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)     

Association between physical properties of cervical mucus and ovulation rate in superovulated cows

Possible associations between certain physical properties of cervical mucus (CM) and ovulation rate were studied in 21 superovulated Holstein cows. In CM samples collected at the beginning of estrus (0 h) and in 4 h intervals for the following 24 h, the pH, the spinnbarkeit (spinability), and the crystallization value were measured. Blood samples, collected at the same time points with CM samples, were assessed for progesterone and estradiol concentrations. At 48 h the number of ovulated follicles was counted by transrectal ultrasonography and the animals were allotted into 2 groups according to the occurrence of at least one (group A, n = 16) or no (group B, n = 5) ovulations. The pH was lower (P < 0.05) at 8 h (7.00 + 0.24) in group A compared with group B (7.55 + 0.12). In group A, spinnbarkeit was significantly lower at 0 h and 20 h, and higher at 8 h and 16 h compared with group B (0 h: 2.50 + 0.82 versus 6.95 + 0.41; 20 h: 3.00 + 1.89 versus 5.38 + 0.94; 8 h: 7.00 + 0.87 versus 2.75 + 0.43; 16 h: 7.00 + 1.41 versus 4.30 + 0.71, for groups A versus B, respectively). Crystallization was significantly lower at 4 h (2.00 + 0.63) and 20 h (1.50 + 0.82) in group A compared with group B (3.13 + 0.32 at 4 h and 3.00 + 0.41 at 20 h). Progesterone at all time points, and estradiol at 16 h, 20 h, and 24 h were lower (P < 0.05) in group A than in group B. The pH, crystallization, estradiol, and progesterone differed (P < 0.05) within one group, while sbk differed within both groups.Our results imply that during the periovulatory period, steadily low progesterone concentrations trigger alterations of certain CM characteristics, while extremely high estradiol concentration could prevent the occurrence of these alterations.     

Incidence of Error in Oestrus Detection Based on Secondary Oestrus Signs in a 24-h Tie-Stalled Dairy Herd with Low Fertility

Oestrus detection error and conception rates after AI based only on secondary oestrus signs were evaluated in a high yielding, 24-h tie-stalled dairy herd with low fertility, using milk progesterone profiles. Oestrus detection was based on the secondary oestrus signs such as restlessness, swelling, congestion of vulva and clear mucus discharge. Sixty eight AI conducted after observing the secondary oestrus signs in 44 animals were included in the study. Of the 68 AI, 53 (77.9%) were conducted in the follicular phase, and 13 (19.1%) and 2 (2.9%) were carried out in the luteal phase and during pregnancy, respectively. The overall error in oestrus detection based on milk progesterone profiles was 22.1%. The oestrus detection error did not differ significantly among different secondary oestrus signs. None of the AI conducted in the luteal phase resulted in conception, whereas 20.8% of AI conducted in the follicular phase resulted in conception. No significant difference in the conception rates among the groups of cows with different secondary oestrus signs was shown. The high incidence of oestrus detection error in this study might have been caused by the detection of cows in oestrus based only on secondary oestrus signs due to the confinement of animals. In conclusion, there was a high incidence of heat detection error in the 24-h tie-stalled dairy herd and oestrus detection based only on secondary oestrus signs resulted in low conception rate.     

Relation between cervical mucus sperm toxicity and pregnancy in cows]

Cervical secretion was collected from 99 dairy cows of the Black Pied Lowland breed at an age of 24 to 109 months with a minimum performance of 4000 kg of milk annually in spontaneous oestrus 42 days post partum at the minimum. It was demonstrated by the radioimmunological determination of progesterone in skim milk that from all the breeding cows (n = 99) the oestral secretion was collected during an optimum insemination time (x = 0.19 ng.ml-1 progesterone). Of the statistical set of 99 cows, 55 (i.e. 56.57%) got in calf and 43 (i.e. 43.43%) remained barren. As found, the conception results were not influenced by the rank of the insemination after parturition and the conception capacity of the cows was not influenced by the length of time from parturition to the respective inseminations. It was demonstrated in our investigation that the conception capacity of the cows increases as the time of sperm survival prolongs in the cervical secretion in vitro. The highest conception capacity (80%) was recorded in the cows whose cervical secretion was free of spermiotoxic action. In such cases the motility of the spermatozoa in the oestral mucus was maintained at a temperature of 38 degrees C for longer than 300 minutes. On the other hand, it was demonstrated that the conception capacity of the cows declines with shortening time of sperm survival in the cervical mucus.     

