosterone concentration. Ten healthy hound dogs were used in this study. The effect of furosemide (2 mg/kg p.o., q12h; Group F; n = 5) and furosemide plus benazepril (1 mg/kg p.o., q24h; Group FB; n = 5) on circulating RAAS was determined by plasma ACE activity, 4–6 h posttreatment, and urinary aldosterone to creatinine ratio (UAldo:C) on days ?1, ?2, 1, 3, and 7. There was a significant increase in the average UAldo:C (μg/g) after the administration of furosemide (Group F baseline [average of days ?1 and ?2] UAldo:C = 0.41, SD 0.15; day 1 UAldo:C = 1.1, SD 0.56; day 3 UAldo:C = 0.85, SD 0.50; day 7 UAldo:C = 1.1, SD 0.80, P < 0.05). Benazepril suppressed ACE activity (U/L) in Group FB (Group FB baseline ACE = 16.4, SD 4.2; day 1 ACE = 3.5, SD 1.4; day 3 ACE = 1.6, SD 1.3; day 7 ACE = 1.4, SD 1.4, P < 0.05) but did not significantly reduce aldosterone excretion (Group FB baseline UAldo:C = 0.35, SD 0.16; day 1 UAldo:C = 0.79, SD 0.39; day 3 UAldo:C 0.92, SD 0.48, day 7 UAldo:C = 0.99, SD 0.48, P < 0.05). Benazepril decreased plasma ACE activity but did not prevent furosemide‐induced RAAS activation, indicating aldosterone breakthrough (escape). This is particularly noteworthy in that breakthrough is observed at the time of initiation of RAAS suppression, as opposed to developing after months of therapy.     

Effects of Female Dietary Restriction in a Rabbit Growth Line During Rearing on Reproductive Performance and Embryo Quality

Maternal diet prior to mating has an effect on reproductive performance. We analysed the effect of maternal dietary restriction during rearing on reproductive performance, the embryo development and foetal growth. Females were categorized in two groups: (i) does with ad libitum access to feed or (ii) restricted. Two experiments were performed: (i) after 1 month, receptive females from both experimental groups were artificially inseminated and the reproductive performance was recorded during three reproductive cycles; at the first insemination, the body weight and perirenal fat thickness were recorded, and (ii) females from both experimental groups were inseminated, and 24 h later, embryos were recovered and transferred to recipient females from a maternal line. Later, embryonic implantation was assessed at day 14 by laparoscopy and foetal growth was monitored by ultrasound examination. In experiment 1, no differences in kindling rate was found, but prolificacy was showed to be higher in ad libitum does, which also were heavier than restricted ones. In experiment 2, no differences among does either in body weight, in perirenal fat thickness or in reproductive performance (ovulation rate and embryo recovery rate) were related to differences in feed intake. However, despite similar embryonic implantation losses, embryos from restricted females demonstrated higher foetal and gestational losses. Embryos from restricted does presented lower foetal growth than embryos from ad libitum does. Therefore, our results demonstrated that nutrition before first conception in a rabbit line selected for growth rate may impact on the embryo and results in a disturbance in gestational losses and foetal growth over all reproductive life.     

精液品质及其体内和体外受精能力的相关性研究

本试验研究了公猪精液的精子密度、活率和畸形率等精液品质指标与其在自然交配、人工输精和体外受精中受精能力之间的关系。研究表明,现有的精液品质评价参数可以反映该公猪在自然交配或人工输精后对体内卵母细胞的受精能力,但相似品质的精液在体外受精能力上差异显著(P<0.05),现有的精液质量评价参数不能反映其体外受精能力。     

A study on the effect of GnRH administration on the ovarian response and laparoscopic intrauterine insemination of Awassi ewes treated with eCG to induce superovulation

