Chemical contamination of the cervical mucus in cows in relation to pregnancy and age factors]

Applying the method of absorption atom spectrometry (AAS), the contamination of cervical mucus by chemical elements (Cd, Pb, Hg, Cr, Cu, Zn) was demonstrated in the oestrus period of cows in different ecological agricultural regions of the North Moravian region. The results of observation revealed only a statistically significant difference (P less than 0.05) in Cd contents in the test groups; test group mean = 0.015 micrograms.g-1 Cd, control group mean = 0.006 micrograms.g-1. Cr findings in cervical mucus are of priority importance, the same applies to Cu findings. Zinc was found to be an element influencing negatively the conception of cows. The Zn values in cervical mucus of nonpregnant cows were demonstrated to be significantly higher (P less than 0.01) (conception--group = 0.841 micrograms.g-1, conception + group = 0.219 micrograms.g-1 Zn. So called sum of chemical elements: Cd + Pb + Hg + Cr + Cu + Zn was proposed and evaluated as a picture of the total contamination of cervical mucus. This characteristic was also influenced by the Zn findings in the group of pregnant and nonpregnant cows. Zn: Cd antagonism in cervical secretions of barren and pregnant cows was statistically highly significant (P less than 0.01). Chemical elements in cervical mucus were determined for the first time in a digested sample of cervical secretion. The correlation coefficients used for the cows (n = 99) from a contaminated region showed that the content of chemical elements in cervical secretion was not influenced by the age of cows. The content of chemical elements in cervical secretion was not increasing with the age.     

Reproductive performance of anovulatory anoestrous postpartum dairy cows following treatment with two progesterone and oestradiol benzoate-based protocols, with or without resynchrony

AIMS: (a) To compare the reproductive performance of anovulatory anoestrous (AA) postpartum dairy cows following treatment with 1 of 2 progesterone (P4) and oestradiol benzoate (ODB)-based treatment regimens; (b) To determine whether resynchronisation of cows initially treated for AA would improve reproductive performance and; (c) to determine whether cows not detected in oestrus but with a corpus luteum (CL) present (NDO/CL+), treated with P4 and ODB, would conceive earlier than untreated controls. METHODS: Cows (n=1386) from 11 herds, that had not been detected in oestrus before the start of the seasonal mating period (PSM) and in which a CL was not detected were diagnosed AA, blocked by age (2 or >2 years old), then randomly assigned to be treated with an intravaginal P4-releasing device for either 6 (6-Day group) or 8 days (8-Day group). Cows in the 8-Day group were injected intramuscularly (IM) with 2 mg ODB at device insertion and all cows were injected with 1 mg ODB 24 h after device removal (Day 0). Cows detected in oestrus from Days 0-3 were subsequently assigned to be either resynchronised or left as untreated controls. Resynchronised cows had a used P4-releasing device reinserted on Day 14 for 8 days and were injected with 1 mg ODB at device reinsertion and again 24 h after device removal. NDO/CL+ cows were assigned to be either treated the same as the 8-Day group or left as untreated controls. All cows were inseminated on detection of oestrus and pregnancy tested approximately 10 weeks after the PSM and again 6-8 weeks after the end of the mating period. RESULTS: For AA cows, the 14-day submission rate was similar between 6-Day and 8-Day groups (p0.1). However, the pregnancy rate by Day 14 was higher for the 8-Day than the 6Day group (43.0% vs 35.2%; p=0.006). Resynchrony treatment decreased the 14-day pregnancy rate compared with untreated controls (35.2% vs 42.5%; p=0.026). The resynchrony treatment increased the submission rate between Days 14-28 for non-pregnant cows compared with untreated controls (80.6% vs 57.4%; p=0.049). However, conception rate to resynchronised heats was lower than for cows that returned to oestrus naturally (56.6% vs 67.9%; p=0.025). Neither initial treatment type nor resynchrony treatment increased the 28-day pregnancy rate (p>0.1). There were no differences between treatment groups in the final non-pregnant rate (4.5% vs 4.6%; p>0.1). Treated NDO/CL+ cows had a higher 14-day submission rate (88.1% vs 49.4%; p>0.001), higher 14-day and 28-day pregnancy rates (42.9% vs 20.7%, p>0.001 and; 56.0% vs 42.5%, p=0.094, respectively) and conceived earlier (21 vs 36 days from PSM to median day of conception; p>0.05), than untreated NDO/CL+ cows. CONCLUSIONS: The 8-Day, ODB-P4-ODB treatment regimen resulted in a higher pregnancy rate by 14 days but not 28 days than the 6-Day, P4-ODB treatment. The resynchrony treatment increased the proportion of non-pregnant cows inseminated on days 14-28, but did not increase the 28-day pregnancy rate or final pregnancy rate. Treatment of NDO/CL+ cows with the 8-Day, ODB-P4-ODB treatment improved reproductive performance compared with no treatment.     

