Comparison of ultrasonography, bovine pregnancy-specific protein B, and bovine pregnancy-associated glycoprotein 1 tests for pregnancy detection in dairy cows

At Days 26 to 58 after AI, 138 Holstein-Friesian dairy cows were repeatedly examined by ultrasonography, using a 7.5 MHz linear-array rectal transducer. The total calving rate was 37.6% (52/138), and late embryonic mortality occurred 8.6% of the cows (12/138). On the days of ultrasound scanning, blood samples were drawn from the jugular vein for measuring the concentration of bovine pregnancy-specific protein B (bPSPB) and bovine pregnancy-associated glycoprotein 1 (bPAG 1). When compared with calving results, there were no significant differences in accurate diagnosis of pregnant cows were found between the 3 methods. However, when recognition of an embryo proper with a beating heart was used as the criterion for positive ultrasonographic diagnosis significantly fewer (P < 0.001) pregnant cows were correctly identified than by the other 2 tests. When compared with the noncalving cows, significantly fewer (P < 0.001) false positive diagnoses were made by the 2 ultrasonographic tests than by the PSPB and bPAG 1 tests, while significantly fewer (P < 0.001) false positive diagnoses were made by the bPSPB test than by the bPAG 1 test. The accuracy of detecting nonpregnant animals by both protein tests was limited by the relatively long half-life of these proteins after calving and by early embryonic mortality.     

Sire effect on early and late embryonic death in French Holstein cattle

We investigated the effect of maternal sire on early pregnancy failure (between D0, day of insemination and D90) in their progeny during the first and second lactations (n=3508) in the Holstein breed. The estimated breeding value (EBV) for cow fertility of 12 bulls (reliability⩾0.95) was used to create the following three groups: low, medium and high EBV (EBV from −0.7 to 1 expressed as genetic standard deviation relative to the mean of the breed). In their daughters (93 to 516 per bull), progesterone measurement was carried out on the day of artificial insemination (AI; D0) to check whether the cows were in the follicular phase and on D18 to 25 to assess non-fertilisation-early embryonic mortality (NF-EEM). Late embryonic mortality (LEM) and early foetal death (FD) were determined by ultrasonography on D45 and D90 and by the return to oestrus after the first AI. Frequencies of NF-EEM, LEM, FD and pregnancy were 33.3%, 11.7%, 1.4% and 48.5% and incidences were 35.1, 19.0, 2.7 and 51.1, respectively. Sire EBV was significantly related to the incidences of pregnancy failure between D0 and D90, fertilisation failure-early embryonic mortality (FF-EEM) and LEM but not to the incidence of FD between D45 and D90 of pregnancy. The relative risk (RR) of FF-EEM was significantly higher (RR=1.2; P<0.05) for the progeny group of low EBV bulls when compared with high EBV bulls. The same effect was observed when comparing LEM of the progeny groups from the low EBV bulls to those from moderate and high EBV bulls (RR, respectively, of 1.3 and 1.4; P<005). The incidence of FF-EEM was significantly higher when cows were inseminated before 80 days postpartum compared with later, and for the extreme values of the difference between milk fat and protein content measured during the first 3 months of lactation. FF-EEM was also significantly related to the year of observation. The incidence of LEM was higher for the highest producing cows and was influenced by interaction between milk yield×lactation rank and milk yield×milk protein content. In conclusion, this study showed large differences in early pregnancy failure between progeny groups and highlights the interest of accurate characterisation of embryonic death in order to identify potential candidate genes for female fertility.     

