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PubMed1991

Effect of a prostaglandin F2 alpha injection 96 hours after introduction of intact bulls on estrus and calving distribution of beef cows.

Most estrus synchronization schemes facilitate the use of artificial insemination; however, combining estrus synchronization with natural service also offers several benefits to beef producers. This experiment was designed to study the effectiveness of one injection of prostaglandin F2 alpha (PGF2 alpha) 96 h after introduction of intact bulls on estrus synchronization and calving distribution of beef cows and heifers. Three hundred sixty beef cows and 45 beef heifers in seven trials were allotted by age, breed, and prior calving date to one of two treatments. Within each subclass, one group was injected with an appropriate dose of PGF2 alpha and the second group at each location received 5 ml of saline (SAL). Cows were classified as estrual or anestrual at the start of breeding based on serum progesterone levels and were observed for behavioral estrus regularly during the first 25 d of the breeding season in two of the trials (d 0 = day before bull turn-in). Pregnancy data and calving dates were recorded in each of the studies. All cows were palpated per rectum for pregnancy approximately 70 d after the introduction of bulls. During d 5 to 9 after treatment, the percentage of cows exhibiting behavioral estrus (P = .02) and the pregnancy rate (P = .02) obtained was greater for PGF2 alpha-treated cows than for SAL-treated cows. There were 6.5% more (P = .05) calves born during the overall calving period from animals treated with PGF2 alpha compared with those in the SAL group. In summary, treatment of cows and heifers with PGF2 alpha 96 h after bull turn-in was effective in synchronizing behavioral estrus of beef cows and heifers and increasing the calving rate during the subsequent calving season.

Animals↗
PubMed1986

Synchronization of estrus in dairy cows with prostaglandin F2 alpha and estradiol benzoate.

A field study using 322 lactating dairy cows in seven commercial and two university herds was conducted to determine if treatment with estradiol benzoate 40 to 48 h after treatment with prostaglandin F2 alpha would enhance synchronization of estrus. Estrogen treatment tended to increase the proportion of cows in estrus within 5 d (synchronized) after prostaglandin treatment (66.9% versus 58.9%). Of synchronized cows, a greater proportion treated with estrogen (66.9%) were in estrus on d 3 than those not receiving estrogen (48.2%). First service conception rate (31.9%) and interval to second service (35.6 d) were not affected by treatment with estrogen. Milk progesterone was measured in university herds. More cows with milk progesterone concentrations greater than or equal to 8 ng/ml were synchronized (75.4%) than those with less than 8 ng/ml (63.3%). Treatment with estrogen increased synchrony of cows with high progesterone (90.3%) more than prostaglandin alone (60.0%). Based on progesterone concentrations at breeding and 22 to 24 d later, estimated conception rate was 58.7%, and net conception rate based on palpation was 41.3%. Tighter synchrony of estrus can be achieved by using estradiol benzoate 40 to 48 h after prostaglandin. Concentrations of milk progesterone might predict success of treatment.

Animals↗
PubMed1984

Intravaginal controlled administration of flurogestone acetate I: Development of a stability-indicating liquid chromatographic method and stability kinetics of flurogestone acetate.

Flurogestone acetate is a synthetic progestin useful for estrus synchronization in sheep. The estrus synchronization is achieved by inserting the drug-impregnated vaginal sponge in the sheep for up to 15 d, during which time flurogestone acetate is administered continuously by intravaginal absorption to suppress estrus and ovulation. The sponge is then withdrawn to regain estrus within 2-4 d. A review of the literature suggests that the analytical methods currently available are not specific, sensitive, and rapid enough. A stability-indicating high-performance liquid chromatographic method was developed, which is capable of characterizing the stability kinetics of flurogestone acetate under various environmental conditions and quantifying the release and absorption profiles of the drug from the vaginal sponges.

Animals↗
PubMed2006

Developmental programming in sheep: administration of testosterone during 60-90 days of pregnancy reduces breeding success and pregnancy outcome.