Enzyme activity in bovine cervical mucus during spontaneous and induced estrus

The purpose of the present research was to compare the enzyme activity of alkaline phosphatase (ALP), lactate dehydrogenase (LDH), α-amylase, α-manosidase, β-N-acetyloglucosaminidase, β-glucuronidase, and β-galactosidase in the cervical mucus of cows during spontaneous and induced estrus. Friesian cows (n = 106) were assigned to 4 groups: 1) no treatment; 2) progesterone releasing intervaginal device (PRID) for 12 days plus pregnant mare serum gonadotrophin (PMSG) at the removal of the PRID; 3) PGF2α2 doses 11 days apart; and 4) PRID for 7 days plus PGF2α 1 dose, 24 hours before removal of the PRID. Fourteen cows were excluded from the trial because of an inadequate quantity of cervical mucus collected or a lost PRID. The cows from the 3 induced estrus groups were artificially inseminated (AI) twice, while those with spontaneous estrus received only a single AI. Cervical mucus samples were collected from all cows 5 to 30 min before the first AI. The results are summarized as follows: 1) ALP and α-amylase activity for spontaneous estrus were similar to those for induced estrus; 2) LDH activity levels during spontaneous estrus were significantly lower (P < 0.001) than that in the P4 and P4+PGF2α induced estrus groups; and 3) glycosidases' activity was significantly lower (P < 0.001) in the spontaneous estrus group than that in the induced estrous groups. In conclusion, the activity of most enzymes in the cervical mucus of cows, in the present study, was significantly different between the spontaneous and the induced estrus groups.     

Role of the sensitivity of detection of oestrus in the submission rate of cows treated to resynchronise oestrus

OBJECTIVE: To determine if failure to detect oestrus in cows treated to resynchronise oestrus leads to fewer cows being inseminated than are truly in oestrus. PROCEDURE: Cows in three herds were enrolled in a controlled breeding program that involved synchronisation of oestrus for a first round of artificial insemination (AI) followed by resynchronisation for a second round of AI. Just before oestrus was expected at the second round of AI, aids for the detection of oestrus were fitted, which included pedometers, radiotelemetric transmitters (HeatWatch), tail-paint and heatmount detectors. Milk samples were collected at the second round of AI (day 33, herds A and B; day 35, herd C of the treatment program) and were used in combination with pregnancy testing to determine the number of cows that were in oestrus (milk progesterone < 2.0 ng/mL) and cows that were not in oestrus (milk progesterone > 2.0 ng/mL or pregnant at second round of AI) at the time samples were collected. RESULTS: The mean sensitivity of detection of oestrus at the resynchronised oestrus was 92.5% and did not differ significantly between herds (P = 0.19). A total of 75% (60/80) of cows that were retrospectively determined to be not pregnant at the time of the second round of AI were classified as having high (> or = 2.0 ng/mL) concentrations of progesterone in milk at that time. Pregnancy testing of cows about 35 days after AI suggested that early pregnancy loss also contributed to a reduction in submission rates at the resynchronised oestrus. CONCLUSION: Failure to submit cows for insemination at a resynchronised oestrus was mainly due to cows not being in oestrus rather than due to a failure to detect oestrus.     

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.     

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.     

Mucus and hormonal traits in three gestation patterns (pre-, full- and post-term) of Egyptian Nubian (Zaraibi) crossbred doe goats

In the present study, 48 crossbred does (Nubian × Baladi) were used to investigate physiological (mucus and hormonal) traits as affected by gestation pattern (pre‐, full‐ and post‐term parturitions). The incidence of full‐term (does with a gestation length of 146–152 days) was the highest (54.5%), followed by pre‐term (does with a gestation length of 140–145 days; 36.9%) and post‐term (does with a gestation length of 153 days; 8.9%), respectively. Prediction of gestation pattern by using some body measurements was also studied. Cervical mucus samples were collected during estrus to determine spinnbarkeit (i.e. strength, viscosity or stretchability) and pH values of the mucus. Mucus was also collected pre‐parturition daily from day 140 of gestation until delivery, to evaluate the ferning arborization. Blood samples were collected on the day before mating (0 time), 1 (at mating), 30, 60, 90 and 145 days after mating. The results showed that spinnbarkeit and pH in cervical mucus at estrus, serum estradiol‐17α (E2) at day 5 before delivery, and progesterone (P4) levels differed insignificantly according to gestation pattern. The fern degree between day 140 of gestation and day of delivery was the highest in pre‐term does, while it was the lowest in post‐ and full‐term does. The gestation length was the highest in post‐term does (157.5 days), and the lowest in pre‐term does (141.5 days). During winter, the incidence of pre‐term deliveries was the highest (54.5%), but in spring, full‐term deliveries were the most common (58.3%). Most of the traits studied were insignificantly affected by season of birth. Post‐term delivery can be estimated by doe weight and wither height, while full‐term delivery can be anticipated using by hip height and abdomen girth. Pre‐term does can be detected by cervical mucus fern between day 140 of gestation and day of delivery. Post‐term does can be defined by doe weight and wither height, while full‐term deliveries can be defined by hip height and abdomen girth, during pregnancy.     