Genetic and environmental factors influencing first service conception rate and late embryonic/foetal mortality in low fertility dairy herds

The objective of this study was to identify factors affecting variation in conception rate to first artificial inseminations (AI) (CR: number of pregnant cows on D80-100/inseminated cows) and the incidence of embryonic/foetal loss (LEM) between 21 and 80 days of pregnancy (number of cows non-pregnant on D80-100/pregnant on D21) in 44 low fertility dairy herds of the west-central region of France. Reproductive status was assessed using progesterone milk concentration on D0 = Day of AI and D21-24, plasma PSPB concentration on D30-35, rectal palpation on D80-100 and observed return to oestrous. The final data set contained 1285 Prim'Holstein cows, 5.0% (64/1285) were inseminated in the luteal phase (progesterone > or = 3 ng/ml on D0), 61.3% (787/1285) were pregnant on D21-24 (progesterone < 3 ng/ml on D0 and > or = 5 ng/ml on D21-24), 15.4% lost their embryo/foetus between D21-24 and D80-100 (198/1285) and 45.8% (589/1285) were pregnant on D80-100. The incidence of late embryonic/foetal loss (LEM) was 25.2% (198/787). Multivariate logistic regression models including the random herd effect were used to analyse the relationship between AI centre, AI sire, cow's sire, parity, interval between calving and AI, milk production, milk protein content, body condition score (BCS) on D0, season of calving, season of AI, estimated genetic index on CR and LEM incidence. CR was significantly related to parity (p < 0.05), milk production after calving (p < 0.05) and estimated genetic value (p < 0.01). A significant difference in CR was observed for calving to AI interval > or = 70 days versus > or = 90 days, but the overall effect of the interval was not significant (p = 0.11). LEM incidence was affected by period of AI (p < 0.05), milk production (p < 0.05) and BCS (p < 0.05), but was not related to estimated genetic index. In conclusion, in these low fertility herds, the incidence of LEM was high and 25% of the cows lost their embryo after 21 days of pregnancy. LEM was affected by specific factors (season, BCS), which were not related to CR. The absence of a relationship between estimated genetic index and LEM in spite of its effect on CR indicates that estimated genetic merit has a greater effect on early embryonic loss or fertilisation failure than on later stages of embryo development.     

Effect of human chorionic gonadotrophin on dominant follicles in cows: formation of accessory corpora lutea, progesterone production and pregnancy rates.

Thirty-four lactating Holstein cows were randomly assigned to four groups for treatment with human chorionic gonadotrophin (hCG, 1000 iu) at insemination day 0 (n = 8) or 7 (n = 9) or 14 days (n = 9) after insemination or with no hCG treatment (control, n = 8). Ultrasound imaging of the ovaries and plasma progesterone measurements were carried out to determine follicular dynamics and corpus luteum growth and function. Rates of formation of accessory corpora lutea were higher among cows treated on days 0 (three cows), 7 (seven cows) or 14 (four cows) than in the controls (one cow). Total corpus luteum diameter was greater (P less than 0.01) among hCG-treated cows than in controls 7-42 days after insemination. Concentrations of progesterone in plasma were significantly (P less than 0.05) higher in cows treated with hCG on days 7 or 14 than in those treated on day 0 or in controls, at days 18, 35 or 42 after insemination. Seven of the cows treated on day 7 became pregnant, whereas four, four and three cows treated on days 0 or 14 and control cows became pregnant, respectively. The results suggest that hCG treatment at 7 days after insemination could be used to produce accessory corpora lutea, raise plasma progesterone concentration and hence reduce the incidence of early embryonic mortality in cattle.     

Duration of fertility and hatchability of the common duck (Anas platyrhynchos) in pure- or crossbreeding with Muscovy drakes (Cairina moschata)