Evidence suggests that exposure to excess steroids during critical periods of fetal development leads to reproductive disorders. Exposure of female lambs to excess testosterone (T) from Days 60 to 90 of gestation (T60-90; term, 147 days) delayed onset of the LH surge and resulted in to male-typical reproductive behavior. The objectives of this study were to test the ability of T60-90 ewes to mate, conceive and lamb during the first three breeding seasons (Years 1, 2 and 3). Pregnant Suffolk ewes were injected with T propionate in cottonseed oil (100mg, im twice weekly) or vehicle (control; C) from Days 60 to 90 of gestation. In Year 1, ewes (C=12, T60-90=12) were kept with a vasectomized ram for 3 months and markings/visual observation of copulations were recorded. Rams had paint applied to their chest to facilitate detection of estrus and mating. All C but only three T60-90 ewes were marked (P<0.001). All ewes were then estrus-synchronized with two injections of prostaglandin F2alpha (20mg, im) given 11 days apart and allowed to mate with a painted, fertile ram. Nine of 12 C and 4 of 12 T60-90 ewes (P=0.1) were mated. Based on estrus and long-term monitoring of progesterone, more C than T60-90 became pregnant (82 and 18%, respectively; P<0.01). In Year 2, to maximize ram exposure, two C and two T60-90 estrus-synchronized ewes were placed with a painted, fertile ram at a time and mated ewes were removed to a nearby pen to force mating with others. Twenty-four hour video monitoring revealed the rams mated more C than T60-90 ewes (83 and 25%, respectively; P=0.01). In both Years 1 and 2, the rams preferred C over T60-90 ewes; therefore in Year 3 rams were given access only to T60-90 ewes. Only four T60-90 estrus-synchronized ewes were placed with a painted ram at a time. Not given an option, 91% of the T60-90 ewes were marked resulting in 4 of 11 (36%; first-service pregnancy rate in the breeding herd was 91%) ewes becoming pregnant to the synchronized estrus. Collectively these studies showed that fertility in T60-90 females was severely compromised, even after overcoming ram preference for controls.

Animals↗
PubMed2005

Fertility response of yearling beef heifers after prebreeding energy manipulation, estrous synchronization and timed artificial insemination.

The effect of dietary energy and weight class on the fertility of yearling beef heifers (Angus, Hereford, and Angus x Hereford) was investigated over 2 years. In year 1, heifers (n=58) were classed as heavy (HW; > or =340 kg) or light weight (LW; <340kg) and then assigned to receive either a low (LE; 0.23 kg/day) or high energy (HE; 0.68 kg/day) diet. In year 2, heifers (n=60) were also classified as heavy (> or =335kg) or light weight (<335 kg), but the energy content of the diet was raised so that heifers on the LE and HE were targeted to gain 0.46 and 0.79 kg/day, respectively. Heifers in the four groups, LELW (n=14 and 12), LEHW (n=16 and 17), HELW (n=13 and 15), and HEHW (n=15 and 16) received restricted amounts of concentrate (HE > LE) and free choice hay over 47 or 42 days (year 1 and year 2, respectively). To synchronize estrus, heifers were fed capsules containing MGA (0.5 mg/animal each day) beginning 11 days before the end of the feeding trial (day 0), PGF(2alpha) (25mg i.m.) and estradiol benzoate (Ebeta; 400 microg i.m.) was given on days 8 and 10, respectively. Estrous behavior was observed (days 10 and 11) and all heifers were inseminated on day 11. Following AI, heifers were re-grouped and a bull was introduced (days 27-39) for the second service in both years. Pregnancy diagnosis for the first (days 41-42) and second services (days 69-97) was performed by transrectal ultrasonography. Transrectal ultrasonic observations of ovarian follicle number and size were completed for a subset of heifers (n=5-8) from each experimental group at the end of the feeding trial. The effect of year was not significant for any of the reproductive performance variables measured. The mean ADG was (0.72 +/- 0.04 kg/day) and was greater in LW than HW heifers and in heifers in the HE than LE treatment groups (P <0.05). In heifers receiving the LE diet, ADG was lower in HW than LW heifers (weight x diet; P=0.02; 0.54 +/- 0.04 and 0.62 +/- 0.03 kg/day for HW and LW heifers, respectively). The diameter of the largest follicle was greater in heifers receiving the HE diet (P < 0.05; 11.3 +/- 0.4 mm) than those on the LE diet (10.3 +/- 0.3), and in LW (P <0.05) compared to HW heifers. The HE diet increased the size of the largest follicle in LW but not HW heifers (diet x weight, P <0.05). The percentage of pubertal heifers at the end of the feeding period (59.3%), estrous response (56.4%), conception rate (47.7%), ovulation rate (88.9%), and first service pregnancy rate (36.2%) were not significantly affected by initial weight or diet. There was a tendency for first service pregnancy rates to be greater in LW than HW heifers consuming the LE diet (diet x weight, P <0.1; 54.2 +/- 15 and 30.3 +/- 10% for LELW and LEHW heifers, respectively). Pregnancy rate after two services was greater (P=0.01) in LW (82 +/- 10%) than in HW (64.5 +/- 10%). The LE diet achieved moderate rates of gain and allowed high level of reproductive performance in LW but not HW heifers.

