Ovulation In Dairy Cattle Research Articles

Modifying the double-Ovsynch protocol to include human chorionic gonadotropin to synchronize ovulation in dairy cattle

The objectives were to determine whether rates of conception, ovulation, presynchronization, or follicle and CL characteristics were altered after modifying the Double-Ovsynch (DO) protocol to include hCG compared with the DO protocol. Primiparous and multiparous lactating dairy cows (N = 183), and nulliparous dairy heifers (N = 51) were used. Cows were blocked by parity and heifers were stratified by age and breed before being randomly assigned to one of two treatments. All females received either 100 μg GnRH or 2000 IU hCG im, at initiation of the Pre-Ovsynch (PO) portion of the DO protocol (PO: GnRH/hCG, 7 days PGF2α and 3 days GnRH). After 7 days, females started the Breeding-Ovsynch portion of the DO protocol (Breeding-Ovsynch: GnRH, 7 days, PGF2α, 48 or 56 h and GnRH 16 hours timed artificial insemination with sex-sorted semen). Transrectal ultrasonography and blood samples were used to assess ovarian structures, ovulation, pregnancy diagnosis, and concentration of progesterone in plasma. Conception rates were similar in females treated with GnRH or hCG in cows (32.2 and 25.0%) and in heifers (30.8 and 36.0%). Ovulation rates in cows at the onset of PO were increased with hCG compared to GnRH (77.2 vs. 62.2%, P < 0.05). Concentrations of progesterone 7 days post-hCG or GnRH were greater in cows treated with hCG compared with GnRH (least significant mean ± SEM; 4.3 ± 0.3 and 3.0 ± 0.3 ng/mL, P < 0.01), but did not differ in heifers (4.5 ± 0.9 and 2.9 ± 0.9 ng/mL). More cows ovulated within 7 days post-hCG and a greater proportion of these cows tended to have failed luteal regression by Day 3 post-PGF2α compared with cows that had ovulated to GnRH (29.6 vs. 16.1%, P ≤ 0.10). The overall percentage of females which were synchronized to PO did not differ between GnRH- or hCG-treated cows (61.5% and 52.2%) and heifers (42.3% and 40.0%). In conclusion, no overall improvement in fertility was achieved by replacing the first injection of GnRH in the DO protocol with hCG.

Ovulation and pregnancy outcomes in response to human chorionic gonadotropin before resynchronized ovulation in dairy cattle

We first determined a dose of human chorionic gonadotropin (hCG) sufficient to induce ovulation in lactating Holstein cows. Ovaries of 85 previously inseminated cows were mapped using transrectal ultrasonography 7 d before pregnancy diagnosis and assigned randomly to treatments of saline, 100 μg gonadotropin-releasing hormone (GnRH), or 500, 1000, 2000, or 3000 IU hCG. Appearance of new corpus luteum (CL) in response to ≥1000 IU hCG was similar to that for GnRH but greater (P < 0.001) than that for saline. Ovarian structures and serum progesterone then were monitored in 334 previously inseminated Holstein cows 0 and 7 d after treatment with GnRH, hCG (1000 IU), or saline. The incidence of ovulation was greater (P = 0.01) after GnRH than after saline in cows having pretreatment progesterone < 1 ng/mL, whereas in cows having progesterone ≥1 ng/mL, GnRH or hCG was more (P = 0.01) effective than saline, and hCG also differed from GnRH. Holstein cows of unknown pregnancy status in three herds were treated with either GnRH, hCG, or as controls to initiate an ovulation-resynchronization procedure 7 d before pregnancy diagnosis. In 1109 treated pregnant cows, pregnancy loss during 4 wk after treatment tended (P = 0.06) to be greater in those treated with hCG. Treated cows (n = 1343) diagnosed not pregnant were then given prostaglandin F 2α and inseminated and received GnRH 72 h later. A treatment by herd interaction (P = 0.06) resulted in more pregnancies after GnRH in two herds and after hCG in one herd compared with saline. We concluded that (1) ≥ 1000 IU hCG resulted in more CL than did treatment with saline, and the incidence of new CL after either GnRH or hCG depended on pretreatment progesterone status; (2) hCG tended to increase pregnancy loss in pregnant cows; and (3) pregnancies per artificial insemination after initiating resynchronization with either hCG or GnRH produced ambiguous results.