A total of 540 common duck dams were used for a comparison of duration of fertility and hatchability between eggs issued from common dams inseminated with sperm (175 x 10(6) dose(-1)) from either common (pure-breeding or PB) or Muscovy (crossbreeding or CB) drakes. Artificial inseminations (AI) were performed at 3 periods of the reproductive season (27-35, 39-43 and 49-56 weeks) with 2 alternate inseminations/period at 3-week intervals (one with semen from common and the other from Muscovy). Fertility was estimated from egg candling while early embryo mortality (EEM), medium embryo mortality (MEM) and late embryo mortality (LEM) was estimated on Days 0-6 (PB+CB), Days 7-25 (PB) or Day 28 (CB) of incubation, and after, respectively. Overall fertility from Days 2-12 after AI was 61.1% in PB and 42.8% in CB. The maximum duration of fertility (time interval between AI and last fertile egg) was 8.1 days in PB versus 6.4 days in CB (p<0.05). The age of the dam influenced this interval, particularly in PB, with a longer duration at 40 weeks compared to 50 (p<0.05). On average, EEM represented 2.5% of fertile eggs while MEM accounted for 5% of surviving embryos on Day 6 and LEM, for 11.5% of hatched eggs. MEM was significantly higher in CB (6.3%) compared to PB (3.9%; p<0.05). Overall, an increase in EEM and MEM was observed in both types of eggs at and after 50 weeks of age. An increase in EEM (regardless of dam's age) and in MEM (only in the oldest females) was observed with sperm storage duration. Sex ratio at hatching (49.2% males in PB vs. 53.0% in CB) was particularly unbalanced on the first fertile day (54.7% and 57.1%, respectively).     

Relationship of pre-ovulatory follicle size, estradiol concentrations and season to pregnancy outcome in dairy cows

This study was carried out to evaluate effects of pre-ovulatory follicle size, plasma concentrations of estradiol and progesterone, and season on pregnancy outcomes in dairy cows. Holstein cows (n = 144) were synchronized and inseminated (Ovsynch/TAI protocol) in two distinct periods (cold versus warm season). Blood samples were collected daily from AI (day 0) to day 8 and on days 15, 22, 29, 36 and 64 to measure progesterone and estradiol. Pregnancy diagnosis was performed at days 29, 43 and 64. The pre-ovulatory follicle size was larger and the plasma estradiol concentrations on the day of AI were greater in animals that became pregnant. Plasma progesterone concentrations diverged and became greater after day 5 post-AI, in cows diagnosed pregnant, as compared to non-pregnant cows. The overall pregnancy rate (33%) or late embryonic/early fetal losses (23%) did not differ between seasons, but plasma estradiol concentrations on the day of AI and plasma concentrations of progesterone in pregnant cows were lower in the warm season. Reduced CL function, measured as plasma progesterone concentrations, from days 22 or 29 post-AI onward for cold and warm season, respectively, was associated with subsequent late embryonic/early fetal mortality. Overall, pregnancy was related to diameter of the pre-ovulatory follicle and plasma E2 on the day of AI, but embryonic/fetal losses were not. Season did not affect these outcomes, even though it influenced luteal function after AI.     

Luteal blood flow increases during the first three weeks of pregnancy in lactating dairy cows

The objectives of this experiment were to characterize luteal blood flow in pregnant and non-pregnant cows and to determine its value for early pregnancy diagnosis. Lactating dairy cows (n = 54), 5.2 ± 0.2 y old (mean ± SEM), average parity 2.4 ± 0.2, and ≥ 6 wk postpartum at the start of the study, were used. The corpus luteum (CL) was examined with transrectal color Doppler ultrasonography (10.0-MHz linear-array transducer) on Days 3, 6, 9, 11, 13, 15, 18, and 21 of the estrus cycle (estrus = Day 0). Artificially inseminated cows (n = 40) were retrospectively classified as pregnant (embryonic heartbeat on Day 25; n = 18), nonpregnant (interestrus interval 15 to 21 d, n = 18), or having an apparent early embryonic loss (interestrus interval >25 d, n = 4). There was a group by time interaction (P < 0.001) for luteal blood flow from Days 3 to 18; it was approximately 1.10 ± 0.08 cm² (mean ± SEM) on Day 3, and increased to approximately 2.00 ± 0.08 cm² on Day 13 (similar among groups). Thereafter, luteal blood flow was numerically (albeit not significantly) greater in pregnant cows, remained constant in those with apparent embryonic loss, and declined (not significantly) between Days 15 and 18 in nonpregnant cows. Luteal blood flow was greater in pregnant than in nonpregnant (P < 0.05) and nonbred cows (P < 0.05, n = 14) on Day 15 (2.50 ± 0.16, 2.01 ± 0.16, and 2.00 ± 0.18 cm², respectively) and on Day 18 (2.40 ± 0.19, 1.45 ± 0.19, and 0.95 ± 0.21 cm²). In cows with apparent early embryonic loss, luteal blood flow was 2.00 ± 0.34 and 2.05 ± 0.39 cm² on Days 15 and 18, which was less (not significantly) than in pregnant cows, but greater (P < 0.05) than in nonbred cows on Day 18. Although mean luteal blood flow was significantly greater in pregnant than nonpregnant (and nonbred) cows on Days 15 and 18, due to substantial variation among cows, it was not an appropriate diagnostic tool for pregnancy status.     