Relationship of pre- and post-ovulatory gonadotropin concentrations to subnormal luteal function in postpartum beef cattle

Early weaning of calves from anestrous cows results in formation of short-lived corpora lutea (CL) unless the animals are pretreated with a progestagen (norgestomet). This study was conducted to investigate the relationship between pre- and post-ovulatory gonadotropin secretion and luteal lifespan. Postpartum beef cows were assigned randomly into two groups, control (n = 5) and norgestomet (implant given at weaning for 9 d; n = 7). Calves from all cows were weaned 30 to 33 d postpartum. Coccygeal artery cannulas were placed into cows in the control group 1 d prior to weaning and 2 d before implant removal in cows in the norgestomet group. Plasma for determination of luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol-17 beta (E) and progesterone (P) was collected daily at 10-min intervals for 6 h from weaning (control) or the day prior to implant removal (norgestomet) to estrus (d 0) and on d 2, 4 and 6 following estrus. Average interval (X +/- SE; P less than .05) from weaning to estrus or implant removal was 4.2 +/- .8 and 2.3 +/- .2 d for the control and norgestomet groups, respectively. Estrous cycle length for the control group was 12.4 +/- 1.8 d compared with 20.4 +/- .3 d for the norgestomet group (P less than .05). Four of five control cows had an estrous cycle length of 7 to 14 d; all cows in the norgestomet group and the remaining control cow had an estrous cycle of normal length (16 to 21 d).2+ estrus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of Different Doses of Prostaglandin on the Area of Corpus Luteum, the Largest Follicle and Progesterone Concentration in the Dairy Cow

Lactating dairy cows with a mature corpus luteum (CL) (diameter of ≥17 mm determined by ultrasonography) and having a follicle with a diameter of 10 mm (n = 49) were randomly assigned to three groups. The first group was treated with a single dose of exogenous prostaglandin (25 mg), while the second group was treated with 35 mg on day 0, and the third group served as control in order to evaluate the effect of rectal manipulation on the CL during ultrasonographic examination. Blood samples were collected daily for analysing progesterone (P4) concentrations. In group 1 the incidence of oestrus and artificial insemination (AI) in 10 days after treatment was 95% (19 of 20). The conception rate was 31.6%, and the average time to oestrus after treatment was 3.7 day. In group 2 the incidence of oestrus and A.I. was 84.2% (16/19). The conception rate was 31.2%, and the average time to oestrus after treatment was 2.8 day. In the untreated group only two cows (2/10) exhibited oestrus during the examined period and none of them became pregnant. There were no significant differences between the two treated groups in terms of reduction in the area of CL and P4 concentrations and of an increase in the area of the dominant follicles. At the same time, the decrease in the percentage changes relative to the area of CL and to the concentrations of P4 were statistically significant in both treated groups.     

Corpus Luteum Development and Function after Supplementation of Long‐Acting Progesterone During the Early Luteal Phase in Beef Cattle

Strategic supplementation of P4 may be used to increase conception rates in cattle, but timing of supplementation in relation to ovulation, mass of supplementary P4 and formulation of the P4‐containing supplement has not been determined for beef cattle. Effects of supplementation of long‐acting progesterone (P4) on Days 2 or 3 post‐ovulation on development, function and regression of corpus luteum (CL) were studied in beef cattle. Cows were synchronized with an oestradiol/P4‐based protocol and treated with 150 or 300 mg of long‐acting P4 on Day 2 or 3 post‐ovulation (6–7 cows/group). Colour‐doppler ultrasound scanning and blood sample collection were performed from Day 2–21.5. Plasma P4 concentrations were greater (p < 0.05) from Day 2.5–5.5 in the Day 2‐treated groups and from Day 3.5–5.5 in the Day 3‐treated cows than in the control group. CL area and blood flow during Day 2–8.5 did not differ (p > 0.05) among groups, suggesting no effect of P4 treatment on luteal development. The frequency of cows that began luteolysis before Day 15 was greater (p < 0.04) in cows treated with 300 mg than in the controls, but there were no differences between non‐treated and 150 mg‐treated cows. The interval from pre‐treatment ovulation to functional and structural luteolysis was shorter (p < 0.01) in the combined P4‐treated groups than in the control cows. In conclusion, was showed for the first time that long‐acting P4 supplementation on Day 2 or 3 post‐ovulation increases P4 concentrations for ≥3 day, has no effect on luteal development, but anticipates the beginning of luteolysis in beef cattle.     