Multiple ovulation in dairy cattle

resulting, normally, in the birth of only one offspring per pregnancy. The reported incidence of twin births in dairy breeds is higher than that in beef breeds and historically ranges from 1.3% for Jerseys through 3.4% for Holsteins and up to 8.9% for Brown Swiss. However anecdotal reports of multiple births in dairy cattle would appear to be on the increase with some farms especially affected (Esslemont and Kossaibati, 1996, Kinsel et al., 1998). So it seems likely that the true incidence is higher than the historical figures suggest. The occurrence of triplets and quadruplets in cattle is even rarer with reported incidences of less than .001%.

Relationship between progesterone concentrations in milk and blood and time of ovulation in dairy cattle

The objective of this study was to investigate whether monitoring progesterone concentrations in milk and blood plasma can be used to predict time of ovulation in dairy cattle. Whole milk was sampled twice daily and blood samples were collected once a day before the morning milking. Ovulation was assessed by trans-rectal ultrasonography at 4 h intervals beginning from the end of estrus. For a parameter to be useful as predictor for time of ovulation, it should be precise (i.e. variation between animals should not exceed 12 h). In milk, progesterone concentration dropped <15 ng/ml at 97.7 ± 17.8 h (range: 54–126 h) before ovulation, to <5 ng/ml at 79.7 ± 11.2 h (range: 54–98) before ovulation to decline further to <2 ng/ml at 70.7 ± 16.8 h (range: 38–90 h) before ovulation ( n = 20). In plasma, progesterone concentration dropped to <4 ng/ml 90.5 ± 19.6 h (range: 66–138 h) before ovulation and to <2 ng/ml at 75.0 ± 12.2 h (range: 50–98) before ovulation. These intervals were not influenced by parity, milk production or days in milk. In conclusion, monitoring of progesterone alone is not sufficient to predict ovulation because of the large variation in timing of decrease of progesterone concentrations relative to ovulation between animals. At best the range is about 2 days.

Pedometer readings for estrous detection and as predictor for time of ovulation in dairy cattle

The objective of this study was to study the relationship between increase in number of steps measured by pedometers, behavioral estrous parameters and time of ovulation, in order to investigate whether the number of steps can be used as a tool for estrous detection and as a predictor for time of ovulation. In total, 63 ovulations were observed in 43 Holstein-Friesian cows. Different behavioral signs of estrus were observed at 3 h intervals. Cows were equipped with pedometers, which stored number of steps in 2 h time periods and pedometer estrus alerts were defined using different algorithms and thresholds. The percentage of behavioral estruses also detected by pedometers measurements, ranged between 51 and 87% for all estrous periods. When only estrous periods where taken into account in which more than one animal was in estrus, detection percentages increased up to 95%. Number of steps taken during the estrous period was higher when more animals were in behavioral estrus at the same time, and number of steps taken during the estrous period was also higher for primiparous cows compared to multiparous cows. Ovulation occurred 29.3 ± 3.9 h after onset of increased number of steps (ranging between 39 and 22 h) and 19.4 ± 4.4 h after the end of increased number of steps (ranging between 35 and 12 h). The intervals were not influenced by the number of animals that were in estrus at the same time or by parity. In conclusion, pedometers can detect estrus accurately and appear to be a promising tool for prediction of ovulation and hence could be a tool for improving fertilization rates.

Use of Estradiol Cypionate as a Substitute for GnRH in Protocols for Synchronizing Ovulation in Dairy Cattle

Our purpose was to determine whether estradiol cypionate (ECP) could be substituted for the second GnRH injection of the standard Ovsynch protocol (injection of GnRH given 7 d before and 48h after PGF2α, with timed AI [TAI] 12 to 20h after the second GnRH injection). Lactating dairy cows ranging from 61 to 82 d in milk at TAI were studied in 14 replicates. Main effects were hormone (ECP vs. GnRH) to induce ovulation and exposure to progesterone (P4) or not during the week preceding PGF2α-induced luteolysis. Four treatments were: 1) 100μg of GnRH at 48h after PGF2α (Ovsynch; n = 27); 2) same as Ovsynch, plus a P4-releasing intravaginal insert (CIDR) placed for 7 d beginning at the first GnRH injection (Ovsynch + CIDR, n = 20); 3) same as Ovsynch, but substituting 1mg of ECP for GnRH, and injecting ECP at 24h after PGF2α (Heatsynch; n = 33); or 4) Heatsynch + CIDR (n = 26). The largest follicle was identified by ultrasonography 24h after PGF2α and was monitored every 6h until ovulation. Incidence of estrus was less after GnRH (54%) than after ECP (87%), but more GnRH-treated cows had LH surges detected (95 vs. 65%) and ovulated (100 vs. 86%). Duration of LH surges, but not peak concentrations, was less after GnRH than after ECP (6.1±0.7 vs. 12.2±0.9h). Pre-treatment with P4 reduced the incidence of LH surges but had no effects on incidence of estrus or ovulation. Intervals to the LH surge and ovulation were less after GnRH than after ECP, but intervals between onset of the LH surge and ovulation did not differ (26±2 vs. 30±3h). We concluded that substituting ECP for GnRH resulted in more cows in estrus and slightly fewer ovulating.

