Plasma progesterone profiles and embryo quality in superovulated Japanese Black cattle

The relationship between plasma progesterone (P(4)) levels before and after superovulation treatment and embryo yield and quality was examined in Japanese Black cattle. It is concluded that a plasma P(4) level at the start of follicle stimulating hormone (FSH) injections is related to embryo quality. The P(4) level of over 3.0 ng/ml appears to be useful in preselection of donors when we want to get more than 8 normal (transferable) embryos on the average.     

Factors affecting success of embryo collection and transfer in large dairy herds

Our objective was to evaluate factors that affected the success of embryo transfer programs in large dairy herds. Non-lactating donor cows produced a larger number of ova/embryos (P<0.01) and viable embryos (P<0.01) than lactating cows. The interaction between season and donor class was correlated with the proportion of ova/embryos classified as fertilized (P=0.03), because lactating donors had fewer fertilized ova in the summer. There was no correlation between 305-day mature equivalent milk yield and response to superstimulation. Although the interval between superstimulation protocols was correlated with the number of ova/embryos (P=0.03), there was no correlation with the number of viable embryos. Pregnancy per embryo transfer (P/ET) in heifer recipients was correlated with embryo quality grade (P<0.01), season (P=0.04), and whether embryos were fresh or frozen/thawed (P<0.01). Lactating recipient cows tended to have a lower rate of P/ET during the summer (P=0.12 to P=0.08). Synchronization protocols tended to be (P=0.06; Herd 1) or were (P=0.02; Herd 2) correlated with P/ET. Lactating cows receiving vitrified IVF embryos had a lower (P=0.01) P/ET than those receiving fresh IVF embryos, especially in the summer (P=0.09). Milk yield was not correlated with P/ET. The use of heat abatement systems is critical to improve embryo production and P/ET. Synchronization protocols that optimized synchrony of ovulation may increase fertility of recipient cows and eliminate the need for estrous detection.     

Factors affecting frozen and fresh embryo transfer pregnancy rates in cattle.

The effects of a large number of factors on the pregnancy rates of fresh and frozen cattle embryos were examined over a period of years at several different locations. For fresh embryos, overall pregnancy rates were 68.3% (n=9023) and 77.1% (n=2650) at different locations and time periods. Frozen-thawed embryo pregnancy rates were 56.1% (n=3616) in The Netherlands and 58.4% (n=5297) and 68.7% (n=774) for two studies in the United States. Pregnancy rates of surgical versus nonsurgical transfers were very similar. There were no differences in the pregnancy rates of beef versus dairy embryos, but the pregnancy rate was higher in dairy and beef heifers and beef cows than in dairy cows. Although on-farm pregnancy rates in California were higher than in the northeast United States, there was no influence of season on pregnancy rate. Estrous asynchrony between plus and minus 24 h did not affect pregnancy rate for frozen-thawed or fresh embryos. Neither breed nor parity of recipients affected the influence of asynchrony on pregnancy rates. Embryo grade was a significant factor in pregnancy rate for both fresh and frozen-thawed embryos, but neither embryo stage nor age was a significant factor. Pregnancy rate was not affected by holding embryos after flushing for up to 3 h prior to freezing.     

The use of embryo transfer to produce pregnancies in repeat-breeding dairy cattle