Animals↗
PubMed2005

The variability of ovum pick-up response and in vitro embryo production from monozygotic twin cows.

Oocytes were recovered by ovum pick up (OPU) from nine pairs of monozygotic twin German Simmental cows. The hypothesis was that there is less variability between identical twins versus among non-related individuals in the variation in the recovery of oocytes by OPU and in the efficiency of in vitro embryo production. Estrous cycles were synchronized with two doses of cloprostenol, 11 days apart. Beginning 3-4 days after synchronized estrus, OPU was done twice weekly (every 3 or 4 days; total of 11 sessions). The influence of repeated OPU on estrous cyclicity was established by estrus detection, plasma progesterone concentrations, and ovarian ultrasonography. There were no differences among days of collection for the number and quality of cumulus oocyte-complexes (COCs), and rates of cleavage and blastocyst formation. A total of 1,661 COCs, including 657 (39.6%) good-quality COCs, were recovered. From 1,457 (87.7%) cultured COCs, 827 zygotes cleaved and 314 blastocysts were produced on Day 7. The total number of COCs and the blastocyst rates varied among pairs of monozygotic twins; within pairs, only slight differences were observed. In conclusion, recovery of COCs and production of embryos had substantially less variation within pairs of monozygotic twins than among non-related cattle.

Animals↗
PubMed2002

Development of a new transcervical artificial insemination method for sheep: effects of a new transcervical artificial insemination catheter and traversing the cervix on semen quality and fertility.

The difficulty of traversing the cervix severely limits transcervical artificial insemination (TC AI) in sheep. Cervical trauma and poorly designed instruments can reduce fertility after AI. To overcome problems associated with TC AI, we developed a new TC AI catheter. Three bench experiments were conducted to determine the effects of the new TC AI catheter on semen quality independent of the effects of moving the catheter through the cervix. In each of the three bench experiments, the standard laparoscopic instrument for intrauterine AI in sheep was used as the control for the TC AI catheter. In Experiment 1, the total volume of semen extender expelled and void volumes for both types of AI instrument (TC versus laparoscopic) were determined. In Experiment 2, the effects of each type of AI instrument (TC versus laparoscopic) on semen quality, estimated as percentage motility and percentage forward progressive motility, of frozen-thawed semen was determined. In Experiment 3, the effects of both types of AI instrument (TC versus laparoscopic) on number of spermatozoa expelled was determined. The type of AI instrument affected neither semen quality nor the number of spermatozoa expelled. However, void volume differed (P < 0.01) between the two instruments. After differences in void volume were taken into account, an in vivo experiment was conducted to determine whether using our new TC AI catheter for TC or surgical intrauterine AI affected fertilization and pregnancy rates. For this, ewes were assigned to one of three treatments: (1) TC AI using the new TC AI catheter + sham AI via laparotomy (n = 9); (2) sham TC AI + AI via laparotomy using a laparoscopic AI instrument (n = 8); and (3) sham TC AI + AI via laparotomy using the new TC Al catheter (n = 10). To synchronize estrus, progestogenated pessaries were inserted and left in place for 12 days. On Day 5 after pessary insertion, PGF2alpha (15 mg) was given i.m. At pessary removal, 400 IU of eCG were administered i.m. Ewes were inseminated 48-52 h after pessary removal using fresh diluted semen (200 x 10(6) to 350 x 10(6) spermatozoa per 0.2 ml) pooled from the same four rams each day during the experiment. At 72 h after AI, uteri were collected postmortem and flushed. Oocytes and embryos were recovered and evaluated. Treatments did not affect (P > 0.01) ovum and embryo recovery rate (mean = 87.3%), fertilization rate (59.3%), or Day 3 pregnancy rate (mean = 66.6%). We conclude from these data that the use of our new TC AI catheter for TC AI or intrauterine AI should not impair the success of AI in sheep.