Calving rate following fixed time insemination after a 12-day progesterone treatment in dairy cows, beef cows and heifers.

Farm trials were carried out to determine if cows and heifers could be inseminated on a fixed time basis following a 12-day treatment with progesterone coils and an injection of 5 mg oestradiol benzoate and 200 mg progesterone at the start of treatment. The retention rate of the coils was significantly higher (P less than 0.05) when a 5.5 cm diameter was used compared with a diameter of 7.0 cm. Calving rate was similar in treated cows bred at a detected oestrus, at 56 + 74 hours after treatment or at 56 hours after treatment and injection of 100 microgram gonadotrophin releasing hormone 20 hours previously and in control cows bred at oestrus. Fertility to the first repeat oestrus was also similar in treated and control cows. Significantly (P less than 0.05) more synchronised cows calved following fixed time AI compared with the calving rate in control cows inseminated for a 24-day experimental period. In beef suckler cows, calved at least 50 days, and dairy heifers weighing over 280 kg, calving rate was similar in treated animals bred at 56 and 74 hours after treatment compared to calving rate in control animals bred at oestrus.     

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.     

Effect of norgestomet treatment on plasminogen activator activity in the cervical mucus and the endometrium in dairy cows

The aim of this study was to determine the effect of norgestomet treatment, in the absence or the presence of a functional corpus luteum (CL), on plasminogen activators activity (PAA) in the cervical mucus and the endometrium in dairy cows. Eleven days after oestrus (Day 0 = oestrus), 38 cows were randomly assigned to one untreated control group (n = 9) and three treatment groups (S(1), S(2) and S(3)). Animals of S(1) group (n = 9) received an implantation of norgestomet on the outer surface of the ear for 8 days, simultaneous injection of oestradiol valerate 5 mg and norgestomet 3 mg, i.m., and on Day 19 an injection of ECG 500 IU, i.m. Animals of S(2) group (n = 11) received the treatment of S(1) group, plus an administration of PGF(2)alpha on Day 10 for the regression of CL. Animals of S(3) group received the treatment of S(2) group, plus two additional norgestomet implants inserted on Day 16 for 36 h. Both types of plasminogen activators [the tissue-type (t-PA) and the urokinase-type (u-PA)] were detected in the cervical mucus and the endometrium of the cows. Plasminogen activators activity in the cervical mucus was higher in control group than in S(1), S(2) and S(3) groups (P < 0.001). In contrast, endometrial PAA did not differ among groups (P > 0.05). Oestradiol-17beta concentrations on Day 21 were higher in S(2) group than in control group (P < 0.01) and S(3) group (P < 0.05). Progesterone concentrations did not differ among groups (P > 0.05). Oestradiol-17beta concentrations could positively affect cervical mucus PAA in control group (P < 0.1), but not in other groups (P > 0.05). These findings suggest that control of estrous cycle by norgestomet administration, in dairy cows, exerts a suppressive effect on plasminogen activators synthesis and/or secretion in the cervical mucus, regardless of the absence or the presence of the CL. On the contrary, endometrial PAA is not affected by norgestomet treatment.     

