Effects of Alfaprostol and uterine palpation on postpartum interval and pregnancy rate to embryo transfer in Brahman influenced beef cows

Two trials were conducted to determine the effects of Alfaprostol, a prostaglandin F2 alpha analogue, and uterine palpation on reproductive performance in postpartum beef cows. In Trial J, 143 multiparous and 132 primiparous Brahman crossbred embryo recipient cows were assigned to receive one 5 mg injection of Alfaprostol between 29 and 65 d postpartum or to serve as controls. Alfaprostol treatment between 29 and 42 d postpartum decreased (P < 0.05) postpartum interval in multiparous but not primiparous cows. Alfaprostol treatment increased pregnancy rate to embryo transfer. Trial II utilized 369 multiparous Brangus cows, 17 to 49 d postpartum, that were assigned to one of three groups: 1) Alfaprostol plus uterine palpation (APP), 2) Uterine palpation only (UP) or 3) Control. Completion of uterine involution was determined at treatment. Alfaprostol plus uterine palpation decreased postpartum interval regardless of uterine involution, while UP had a greater effect if uterine involution was not complete. Both APP and UP increased the number of cows which were detected in estrus by 80 d postpartum. Alfaprostol and uterine palpation, alone or in combination, can increase postpartum reproductive performance in Brahman crossbred and Brangus beef cows.     

Multivariate analysis of factors associated with calving interval and calving rate in dairy cows

We collected data on reproductive events of cows (n = 2116) that included dates of calving, first service, last artificial insemination before pregnancy examination, pregnancy examination, abortion, diagnosis of cystic ovary, and treatment with prostaglandin. We used multivariate analysis to evaluate the relationship between the interval from insemination to pregnancy examination and the length of calving interval, adjusting for other factors affecting the calving interval. The effect of the interval from insemination to pregnancy examination on calving rate was estimated using logistic regression analysis. The calving interval was long for cows with a short interval from artificial insemination to first pregnancy examination, it was at a minimum at 55 d and increased thereafter. Other factors affecting the calving interval were cystic ovaries, prostaglandin treatment, abortion, number of artificial inseminations, and days to first service. The calving rate was low among cows with a short interval to pregnancy examination, reached a maximum at 48 d, and then declined. Other factors affecting the calving rate were abortion, number of artificial inseminations and whether the cow was bred by a clean-up bull.     

Progesterone levels and relationship with the diagnosis of a corpus luteum by rectal palpation during the estrous cycle in Zebu cows

To assess the accuracy of rectal palpation for detecting functional luteal tissue during the estrous cycle in Zebu cattle, 20 mature non-lactating Indobrazil cows were palpated twice weekly for 7 1/2 weeks. Blood samples were drawn for progesterone analyses at each palpation. Circulating serum progesterone levels were below 0.5 ng/ml from days 0-4 (Day 0 = day of estrus); they increased thereafter, reaching maximum levels of 3.1 ng/ml on days 9 and 10. Values declined sharply to less than 0.5 ng/ml on day 18. Regardless of the stage of the estrous cycle in 71.3% of the cases (117 out of a total of 164 observations) the circulating progesterone levels corresponded to the results of rectal examination. The criteria to assess this relationship were that the presence of CL as determined by rectal palpation would be accompanied by levels of progesterone higher than 0.5 ng/ml, whereas absence of CL would be accompanied by levels less than 0.5 ng/ml. The correlation was significantly higher (P<0.05) on days 5-17 (77.9%) than on days 0-4 (57.5%) and 18-20 (65%). To assess the correlation of both rectal examination and progesterone levels with the stage of the estrous cycle, we expected that on days 0-4 and 18-20 no palpable CL and progesterone levels less than 0.5 ng/ml would occur, whereas on days 5-17 palpable CL and progesterone levels higher than 0.5 ng/ml would be found. On this basis, a correlation of 45% (18 out of 40 observations) between expected and observed values was found on days 0-4, 76% (79 out of 104) on days 5-17 and 60% (12 out of 20) on days 18-20 of the estrous cycle. Of the total of 55 observations which fell outside the expected values, 71% was due to a wrong diagnosis of CL; 14.5% was due to progesterone levels higher or lower than the expected values, and 14.5% to both laboratory and rectal palpation findings.     