EGF receptors on plasma membranes purified from bovine mammary gland of lactating and pregnant animals

A procedure for purification of plasma membranes from bovine mammary gland has been developed. The binding capacity of EGF to the plasma membranes from mammary tissue of pregnant cows was equal to 335 fmol per mg of protein thus being twofold higher than in membranes from lactating gland. The KD values were not changed. Autoradiographs of the membrane receptor linked to [125J]-EGF revealed three labeled bands corresponding to 160 kDa, 145 kDa and 115 kDa polypeptides. The main band of 145 kDa was labeled stronger in membranes from pregnant animals. The results suggest that the EGF receptor level is enhanced in fast proliferating normal mammary tissue.     

Reproductive failure in moose (Alces alces) due to embryonic mortality and unfertilized oocytes

Knowledge on reproductive success is vital for successful management of large ungulates and is often measured by means of observing surviving offspring. In harvested ungulates, postmortem investigations of reproductive organs are used to estimate reproductive potential by obtaining ovulation rates and fetus numbers. However, there are differences in numbers of offspring observed, fetal/embryo counts, and ovulation rates. We hypothesize that the discrepancy between estimated reproductive potential and reproductive outcome in large ungulates is not only due to ova loss but also due to embryonic mortality. We investigated reproductive status in early pregnancy by sampling hunter-harvested moose (Alces alces) in southern Sweden from 2007 to 2011. In all, 213 reproductive organs were examined postmortem, and in confirmed pregnant moose (n?=?53), 25 % (19 of 76) embryos were nonviable and 6 % of ova was unfertilized. The discrepancy between the ovulation rate of all pregnant moose (1.49) and the number of expected offspring per pregnant female, when embryonic mortality and unfertilized oocytes were accounted for (1.08), was 27.5 %. An association between inflammation of the inner mucous membrane (endometritis) of the moose's uterus and embryonic mortality was observed. This is the first comprehensive report of embryonic mortality and endometritis in moose. The observed discrepancy between ovulation rates and early embryonic development/survival shows that ovulation rates are indicative but not accurate estimates of moose reproductive rate. The use of ovulation rates as a sole estimator of future offspring rates may lead to an overharvest of a managed moose population.     

Extent and pattern of pregnancy losses and progesterone levels during gestation in Swedish Red and Swedish Holstein dairy cows

Background

Pregnancy loss is a major source of infertility in dairy cows. Despite a fertilization rate after insemination (AI) of approximately 90%, calving rates are 30%–50%, indicating the occurrence of extensive embryonic and foetal losses. The aim of this study was to establish the extent and pattern of embryonic and foetal loss in Swedish Red (SR) and Swedish Holstein (SH) dairy cows, as well as, the relationship to oestrus intensity (OI) and progesterone (P4) concentration. In total, 2130 AIs and 16,176 milk P4 samples from 359 SR and 212 SH dairy cows were included in the study. Pregnancy losses were estimated using data from P4 values combined with AI information and calving data.