The effect of GnRH administration on superovulatory response of ewes treated with equine chorionic gonadotrophin (eCG) in breeding and nonbreeding seasons and the contribution of laparoscopic insemination to the improvement of fertilization and embryo recovery were investigated. Twenty-four nonpregnant Awassi ewes of 3–4 years of age were randomly allocated into two groups (n = 12). Each ewe was treated with a progesterone impregnated intravaginal sponge for 12 days. The following superovulation treatment was used: ewes of group 1 received 1,200 IU of eCG once as an intramuscular injection 48 h prior to sponge withdrawal; ewes of group 2 also received 1,200 IU of eCG once as an intramuscular injection, 48 h prior to sponge withdrawal and after 24 h of sponge removal. Ewes were injected with 80 μg of GnRH. Ewes of groups 1 and 2 were further subdivided into four equal groups (n = 6). Subgroups A and C (superovulated with eCG and eCG plus GnRH, respectively) were mated naturally at least two times with Awassi rams of proven fertility at 8-h intervals. Subgroups B and D (same as A and C) had intrauterine insemination at 44–46 h after sponge removal, under laparoscopic visualization of uterine horns, depositing 1 ml of diluted semen containing 100 × 10⁶ motile sperm in the distal portion of each uterine horn. Ovarian response was assessed by determining the number of corpora lutea by laparoscopy at day 6 after mating. Embryo recovery was performed by using a semi-laparoscopic flushing procedure in both uterine horns. Results of the present study showed that ewes treated in breeding season with eCG plus GnRH has a higher number (P < 0.05) of corpora lutea than eCG alone as 7.33 ± 0.54 and 4.33 ± 0.39, respectively. There was no significant difference in the number of corpora lutea in nonbreeding season when ewes treated with eCG and eCG plus GnRH. The number of unovulated follicles was significantly higher (P < 0.05) in eCG treated ewes than in ewes treated with eCG plus GnRH, both in the breeding and nonbreeding seasons. The number of recovered embryos from ewes treated with eCG plus GnRH and eCG differ significantly (P < 0.05) as 4.32 ± 0.56 and 1.06 ± 0.26, respectively, in the breeding seasons. No significant difference was observed when these hormones used for superovulation in the nonbreeding season. A higher number of unfertilized ova (P < 0.05) was observed in ewes when naturally inseminated than in ewes inseminated using the intrauterine laparoscopic technique. Higher rate of embryo recovery (P < 0.05) was achieved when ewes were inseminated via intrauterine (4.66 ± 0.66) compared with ewes naturally mated (2.16 ± 0.74). The fertilization rate in ewes inseminated intrauterine using laparoscopic techniques and naturally mated were 91.5% and 44.8%, respectively. Fertilization failure in ewes inseminated intrauterine using laparoscopic techniques and naturally mated were 8.4% and 55.2%, respectively. It could be concluded that administration of GnRH 24 h after sponge removal increased ovulation rate of Awassi ewes treated with eCG for superovulation in the breeding season. The use of eCG to induce superovulation in Awassi ewes combined with laparoscopic intrauterine insemination increases the fertilization rate.     

Effects of cow parity on voluntary hay intake and performance responses to early weaning of beef calves

The objective of this study was to investigate the effect of early calf weaning from both primiparous and multiparous beef cows on hay intake and measures of performance. Over two consecutive years, 96 Brahman × British cows (48 cows/year) and their calves were stratified by parity and calving date and randomly assigned to one of two weaning treatments (n = 24 cows/weaning treatment; 12 primiparous and 12 multiparous). Weaning treatments consisted of normal-weaned (calf remaining with cow throughout the study) or early weaned (calves removed from cow at 86 ± 5 days of age). An estrus synchronization and fixed-timed artificial insemination protocol (CO-Synch + CIDR) was applied to all cows at 21 days after early weaning. Following fixed-timed artificial insemination, cows were put onto bahiagrass (Paspalum notatum) pastures (3 pastures/treatment; 4 cows/pasture) for a 60-day period to evaluate voluntary hay intake. During this time, cows were provided free-choice access to grass hay (‘Florona’ stargrass; Cynodon nlemfuensis) and 2.3 kg per head daily of a urea-fortified molasses supplement. Hay intake was determined by subtracting the dried weight of residual hay from the amount offered over the 60-day evaluation period. Cow body weight and body condition score were measured on day 0 and 60. Immediately following the hay intake determination period, all cows were grouped by weaning treatment and exposed to mature Angus bulls for 21 days. Pregnancy determination to artificial insemination and natural service was determined by transrectal utrasonography on two occasions conducted 60 days after artificial insemination and again 40 days after bull removal. Multiparous cows had greater hay dry matter intake (P < 0.001), body weight (P < 0.001), and body condition score (P < 0.001) than primiparous cows throughout the study. Overall, early weaning resulted in greater than a 16% decrease (P < 0.01) in hay dry matter intake, irrespective of parity. Early-weaned cows had greater (P < 0.01) body weight and body condition score than normal-weaned cows on day 60, but not day 0. Pregnancy rate to artificial insemination was greater (P < 0.01) for multiparous compared to primiparous cows. There was a weaning treatment × parity interaction for overall pregnancy rate, whereas early-weaned primiparous, but not multiparous, cows had a greater (P < 0.05) overall pregnancy rate compared to their normal-weaned contemporaries. These data imply that early calf weaning (90 days of age) will increase body weight and body condition in both multiparous and primiparous cows; however, early-weaning provides a greater advantage to overall pregnancy rate when applied to primiparous versus multiparous cows.     

Oxytocin increases pregnancy rates after fixed time artificial insemination in Kazak ewes