Oestrus during pregnancy in the cow

Forty-three oestruses were observed in 35 pregnant cows in one beef suckler herd and 17 dairy herds; at each oestrus the pregnant cow stood willingly to be mounted by another cow or bull. Such oestruses were observed at all stages of pregnancy, although more often between 121 and 240 days, occurred more than once per pregnancy and were also seen in successive pregnancies. On one farm where the dairy cows were observed for four 30 minute periods daily, oestrus was recorded in 5.7 per cent of pregnant cows. The behavioural signs associated with oestrus during pregnancy were indistinguishable from those of true oestrus in non-pregnant animals and although its duration was shorter (mean 5.6 hours), its intensity was comparable to that of the true oestrus. Pregnant cows showing oestrus were usually seen interacting with other oestrous cows in the sexually active group. Pregnant cows showing oestrus had a higher mean condition score (3.9 +/- 0.64) than control pregnant cows (3.0 +/- 0.36). Physiological changes in the genital tract normally associated with true oestrus were not observed in pregnant cows showing oestrus. There was no ovulation or metoestrous bleeding. The characteristics of cervical mucus, including ferning patterns, were similar to those of pregnant cows at the same stage of pregnancy. Hormonal changes associated with oestrus in non-pregnant cows were not observed in the pregnant cows exhibiting oestrus. Seven of nine pregnant cows at oestrus stood willingly to be mounted by a bull. On seven occasions, bulls exposed only to cervical mucus from pregnant cows showing oestrus did not display flehmen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Resynchrony of previously anoestrous cows and treatment of cows not detected in oestrus that had a palpable corpus luteum with prostaglandin F(2 alpha)

AIMS: To determine if resynchrony, using a progesterone (P4) / oestradiol benzoate (ODB) regime, of previously treated, anovulatory anoestrous (AA) cows would increase the probability of oestrus, conception and pregnancy compared to no resynchrony. Additionally, the effect of prostaglandin F2alpha (PG) treatment of cows not detected in oestrus, but in which a corpus luteum (CL) was palpable transrectally (NDO/CL+), was compared with no treatment. METHODS: Cows not detected in oestrus by 1 week before the start of the seasonal breeding programme were categorised as AA or NDO/CL+, based on absence or presence of a palpable CL, respectively. All AA cows were treated with an intravaginal device containing 1.36 g P4 (CIDR-B) for a period of 6 days, and with 1 mg ODB by intramuscular (I/M) injection 1 day after the device was removed (Day 0). Half the AA cows that were detected in oestrus between Days 0 and 3 were randomly assigned to be resynchronised by reinsertion of a clean used CIDR-B device on Day 15, for a period of 6 days, followed by an I/M injection of 0.5 mg ODB, 1 day after the device was removed (resynchrony, RS), while the other half were not resynchronised (no-RS). NDO/CL+ cows were alternately assigned to be either treated with 25 mg of the PG, dinoprost tromethamine, on Day 0 or left as untreated controls (Con). RESULTS: Resynchrony increased the percentage of cows detected in oestrus between Days 14 and 28 (212/282 = 75.2% vs 155/285 = 54.4%, for RS vs no-RS, respectively; p<0.001), but had no effect on conception rate to a service within the first 3 days of the mating period (146/397 = 36.8% vs 148/399= 37.1%, for RS vs no-RS cows, respectively; p>0.9), or to a service between Days 14 and 28 (84/159 = 52.8% vs 114/217 = 52.5%, for RS vs no-RS cows, respectively; p>0.9). Resynchrony increased the Day 28 pregnancy rate (264/432 = 61.1% vs 237/435 = 54.5%, for RS vs no-RS cows, respectively; p=0.03), but had no effect on the Day 56 or final pregnancy rates (p>0.1).Prostaglandin treatment of NDO/CL+ cows did not affect the percentage of cows detected in oestrus by Day 7 (43/106 = 40.6% vs 51/101 = 50.5%, for Con vs PG, respectively; p=0.15), or Day 28 (92/106 = 86.8% vs 91/101 = 90.1%, for Con vs PG, respectively; p>0.4). Treatment did not affect the Day 28 pregnancy rate (55/103 = 53.4% vs 54/98 = 55.1%, for Con vs PG, respectively; p>0.9), the Day 56 pregnancy rate (81/103 = 78.6% vs 74/98 = 75.5%, for Con vs PG, respectively; p>0.6), or the final pregnancy rate (98/103 = 95.1% vs 89/97 = 91.8%, for Con vs PG, respectively; p>0.3). CONCLUSIONS: Resynchrony of AA cows treated using the present protocol increased the proportion of non-pregnant cows detected in oestrus between Days 14 and 28 and increased the Day 28 pregnancy rate. This resynchrony protocol may be useful for increasing the proportion of the herd pregnant in the first month of the breeding programme, especially in herds that have a history of a low proportion of non-pregnant cows detected in oestrus between Days 14 and 28. There was no benefit in treating NDO/CL+ cows with PG compared to no treatment. KEYWORDS: Dairy cows, anoestrus, treatment, resynchrony, prostaglandin, progesterone, oestradiol benzoate.     