Embryonic loss from 30 to 60 days post breeding and the effect of palpation per rectum on pregnancy

This study was conducted over a 12-mo period to determine the rate of bovine embryo death between 30 and 60 d of gestation. In addition, palpation per rectum as a means of pregnancy detection was evaluated as a possible cause of embryo death. Estrus was synchronized in Holstein heifers (n = 1358), weighing > or = 385 kg, with a single intramuscular injection of 25 mg prostaglandin F(2alpha). Estrus was primarily detected by the absence of paint marks on the tailhead. The heifers were artificially inseminated with semen from 5 Holstein sires. Blood was collected between 30 and 45 d after breeding, and sera were evaluated for the presence of bovine pregnancy-specific protein B (bPSPB) by RIA to determine pregnancy. Palpation for fetal membrane slip was conducted by an experienced technician in approximately one-half of the inseminated heifers. To determine embryonic survival, a second blood sample was collected at approximately 60 d from 862 heifers that were determined to be pregnant at the first blood sampling. Embryonic loss averaged 5.3% during the interval between the initial detection of pregnancy at 30 to 45 d and the subsequent detection of pregnancy at 60 d of gestation. Embryo loss in heifers that were palpated was 6.5% compared with that of 4.3% in the control heifers (X(2): P = 0.145). These findings establish that there was substantial loss of embryos between 30 and 60 d post breeding but that embryo loss was not affected by palpation per rectum.     

Influence of a CIDR prior to bull breeding on pregnancy rates and subsequent calving distribution

We determined whether insertion of a CIDR for 7 days prior to the breeding season enhanced pregnancy rates and altered the date of conception in suckled beef cows mated naturally. Suckled beef cows (n=2033) from 15 locations were randomly assigned to one of two treatments: (1) cows received a CIDR 7 days prior to the breeding season for 7 days (CIDR; n=999); (2) cows received no treatment (Control; n=1034). On the first day of the breeding season bulls were introduced to herds at a rate of 15-25 cows per yearling bull or 20-30 cows per mature bull. Pregnancy status and the date of conception were determined via transrectal ultrasonography at 56 and 120 days after initiation of the breeding season. Overall pregnancy rates ranged from 59.3 to 98.9% among the 15 locations. The percentage of cows becoming pregnant during the first 30 days of the breeding season was similar between CIDR (68.2%) and Control (66.7%) cows, and overall pregnancy rates were similar between CIDR (88.9%) and Control (88.6%) cows. The average day of conception after initiation of the breeding season was shorter (P<0.01) for CIDR (20.1+/-0.8 days) compared to Control cows (23.2+/-0.8 days). Of cows conceiving during the breeding season, more (P<0.05) CIDR cows (35.9%) conceived during the first 10 days of the breeding season than Control cows (30.8%). Neither body condition score and nor parity affected pregnancy rates or days to conception, whereas pregnancy rates and days to conception were affected (P<0.01) by location and days postpartum. Days to conception were greater for cows that calved within 40 days (31.6+/-1.2 days) of initiation of the breeding season compared to cows calving between 40 and 50 days (25.3+/-1.2 days) prior to initiation of the breeding season, which were greater than those cows calving between 50-60 days (20.0+/-0.8 days) and 60-70 days (21.3+/-1.0 days) prior to initiation of the breeding season. Cows calving greater than 70 days (17.3+/-1.5 days) from initiation of the breeding season had the shortest interval to conception. We concluded that insertion of a CIDR prior to the breeding season failed to increase overall pregnancy rates, but did influence the average day of conception.     