It is probable that reduced pregnancy rates in ewes after fixed time artificial insemination (FTAI) is attributable, in part, to the reduced number of normal spermatozoa that colonize the oviduct. Administration of oxytocin stimulates both cervical dilation and uterine/oviductal contractility. The hypothesis that oxytocin can enhance sperm transport into the uteri and the oviducts, and thereby increase pregnancy rates, was tested in the present study. Oestrus was synchronized in 199 multiparous Kazak ewes using intravaginal flurogestone-impregnated sponge. The sponge was left in the vagina for 12 days followed with an injection of 330 IU of eCG at sponge removal. Each ewe was intracervically inseminated twice at 50 hr and 62 hr after the removal of sponges using an insemination catheter containing 0.25 ml of diluted semen. Semen was collected from seven Texel rams and all the ejaculates were pooled and diluted in ultra-high temperature-treated commercial skimmed milk without (Control group, 0.05 ml of saline per mL milk, n = 144) or with oxytocin supplement (Oxytocin group, 0.5 U of oxytocin per ml milk, n = 55). Pregnancy status was determined by transabdominal ultrasound examination 45 days after insemination. Lambing performance was recorded at delivery. Significant differences were observed between the Oxytocin group and the Control group in terms of the pregnancy rate and the fecundity rate (85.5% and 92.7% versus 68.8% and 72.9%, respectively). In conclusion, low dose oxytocin supplementation of semen extender significantly increased pregnancy and fecundity rates in oestrus-synchronized Kazak ewes after FTAI.     

Interaction of Intact Porcine Spermatozoa with Epithelial Cells and Neutrophilic Granulocytes during Uterine Passage

New insemination techniques allow a tremendous sperm reduction for successful artificial insemination (AI) if highly diluted semen is deposited in the tip of the uterine horn and close to the utero‐tubal junction. High sperm losses are known to occur during uterine passage and it was the general question whether specific binding mechanisms are involved. Upon arrival in the uterus, spermatozoa are confronted with mainly two different cell types: uterine epithelial cells (UEC) and neutrophilic granulocytes (polymorphonuclear neutrophil, PMN). As cell–sperm interactions can hardly be observed in vivo, an ex vivo system was established to study the interaction between spermatozoa and the UEC. Uterine segments (10 cm) from freshly slaughtered synchronized juvenile gilts were inseminated for 60 min at 38°C. Thereafter spermatozoa were recovered, counted flow cytometrically and examined for changes in viability and mitochondrial membrane potential (MMP). Significantly less spermatozoa with a functioning MMP and intact plasma membranes could be retrieved (55 ± 7%), while the number of damaged spermatozoa hardly changed (93 ± 12%), indicating retention of viable sperm cells in the uterine lumen. The interactions between porcine PMN and spermatozoa (motile, immotile, membrane‐damaged) were studied in coincubation assays in vitro. The binding of membrane‐damaged sperm cells to PMN was virtually non‐existent (3 ± 2%). Viable and motile spermatozoa attached to PMN without being phagocytosed within 60 min (45 ± 3%), whereas binding to sodium fluoride (NaF)‐immobilized spermatozoa was reduced to 20 ± 2%. The binding of viable sperm to PMN is most likely not lectin‐dependent; although both viable cell types were shown to express a broad range of different lectin‐binding sugar residues, none of the lectins tested was able to selectively block PMN‐sperm binding significantly. The results of the study suggest that viable spermatozoa are already subject to selective processes within the uterus before further selection is initiated at the utero‐tubal junction and in the oviductal isthmus.     

Endometrial Explant Culture to Study the Response of Equine Endometrium to Insemination

Mating‐induced endometritis (MIE) is ubiquitous in the horse after natural mating and artificial insemination with frozen/thawed semen causing the most aggressive response. The majority of mares eliminate MIE 24–48 h after insemination. An endometrial explant culture was tested as a potential in vitro exemplar for sperm‐induced MIE. Endometrial prostaglandin F_2α (PGF_2α) secretion and expression of interleukin‐8 (IL‐8) were used as markers of inflammation. Endometrial explants were cultured from uteri collected from follicular phase mares. Explants were challenged with 1 or 10 × 10⁶ sperm/ml frozen/thawed semen, chilled semen, washed sperm or seminal plasma. Medium was collected 24 and 72 h after challenge and assayed for PGF_2α by radioimmunoassay. Treatment of endometrial explants with frozen/thawed, chilled semen or washed sperm did not change the secretion of PGF_2α compared with untreated controls. However, 24 h after challenge cultured explants expressed IL‐8. The in vitro endometrial explant system did not represent the in vivo response to semen when PGF_2α was used as a marker of inflammation, yet the use of gene expression as an inflammatory marker warrants further investigation.     

Pregnancy rate after fixed‐time transfer of cryopreserved embryos collected by non‐surgical route in Lacaune sheep

This study investigated the feasibility of applying fixed‐time (cryopreserved) embryo transfer in ewes. Embryos (n = 106) were non‐surgically recovered from superovulated donors (n = 39) on day 6–7 after oestrus. Straws containing one or two embryos (morulae and/or blastocysts) subjected to either slow freezing (SF, n = 62) or vitrification (VT, n = 44) were randomly used within fixed‐time embryo transfer on Day 8.5. Recipient ewes were nulliparous (n = 58) bearing corpora lutea after synchronous oestrous induction protocol. The pregnancy rate was higher (p = .03) in SF (39.4%) than VT (16.9%) and survival rate tended (p = .08) to be higher in SF than in VT (25.8% vs. 15.9%). Lambing rates were similar (p = .13) between SF (20.9%) and VT (15.9%). Embryos recovered by non‐surgical route after cervical dilation treatment and later cryopreserved by either slow freezing or vitrification produced reasonable pregnancy rates after FTET.