Insemination at the second of two induced oestrous periods in anoestrous dairy cows increases conception rates to first service

AIM: To determine whether mating previously anoestrous cows on their second, rather than first, oestrus post pm-turn could increase conception rates to that service. METHODS: Cows diagnosed as anovulatory anoestrus were allocated to two groups, starting treatment on Day -17 (OES2) or on Day -7 (OESI) where the date of the planned start of mating = Day 0. All cows were treated with intravaginal progesterone (CIDR device) for 6 days and an injection of 1 mg oestradiol benzoate 24 h after removal of the device. Cows in the OES2 group were also injected with prostaglandin F2alpha on Day 0. RESULTS: During the first 7 days of mating, 61.8% (207/335) and 88.2% (328/372) of cows in the OES2 and OESl groups, respectively, were inseminated on detection of oestrus (p <0.001). Oestrus without ovulation occurred in 1.5% of cows in the OES2 group and 6.2% of cows in the OESl group during this period (p <0.01). Of those cows inseminated in the first week of mating, conception rates were 54.0% in the OES2 group and 45.5% in the OESl group (p = 0.05). There was no significant difference in median interval from start of mating to conception between the two groups (24 and 22 days for OES2 and OESl, respectively, p >0.05). CONCLUSION: Mating previously anoestrous cows on their second, rather than first oestrus post partum increased conception rates to that service. However, median intervals from start of mating to conception were not altered.     

Comparison between Cloprostenol-induced and Spontaneous Oestrus Fertility in Dairy Cows

A short calving to conception interval is of main importance to achieve high economic efficiency in dairy cow industry. In order to reduce this interval, several hormonal treatments have been put on the market, in which cloprostenol, a synthetic analogue of prostaglandin F2alpha (PGF2alpha). The aim of this study was to compare fertility of cloprostenol-induced oestrus to that of spontaneous oestrus in dairy cows. In a group of 525 cows, 280 (treated group) were administered 0.5 mg cloprostenol i.m. after transrectal corpus luteum (CL) detection, and inseminated at detected oestrus during the following week. The other 245 cows (control group) were inseminated during spontaneous oestrus. Whey progesterone concentrations were checked at treatment and at insemination in order to remove from the study cows whose P4 levels indicate a non-functional CL, or a lack of luteolysis respectively. Moreover, cows that were not inseminated due to genital problems were also excluded from this study. Conception (59% vs 54.5%) and calving rates (93.7% vs 93%) were not significantly different between the two groups.     

Plasma progesterone and gonadotrophin concentrations following norgestomet treatment with and without cloprostenol in beef cows

Twelve Hereford cross Friesian cows received subcutaneous implants containing 6 mg norgestomet and intramuscular injections of 5 mg oestradiol valerate and 3 mg norgestomet. Six of the cows also received 0.5 mg cloprostenol eight days later and all implants were removed on day 9. When treatment was commenced between days 3 and 5 of the ovarian cycle, luteal function was not prevented although the luteal phase was shortened in some cases. When treatment was commenced between days 8 and 14 of the cycle progesterone concentrations remained above basal levels for five to seven days. Cows with corpora lutea that were given cloprostenol underwent rapid luteolysis. It is concluded that oestradiol valerate does not control luteal function adequately, particularly if administered early in the cycle, and this may explain failure of oestrus synchronisation in some cases. Administration of prostaglandin 24 hours before norgestomet implant removal may improve the degree of oestrus synchronisation in groups of cyclic cows.     

