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PubMed1985

Comparison of the rate of decline in plasma progesterone concentrations at a natural and progesterone-synchronized oestrus and its effect on tonic LH secretion in the ewe.

The pattern of change in plasma progesterone and LH concentrations was monitored in Clun Forest ewes at a natural oestrus and compared to that observed after removal of progesterone implants. The rate of decline in plasma progesterone concentrations after implant withdrawal (1.8 +/- 0.2 ng/ml h-1) was significantly greater (P less than 0.001) than that observed at natural luteolysis (0.2 +/- 0.1 ng/ml h-1), and this resulted in an abnormal pattern of change in tonic LH secretion up to the time of the preovulatory LH surge. This more rapid rate of progesterone removal was also associated with a shortening of the intervals from the time that progesterone concentrations attained basal values to the onset of oestrus (P less than 0.05) and the onset of the preovulatory LH surge (P less than 0.01). However, there were no significant differences in the duration of the LH peak, preovulatory peak LH concentration, ovulation rate or the pattern of progesterone concentrations in the subsequent cycle. It is suggested that the abnormal patterns of change in progesterone and tonic LH concentrations may be one factor involved in the impairment of sperm transport and abnormal patterns of oestradiol secretion known to occur at a synchronized oestrus.

Animals↗
PubMed2003

Effect of supplemental nutrient source on heifer growth and reproductive performance, and on utilization of corn silage-based diets by beef steers.

Two experiments were conducted to determine effects of oilseeds or soybean hulls on growth and reproductive performance of heifers and utilization of corn silage diets by growing beef cattle. In Exp. 1, 96 beef heifers (249 kg of BW) were used in a randomized complete block design. Treatments were as follows: 1) corn and soybean meal (CON) at 56% of the DMI; 2) whole linted cottonseed at 15% of the DMI (COT); 3) whole raw soybeans at 15% of the DMI (SB); or 4) pelleted soyhulls at 30% of the DMI (SH). Diets were formulated to be isonitrogenous (13.8% CP) and fed to achieve target weights equal to 65% of expected mature BW at the time of AI. Estrus was synchronized and heifers were inseminated by AI in response to detected estrus. Because the energy value for SH was underestimated, cumulative ADG for SH (1.03 kg/d) was greater (P < or = 0.03) than for CON (0.89 kg/d), COT (0.87 kg/d), or SB (0.86 kg/d). Treatment did not affect (P > 0.10) the proportion of pubertal heifers at the beginning of the breeding season: CON (60%), COT (53%), SB (69%), SH (71%), or first-service conception rates: CON (37%); COT (38%); SB (57%); SH (42%). In Exp. 2, crossbred steers (387 kg) were used in a 6 x 6 Latin square design to evaluate the effects of supplemental nutrient source on utilization of corn silage diets. Treatments included diets used in Exp. 1, plus a negative control (soybean meal at 10% of the DMI; SIL) and whole raw soybeans at 25% of the DMI (SB25). Diets were formulated to be isonitrogenous (13.8% CP) except SB25 (17% CP), and were fed twice daily at 1.8 x NEm. Oilseed inclusion decreased (P < 0.10) acetate:propionate ratios and (P < 0.10) apparent ruminal OM and ruminal and total tract NDF digestibilities. The CON and SH diets had the greatest (P < 0.10) total-tract OM digestibilities. Microbial efficiencies were greatest (P < 0.10), and long chain fatty acid flow to the duodenum increased (P < 0.10) with oilseeds. Biohydrogenation averaged 90.4% and increased slightly (P < 0.10) when oilseeds were added to the diet. Adding oilseeds or soybean hulls to corn silage-based diets did not affect reproductive performance of heifers. Although oilseed additions increased total fatty acid flow to the duodenum, a high degree of biohydrogenation occurred, greatly increasing C18:0, with only marginal increases in unsaturated fatty acid flow. Depending on diet and feeding conditions, inclusion of whole oilseeds may not be an effective means of increasing linoleic acid supply for ruminant animals.

Age Factors↗
PubMed2004

Effect of bST and reproductive management on reproductive performance of Holstein dairy cows.