Results

Total pregnancy loss from AI to the day of calving was 65%. Early embryonic loss, late embryonic loss and foetal loss were estimated to be 29, 14 and 13%, respectively. There is strong evidence in the literature that P4 concentrations at different time points are associated with pregnancy loss. In the present study, cows with pregnancy losses had significantly higher P4 levels at the day of AI and significantly lower P4 concentration at days 10, 21 and 30 after AI compared to pregnant cows. Swedish Red cows had significantly lower total pregnancy losses compared to SH cows (62% and 68% respectively, P?=?0.017). Early embryonic loss was 6.7% points lower for cows inseminated at a stronger OI (OI?=?3) compared to at a weaker OI (OI?=?2, P?=?0.006). Cows inseminated at ovulation number?≥?5 had significantly lower early pregnancy losses compared to cows inseminated at first or second ovulation (11.5 and 8% points, respectively, P?<?0.05). With an increase of one SD of milk (448 kg ECM) during the first 60 days in milk, early embryonic loss increased by 4.7% points (P?=?0.006).

Conclusions

It is important to increase the number of cows calving per insemination by reducing embryo/foetal loss. This outcome can be achieved by management and breeding for optimal P4 levels at critical time points, and by considering oestrus expression in the breeding programmes to facilitate the correct timing of insemination.

     

Use of bovine pregnancy-associated glycoproteins to predict late embryonic mortality in postpartum Nelore beef cows

The primary objective was to determine if circulating concentration of bovine pregnancy-associated glycoproteins (bPAGs) on Day 30 after artificial insemination (AI) may serve as a marker of late embryonic mortality in Bos indicus (Nelore) beef cows. In experiment 1, postpartum Nelore beef cows (n = 56) were artificially inseminated at a fixed time (Day 0) after synchronization of ovulation. Serum samples were collected on Days 0, 21, 24, 27, and 30 after AI. The first significant increase (P < 0.0001) in serum bPAGs after insemination occurred on Day 24 of gestation. In experiment 2, ovulation was synchronized in postpartum Nelore beef cows (n = 1460) and AI was received at a fixed time. Pregnancy diagnosis and blood sample collection were carried out on Days 28 to 30 after insemination. Cows that maintained a pregnancy from Days 28 to 100 of gestation (n = 714) had significantly (P < 0.0001) higher circulating concentrations of bPAGs on Day 28 compared with cows that did not maintain a pregnancy (embryonic mortality [EM]) until Day 100 (n = 89). When Day 28 bPAG concentration was included in a logistic regression model to predict pregnancy maintenance until Day 100 of gestation, there was an increase (P < 0.0001) in the probability of maintaining pregnancy as maternal concentrations of bPAGs increased. A receiver operating characteristic curve was generated to determine bPAG concentrations on Day 28 that should predict embryonic survival or mortality with an accuracy of 95% or more. On the basis of the positive and negative predicative value analysis, at Day 28 of gestation a circulating concentration of bPAGs greater than 7.9 ng/mL was 95% accurate in predicting embryonic maintenance (to Day 100); a concentration of bPAGs less than 0.72 ng/mL was 95% accurate in predicting EM by Day 100. In experiment 3, the preceding model was tested in a separate set of Nelore beef cows to validate whether bPAGs would serve as an accurate measure of late embryonic mortality. Ovulation was synchronized in 650 Nelore cows and received AI at a fixed time. Pregnancy diagnosis and bPAG sampling were performed at Day 28 of gestation. Only pregnant cows were included in the analysis. On the basis of the previously reported bPAG cutoff values, the test was 95% accurate in predicting late embryonic mortality at Day 28 of gestation. In summary, bPAGs seem to be a good marker for predicting EM between Days 28 and 100 of gestation and suggest that this model could help dissect the molecular mechanisms leading to late EM.     