Various behavioral signs of estrous and their relationship with time of ovulation in dairy cattle

The objective of this study was to investigate the relationship between various behavioral signs of estrous and time of ovulation and, determine which behavioral estrous sign(s) best predicted time of ovulation. In total, 94 ovulations were observed in 67 Holstein-Friesian dairy cows. Different behavioral estrous signs were observed at 3-h intervals and their relation with time of ovulation (ultrasound examinations at 3-h intervals) was investigated. In all estrous periods, sniffing and chin resting was displayed, while mounting was displayed in 90% and standing heat in 58% of estrous periods. Estrus was more intense in primiparous cows compared to multiparous cows and when more animals were in estrus at the same time. Although, these factors influenced intensity of estrous behavioral signs, they did not influence time of ovulation. Ovulation occurred 30.0 ± 5.1 h after onset of estrus (ranging between 18.5 and 48.5 h) and 18.8 ± 4.4 h after end of estrus (ranging between 9.5 and 33.5 h). Although informative, these predictors are highly variable between individuals and the method used to determine the onset and end of estrus is time consuming this, therefore limits in their use as a practical predictor of ovulation. Sniffing and chin resting were displayed during the non-estrous period and are therefore, not useful predictors of ovulation time. For animals that displayed standing heat, onset of standing heat was a good predictor for ovulation time (occurring 26.4 ± 5.2 h before ovulation). However, standing heat was only displayed in a limited number of cows, especially when only one cow was in estrus at a time. Onset of mounting was the best predictor for time of ovulation (occurring 28.7 ± 5.3 h before ovulation), and it was displayed in 90% of the estrous periods. However, mounting cannot yet be assessed automatically, which limits its practical use as ovulation predictor.

Ovulation failure and double ovulation in dairy cattle: risk factors and effects

Ovulation failure and double ovulation rates were examined in 1917 inseminations performed in high-yielding dairy cows under standard commercial conditions. The ovulation rate was determined 11 days post-insemination by ultrasound detection of at least one corpus luteum in the ovaries. Analyzing the double ovulation and pregnancy rates, the study population consisted only of ovulated cows ( n = 1792). Data were analyzed using logistic regression methods. A failure to ovulate was recorded in 125/1917 (6.5%) services: 82/663 (12.4%) during the warm and 43/1254 (3.4%) during the cool period. Based on the odds ratios, the risk of ovulation failure was 3.9 times higher for inseminations performed during the warm period. No significant effects of estrous synchronization, milk production and days in milk at AI, and service and lactation number on ovulation failure were found. Double ovulation was recorded in 277/1792 (15.5%) services: 146 (52.7%) unilateral double ovulations (42.5% left versus 57.5% right); 115 (41.5%) bilateral double ovulations; and 16 (5.8%) triple ovulations. Double ovulation was recorded in 72 (12.4%) and 205 (16.9%) AI during the warm and the cool period, respectively. The percentages of double ovulation for first, second and third or more lactations were 6.7, 16.6 and 25%, respectively. Double ovulation rates for early (less than 90 days), mid- (90–150 days) and late (more than 150 days) lactation periods were 13, 20.7 and 14.2%, respectively. Reaching estrus during the warm period decreased the likelihood of double ovulation by a factor of 0.86; the risk of double ovulation was lower in cows with higher milk production (a 1 kg increase in milk yield led to a 0.97-fold reduced risk of double ovulation); cows in their second and in their third or more lactations showed a likelihood of double ovulation (using the first lactation as reference) increased by factors of 3.4 and 5.6, respectively; and reaching estrus during the early and late lactation period was related to a decreased probability of double ovulation (using the mid-lactation period as reference) by factors of 0.56 and 0.84, respectively. No significant effects of synchronization and service number on the double ovulation rate were found. Pregnancy was recorded in 914/1792 (51%) services: rates of 53.5% (811/1515) were recorded for single ovulations; 37.2% (103/277) for double ovulations: 28.8% (42/146) for unilateral double ovulations; 45.2% (52/115) for bilateral double ovulations; and 56.3% (9/16) for triple ovulations. The likelihood of pregnancy diminished in cows: inseminated during the warm period (by a factor of 0.5); inseminated by one particular bull (by a factor of 0.33); with higher milk production (a 1 kg increase in milk yield decreased the probability of pregnancy by a factor of 0.98); or undergoing unilateral (by a factor of 0.31) and bilateral (by a factor of 0.64) double ovulation. Logistic regression analysis indicated no significant effects of synchronization, days in milk, lactation number and service number on pregnancy rate. Collectively, our results indicate that cows showing estrus in conditions of heat stress had a high risk of ovulation failure. The effect of milk production on double ovulation was negative, whereas lactation number was positively correlated with this factor; the highest incidence of double ovulation occurring during the mid-lactation period.