The objective was to determine the effects of bovine somatotropin (bST) and two artificial insemination (AI) protocols on reproductive performance of Holstein cows. Lactating cows (n = 840) were assigned at 37 d in milk (DIM) to one of four treatments in a 2 x 2 factorial arrangement. Treatments consisted of either bST (500 mg/14 d) starting at 63 +/- 3 DIM or no bST (control), with cows either submitted for timed AI following a synchronized ovulation (Ovsynch) protocol or assigned to receive AI based on estrus detection (ED). Two injections of PGF2, at 37 +/- 3 and 51 +/- 3 DIM were used to presynchronize estrous cycles. Cows then received an injection of GnRH at 63 +/- 3 DIM, followed 7.5 d later by PGF2. Cows assigned to ED treatments were inseminated after observed estrus during a 7-d period. Cows in Ovsynch treatments received a second GnRH injection 48 h after the last PGF2alpha and received timed AI 16 to 18 h later. Pregnancy was diagnosed by ultrasound at 31 d after AI and confirmed 14 d later. Frequency of anovulation (18.5%) at 63 DIM was similar across treatments, but proportions of anovulatory cows decreased quadratically as body condition at 70 DIM increased from 2.25 to 3.75. Estrus detection rate after PGF2alpha tended to be lower in multiparous cows receiving bST, and bST reduced returns to estrus in nonpregnant cows. Conception rates were higher in cows receiving AI after ED and bST improved conception rates to first AI in cyclic cows by reducing embryonic mortality. Pregnancy loss was similar for cows inseminated following ED or the Ovsynch protocol. There was a positive impact of bST on fertility of cyclic cows inseminated at fixed time or at detected estrus, but effective resynchronization protocols are needed to optimize reinsemination of non-pregnant bST-treated cows.

Abortion, Spontaneous↗
PubMed2000

Comparison of synchronization of ovulation and induction of estrus as therapeutic strategies for bovine ovarian cysts in the dairy cow.

The benefit of using timed-insemination in lactating dairy cows for the treatment of ovarian cysts lies in the fact that cows do not have to be detected in estrus for insemination and achieving pregnancy. We compared the effectiveness of synchronization of ovulation with timed-insemination and induction of estrus with insemination at estrus in the treatment of bovine ovarian cysts in lactating dairy cows. After Day 65 post partum, a total of 368 lactating dairy cows was divided into 3 groups. Cows in Group 1 (n = 209, normal, noncystic) were treated with 100 ug, i.m. GnRH on Day 0; 25 mg, i.m. PGF2 alpha on Day 7; and 100 ug, i.m. GnRH on Day 9 and then were time-inseminated 16 h later. Cows in Group 2 (n = 76, abnormal, cystic) were treated with 100 ug, i.m. GnRH on Day 0; 25 mg, i.m. PGF2 alpha on Day 7; and 100 ug, i.m. GnRH on Day 9 and time-inseminated 16 h later. Cows in Group 3 (n = 83, abnormal, cystic) were treated with 100 ug, i.m. GnRH on Day 0; 25 mg, i.m. PGF2 alpha on Day 7; and inseminated at induced estrus within 7 d after treatment with PGF2 alpha. Day 0 was the day of initiation of the study. Conception and pregnancy rates among groups were compared using logistic regression and adjusted for parity, time of year and days in milk. Conception and pregnancy rates of Group 1 cows (31.5%) were not significantly different from those of Group 2 cows (23.6%). However, the pregnancy rate in normal cows (Group 1) was higher (P < 0.01) than in cystic cows (Groups 2 and 3). Cows in Group 3 had a higher conception rate than cows in Group 2 (51.7% > 23.6%; P < 0.01). However, pregnancy rates for cows in Groups 2 (23.6%) and 3 (18%) were not significantly different. The finding indicated that synchronization of ovulation and timed-insemination resulted in pregnancy rates similar to those of synchronization of estrus and insemination at an induced estrus within 7 d for the treatment of ovarian cysts in lactating dairy cows.

Animals↗
PubMed2004

Comparison of timed AI after synchronized ovulation to AI at estrus: reproductive and economic considerations.