Plasma progesterone profiles and factors affecting embryo-fetal mortality following embryo transfer in dairy cattle

The relationship between plasma progesterone (P4) levels and embryo survival, and the value of P4 profiles for the selection of cattle embryo transfer recipients is still a matter of controversy. This study reports a comparison between lactating cows and heifers (n = 407) from a single dairy herd, after transfer of either fresh or frozen-thawed good quality embryos, of their ability to sustain embryo-fetal development to term. Plasma P4 concentrations on the day of estrus (Day 0 = D0), Day 4, Day 7 and on Day 21 were measured and related to embryo survival. Plasma P4 levels on Days 0, 4 and 7 were similar in recipients later found pregnant or open. Plasma P4 levels on Day 7 were significantly higher (P < 0.01) in heifers than in cows, but they were similar in pregnant and nonpregnant heifers and in pregnant and nonpregnant cows. Pregnancy rates for fresh and frozen-thawed embryos were higher in heifers than in cows, but the differences did not reach significance. However, the overall late embryonic mortality was significantly higher (P < 0.01) and the calving rate for frozen-thawed embryos was significantly lower (P < 0.05) in cows than in heifers. As expected, plasma P4 on Day 21 was significantly higher (P < 0.001) in pregnant than in nonpregnant recipients, but there was no difference between pregnant cows and pregnant heifers. Plasma P4 levels on Day 7 of recipients presumed pregnant on Day 21 and later found pregnant or nonpregnant were similar, but plasma P4 levels on Day 21 were significantly higher (P < 0.001) in pregnant than in nonpregnant recipients. The results of this study suggest that plasma P4 levels until the day of transfer, except for the rejection of recipients with abnormal luteal function, are of limited practical use for embryo transfer recipient selection. However, in lactating cows low plasma P4 values on Day 7 might negatively affect embryo survival, while in heifers this effect is not noticeable. Lactating cows are more prone to embryo loss than heifers, especially in the case of frozen-thawed embryos; this is associated with a lower competence of the corpus luteum at Day 7.     

Soybean-derived phytoestrogens regulate prostaglandin secretion in endometrium during cattle estrous cycle and early pregnancy

Phytoestrogens acting as endocrine disruptors may induce various pathologies in the female reproductive tract. The purpose of this study was to determine whether phytoestrogens present in the soybean and/or their metabolites are detectable in the plasma of cows fed a diet rich in soy and whether these phytoestrogens influence reproductive efficiency and prostaglandin (PG) synthesis during the estrous cycle and early pregnancy in the bovine endometrium. In in vivo Experiment 1, we found significant levels of daidzein and genistein in the fodder and their metabolites (equol and p-ethyl-phenol) in bovine serum and urine. The mean number of artificial inseminations (AIs) and pregnancy rates in two kinds of herds, control and experimental (cows fed with soybean 2.5 kg/day), were almost double in the soy-diet herd in comparison with the control animals. In in vivo Experiment 2, three out of five heifers fed soybean (2.5 kg/day) became pregnant whereas four out of five heifers in the control group became pregnant. The concentrations of a metabolite of PGF2alpha (PGFM) were significantly higher in the blood plasma of heifers fed a diet rich in soybean than those in the control heifers throughout the first 21 days after ovulation and AI. The higher levels of PGFM were positively correlated with equol and p-ethyl phenol concentrations in the blood. In in vitro experiments, the influence of isoflavones on PG secretion in different stages of the estrous cycle was studied. Although all phytoestrogens augmented the output of both PGs throughout the estrous cycle, equol and p-ethyl-phenol preferentially stimulated PGF2alpha output. The results obtained lead to the conclusion that soy-derived phytoestrogens and their metabolites disrupt reproductive efficiency and uterus function by modulating the ratio of PGF2alpha to PGE2, which leads to high, nonphysiological production of luteolytic PGF2alpha in cattle during the estrous cycle and early pregnancy.     