A clinical trial using a regimen which includes a norgestomet implant and norgestomet plus oestradiol valerate injection as a treatment for anoestrus in dairy cows

In seasonally calving dairy herds in the Macalister Irrigation Area of Gippsland, Victoria, cows that had not been observed in oestrus by the start of the mating season and which had inactive ovaries based on rectal palpation and progesterone assay were treated with a hormonal treatment (n = 49). Mature cows had calved at least 40 days previously and 2-year-olds had been calved at least 60 days. The treatment consisted of a norgestomet implant and a norgestomet and oestradiol injection on day 1; prostaglandin analogue Prosolvin) on day 8; withdrawal of implant on day 10 and an injection of PMSG; and fixed time artificial insemination 54 to 56 h after implant withdrawal. This treatment was called the Syncro-mate regimen. Control cows (n = 46) were injected with water on days 1, 8 and 10 and artificially inseminated or served by a bull when seen on heat. Forty seven percent of the treated cows became pregnant within 14 days from the start of treatment compared with 20% of control cows (P less than 0.01). There was an effect of age group on the response to treatment. A greater proportion of 2-year-old cows than mature cows became pregnant within 14 days of treatment (79% of 19 v. 27% of 20; Chi square interaction, treatment by age, 6.4, P less than 0.05). In the younger cows there was also a gain of 22 days in the treatment to conception interval over the control cows (P less than 0.001). It was concluded that the Syncro-mate regimen can be an effective treatment for post partum anoestrus in dairy cows under certain conditions.     

Oestrus synchronisation with a prostaglandin analogue III. Special aspects of synchronisation

Two groups of lactating dairy cows in each of 4 dairy herds were injected with either 0.5 mg (219 cows) or 0.3 mg (118 cows) of Ooprostenol (I.C.I.) The first group of cows were injected from Day 6 to Day 17 of the oestrous cycle (Day 0 — oestrus) and the second group from Day 6 to Day 12. The four herds were selected specifically because oestrus-detection procedures were thorough and reliable. Of the cows receiving the 0.5 mg dose rate, 54.3% were observed in oestrus within 4 days of treatment. The remainder were in groups which were: (i) in oestrus from 5 to 10 days post-treatment (20.5% with prolonged response intervals), and 11 to 20 days post-treatment (15.5% with unaltered cycle lengths); or (ii) experienced a “silent oestrus” in the immediate post-treatment period and either did not show oestrus for a further 3 weeks (6.4% in oestrus from 21 to 29 days post-treatment) or conceived to a single set-time insemination 72 h after treatment (0.9%). Use of the lower dose rate resulted in fewer cows being observed in oestrus within 72 h (43.8% v 31.4%) and a corresponding rise in the percentage experiencing a “silent oestrus” and returning to service (6.4% v 13.6%) or conceiving to set-time insemination (0.9% v 3.4%). Most of the unaltered cycle lengths occurred with cows being treated on Day 6 of the oestrous cycle. The pregnancy rate for the 171 cows observed in oestrus within 4 days of treatment and inseminated at 72 h, or 72h and 96 h, was 57.3%.

Records from this trial, as well as previous trials in which cows were injected with 0.5 mg of Cloprostenol, showed that 446 of 524 cows (85%) injected at from Day 6 to Day 17 of the oestrous cycle were observed in oestrus within 5 days (144 h) of treatment. Amongthese 446 cows, the interval to post-treatment oestrus was influenced by the stage of the cycle at injection. Whereas 89% of the oestrous responses in cows treated on Days 6 to 9 were observed within 72 h of injection, the comparable figures for cows treated on Days 10 to 13 and Days 14 to 17 were 48% and 70% respectively.

Variation in the post-treatment interval to oestrus is greater in lactating dairy cows than in heifers and is not resolved by using double-injection regimes. The reasons for this variation have not been identified. The most effective use of prostaglandins for oestrus synchronisation in lactating dairy cows requires the treatment of groups of animals at similar stages of theiroestrous cycles and their post-treatment insemination at observed oestrus. These requirements may limit the usefulness of this technology in herds with poor breeding management.     