Fetal survival in the cow after pregnancy diagnosis by palpation per rectum

It is desirable to determine wheter a cow has failed to become pregnant as early as possible, preferably prior to 50 d after insemination. Although palpation per rectum has been the generally accepted method of pregnancy diagnosis in cattle, the procedure may be a significant iatrogenic cause of fetal attrition. In a study conducted at a North Florida dairy from January through June 1982, pregnancy was determined in 192 Holstein-Friesian cows by measuring low milk progesterone (P4) content on day of insemination (Day 0) and elevated P4 on Days 21 and 24. Pregnant cows were randomly assigned to a treatment and a control group. Cows in the treatment group (n = 85) were palpated per rectum twice between Days 42 and 46 after insemination. Cows in the control group (n = 107) were not palpated until both groups were palpated at Day 90. Palpation, done by two experienced clinicians, consisted of palpation of fetal fluid fluctuation, identification of the amniotic vesicle, and slipping of the chorioallantoic membranes. In both groups of cows fetal viability was monitored by milk P4 content. Last milk (5 to 15 ml) was collected from one front quarter on Days 0, 21, and 24 and twice weekly thereafter through Day 63. Milk was defatted by centrifugation and the fat-free milk progesterone content measured by a radioimmunoassay without extraction. The milk P4 test was 80.0% accurate in determining pregnancy in the palpated and nonpalpated cows. In the cows palpated on Days 42 to 46, pregnancy rates declined by 7.5% as determined by palpation at Day 90, or by 11.4% as determined by milk P4 content through Day 63 (both values P < 0.05). Cows that were not palpated on Days 42 to 46 showed a 1.9% increase or a 4.3% decline in pregnancy rates as determined by the same criteria. Before palpation, at Days 42 to 46, pregnancy rates were better in cows that were inseminated in winter (January to March) than in spring (April to June) (82.3% vs 61.6%; P < 0.05); P4 content was higher (winter > spring = 2.13 ng/ml vs 1.38 ng/ml; P < 0.05). First-lactation cows had higher P4 values on Days 21 and 24 than older cows (P < 0.01).     

Transrectal Doppler sonography of uterine blood flow in cows during pregnancy

Transrectal Doppler ultrasound was used for the noninvasive investigation of uterine blood flow in three cows during pregnancy. The uterine arteries ipsi and contralateral to the conceptus were scanned monthly. Blood flow was reflected by the following parameters: resistance index (RI), time-averaged maximum velocity (TAMV), diameter of the vessel (D) and the volume of blood flow (VOL). RI values were negatively correlated to all other blood flow parameters (P < 0.01). Positive correlations occurred between TAMV, D and VOL (P < 0.0001). While blood flow parameters did not differ between cows (P > 0.05), the month of gestation showed a positive effect on RI and negative effects on TAMV, D and VOL (P < 0.0001). The RI was lower and TAMV, D and VOL higher in the uterine artery ipsilateral to the conceptus (P < 0.05). RI values decreased continuously during the first 8 months of gestation and remained from then until birth at a relatively constant level. While TAMV increased especially in two-thirds of pregnancy, a relatively uniform rise of D was noticed. VOL increased exponentially with stage of gestation. The results show that transrectal Doppler sonography is a suitable, noninvasive method for the examination of uterine blood flow during pregnancy in cows. Using this technique it might be possible in the future to determine the role of uterine blood flow in cows at the risk of abortion.     