Relationship between peripheral estrogen concentrations at insemination and subsequent fetal loss in cattle

In a survey on pregnancy rate and embryonic losses in dairy cattle on 6 Israeli farms, cows (n = 78) were divided into 3 groups on the basis of ultrasonography at 21 d post insemination; pregnancy diagnosis at 40 to 50 d post insemination and blood progesterone (P4) levels at 21 d. The groups were either pregnant (P4 level > 1.0 ng/ mL); not pregnant (P4 < 0.5 ng/mL), or showed early embryo loss (P4 > 1.0 ng/mL and the presence of an embryonic vesicle on D 21 but later returned to estrus or were found not pregnant on D 40 to 50). On the day of insemination, peripheral estrogen was significantly higher (P < 0.05) in the early embryo loss group (15.3 +/- 1.1 pg/mL, n = 27) than in pregnant (9.4 +/- 0.6 pg/mL, n = 26) or not pregnant (9.6 +/- 0.7 pg/mL, n = 25) group. The cows on 3 farms which were fed 1 to 2 kg/d of vetch (Vicia sativa), an estrogenic legume, had higher estrogen concentrations on the day of insemination than cows (2 farms) fed other legumes (13.7 +/- 0.64, n = 58 vs 10.7 +/- 0.8 pg/mL, n = 42; P < 0.01). On one of the 3 farms, vetch was replaced with alfalfa after the first year. Following the cessation of vetch feeding the estrogen concentrations in the blood decreased from 32 +/- 5 pg/mL to 14 +/- 2 pg/mL (n = 9). These data suggest that high peripheral estrogen on the day of insemination is associated with early embryonic loss. These data also indicate that estrogen concentrations on the day of insemination can be influenced by diet.     

Alterations in the relative abundance of Haptoglobin (Hp) transcripts in total milk somatic cells during different stages of lactation cycle in high yielding cross-bred cows

The expression profile of Haptoglobin (Hp) gene in total milk somatic cells (SCC) of high-yielding cross-bred Karan Fries (KF) was studied during early, mid, and late lactation cycle. Milk samples (200 ml/animals) were collected from 10 high-yielding and 10 low-yielding cows throughout the lactation cycle (from day 7 to day 300) with an interval of one month. Relative mRNA expression profiles of Hp by RT polymerase chain reaction was studied in high-yielding cows, whereas low-yielding cows were taken as control. The folds of induction of Hp was significantly (p < 0.001) downregulated by a mean factor of 0.207 in milk SCC during early lactating cows. Whereas, it was significantly (p < 0.01) upregulated by a mean factor of 20.888 during mid lactation. The expression was unaltered during the late lactation. The study demonstrates that Hp is synthesized within the mammary gland and significantly upregulated during mid-lactation period compared to other stages of lactation cycle.     

Prostaglandin secretion by perifused bovine endometrium: Secretion towards the myometrial and luminal sides at day 17 post-estrus as altered by pregnancy

Bilateral perifusion devices were utilized to measure prostaglandin secretion towards luminal and myometrial sides of bovine endometria. Tissues were collected at Day 17 post-estrus from cyclic (n=4), pregnant (n=5) and bred but subsequently non-pregnant (n=6) cows. Tissue from each cow was placed into two perifusion devices, perifused with Krebs-Ringer Bicarbonate solution (3 ml/10 min) for 2.5h and fractions collected every 10 min. Oxytocin (1 IU/ml) was perifused during fractions 7–12 to the luminal side of one device and to the myometrial side of the other device. Regardless of stratus, prostaglandin secretion rates (PGF and PGE₂) were higher (P< 0.01) from the luminal side than the myometrial side. Secretion rates of PGF were lower (P< 0.01) for endometria from pregnant cows than for endometria from cyclic or bred/non-pregnant cows, whereas secretion rates of PGE₂ were not affected by pregnancy status. Regardless of the side of perifusion, secretion rates of PGF and PGE₂ from endometria of cyclic and bred/non-pregnant cows were elevated (P< 0.01) throughout the period of oxytocin treatment, whereas prostaglandin secretion by endometria from pregnant cows wasnot stimulated by oxytocin. Decreased secretion of PGF from endometria of pregnant cows suggests that the corpus luteum and pregnancy are maintained because of an inhibition of endometrial prostaglandin synthesis or an inability to responsd to stimulators of prostaglandin synthesis (i.e. oxytocin).     