Inhibition of intrafollicular PGE2 synthesis and ovulation following ultrasound-mediated intrafollicular injection of the selective cyclooxygenase-2 inhibitor NS-398 in cattle.

Ultrasound-mediated intrafollicular injection and aspiration procedures were used to investigate the ability of the selective cyclooxygenase-2 inhibitor, NS-398, to inhibit intrafollicular PGE2 synthesis and suppress ovulation in dairy cattle. Follicular growth and timing of the preovulatory gonadotropin surge were synchronized in 55 Holstein cows and the position of the ovulatory follicle was determined by daily ultrasound scanning. Preovulatory follicular fluid was aspirated from the largest follicle in four animals at 0, 6, 12, 18, and 24 h after GnRH injection (n = 20). The remaining 35 animals were subjected to ultrasound-mediated intrafollicular injection of NS-398 (10 microM final concentration; n = 19) or diluent (n = 16; controls). At 24 h after GnRH injection, follicular fluid was harvested from a subset of NS-398- (n = 9) and diluent-treated animals (n = 6). The remaining NS-398- and diluent-treated animals were subjected to ultrasonography every 6 h for 36 h after intrafollicular injection, and then daily through d 7 of the subsequent luteal phase to monitor ovulation and corpus luteum development. Follicular fluid PGE2 concentrations were increased following GnRH injection and reached a maximum at 24 h (P < 0.05). Follicular fluid PGE2 concentrations were decreased in NS-398- vs. diluent-treated follicles (7.2 vs. 52.2 ng/mL respectively; P < 0.05), but progesterone concentrations did not differ. Intrafollicular injection of NS-398 also inhibited follicle rupture (P < 0.001). All 10 control animals ovulated within 30 h of GnRH injection. Nine out of the ten NS-398-injected animals failed to ovulate. The NS-398-injected follicles developed morphological and endocrine characteristics resembling luteinized, unruptured follicles. Thus, intrafollicular PGE2 synthesis and follicle rupture, but not luteinization, were inhibited in cattle following ultrasound-mediated intrafollicular injection of NS-398. Ultrasound-mediated intrafollicular injection of NS-398 is a useful tool for mechanistic studies of intrafollicular regulation of the ovulatory process in cattle.

Influence of repeated rectal ultrasound examinations on hormone profiles and behaviour around oestrus and ovulation in dairy cattle

Frequent rectal ultrasound is often used to assess time of ovulation. This study investigated whether frequent rectal ultrasound examination, affects behavioural oestrus and peri-ovulatory hormone profiles (LH, oestradiol and progesterone). Additionally, the relation between peri-ovulatory hormone profiles, oestrous behaviour and time of ovulation was studied. Oestrus was synchronised in two consecutive cycles of Holstein Friesian cattle (parity from 1 to 6; n=24 cycles). In 12 of these cycles, time of ovulation was assessed by three-hourly rectal ultrasound (assessment of ovulation time with ultrasound group: UG) the other half served as controls ( n=12; no assessment of ovulation time group: CG). There were no significant differences between the onset of oestrus (33.8±1.6 h), duration of oestrus (13.4±0.9 h) or intensity of oestrous behaviour (1047±180 points) between UG and CG treated animals. Furthermore, LH, oestradiol and progesterone profiles were similar between UG and CG. For UG, ovulation took place 30.2±1.9 h after onset of oestrus. This interval had the largest variation (21 h) of all parameters studied, ranging between 19 and 40 h after onset of oestrus. The smallest variation (6 h) was found in the timing of ovulation in relation to the LH-peak; ovulation took place 25.3±0.6 h (range: 21.5–27.5 h) after the peak in LH. This study demonstrated that repeated rectal ultrasound does not alter behavioural oestrus or peri-ovulatory hormone profiles and is therefore a useful tool for assessing time of ovulation. Further research, using ultrasound, can now be carried out to find predictors for time of ovulation.