Transrectal Doppler sonography for evaluation of uterine blood flow throughout pregnancy in 13 cows

Once weekly from 30 to 270 days of gestation in 13 cows, Doppler ultrasound scanning (triplex Doppler system) was done to assess blood-flow parameters of both median uterine arteries. Resistance, velocity and volume indices were measured. Resistance index values were negatively correlated to all other blood-flow parameters (P<0.05), but there were positive correlations between velocity and volume indices (P<0.05). Resistance indices were lower, and velocity and volume indices were significantly higher in the median uterine artery ipsilateral versus contralateral to the fetus. Resistance indices decreased continuously during the first 36 weeks of pregnancy. Velocity values rose three-fold, whereas the area increased 20-fold and the volume increased 17-fold by the end of gestation (P<0.05). Birth weight of calves was positively correlated with blood-flow volume (r=0.34) but negatively correlated with the resistance index (r=-0.45). There were no significant differences between male versus female calves (at any stage of gestation) in the resistance, time-average maximum velocity, and volume indices (P>0.05). In conclusion, arterial blood flow was monitored with transrectal Doppler sonography in both median uterine arteries weekly throughout pregnancy in cattle; this could be very valuable for monitoring pregnancies at high risk for abnormalities of the placenta, fetus or both, e.g. cloned calves.     

Cervical diameter in relation to uterine and cervical EMG activity in early postpartum dairy cows with retained placentas after PGF2alpha induced calving

The cervix must regain its normal diameter after parturition. Until now, little has been known about the pattern of cervical closure and the possible influences of myometrial and cervical contractions in this process. We continuously measured the cervical diameter with ultrasound cervimetry during the first 48h after calving in six cows with retained fetal membranes, while uterine (n=6) and cervical outer muscular layer (n=4) electromyographic (EMG) activity was measured with bipolar EMG electrodes. We found that the cervical diameter which was 6.2cm (+/-0.7) at 1.4h after calving, initially increased to 9.0cm (+/-1.0) during the first 14.8h (+/-2.8) postpartum. After this time, the diameter decreased gradually to 5.3cm (+/-1.0) at 48h after calving. The overall EMG activity after parturition decreased by 59% (+/-6) and 35% (+/-17) for the uterus and cervix, respectively. The decrease in EMG activity was due to a 50% (+/-7) decrease in EMG amplitudes of the myometrium; the EMG amplitudes of the cervix decreased by only 8% (+/-21) (P>0.05). At the same time in the cervix, burst frequency decreased by 69% (+/-17), while the decrease in burst frequency of the myometrium was only 11% (+/-5) (P>0.05). Uterine myometrial and cervical EMG activity after parturition showed burst patterns. These contractions of the uterus and cervix were accompanied by and correlated with transient dilatations of the caudal cervix. This could have functional relevance in the evacuation of the uterus.     

Use of milk progesterone enzyme immunoassay for early pregnancy diagnosis in cows

An enzyme immunoassay using beta-galactosidase as the tracer was applied to determine milk progesterone level in cows. The novel method was reliable and practicable and required only a spectrophotometer and a centrifuge as major equipment. The milk progesterone enzyme immunoassay successfully diagnosed early pregnancy in cows. Milk samples were collected from 268 Holstein-Friesian cows in commercial dairy herds on 20, 21 or 22 days(usually 21 days) after insemination. Progesterone level in skim milk higher than 1.0 ng/ml indi-cated pregnancy. Pregnancy was confirmed by rectal palpation on 60 to 120 days after insemination. The accuracy of the milk progesterone test was 60.0 % (132 220 ) for a positive diagnosis and 100 % (48 48 ) for a negative result. A high incidence of embryonic death, 27.9 % (51 183 ), may have reduced accuracy for a positive test result. The enzyme immunoassay may be an alternative to radioimmunoassay in milk progesterone analysis for pregnancy diagnosis.     