The impact of body condition after calving on metabolism and milk progesterone profiles in two breeds of dairy cows

Background

Optimal body condition in early lactation is generally accepted as a prerequisite for good reproductive performance. Examination of milk progesterone profiles offers an objective method for characterization of postpartum ovarian activity in dairy cows. The present study investigated the relationship between body condition after calving, some metabolic parameters in blood plasma, and fertility, as reflected by milk progesterone profiles in the two dairy breeds Swedish Red (SR) and Swedish Holstein (SH).

Results

Multiparous dairy cows (n = 73) of SR and SH breeds were selected and divided into three groups based on their body condition score (BCS) after parturition. Selected plasma metabolites were determined, milk progesterone profiles were identified and body condition was scored. Over-conditioned cows and atypical progesterone profiles were more common among SR cows. Insulin sensitivity was lower and IGF 1 higher among SR cows. Insulin was positively related to body condition, but not related to breed.

Conclusions

Atypical progesterone profiles were more common and insulin sensitivity lower in SR than in SH cows, but the SR breed had a higher proportion of over-conditioned SR cows. It is reasonable to assume that breed differences in body condition contributed to these results.

     

A study of altered cytokine rhythms associated with successful implantation in cows

Implantation is a critical process wherein the dam accepts the semi-allogenic embryo, characterized by certain vital immunological changes involving certain factors and cytokines. The current study was undertaken in Sahiwal cows to analyze the changes in certain selective immunological components of the body during peri-implantation period. Post-insemination the study was performed for a period till day 40 and the plasma was used to estimate the levels of progesterone, interleukin 1β (IL-1β), IL-2, IL-4, IL-6, and leukemia inhibiting factor (LIF) using Bovine specific ELISA Test Kits. The phagocytic activity and mRNA expression of progesterone-induced blocking factor (PIBF) were also analyzed. It was observed that in pregnant cows, the expression of PIBF increased from day 16th onward and remained high throughout the study period whereas the phagocytic activity was higher in non-pregnant cows all through the study period. The IL-1β, IL-2, and IL-6 were significantly higher in non-pregnant cows from 16th to 18th day post-AI as compared to P cows. On the other hand, IL-4 and LIF showed a significantly higher concentration in pregnant cows during peri-implantation period. Hence, it can be concluded that early embryonic survival is dependent on interplay of certain critical immunological factors in the body.     

The use of milk progesterone profiles to characterise components of subfertility in milked dairy cows

Milk progesterone (P₄) concentrations of 1682 postpartum (PP) dairy cows during 2503 lactations were used to define and quantify the incidence of atypical ovarian patterns and to assess their impact on reproductive performance. A total of 257 animals (10.94%) with their first significant luteal activity after day 44 PP were considered a result of delayed ovulation type I (DOVI). Prolonged luteal activity (P₄>3 ng/ml for at least 19 days) observed in 170 (7.3%) and 161 (6.35%) animals during first and subsequent cycles was considered a result of the presence of a persistent corpus luteum (CL), respectively denoted as PCLI and PCLII. Following the demise of an oestrous cycle CL, a total of 322 (12.85%) animals showed a delayed ovulation Type II (DOVII) with P₄<3 ng/ml for >12 days. In 238 inseminated animals (9.92%) prolonged luteal activity was followed by the CL demise which may indirectly indicate the incidence of a late embryo to early foetal mortality (LEM). In this study animals during 794 (31.7%) lactations had at least one atypical ovarian pattern before insemination that, in comparison to those with typical P₄ patterns, contributed to a delayed conception (88.2 vs. 106.2 days), higher number of services per conception (1.49 vs. 1.8), lower first service conception rate (60.9 vs. 43.7%) and a reduced total conception rate (92.6 vs. 82.1%), all of which were significantly different at P<0.001. The incidence of PCLI and PCLII before insemination resulted in a higher level of LEM. Milk progesterone monitoring offers an accurate and objective measurement of factors associated with PP ovarian activity which will assist in investigating the genetic and environmental factors affecting fertility.