Repeat breeding is an important factor affecting economic success in dairy management. The objective of this study was to investigate the effectiveness of transfer of frozen-thawed IVF embryos in establishing pregnancy in repeat-breeding Holstein cattle. Cumulus oocyte complexes were collected by aspiration of 2-5 mm follicles from ovaries obtained at two local abattoirs. After IVF, days 7 and 8 blastocysts were frozen either in 1.5M ethylene glycol with 0.1M sucrose, or in 1.4M glycerol with 0.1M sucrose. Holstein recipients (122 heifers and 410 cows) included those that had not conceived after 3-21 inseminations. Embryos frozen in ethylene glycol were transferred directly, and embryos frozen in glycerol were transferred after dilution of the cryoprotectant in sucrose into recipients 7 or 8 days after estrus (without-AI group), or following AI (with-AI group). Pregnancy rates were compared by the Chi-square test. Significantly higher pregnancy rates were achieved by embryo transfer following AI (with-AI group) than by embryo transfer alone (without-AI group) in both heifers (49.2 and 29.5%, respectively) and cows (41.5 and 20.4%, respectively; P<0.05). Pregnancy rates were not significantly different between heifers and cows. However, pregnancy rate decreased as the number of inseminations prior to embryo transfer increased in the with-AI group, but not in the without-AI group. Therefore, transfer of frozen-thawed IVF embryos during the same cycle in which AI was done improved pregnancy rates in repeat-breeding Holstein heifers and cows, and suggested that embryo transfer is an alternative in the treatment of repeat breeding.     

Pregnancy rates in lactating dairy cattle following supplementation of progesterone after artificial insemination

Poor conception rates in highly productive lactating cattle is especially prevalent in large, intensively-managed commercial herds. One of the causative factors is sub-optimal pre-implantation embryonic development which appears to result from inadequate circulating concentrations of progesterone. In the present study, the efficacy of very modest progesterone supplementation, between Days 3.5 and 10 post-AI, on pregnancy rates was determined in a commercial herd where bovine somatotropin (bST) was used as a management tool. All lactating cattle that were deemed to be in estrus and inseminated over a 4-week period were randomly assigned to either a control group (no treatment) or CIDR-1.9g (previously used for estrous synchronization) treatment from Day 3.5 to Day 10 post-AI. Milk samples were collected four times: on the day of AI, at Day 2 or 3, at Day 4 and at Day 22 post-AI and were analyzed for progesterone content. Data from a total of 130 breedings were used in the final analysis. The CIDR treatment increased circulating concentrations of progesterone in treated animals over those of control animals on Day 4 by 0.7ng/ml (P<0.05) and increased pregnancy rate from 35% (22/63) to 48% (32/67) (P=0.068). The effect of treatment was greater in first and second lactation cows, where pregnancy rates were 33% (18/55) in controls and 51% (31/61) in treated animals (P=0.03). The results of this study indicate that the timing of onset of the progesterone influence is important for successful pregnancy outcome, particularly in first and second lactation cows.     

Non-surgical embryo transfer in cattle

Embryos collected surgically from donors superovulated with PMSG and synchronized with either prostaglandin F(2)alpha or progestagen impregnated sponges were transferred non-surgically to prostaglandin or progestagen synchronized recipients. One embryo was transferred to the uterine horn ipsilateral to the corpus luteum either through a flexible catheter introduced through a steel tube and passed to the uterine tip, or through a Cassou inseminating gun passed approximately 6 cm into the horn. Of 16 recipients receiving 5 or 6 day old embryos through the catheter (1976), 6 (38%) were palpated pregnant at 42 days and 4 (25%) subsequently calved. Of 16 recipients receiving 7 or 8 day old embryos through the straw and 16 through the catheter (1977), 10 (63%) and 3 (19%), respectively, were palpated pregnant (P<0.05) and 8 (50%) and 3 (19%), respectively, had normal embryos at slaughter 4 to 29 days after palpation (P reverse similar0.10 ). Forty 7 to 9 day old embryos were transferred through the straw in 1978. Eighteen (45%) of the recipients were palpated pregnant and 16 (40%) had normal embryos at slaughter 98 to 168 days after palpation. The success of the transfers in 1978 was affected by embryo quality [good vs poor embryos; 64% vs 22% recipients pregnant (P<0.01) and 59% vs 17% embryos surviving to slaughter (P<0.05)]. Also, in 1978, pregnancy rate was affected by the time taken to transfer the embryo with the highest rate achieved with the fastest transfers (P<0.10, b = -0.47). Injection of Indomethacin near the time of transfer, synchronization between donor and recipient onset of estrus and embryo age did not affect pregnancy rates. The pregnancy rate achieved after the transfer of good quality embryos by the straw technique was equal to that expected from surgical techniques.     