Animals↗
PubMed1983

Should we worry about animal growth promoters?

Estrogens and compounds with estrogenic activity have been used for many years as animal growth promoters and to synchronize estrus in cows. The resorcylic acid lactones (RALS), which include zearalenone, are being used increasingly for these purposes. These estrogenic mycotoxins, now produced commercially, have teratogenic, mutagenic, and carcinogenic properties. There is some evidence that their residues could remain in certain organs at the time the animal products come to market, and this may be of medical significance.

Animal Husbandry↗
PubMed1991

Effects of differential ewe condition at mating and early postmating nutrition on embryo survival.

Ewes in two trials were given either a high (H) or a low (L) level of premating nutrition for 19 wk followed by 6 wk of either H or L postmating nutrition to examine effects on reproductive performance. Trial 1 ewes were 5- to 8-yr-old Polypays and Trial 2 ewes were 3-yr-old Polypay and Coopworth x Polypay crosses. Ewes given L nutrition premating were either immunized with androstenedione-7-carboxyethylthioether:human serum albumin (also known as ovandrotone or Fecundin) in (diethylamino)ethyl-dextran adjuvant (Trial 1) or flushed for 3 wk premating (Trials 1 and 2) to enhance ovulation rates. All ewes were synchronized for mating in both trials. Trial 1 premating treatments created a difference of 10 kg in BW and 1.1 in condition score units between H and L ewes preflushing; flushing halved the BW difference. Ovulation rates averaged 2.58 and were similar for H, L-flushed, and L-immunized (LI) ewes; however, both conception rate and litter size were lowest for immunized ewes. Among both twin and triple-ovulating ewes, highest mean litter size was produced by H ewes, followed in order by L and LI ewes. High postmating nutrition increased BW by 6 kg vs slight weight loss in L ewes, but postmating treatments did not affect litter size of either twin or triple ovulators. The H and L premating groups of Trial 2 differed by 18 kg and 2.2 condition score units preflushing. The H ewes exhibited higher ovulation rates (overall mean = 2.63) but lower conception than the L ewes to synchronized estrus. Litter size averaged 2.15 for H ewes vs 1.82 for L ewes. Among both twin and triple ovulators, L ewes produced fewer lambs than H ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Nutritional Physiological Phenomena↗
PubMed1998

Duration of treatment with progesterone and regression of persistent ovarian follicles in cattle.