Relationship between certain physical properties of cervical mucus and fertility in cows

The object of the present investigation was to determine several physical properties of cervical mucus in spontaneous oestrus cows in relation to fertility. Because, it is very difficult to determine the exact time of the beginning of oestrus in cows, the aim of the present study was to investigate if physical properties of cervical mucus at the time of artificial insemination (AI) are related to conception or not. A total of 93 cows of Friesian breed were used. The animals exhibited spontaneous oestrus, without being submitted to any hormonal treatment. Samples of cervical mucus were collected 5-30 min before AI and pH, viscosity, spinnbarkeit (spinability), crystallization and penetration were measured. Pregnancy diagnosis was performed by rectal palpation 3 months later. The results obtained from cows that conceived (44 animals), compared to those obtained from cows that did not conceive (49 animals), were the following: a) viscosity had been significantly lower (p < 0.05), b) crystallization had been significantly higher (p < 0.05), and c) pH, spinnbarkeit and penetration of spermatozoa into cervical mucus did not differ. In conclusion, the best time for AI is when viscosity is below 20 mm H2O and crystallization is above 3. Viscosity and crystallization could be related to ovulation time, but this needs further investigation.     

Effects of Twice-Weekly Follicular Punctures of Ovaries With or Without the Corpus Luteum on Follicular and Luteal Dynamics

We investigated the effects of twice-weekly follicular punctures of ovaries with or without corpus luteum (CL) on follicular and luteal dynamics. A cross-over design was used, with each cow (seven Japanese Black beef cows) being assigned to one of the three groups at 2-month intervals. Follicular punctures were performed twice weekly for three consecutive weeks until day 20 (oestrus = day 0). All visible follicles (diameter >3 mm) in the ovaries bearing CL (ipsilateral group) or those in the contralateral ovaries (contralateral group) were aspirated. As a control, all visible follicles in both ovaries were aspirated (bilateral group). Follicular development, CL formation and progesterone concentrations in each cow were monitored from days 0 to 30. Follicular growth profiles in the punctured ovaries during/after puncture treatment were similar, irrespective of the presence of follicles in the unpunctured ovary and the CL in the punctured or unpunctured ovaries. After puncture, two cows (28.6%) each in the ipsilateral and bilateral groups did not exhibit behavioural oestrus until day 30, whereas all cows in the contralateral group exhibited oestrus. CL growth and increase in progesterone concentrations after the last follicular puncture in the bilateral group were delayed when compared with those in the ipsilateral group. Our results indicate that the presence of follicles in the unpunctured ovary and the CL in the punctured or unpunctured ovaries does not significantly influence follicular growth in punctured ovaries during/after puncture treatment. However, follicular puncture in ovaries bearing CL may disturb or delay oestrus occurrence after treatment.     

Effect of the Type and Number of Prostaglandin Treatments on Corpus Luteum, the Largest Follicle and Progesterone Concentration in Dairy Cows

Lactating dairy cows (n = 72) with a mature corpus luteum (CL) (diameter of > or = 17 mm) determined by ultrasonography and having a follicle with a diameter of > or = 10 mm were randomly assigned to four groups. Cows were treated with cloprostenol i.m. once or twice, or with dinoprost i.m. once or twice with an 8-h interval. The ovaries of each cow were scanned daily by transrectal ultrasonography to measure the changes in the areas of CL and the largest follicle and to determine the occurrence of ovulation. Oestrus was verified twice daily. In addition, blood sample was withdrawn from each cow daily for measuring progesterone (P4) concentrations. Significant decreases in the percentage changes relative to areas of CL and P4 concentrations or increases in the percentage changes in the area of the largest follicle on day 0 were detected in each group during the experiment. However, the type of the drug and the number of the treatments had no significant effect on those parameters. Cows ovulated with or without showing oestrus (group A) and cows exhibiting no oestrus and ovulation (group B) were also evaluated. In contrast to the mean area of the CL and the mean concentration of P4 on day 0, the mean area of the largest follicles between the two groups on day 0 differed significantly. Significant decreases in the percentage changes relative to the area of the CL and P4 concentration or increases in the percentage changes relative to the area of the largest follicle during the experiment were detected in both groups; however, there were no group differences. Treatment of dairy cows with two injections of prostaglandins (cloprostenol or dinoprost) at an 8-h interval resulted in more cows being observed in oestrus within 5 days after treatment and having significantly higher pregnancy rate than those treated with a single prostaglandin injection.     