Influence of summer heat stress on pregnancy rates of lactating dairy cattle following embryo transfer or artificial insemination

Lactating Holstein cows were used to determine if pregnancy rate from embryo transfer (n = 113) differed from contemporary control cows (n = 524) that were artificially inseminated (AI). Holstein heifers (n = 55) were superovulated with FSH-P (32 mg total) and inseminated artificially during estrus and subsequently managed under shade structures. On Day 7 post estrus, embryos were recovered, and primarily excellent to good quality embryos (90.3%) were transferred to estrus-synchronized lactating cows. Cows were managed under conditions of exposure to summer heat stress. Pregnancy status was determined by milk progesterone concentrations at Day 21 and palpation per rectum at 45 to 60 d post estrus. Pregnancy rates of cows presented for AI (Day 21, 18.0%; Days 45 to 60, 13.5%) were typical for lactating cows inseminated during periods of summer heat stress in Florida. Pregnancy rates of embryo recipient cows were higher (P<0.001) than those of control cows (Day 21, 47.6%; Days 45 to 60, 29.2%). Summer heat stress had no adverse effect on heifer superovulatory response, but it increased (P<0.05) the incidence of retarded embryos (相似文献   

Plasma progesterone profiles and fertility status of anestrus Zebu cattle treated with norgestomet-estradiol-eCG regimen

Zebu cattle are notorious for poor fertility characterized by late maturity and long intercalving intervals attributed to a variety of factors, including genetic, nutritional and climatic. The aim of the present investigation, therefore, was to induce fertile estrus in acyclic pubertal heifers and postpartum anestrous Zebu cows by hormonal intervention. Pubertal Hariana and Sahiwal anestrous heifers (n=51) and postpartum cows (n=55) were either assigned a placebo (controls, N=6 for each breed and parity) or treated with 10-d norgestomet (3 mg) subcutaneous ear implants, with an initial injection of 3 mg, im norgestomet + 5 mg estradiol valerate, followed by 500 IU eCG at implant withdrawal (NOR-treated groups). Jugular venous plasma samples were obtained from a total of 28 animals (controls : 4 heifers and 4 cows; NOR-treated : 12 heifers and 8 cows) on Days 0 (implant insertion), 3, 7, 9 and Day 10 (implant withdrawal), every 12 h on Days 11 and 12, and then once daily on Days 17, 24 and 31. All the samples were assayed for progesterone. Almost all (97%) heifers and 81% cows were induced to estrus, the majority (92% heifers and 79% cows) within 120 h of implant removal. Synchrony of the induced estrus was better in cows, but interval to estrus and estrus duration were significantly longer in heifers (P<0.05). Post-treatment fertility, based on Day 28 nonretum rate, first service, and overall conception rates, was better in heifers (78.9, 60.5 and 73.7%, respectively) than cows (77.1, 48.6 and 62.9%, respectively), but the differences were significant only for the overall pregnancy rate (71.8% for heifers and 51.2% for cows; P<0.05). Low pre-treatment plasma progesterone values (<0.5ng/mL) were consistent with ovarian inactivity, confirming the true anestrus status of experimental animals. Controls failed to exhibit estrus and maintained low progesterone concentrations throughout the study. In treated animals, high progesterone values from Day 17 onwards suggested ovulatory estrus. These early luteal phase progesterone concentrations in nonpregnant (P=0.06) and nonpregnant, nonretum (P<0.05) animals were low in comparison with those of pregnant animals. Good fertility resulting from breeding according to estrus, inspite of variable intervals to estrus and estrus duration, advocates its advantage over fixed-time insemination in norgestomet-treated anestrous Zebu cattle.     