The objective of the present study was to determine the duration of elevated concentrations of progesterone necessary to induce atresia of persistent ovarian follicles. Heifers were administered 25 mg of PGF2alpha on d 6 and 7 (d 0 = d of synchronized estrus) and a norgestomet implant from d 6 to 14. Ovaries were monitored by ultrasonography, and blood samples were collected on d 3, 5, 7, 9, 11, and 12 and daily from d 14 until ovulation. On d 12, heifers received either two progesterone-releasing intravaginal devices (PRID) for 6 h (6-h; n = 5), two PRID for 24 h (24-h; n = 5), or no treatment (CON; n = 5). Blood samples were collected at 15-min intervals from h -6 to 30 (PRID insertion = h 0) and analyzed for concentrations of LH. Characteristics of LH secretion were determined for consecutive 6-h periods (Period 0 to 5). Hourly blood samples, collected from h 0 to 29, were analyzed for concentrations of 17beta-estradiol (estradiol) and progesterone. The dominant ovarian follicles present on d 7 increased in size to 15.4+/-.3 mm on d 12 ("persistent follicle"). Following removal of the PRID and norgestomet implants, atresia of persistent follicles and ovulation of new follicles were induced in one of five and in four of five heifers in the 6-h and 24-h treatments, respectively. Persistent follicles ovulated after withdrawal of norgestomet in all other heifers. Concentrations of progesterone were increased from h 1 to 7 in the 6-h and h 1 to 26 in the 24-h treatment. Frequency of LH pulses was reduced (P < .05) during Periods 1 to 2 in the 6-h and Periods 1 to 5 in the 24-h treatment relative to the CON treatment. By h 10, concentrations of estradiol in the 6-h and 24-h treatments were lower (P < . 05) than in the CON treatment. This suppression continued through h 29 in the 24-h treatment (P < .05), whereas concentrations in the 6-h treatment were intermediate to those of the CON and 24-h treatments after h 14. Suppression of pulsatile LH release and estradiol secretion was evident with 6 and 24 h of treatment with progesterone, but only the 24-h treatment induced atresia of persistent follicles in a majority of the heifers.

Administration, Intravaginal↗
PubMed2002

Evaluation of a fixed-time artificial insemination protocol for postpartum suckled beef cows.

Treatment with melengestrol acetate (MGA), an oral progestin, prior to administration of gonadotropin-releasing hormone (GnRH) and prostaglandin F2alpha (PG) effectively synchronizes estrus and maintains high fertility in postpartum beef cows. The objective of this experiment was to determine whether treatment with MGA prior to a GnRH-PG-GnRH protocol would improve pregnancy rates resulting from fixed-time artificial insemination (AI). Multiparous crossbred beef cows at two University of Missouri-Columbia farms (n = 90 and n = 137) were assigned by age and days postpartum to one of two treatments. Cows were fed carrier (1.8 kg x animal(-1) x d(-1)) with or without MGA (0.278 mg x kg(-1)) for 14 d. All cows were administered GnRH (100 microg; intramuscularly) on d 12 after MGA or carrier withdrawal and 7 d before PG (25 mg; intramuscularly). All cows received a second injection of GnRH and AI 72 h after PG. Mean days postpartum for MGA and control cows at the initiation of treatment were 39.6 and 38.9 d for herd 1; and 51.9 and 50.9 d for herd 2, respectively (P > 0.70 within herds). Blood samples were collected from all cows at 10 and 1 d before the feeding of MGA or carrier began and at the times GnRH and PG were administered. Concentrations of progesterone in serum at the initiation of treatment were elevated (>1 ng/mL) in 0% of MGA and 7% of control cows in herd 1, and 54% of MGA and 49% of control cows in herd 2 (P > 0.05 within herds). Pregnancy rates to fixed-time AI were determined by transrectal ultrasonography 50 d after AI. Pregnancy rates in herd 1 were 58% (26/45) and 51% (23/45) for MGA-treated and control cows, respectively (P = 0.52), and 63% (44/70) and 45% (30/67) for MGA-treated and control cows in herd 2, respectively (P = 0.03). Differences in pregnancy rates to fixed-time AI were significant (P = 0.04) when data from the two herds were combined (with MGA = 70/115 [61%]; control = 53/112 [47%]). There was no difference (P > 0.20) in final pregnancy rates (timed AI plus 45 d exposure to bulls) between treatments, within herds, or when herds were combined. In summary, pregnancy rates resulting from fixed-time AI may be improved with treatment of MGA prior to a GnRH-PG-GnRH protocol.

Animals↗
PubMed1989

Evaluation of luteolysis and estrous synchronization by a prostaglandin analog (Luprostiol) in Brahman cows and heifers.