Synchronisation of oestrus and reproductive performance of dairy cows following administration of oestradiol benzoate or gonadotrophin releasing hormone during a synchronised pro-oestrus

OBJECTIVE: To compare the use of gonadotrophin releasing hormone (GnRH) and oestradiol benzoate (ODB) administered following a synchronised pro-oestrus on reproductive performance of lactating dairy cows and the submission rates of non-pregnant cows following resynchronisation. DESIGN: Cohort study. PROCEDURE: Lactating Holstein cows enrolled in a controlled breeding program were first treated with an intravaginal progesterone releasing insert (IVP4) for 8 days, 2.0 mg of ODB intramuscular (i.m.) at device insertion (Day 0), an analogue of PGF2alpha at device removal and either 1.0 mg of ODB i.m., 24 h after device removal (ODB group, n = 242), or 0.25 mg of a GnRH agonist (GnRH group, n = 152) injected i.m. approximately 34 h after device removal. Every cow was artificially inseminated between 49 and 56 h after removal of its insert (Day 10). Cows detected in oestrus 1 day after artificial insemination (AI) that were not detected in oestrus on the previous day were re-inseminated on that day. All cows treated on Day 0 were resynchronised for reinsemination by insertion of a used IVP4 device on Day 23. Oestradiol benzoate at a dose of 1.0 mg was administered i.m. at the time of device insertion. Inserts were removed 8 days later (Day 31) and 1.0 mg of ODB was injected i.m. 24 h later. Those cows detected in oestrus between Days 31 and 35 were artificially inseminated. On Day 46 these cows were resynchronised for a third round of AI by insertion of an IVP4 device, used previously to synchronise cows for the first and second rounds of AI, and administration of 1.0 mg of ODB i.m.. Eight days later inserts were removed. Cows detected in oestrus between Days 54 and 58 were artificially inseminated. Bulls were run with the herd between rounds of AI and removed after 21 weeks of mating. RESULTS: Treatment with ODB or GnRH at the first synchronised pro-oestrus did not significantly alter the reproductive performance over three rounds of AI or over a 21-week breeding period. Treatment also did not alter submission rates at the second round of AI or the proportion of non-pregnant and non-return cows ('phantom' cows) detected and did not result in significant differences in concentrations of progesterone in plasma 10 and 18 days after removal of inserts at the first round of AI. Treatment with GnRH reduced the proportion of cows detected in oestrus at the first round of AI (36.2 vs 97.5%; P < 0.001). CONCLUSION: Administration of GnRH compared to ODB at a synchronised pro-oestrus results in similar reproductive performance. Treatment with GnRH reduced the proportion of cows detected in oestrus following treatment. This may offer advantages to the way AI is managed by enabling insemination at a fixed-time and removing the need for the detection of oestrus.     

A Comparative Study on the Oestrous Response to PGF2α Analogue Treatment,and Conception Rates According to Time of Artificial Insemination,in Zebu (Bos indicus) and Baoulé (Bos taurus) Cattle

The oestrous response, interval and conception rates were studied after synchronization with a prostaglandin analogue (cloprostenol) and artificial insemination (AI) performed at different times in 50 Zebu (Bos indicus) and 83 Baoulé (Bos taurus) cattle indigenous to Burkina Faso. The overall proportion of cows responding to synchronization was 70% (93/133). Although the response was higher for the Baoulé cattle, at 73.5% (61/83), than for the Zebu, at 64% (32/50), the difference was not statistically significant (p>0.05). The mean oestrous interval from treatment to the onset of oestrus (TOI) was shorter in the Zebu (54.1 h, SD 6.7) than in Baoulé (65.2 h, SD 12.9) cattle (p<0.001). Of the Zebu (n = 32) that responded, 65.7% presented oestrus over a period of 12 h ranging from 48 h to 60 h after treatment. For the Baoulé cows, the highest proportion of animals in oestrus over a period of 12 h was 41% between 60 h and 72 h after treatment. The frequency distribution of onset of the oestrus indicated that up to 64.5% of the Zebu and 79.5% of the Baoulé cattle showed onset of oestrus during the daytime. For Zebu and Baoulé cows inseminated 13 h or 18 h after the onset of oestrus, conception rates were 56% and 57% (p>0.05) and 33% and 64% (p<0.05), respectively. Based on these findings, it appears that the oestrous response to synchronization was adequate for both Zebu and Baoulé cattle and that the time to onset of oestrus varied according to genotype. It was also concluded that conception rates were satisfactory for both genotypes but that, for Baoulé cattle, AI performed 18 h after oestrus significantly increased conception rates compared to AI at 13 h after oestrus.     