A timed artificial insemination (TAI) protocol using OvSynch was compared to artificial insemination (AI) at detected estrus in 2 large dairy herds differing in reproductive management. Cows were synchronized for TAI starting at 62 and 42 d in milk in herds 1 and 2, respectively. The OvSynch regimen included: GnRH (buserelin) at 0.02 mg (i.m.) on d 0; PGF2alpha (tiaprost) at 0.75 mg (i.m.) on d 7; buserelin at 0.02 mg (i.m.) on d 9; and TAI 16 to 20 h later. After TAI, cows seen in estrus received AI, whereas cows diagnosed not pregnant were resynchronized for TAI. Control cows received AI based on detected estrus after voluntary waiting periods of 72 d in herd 1 and 50 d in herd 2. An economic analysis included costs associated with days open, culling, AI, synchrony products, treatment, and examinations. A sensitivity analysis of those variables determined effects on total costs per pregnancy. Use of OvSynch reduced intervals to first AI and days open in both herds and reduced culling for infertility in herd 2. Conception rates for first AI at detected estrus were significantly higher compared to TAI in both herds and for overall AI at estrus in herd 2. For groups assigned to AI at estrus, mean 21-d submission rates over 200 d for AI were higher in herd 1 than in herd 2 (55.6 vs. 28.6%). Days open and culling were the major cost factors. Although OvSynch improved reproduction in both herds, AI based on detected estrus was economically superior in herd 1, whereas OvSynch was superior in herd 2. This was consistent across ranges of cost factors evaluated. Evaluation of synchrony protocols should include reproductive performance along with appropriate costs associated with treatments. Such costs may offset benefits to reproduction in herds with good estrous detection rates.

Animals↗
PubMed2004

Fertility of holstein dairy heifers after synchronization of ovulation and timed AI or AI after removed tail chalk.

Nonlactating Holstein dairy heifers (n=352) 13 mo of age were managed using a 42-d artificial insemination (AI) breeding period in which they received AI after removed tail chalk evaluated once daily. At AI breeding period onset (d 0), heifers were randomly assigned to receive synchronization of ovulation (100 microg of GnRH, d 0; 25 mg of PGF2alpha, d 6; 100 microg of GnRH, d 8) and timed AI (TAI; d 8) and AI after removed tail chalk for the entire AI breeding period (GPG; n=175), or AI after removed tail chalk for the entire AI breeding period (TC; n=177). As expected, 17.7% (31/175) of GPG heifers received AI after removed tail chalk before scheduled TAI. Pregnancy rate per artificial insemination (PR/AI) at approximately 30 d after first AI tended to be greater for TC (46.5%) than for GPG (38.3%) heifers. No treatment x inseminator interaction was detected; however, overall PR/AI was low for heifers in both treatments due to variation among the 3 inseminators (24.8, 30.0, and 58.0%). Pregnancy loss from approximately 30 to approximately 75 d after first AI was 10% and did not differ between treatments. Based on survival analysis, days to first AI was greater for TC than for GPG heifers, whereas days to pregnancy across the 42-d AI breeding period did not differ between treatments. Overall, 81.2% of GPG heifers receiving TAI synchronized luteal regression and ovulated within 48 h after the second GnRH injection. We conclude that this synchronization protocol can yield acceptable fertility in dairy heifers if AI to estrus is conducted between treatment with GnRH and PGF2alpha and AI efficiency is optimized.

Animals↗
PubMed1993

Characterization of the management practices of the top milk producing herds in the country.

Out of 128 surveys mailed to dairy farms that had been identified by the nine DHI processing centers as the top milk producing herds in the country, 61 surveys were returned. The predominant forage being fed was corn silage, followed by legume hay and haylage. On average, 6.7 feed additives and 3.5 alternative feeds were fed. Producers reported the following incidences of metabolic disorders: parturient paresis, 7.2%; displaced abomasum, 3.3%; ketosis, 3.7%; and nonspecific downer cow syndrome, 1.1%. Producers scheduled detection of estrus 3.1 times per day. Only 18.3% of the herds used routine synchronization of estrus. Artificial insemination was used on 94.8% of the cows and 88.5% of the heifers. The most important trait in sire selection was PTA for milk. For mastitis control, 75.4% of the producers practiced predipping, 85.2% used individual paper towels, 93.4% practiced postdipping, and 95.1% treated all cows at cessation of milking. Increased profitability and lower costs or higher returns were the primary motivators of these producers. Veterinarians were the most frequent source of information, followed by farm magazines. Satellite delivery of educational programs was the least acceptable delivery method. Extension professionals need to be cognizant of the producers' preferred information sources and delivery systems to ensure accurate, timely, cost-effective transfer of technological advances.