Calving rates in a tropical beef herd after treatment with a synthetic progestagen, norgestomet, or a prostaglandin analogue, cloprostenol

Maiden heifers and lactating cows of known ovarian status and of several breeds were treated with a synthetic prostaglandin, cloprostenol, or a synthetic progestagen, norgestomet, at the start of an artificial insemination (AI) program. Animals in the cloprostenol treatment received 2 injections 10 days apart. Over the next 26 days those animals that showed oestrous behaviour were inseminated. Synchronisation rates and calving rates to insemination over the first 7 days were calculated. Those in the norgestomet treatment received an implant of norgestomet plus an injection of norgestomet and oestradiol valerate. The implant was removed 10 days later and the animals were given an injection of pregnant mare serum gonadotrophin (PMSG). They were inseminated at 48 h (maiden heifers) or 56 h (lactating cows) after implant removal. Calving rates to fixed-time insemination were recorded. After completion of the AI program the animals in both treatments were joined with bulls. Overall calving rates (AI plus bulls) were calculated. By day 7 of the program, 82% of the maiden heifers and 76% of the lactating cows in the cloprostenol treatment had been detected in oestrus. By day 21 the respective figures were 99% and 81% Norgestomet treatment had an immediate and a prolonged effect on ovarian activity in those females classified as having inactive ovaries at the start of the AI program. Calving rates of those females to fixed-time AI and overall were similar to those of the females with active ovaries in both treatments. Their calving rates to fixed-time insemination, and overall calving rates for the lactating females, were significantly higher than the corresponding values of their contemporaries treated with cloprostenol and inseminated on observed oestrus over 7 days. For those females classified as having active ovaries at the start of the AI program, calving rates to first insemination and overall were similar for both treatments. Overall calving rates of lactating cows of each breed were, with one exception, higher in the norgestomet treatment than in the cloprostenol treatment. Although norgestomet treatment was more expensive than cloprostenol treatment, the advantage in calf crop resulted in an overall monetary advantage to the norgestomet treatment.     

Pregnancy Rates in Angus Cross Beef Cows Bred at Observed Oestrus With or Without Second GnRH Administration in Fixed‐Time Progesterone‐Supplemented Ovsynch and CO‐Synch Protocols

Crossbred cows (n = 1073) from five locations had oestrous cycles synchronized with 100 μg of GnRH IM and insertion of controlled internal drug release device (CIDR) on Day 0 followed by 25 mg of PGF_2α IM and CIDR removal on Day 7. Kamar^® patches were placed on all cows at CIDR removal. Cows were observed three times daily for oestrus after PGF_2α administration. In the Ovsynch‐CIDR group, cows detected in oestrus (n = 193) within 48 h after PGF_2α were inseminated using the AM–PM rule. Among these cows, 80 received and 113 did not receive a second GnRH at 48 h after PGF_2α. Cows (n = 345) not detected in oestrus received a second GnRH at 48 h after PGF_2α on Day 9, and fixed‐time AI 16 h after the GnRH on Day 10. In the CO‐Synch‐CIDR group, cows detected in oestrus (n = 224) within 48 h after PGF_2α were inseminated using the AM–PM rule. Among these cows, 79 received and 145 did not receive a second GnRH at 64 h after PGF_2α. Cows (n = 311) not detected in oestrus received a second GnRH on Day 10 at the time of AI, 64 h after PGF_2α. The AI pregnancy rates were not different between the Ovsynch‐CIDR and CO‐Synch‐CIDR groups (p = 0.48). There were no differences in the AI pregnancy rates for cows inseminated at a fixed time (p = 0.26) or at detected oestrus (p = 0.79) between the treatment groups. Among cows inseminated in oestrus, there were no differences in the AI pregnancy rates between cows that received or did not receive the second GnRH (p = 0.47). In conclusion, acceptable AI pregnancy rates can be achieved with or without inclusion of oestrus detection in the Ovsynch‐CIDR and CO‐Synch‐CIDR protocols. Among cows detected in oestrus, cows that received a second GnRH yielded similar pregnancy rates when compared with cows that did not receive the second GnRH.     