Milk progesterone profiles in crossbred Brown Swiss x Nellore cattle following natural service

Ovarian activity and estrous behaviour were monitored through milk progesterone determinations and twice daily visual observations in 70 crossbred Brown Swiss x Nellore cows following natural service. Whole milk samples were collected on the day of estrus (Day 1), Day 11, and every 5 d thereafter until the next estrus or pregnancy confirmation. Seventy percent of the cows behaved as expected, i.e. they showed a 19-to 25-d interval between estrus and the next ovulation, or they became pregnant. Estrous cycles of regular length (18 to 24 d) were found in 54% of the cases. Prolonged luteal phases (interval from estrus to next ovulation > 28 d) were found in 15.7% of cows. Short estrous cycles (interestrous interval < 18 d) were found in 7.1% of the cases. Periods of acyclicity (basal progesterone levels for periods >/= 15 d) were found in 5.8% of the cases, and one cow exhibited estrus while pregnant and had a high progesterone concentration. Cows with a prolonged luteal phase and those with a short estrous cycle had an interval between ovulations of 35.0 +/- 6.7 d (x +/- SD) and 9.6 +/- 3.1 d, respectively. Signs of estrus were not detected in 33.3% of the ovulations confirmed by progesterone determinations. Low conception rates, failures in estrus detection and a high frequency of abnormal postbreeding luteal phases were found.     

Evaluating recipient and embryo factors that affect pregnancy rates of embryo transfer in beef cattle

The objectives of this experiment were to determine the effects of corpus luteum characteristics, progesterone concentration, donor-recipient synchrony, embryo quality, type, and developmental stage on pregnancy rates after embryo transfer. We synchronized 763 potential recipients for estrus using one of two synchronization protocols: two doses of PGF2alpha (25 mg i.m.) given 11 d apart (Location 1); and, a single norgestomet implant for 7 d with one dose of PGF2alpha (25 mg i.m.) 24 h before implant removal (Location 2). At embryo transfer, ovaries were examined by rectal palpation and ultrasonography. Of the 526 recipients presented for embryo transfer, 122 received a fresh embryo and 326 received a frozen embryo. Pregnancy rates were greater (P < 0.05) with fresh embryos (83%) than frozen-thawed embryos (69%). Pregnancy rates were not affected by embryo grade, embryo stage, donor-recipient synchrony, or the palpated integrity of the CL. Corpus luteum diameter and luteal tissue volume increased as days post-estrus for the recipients increased. However, pregnancy rates did not differ among recipients receiving embryos 6.5 to 8.5 days after estrus (P > 0.1). There was a significant, positive simple correlation between CL diameter or luteal tissue volume and plasma progesterone concentration (r = 0.15, P < 0.01 and r = 0.18, P < 0.01, respectively). There were no significant differences in mean CL diameter, luteal volume or plasma progesterone concentration among recipients that did or did not become pregnant after embryo transfer. We conclude that suitability of a potential embryo transfer recipient is determined by observed estrus and a palpable corpus luteum, regardless of size or quality.     

Factors affecting gestation length in dairy cattle

Data were collected through a special record keeping system for 2,254 herds that used artificial insemination, 37% of which were enrolled in Dairy Herd Improvement Associations. Information was available on a total of 35,162 gestations, consisting of 24,367 Holstein, 5,849 Guernsey, 2,872 Jersey, 1,667 Ayrshire and 407 Brown Swiss pregnancies resulting in single births plus 930 multiple births. Breeds, twinning, sex of calf, parity of the cow and time of day on which estrus occurred were associated with differences in gestation length. Month of insemination had no effect. Mates and sires of the cows both affected gestation length slightly, but significantly. Selection of sires for high milk production of their daughters over a 23-year period appears to have had little, if any, effect on gestation length, as the mean gestation length has increased only one day, from 278 to 279 days for Holsteins during that time.     