18. Altered luteal function following induced ovulation in dairy cattle

18. Altered luteal function following induced ovulation in dairy cattle

The Relationship between Estrous Behavioral Score and Time of Ovulation in Dairy Cattle

One of the major contributors to poor fertility of a dairy herd is ineffective detection of estrus. Recently, it has become evident that cow factors contribute largely to low detection rates. Until now, standing behavior has been the symptom used to determine the right moment for insemination. However, standing behavior is not observed in over 50% of the cows in estrus in a number of herds, and no data are available to relate the moment of ovulation to other estrous symptoms. Therefore, in the present study, cows were observed for a number of visual signs of estrus, twice per day for 30min, and the moment of ovulation was estimated by transrectal ultrasonographic scanning of the ovaries. In this study, 100 cows were detected in estrus visually, using a scoring system. Standing behavior was observed in 50% of those cows, although there was more than one cow in estrus at a time in most (85%) cases. There was no correlation between follicular size and ovulation time or estrous behavior score. Levels of 305-d milk yield and parity were also not correlated with estrous behavior scores. However, a significant correlation (0.31) was found between detection score and day of ovulation. A retrospective analysis revealed that cows that ovulated 0 to 24h after artificial insemination (AI) scored almost three times the number of estrous behavior points compared to the ones that ovulated 24 to 48h after AI. Ovulation more than 48h after AI resulted in pregnancy in only 15% of the cows.

Effect of Progesterone on the Expression of Estrus at the First Postpartum Ovulation in Dairy Cattle

Fifty-two lactating Holstein cows were randomly assigned to receive either a progesterone-releasing (2g of progesterone) or a control-releasing intravaginal device (0g of progesterone). Intravaginal devices were inserted on d 10 and removed on d 15 postpartum. Daily blood samples were collected from d 10 to 90 postpartum for subsequent determination of progesterone concentrations. Observations for estrus were conducted three times daily in a dirt paddock containing a testosterone-treated cow.Serum concentrations of progesterone in the progesterone-releasing intravaginal device group were elevated on d 11, 12, 13, 14, and 15 compared with those of the control group. The days to first postpartum ovulation were similar between the treated and control groups, respectively (30.6 vs. 30.5 d). Also similar was the proportion of cows expressing estrus at first, second, and third postpartum ovulations (9/27 vs. 3/24, 14/23 vs. 15/ 21, and 14/21 vs. 9/15, respectively), length of the first postpartum estrous cycle (17.9 vs. 18.3 d), and peak serum concentrations of progesterone during the first estrous cycle (3.5 vs. 2.9ng/ml). These data indicate that administration of progesterone early postpartum did not increase the proportion of cows expressing estrus at the first ovulation.

Fertility of dairy cattle following oestrus and ovulation controlled with cloprostenol, oestradiol benzoate and progesterone or progesterone and cloprostenol

There have been several approaches to the control of the timing of the oestrous cycle and ovulation in dairy cattle in the last three decades. The first phase involved the use of progestins which were administered in various forms for prolonged periods. Although the timing of oestrus was controlled in most animals after withdrawal of the treatment, this control was not very precise and pregnancy rates from insemination at the first oestrus after treatment were reported to be below normal. Attempts were then made to combine short-term progestin treatments with oestrogens as luteolytic agents to gain better control of the timing of oestrus and ovulation. These studies resulted in some cases in better synchronization of oestrus and improved pregnancy rates. The discovery that prostaglandin F 2α (PGF 2α) and its synthetic analogue, cloprostenol were potent luetolytic agents in the cow led in the past decade to the use of these agents for oestrus and ovulation control in cattle. Prostaglandins for this purpose are ineffective in anovulatory cows, in cows with deficient luteal function and in the first 5 days of the oestrus cycle when a new corpus luteum is being formed. This limitation in their use has encouraged investigations into the combined use of short-term progestin treatment with prostaglandins to give more effective control of the timing of oestrus and ovulation and to avoid the adverse effects on fertility of long-term progestin treatment. Short-term progestin treatment combined with prostaglandins should mean that fewer cows would have ovulation suppressed for long periods and fertility of treated cows should be improved. A comparison of three procedures of ovulation control and fertility results shows the short-term progestin treatment combined with prostaglandin to be the most effective.