Cervical mucus in the heifer uterus during heat and insemination after feeding with synthetic beta-carotene

The effect of beta-carotene was studied, as exerted on the amount, ductility, pH value, arborization and sperm survival time in the medium of the cervical mucus of heifers included in the breeding stock. The measurements were taken during oestrus and mating. The animals were divided into four groups. The first group was given diet containing no carotene. In the other groups (II, III, IV) the animals were fed a supplement of synthetic beta-carotene, the doses being 100, 200 and 400 mg per head/day. The survival of spermatozoa in the medium of cervical mucus was found to be significantly longer in the fourth group (115.2%) as compared with the first group (61.8%). In the statistical comparison of these results the P level was less than 0.05. Statistically significant differences were observed in the amount, ductility and arborization between the pregnant heifers and oestrus return ones in the first group. These differences were reduced after the addition of beta-carotene to feed. Beta-carotene saturation in the feed ration was not found to exert any significant influence on the pH value of cervical mucus. As suggested by the evaluation of the results and their comparison with literary data, sperm survival time in cervical mucus was the only trait influenced significantly by beta-carotene: no significant effect was exerted on the other parameters under study. Beta-carotene seems to influence the role of polyfactorial factors in the control of steroidogenesis.     

Reproductive performance of dairy cows not detected in oestrus but with a detectable corpus luteum, in response to treatment with progesterone, oestradiol benzoate and prostaglandin F2alpha

AIM: To determine if the reproductive performance of dairy cows not previously detected in oestrus but with a detectable corpus luteum before the planned start of mating (PSM), could be improved by treatment with progesterone, oestradiol benzoate (ODB) and prostaglandin F2alpha (PGF). METHODS: Cows in 18 herds which had not been detected in oestrus, but which had a detectable corpus luteum present at veterinary examination 7 days prior to the PSM (Day -7), were allocated to 1 of 2 groups. Treated cows (n=232) received an injection of 2 mg ODB and an intravaginal progesterone releasing device (CIDR insert) on Day -7, and an injection of PGF on the day of insert removal 7 days later (Treated group). The Control group (n=243) remained untreated. Cows were mated to detected oestrus from Day 0, and conception dates confirmed by manual palpation or transrectal ultrasonography. RESULTS: During the first 7 days of mating, 37.4% of Control cows and 65.9% of Treated cows were inseminated on detection of oestrus (p<0.001). Pregnancy rates for this period were 20.4% and 36.3%, respectively (p=0.001). Conception rates to first insemination, pregnancy rates after 21 days of mating and at the end of the mating period were similar between groups (p>0.1). Median interval from the PSM to conception did not differ between treatment groups (24 and 23 days for Control and Treated, respectively, p>0.1). CONCLUSION: Treating postpartum dairy cows which had not previously been detected in oestrus but which had a detectable corpus luteum, with progesterone, ODB and PGF did not significantly improve their reproductive performance compared with no hormonal intervention. KEY WORDS: dairy cattle, postpartum, anoestrous, reproduction, progesterone treatment.     

Role of prostaglandin F2 alpha in follicular development and subsequent luteal life span in early postpartum beef cows.

In postpartum cows expected to have corpora lutea (CL) of normal (norgestomet-treated) compared to short (control) life spans, function of the largest follicle increases after an increase in concentrations of prostaglandin F2 alpha (PGF). To determine whether PGF alters follicular growth and subsequent life span of the CL, 43 crossbred beef cows (19 to 22 d postpartum) were assigned to one of four treatments: 1) control (C; n = 10), 2) control+PGF (CPGF; n = 10), 3) norgestomet (N; n = 13), 4) norgestomet+flunixin meglumine (NFM; n = 10). Flunixin meglumine inhibits prostaglandin endoperoxide synthase. On day 0, N and NFM cows received a 6 mg implant of norgestomet. From days 3 through 8, CPGF and NFM cows were injected every 8 hr with 10 mg PGF im or 1 g FM iv, respectively. Implants were removed on day 9. On day 11, each cow received 1000 IU of hCG im to induce formation of CL. Follicular growth was monitored by daily ultrasonography from days 6 through 11. In a majority of the cases (25/32), the largest follicle present on day 6 was still the largest on day 11; frequency of persistence did not differ with treatment. Rate of growth of the largest follicle was greater in CPGF than in N cows (.6 +/- .1 vs .3 +/- .1 mm/d, respectively; P less than .05) but did not differ between C and NFM cows (.4 +/- .1 and .5 +/- .1 mm/d, respectively). Concentrations of estradiol in NFM cows were higher (P less than .05) on day 3 and declined to concentrations similar to those of the other treatments on day 9.(ABSTRACT TRUNCATED AT 250 WORDS)