Animal Feed↗
PubMed1994

Effects of different stimuli of service on estrus duration in dairy goats.

The object of this experiment was to study the effects of different stimuli of service on estrus duration in dairy goats. Twenty Nubian goats were assigned randomly to 4 groups of 5 animals each: service (SER), mechanical stimulation of vagina (MES), accessory gland fluid insemination (AGF), and control (CON), Estrus was synchronized by using medroxyprogesterone acetate intravaginal pessaries (60 mg) over a 12-d period. Estrus was detected using 1 aproned vasectomized buck at 6-hour intervals during 5 d after pessary removal (at 0600, 1200, 1800 and 2400 h). In the SER group the male was permitted to service each female. In the MES group, stimulation was accomplished using a penis-like device maintained in the vagina 15 sec with light pressure on the fornix. In the AGF group, 1.0 ml of accessory gland fluid was deposited into the external cervical os. The CON group was only permitted to be mounted. All treatments were performed only once within the first 12 h of estrus. Estrus duration for the SER, MES, AGF and CON groups was (mean +/- SD) 22.8 +/- 5.0, 27.6 +/- 6.8, 37.2 +/- 2.7 and 42.0 +/- 9.5 h, respectively. The SER group was different from the AGF and CON groups (P<0.01), but not from the MES group (P>0.05). The MES group was different from the AGF (P<0.05) and CON groups (P<0.01). The AGF and CON groups did not differ from each other (P>0.05). It is concluded that service shortened estrus duration due to the mechanical effect of stimulation of the penis-like device against the vaginal fornix.

Journal Article↗
PubMed1996

Effect of service and vaginal-cervical anesthesia on estrus duration in dairy goats.

The object of this experiment was to study the effect of sterile service and vaginal and cervix anesthesia on estrus duration in dairy goats. During the fall season 21 Nubian goats (9 nulliparous and 12 multiparous) were randomly assigned to 1 of 3 treatment groups (n = 7 animals per group). The following groups were formed: service (SER), vaginal and cervix anesthesia (VCA) and control (CON). Estrus was synchronized using fluorgestone acetate intravaginal pessaries (FGA, 30 mg) over a 14-d period. Estrus was detected using a vasectomized buck at 6-h intervals over 5 d after pessary removal (at 0600, 1200, 1800 and 2400 h). In the SER group the male was permitted to service each female. In the VCA group the vagina and cervix of the does were anesthesied, after which the male was permitted to service the females. Both treatments were done once within the first 12-h initiation of estrus. Does were permitted to be mounted only in the control group (CON). Estrus duration for SER, VCA and CON groups was (mean +/- SD) 24.0 +/- 10.9, 42.0 +/- 15.9 and 40.3 +/- 10.8 h, respectively. The SER group was significantly different from the VCA and CON groups (P < 0.01); however, the VCA group was not different from the CON group (P > 0.05). It is concluded that service shortens the duration of estrus due to the mechanical effect of the penis against the vagina and cervix, and not to the accessory gland fluid.

Journal Article↗
PubMed2001

The repeatability of superovulatory response and embryo recovery in sheep.

Over an 8-year period, a total of 328 Scottish Blackface donor ewes were involved in a MOET program. They were synchronized with fluorogestone acetate sponges and superovulated with ovine FSH. After the onset of estrus, ewes were hand-mated and laparoscopic artificial insemination was performed with fresh semen 44-46 h after sponge removal. Embryos were recovered semi-laparoscopically on either Day 5 or Day 6 after insemination. Of the 328 donor ewes used, 222 ewes were supervoulated only once, while the remaining ewes were superovulated either twice (73 ewes), 3 times (26 ewes) or 4 times (7 ewes) at yearly intervals to generate a maximum of 474 records for subsequent analysis. There was no significant change in either mean ovulation rate or the mean number of embryos recovered per donor ewe at successive treatments. However, significant (P < 0.05 at least) effects of both year and donor ewe age existed for superovulatory response and number of embryos recovered, though only the effect of year was significant (P < 0.001) for percentage embryo recovery. Repeatability was significant (P < 0.05 at least) for both superovulatory response (r = 0.55, s.e. 0.055) and number of embryos recovered (r = 0.38, SE 0.074), but not for percentage embryo recovery (r = 0.04, SE 0.102).