Pregnancy rates and metabolic profiles in cattle treated with propylene glycol prior to embryo transfer

The objective of this study was to determine the effect of a sustained propylene glycol administration to recipients of frozen/thawed in vivo derived bovine embryos. Heifers were treated with oral propylene glycol for the last 20 days before embryo transfer (n = 142), and untreated as controls (n = 133). Progesterone, insulin, insulin-like growth factor-I, glucose, urea and triglyceride were analysed in blood on Day 0 and Day 7 of the estrous cycle corresponding to embryo transfer. The heifers were selected as recipients when showing progesterone levels <2.0 ng/ml (Day 0) and >2.5 ng/ml (Day 7), according to corpus luteum quality on Day 7 by technicians unaware of animals treated. Within treated animals, significantly more recipients were selected, and increased progesterone, corpus luteum quality, pregnancy and calving rates were recorded. Day 7 progesterone concentrations were higher in heifers treated and transferred. Propylene glycol increased insulin and insulin-like-growth factor-I, but glucose, urea and triglyceride did not vary. Furthermore, insulin-like-growth factor-I, glucose and triglyceride increased at estrous time, but urea decreased and insulin remained unaltered. Together with the sustained gain in pregnancy rates throughout the experiment (2 years), other evidences suggested that the observed effects did not rely on nutritional deficiency. Thus, propylene glycol improved pregnancy rates after embryo-transfer, and progesterone, insulin and insulin-like-growth factor-I are probably involved in this effect.     

Risk factors for perinatal mortality in dairy cattle: Cow and foetal factors, calving process

It was the aim of this study to identify risk factors of perinatal mortality (PM) on a large dairy farm in Germany. Four hundred and sixty-three cows were observed continuously around calving. Data such as the lactation number, body condition score, pelvic measurements, duration of second stage of labour (SSL), degree of abdominal press (AP), presentation/position/posture of the calf, calving classification, various measurements of the calves and every action of the barn staff were documented. Calves born dead and those that died within 24 h were classified as cases of PM. Logistic regression was performed to identify risk factors for the dependent variables PM, SSL and AP. 9.7% of all calves born (n = 483) were classified as PM. In the logistic regression model, only SSL and presentation/position/posture of the foetus remained as significant effects for PM. The odds ratio for PM was 0.20, when SSL was ≤120 min, and 0.33, when the calves were born in anterior presentation, upper position and normal posture. With regard to SSL, primipara, insufficient AP, assisted calvings and as a trend, work shift changeover, these were risk factors for a prolonged SSL beyond 120 min. The risk for insufficient AP was lower when the calves were born spontaneously, in anterior presentation and as single calves. In conclusion, the duration of SSL and presentation/position/posture of the calf seemed to be key risk factors for PM. Interventions should be considered when SSL lasts longer than 2 h. Insufficient monitoring around parturition had a negative effect on the duration of SSL and thereby, indirectly on PM.     

Post-insemination milk progesterone concentration and embryo survival in dairy cows

Logistic regression analysis was used to evaluate the relationship between post-insemination milk progesterone concentration and embryo survival, and between milk yield and milk progesterone concentration. Milk samples were collected on Days 1, 4, 5, 6, and 7 (insemination=Day 0) following 871 inseminations in spring-calving dairy cows. Milk progesterone concentrations were measured by enzyme-immunoassay and pregnancy diagnosis was conducted with transrectal ultrasonography at approximately Day 30. There was a negative linear relationship (P<0.01) between milk progesterone concentration on Day 4 and embryo survival while, in contrast, there was a positive linear and quadratic relationship between milk progesterone concentration on Days 5, 6 and 7 (P<0.05) and also between the rate of change in progesterone concentrations between Days 4 and 7 inclusive and embryo survival (P<0.05). There was a weak negative linear relationship between average daily milk yield at the time of insemination and milk progesterone concentrations (P<0.001). There was no association between many production parameters, including liveweight and body condition score measured at various stages between calving and insemination, and milk progesterone concentration between Days 4 and 7 inclusive (P>0.05). In conclusion, low progesterone during Days 5-7 (after insemination) was associated with low fertility in dairy cows and there were indications of a range of progesterone concentrations within which embryo survival was maximal.