Pregnancy rate after timed artificial insemination in early post-partum dairy cows after Ovsynch or specific synchronization protocols

The present study was designed to compare the reproductive performance of pre-synchronized post-partum dairy cows subjected, either to the Ovsynch protocol without screening for ovarian status (control group), or to a specific oestrous synchronization protocol applied according to their ovarian status, as determined by transrectal ultrasound (experimental group). The study was conducted on 428 lactating dairy cows. Cows in the Ovsynch group (n = 205) were synchronized and time inseminated after receiving the Ovsynch protocol treatment. Cows in the specific synchronization (Ssynch) group (n = 223) were weekly subjected to transrectal ultrasound exams for 4 weeks, or until AI or starting treatment, and divided into four subgroups according to their ovarian status: (i). corpus luteum (CL) subgroup (n = 130), cows with a CL; (ii). natural oestrus (NE) subgroup (n = 58), cows showing NE; (iii). anovulatory follicles (AF) subgroup (n = 26), cows considered to have AF; and (iv). ovarian cysts (OC) subgroup (n = 9), cows with OC. Cows in the Ssynch group were synchronized and time inseminated following a specific oestrous synchronization protocol, or inseminated at NE. Logistic regression analysis was carried out for the dependent variables ovulation and pregnancy rates to first and to second AI (second AI: first AI + return AI). Cows subjected to Ssynch were 2.1 times more likely to become pregnant at first and at second AI compared with those synchronized using the Ovsynch protocol (P < 0.0001). Our results show that the response of post-partum pre-synchronized cows to a specific oestrous synchronization protocol applied according to their ovarian status is more effective than the response to the Ovsynch protocol applied without taking into account the ovarian status of the animals.     

Radioimmunoassay of milk progesterone as a tool for fertility control in smallholder dairy farms

This study focused on the use of radioimmunoassay of progesterone in milk for the diagnosis of post-partum ovarian cyclicity and accurate detection of oestrus and non-pregnancy in cows in the artificial insemination (AI) programme in Bangladesh. In Investigation 1, milk samples were collected on day 0 (day of AI), day 9–13 and day 21–24 from 444 milking cows of various breeds presented for the first post-partum insemination by 413 farmers living at 182 villages/regions in Mymensingh District from 6 AI centres and sub-centres. Each cow was then examined three times after each AI until it stopped returning to oestrus. Sixty to 90 days after the last AI, the cows were examined per rectum to confirm the pregnancy. Milk progesterone data on day 21–24 contributed to a clear diagnosis with respect to non-pregnancy in 100% cows, indicating a possible use of this progesterone assay for identifying non-pregnant cows in AI programmes. In Investigation 2, milk progesterone was monitored two times in a month with a 10-day interval in 88 cows. The samples were taken between 10 days after calving and the first detected oestrus, followed by two more samples 10 days apart. The proportion of cows accurately detected in oestrus was 30%. Another 30% were stated to be in oestrus when they were not (false positive) and 40% were not detected when they were in oestrus (false negative). The mean intervals between calving and oestrus and between calving luteal activity were 40 to 362 days (median = 120, n = 82) and 34 to 398 (median = 111, n = 64) days, respectively. The body condition scores at calving and at the initiation of luteal activity influenced the interval between calving and luteal activity (p < 0.05). Cows suckled twice daily initiated luteal activity earlier than their counterparts suckled several times daily (p < 0.05). Determination of progesterone in milk on day 21–24 is a good means for detecting non-pregnant cows.     

Probability of pregnancy to artificial insemination either after detected oestrus or at a fixed time in dairy cows: Influence of intrinsic and extrinsic factors in a large-scale,on-farm study

The first aim of this study was to determine the influence of the procedures [hormonal treatments for fixed time artificial insemination (FTAI) versus insemination at spontaneous oestrus (SEAI)] on several sequential inseminations (AI). A second aim was to determine the influence of some intrinsic and extrinsic factors and their interactions, including characteristics of the animals such as age, season, farm, sire, and AI technician on the response to both procedures. A retrospective analysis was performed from a data base of 120.807 AIs of healthy cows with at least 40–70 days post-partum at first service. Overall, FTAI achieved slighter greater pregnancy rates than insemination after detected oestrus. The second AI seems to be a key insemination as effects of sire and technician were greater than in the following ones. The use of FTAI or SEAI in one AI did not affect the results of the following AIs, regardless if FTAI or SEAI procedures were used in that AI. Technician had greater variation than sire or farm on final pregnancy rate. The results of each sire for pregnancy rate varied according to the type of insemination, with sires achieving greater results with one or other procedure. Pregnancy rate was positively related to the days in milk in the first two AIs. Results were greater in autumn than in spring services.     