Calf survival from embryo transfer-induced twinning in dairy-beef cows and the effects of synchronised calving

In each of 4 years, 94-116 mature cows had two 6-7-day-old embryos, produced by the in vitro fertilisation of oocytes, inserted non-surgically into one uterine horn of each cow. Starting 5 days before the expected date of calving, the cows were continuously observed and assistance at calving was provided when required. In year 1, perinatal calf survival was similar in twin-calving (TC) and single-calving (SC) cows (98.1 versus 100% for calves born to TC and SC, respectively). There was a higher incidence of assistance at birth for TC (52%) than for SC (21%). In years 2 and 3, the calving of 30 SC and 33 TC was synchronised using an injection of Opticortinol (OP) 6-9 days before the injection of Estrumate and Dexol-5 (E+D). A further 34 SC calved naturally. Synchronised calving reduced the spread of calving from 16-25 to 8-9 days without reducing perinatal calf survival and had no significant effect on the incidence of assistance at birth in SC. The TC in years 2 and 3 had a high incidence of retained placenta at 48 h (70%) and a high incidence of assistance at birth (85%). In year 4, calving was synchronised in 16 SC and 21 TC with E+D and no pre-treatment with OP, while 15 SC were treated with both OP and E+D. There were no effects of the hormone treatment on perinatal calf survival and only small effects on the incidence of assisted births for SC. The incidence of retained placenta at 48 h was lower for SC pre-treated with OP (40%) than for SC (88%) and TC (76%) not pre-treated with OP. Continuous supervision over calving produced perinatal calf survival rates for TC that were similar to SC, despite the higher incidence of assistance of TC at parturition. Hormonal synchronisation of calving can halve the time required for continuous supervision of calving, but the hormone treatments exacerbate the already high incidence of retained placenta in TC.     

Effect of month and season of calving on the length of subsequent calving interval in Nili-Ravi buffaloes

Data pertaining to records of 1,274 calving intervals for 400 breeding buffaloes maintained at the Livestock Experiment Station, Qadirabad, District Sahiwal (Pakistan), were analyzed to investigate the magnitude of influence of month and season of calving on the length of subsequent calving interval. The longest average calving interval of 609.9 days was recorded for buffaloes calving in January, while the shortest average calving interval of 502.8 days was observed for those calving in June, the difference being highly significant (P < 0.01). When the data were split in accordance with season of calving, the calving intervals for buffaloes calving in winter, spring, summer and autumn averaged 569.1, 570.6, 506.6 and 515.7 days, respectively. The differences between intervals for winter and spring calvings and between intervals for summer and autumn calvings were non-significant. All other differences were highly significant (P < 0.01). Thus, in most of the buffaloes calving in winter or spring, the first post-partum oestrus and conception are delayed till the following autumn or winter, resulting in significantly longer calving intervals. In contrast, animals calving in summer or autumn exhibit post-partum heat and conception during autumn or winter, resulting in shorter calving intervals.     

Prostaglandin E2 levels in uterine tissues and its relationship with uterine and luteal progesterone during the estrous cycle in dairy cows

Endometrial tissue homogenates obtained at luteal and follicular stages of the estrous cycle were determined for prostaglandin E(2) and progesterone contents by EIA and RIA, respectively. In Experiment 1, the concentrations and changes of PGE(2) in uterine tissues collected by biopsy before slaughfter and subsequent samples collected at 30, 60 and 90 min after slaughter were measured. No significant differences were observed in the concentration of PGE(2) preslaughter or at 30 and 60 min post slaughter. However, there was a significant decrease (P<0.01) in PGE(2) concentration 90 min post slaughter. In Experiment 2, the concentrations of PGE(2) in the ipsilateral and contralateral horns in relation to corpus luteum function were compared. A significant (P<0.05) interaction was found between stages of estrous cycle (luteal vs follicular) based on CL progesterone content, and type of uterine horn (ipsilateral vs contralateral) on uterine PGE(2) levels. The PGE(2) concentration was significantly higher (P<0.01) at luteal phase than at follicular phase. During the luteal phase PGE(2) concentrations in tissues of the uterine horn ipsilateral to the corpus luteum was significantly higher (P<0.01) than the contralateral horn. The PGE(2) concentration was low and did not differ significantly between horns during follicular phase. A parallel increase (luteal: high) and decrease (follicular: low) in PGE(2) and progesterone concentrations were observed. Correlations were observed for CL progesterone and uterine PGE(2) concentrations as well as for PGE(2) and progesterone concentrations in uterine tissues (r=0.70 and r=0.60, respectively). The results show that the increase in PGE(2) concentrations in uterine tissues coincides with the high uterine progesterone concentrations during luteal phase.     