Age Factors↗
PubMed2005

Pellet-freezing of Damascus goat semen in a chemically defined extender.

During the breeding season of goats (12 bucks and 64 does) in Egypt, five experiments were conducted using a chemically defined cryoextender (CDE) to investigate: (1) the influence of rates of semen dilution (1:2, 1:4 and 1:19) and methods of thawing of frozen semen pellets (dry thawing versus wet thawing) on sperm progressive motility (SPM), sperm acrosome abnormalities (SAA) and rate of lipid peroxidation in semen as measured by malonaldehyde (MAL) production, and (2) the effect of insemination of does in natural (n = 38) and cloprostenol-synchronized (n = 26) estrus with frozen semen on their kidding rates and prolificacy. Semen (two successive ejaculates/buck) was collected twice a week via an AV and only ejaculates of >2500 x 10(6) sperm/ml and 70% SPM were diluted in one step at 30 degrees C with the CDE, cooled to 5 degrees C over a 4h-period, frozen in the form of 0.30 ml pellets and stored in liquid nitrogen for 72 h. The results revealed that post-thaw SPM of semen diluted at a rate of 1:4 was significantly (P < 0.01) higher than that of semen diluted at the other rates. Dilution of semen at a rate of 1:19 (< or =151 x 10(6) sperm/ml) not only minimized (P < 0.01) pre-freeze and post-thaw SPM, but also augmented (P < 0.01) pre-freeze and post-thaw rates of lipid peroxidation as evidenced by the high level of MAL production and the ability of antioxidants (1mg/ml EDTA, 200 U/ml bovine liver catalase, 0.61 mg/ml reduced glutathione and 0.11 mg/ml sodium pyruvate) to restore (P < 0.01) pre-freeze and post-thaw SPM. Frozen semen pellets exposed to dry thawing had a greater percentage of SPM (P < 0.01) as well as lower values of SAA and MAL (P < 0.01) than those exposed to wet thawing. Although the kidding rates did not vary significantly among does in natural (55.26%) and synchronized (53.85%) estrus, a higher (P < 0.05) prolificacy was obtained after their insemination in natural (1.81+/-0.16) rather than in synchronized (1.22+/-0.11) estrus.

Animals↗
PubMed1989

Accuracy of predicting the LH surge and optimal insemination time in Holstein heifers using a vaginal resistance probe.

Monitoring changes in vaginal electrical resistance in association with ovarian follicular development during proestrus may provide an alternative to visual estrus detection of cattle for properly timing insemination. In two experiments 94 Holstein heifers were synchronized into estrus with 2 injections of prostaglandin F(2) alpha (PG) 11 d apart. Beginning 12 h prior to the second PG treatment, blood samples and vaginal resistance measurements were taken every 12 h for 60 h, and then every 6 h for the following 48 h. In both Experiments I and II, the lowest resistance value was found to be highly correlated with the luteinizing hormone (LH) preovulatory surge (r = 0.67 P<0.001). The linear regression of time from PG to the LH surge (Y) on time from PG to the lowest resistance value (x) was defined by Y = 17.49 + 0.71 (x) (R(2) = 0.45). This suggests that the lowest resistance value can predict the LH surge and, therefore, the appropriate time to inseminate heifers relative to the expected time of ovulation. This concept was tested in Experiment II by assigning 50 heifers to be inseminated after PG treatment on the basis of their vaginal resistance pattern, by appointment 66 h after PG, or by visual observation of standing estrus. Conception rates were 58, 50 and 50% in these groups respectively, and did not differ significantly. Overall, these results suggest that measurement of vaginal resistance patterns reliably predict the LH surge and can be successfully utilized to inseminate cattle.

Journal Article↗