Progesterone concentration in defatted milk of dairy cows in early pregnancy.

Progesterone concentrations have been measured in defatted milk of British Friesian cows of four herds during the oestrus cycles (other than short cycles) immediately before artificial insemination (AI) at oestrus and immediately after AI (in non-pregnant cows), and during early pregnancy. Differences in mean progesterone concentrations between herds were significant (P less than 0.05) on all days within the day 10-18 period after AI, both in pregnant and in non-pregnant, inseminated cows but were not significant between pregnant and non-pregnant cows within herds until day 17 or 18. It is concluded that up to this time (that of luteolysis in non-pregnant cows) undefined factors, variable among herds, can have a much greater influence on the rate of progesterone secretion by corpora lutea and consequent progesterone concentration in plasma and milk than does the presence of conceptuses. Maximum mean progesterone concentration reached during early pregnancy in two herds did not differ significantly; it was reached in the 11-15-day period in one herd but not until 46-50 days in the second. Mean progesterone concentration declined after day 90.     

Recent Developments in Oestrous Synchronization of Postpartum Dairy Cows with and without Ovarian Disorders

This report reviews the most recent developments in prostaglandin‐based oestrous synchronization programmes for postpartum dairy cows and addresses the efficiency of controlled breeding protocols based on such developments for cows with abnormal ovarian conditions. A double prostaglandin protocol applied 11–14 days apart seems to be capable of bringing most cows to oestrus. Because of varying oestrus onset times, improved conception rates are obtained following artificial insemination (AI) at detected oestrus rather than fixed‐time AI in prostaglandin‐treated cows. The administration of oestradiol or human chorionic gonadotrophin, or both these hormones, after prostaglandin treatment, improves the synchrony of oestrus yet does not enhance the conception rate. Progesterone‐based treatments for oestrous synchronization are considered the most appropriate for non‐cyclic or anoestrous postpartum dairy cows; prostaglandin alone being ineffective because of the absence of a mature corpus luteum in these cows. Improved oestrus synchrony and fertility rate have been reported using short‐term progesterone treatment regimes (7–9 days) with or without oestradiol benzoate combined with the use of a luteolytic agent given 1 day before, or at the time of, progesterone withdrawal. The ovulation synchronization (Ovsynch) protocol, based on the use of gonadotrophin releasing hormone and prostaglandin, was developed to coordinate follicular recruitment, CL regression and the time of ovulation. This protocol allows fixed time insemination and has proved effective in improving reproductive management in postpartum dairy cows. However, timed AI following Ovsynch seems to have no beneficial effects in heifers, because of an inconsistent follicle wave pattern, and in anoestrous cows, given their lack of prostaglandin responsive CL. To date, there are several prostaglandin based, fixed‐time insemination oestrous synchronization protocols for use in early postpartum dairy cows with ovarian disorders such as ovarian cysts and acyclicity.     

Changes in LH Pulsatility Profiles in Dairy Heifers During Exposure to Oestrous Urine and Vaginal Mucus

Difficulty in observing oestrus is a problem for many dairy farmers performing AI. Finding ways to synchronize oestrous cycles or strengthen display of oestrus without hormonal treatments would be of great interest because many consumers object to the use of exogenous hormones on healthy animals. Modification of reproductive cycles through chemical communication has been reported in several species including cattle. LH is an important regulator of the follicular phase and could possibly be subject to pheromonal influence. This study focuses on the effect of volatile compounds from oestrous substances on LH pulsatility preceding the preovulatory LH surge in cattle. Four heifers of the Swedish Red breed were kept individually in isolation. Exposure to water during the control cycle (CC), and bovine oestrous urine and vaginal mucus during the treated cycle (TC), started simultaneously with induction of oestrus. Blood sampling at 15‐min intervals started 37 h after administration of PGF_2α and continued for 8 h. Monitoring of reproductive hormones, visual oestrus detection and ultrasonographic examination of the ovaries continued until ovulation had occurred. The mean concentration of LH at pulse nadir was significantly higher during TC (2.04 ± 0.18 ng/ml) than during CC (1.79 ± 0.16 ng/ml), and peak amplitude was significantly higher during CC (Δ1.03 ± 0.09) than during TC (Δ0.87 ± 0.09). No other parameters differed significantly between the two cycles. We conclude that the difference in LH pulsatility pattern may be an effect of exposing heifers to oestrous vaginal mucus and/or urine and that the mechanism behind this needs further investigation.