The relationship of rheological behavior of the vaginal fluid at the time of insemination to the pregnancy rate in dairy cows

The objective of this study was to determine whether rheological properties of the vaginal fluid at the time of insemination could be used as an indicator of potential fertility in dairy cows. Thixotropy and flow behavior were evaluated. Vaginal samples were collected from 347 cows at the time of insemination, within a 12- to 24-h interval after the onset of a natural estrus. Logistic regression analysis showed no significant effects of thixotropy measurements on the pregnancy rate, while flow behavior and the index of consistency (K) had a significant effect. The decrease in the consistency index (K) was related to the increase in the pregnancy rate (odds ratio = 0.99; P = 0.014), and the risk of nonpregnancy was higher (odds ratio = 0.46; P = 0.024) in cows in which vaginal fluid had a Newtonian behavior. Non-Newtonian behavior was recorded in 294 samples (85%) while 53 behaved as Newtonian fluids. For samples from all cows, the mean value of the consistency index was 310 +/- 28.2 milliPascals.second(n) (x +/- SEM) and ranged from 0 to 3881 milliPascals.second(n). In Newtonian samples, the consistency index mean was 2.6 +/- 0.6 milliPascals.second(n) and 367.6 +/- 30.4 milliPascals.second(n) for non-Newtonian samples. Of the 347 cows, 131 (38%) became pregnant. For flow behavior classification, 15 (28.3%) cows in which samples had Newtonian behavior and 116 (39.5%) cows with non-Newtonian samples became pregnant. Therefore, the highest probability of pregnancy was shown by cows in which samples had non-Newtonian behavior and the lowest consistency index values. Our data suggest that flow behavior measurements of the vaginal fluid at the time of insemination may be an indicator of potential fertility in cattle.     

Comparison of fertility,regular returns-to-estrus,and calving interval between Ovsynch and CO-synch + CIDR protocols in dairy cows

The main aims of the present study were to compare the pregnancy rate (PR), regular returns-to-estrus, and calving interval of a CO-Synch + controlled internal drug release (CIDR) device, commonly used to synchronize ovulations in beef cows, with the classical Ovsynch protocol in high-producing dairy cows. Holstein-Friesian cows (n = 128) from six commercial dairy herds, ≥40 days postpartum and not previously inseminated, were randomly assigned to one of two treatments. Cows submitted to Ovsynch protocol (group OS as control group; n = 66) received 10 μg of a GnRH analogue 7 days before and 48 hours after 25 mg PGF_2α, followed by artificial insemination (AI) 16 hours after the second GnRH administration. Cows submitted to CO-Synch + CIDR (1.38 g of progesterone) inserted for 7 days beginning at the first GnRH administration (group CoS + CD; n = 62) had the second administration of GnRH concurrent with AI, 64 hours after CIDR removal/PGF_2α administration. Nonpregnant cows with return-to-estrus between 18 and 24 days after first AI were reinseminated (second AI). Logistic regressions were used to analyze PR and returns-to-estrus. No effect of group or herd was observed in PR at first timed AI. However, the sum of cows pregnant at first AI and nonpregnant cows with regular returns-to-estrus and the total PR (first + second AI) were influenced by group treatment. Overall, cows of group CoS + CD (total PR = 56.5%) were 2.1 times more likely to became pregnant after AI and until first regular returns-to-estrus than cows of group OS. The calving interval was lower in group CoS + CD (425.9 ± 78.8 days; ±SD) than in group OS (475.3 ± 83.7 days). The CO-Synch + CIDR protocol was reliable to use in dairy herds and provided reproductive advantages when compared with Ovsynch protocol.