A trial was conducted to evaluate the ability of a prostaglandin analog, Luprostiol (LP), to synchronize estrus in Brahman cows and heifers. Animals were injected with either 0, 3.75, 7.5, 15 or 30 mg LP or 500 micrograms cloprostenol (CLP) on d 8 or 9 after estrus (d 0). All concentrations of LP (greater than 0 mg) and CLP caused luteolysis in cows and heifers, as indicated by a decline (P less than .01) in serum progesterone concentration after injection. Animals receiving 0 or 3.75 mg LP had a longer (P less than .04) interval to estrus after injection than did animals in other treatment groups. The proportion of animals exhibiting estrus by 120 h after injection was influenced by dose of LP (P less than .0001; 0, 3.75 mg less than 7.5, 15 and 30 mg and CLP) but not by age. Cows had a lower (P less than .01) progesterone concentration than heifers on d 10, 11 and 12 after LP-induced estrus. Progesterone concentration was lowest (P less than .01) on d 10, 11 and 12 after LP-induced estrus in cows given 15 mg LP or CLP. First-service conception rate was similar between cows and heifers, but it was lower (P less than .01) in animals given 15 or 30 mg LP. Both estrogen and LH concentrations were decreased (P less than .01) at the time of estrus by the 15 and 30 mg of LP. Luprostiol can cause luteolysis and estrous synchrony in Brahman cattle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Reproductive outcomes for dairy heifers treated with combinations of prostaglandin F2alpha, norgestomet, and gonadotropin-releasing hormone.

We conducted three experiments to test various protocols for synchronizing estrus, ovulation, or both before insemination of heifers. In experiment 1, 23 controls received two PGF2alpha injections; 23 heifers were treated like the controls plus a norgestomet implant for 8 d, with the second PGF2alpha injection 24 h before implant removal; and 23 heifers were treated like the previous group plus 100 microg of GnRH 54 h after the second PGF2alpha injection. Although norgestomet and GnRH altered some estrual characteristics, conception rates in experiment 1 (n = 69) and experiment 2 (278 heifers receiving the same treatments as those in experiment 1) generally were not different among treatments. Reproductive outcomes were not improved by adding norgestomet and GnRH to a standard PGF2alpha protocol. In experiment 3, control heifers received PGF2alpha and were inseminated after detected estrus or at 72 to 80 h after a second injection of PGF2alpha given 14 d after the first injection. Select Synch heifers, treated with GnRH either 6 or 7 d before PGF2alpha were inseminated after detected estrus, whereas Ovsynch heifers were treated like Select Synch heifers but also received a second GnRH injection approximately 36 h after PGF2alpha and were inseminated 18 h later. Estrus detection and pregnancy rates after Ovsynch were less than those of controls, whereas conception and pregnancy rates did not differ between control and Select Synch heifers. Therefore, the Select Synch protocol was equivalent to a standard PGF2alpha protocol, whereas Ovsynch was inferior to both of those protocols.

Age Factors↗
PubMed1989

Suppression of preovulatory luteinizing hormone surges in heifers after intrauterine infusions of Escherichia coli endotoxin.

A study was conducted to test the hypothesis that high cortisol concentrations associated with products of infections (endotoxin) cause derangement in the neuroendocrine mechanism controlling ovulation in heifers. Eight Holstein heifers were given 2 injections of prostaglandin (PG), 11 days apart, to synchronize estrus. Starting from 25 hours after the second injection of PG (PG-2), the uterus of each heifer was infused with 5 ml of pyrogen-free water (control, n = 3) or Escherichia coli endotoxin (5 micrograms/kg of body weight) in 5 ml of pyrogen-free water (treated, n = 5), once every 6 hours for 10 treatments. Blood samples were obtained every 15 minutes via indwelling jugular catheter for an hour before and 2 hours after each infusion, then hourly until an hour before the next infusion. Ultrasonography of the ovaries was performed every 12 hours, starting 24 hours after PG-2 injection until 96 hours after PG-2 injection. Serum concentrations of luteinizing hormone and cortisol were determined by validated radioimmunoassays. Changes in cortisol concentrations were not detected in control heifers with preovulatory luteinizing hormone surges at 60 to 66 hours after PG-2 injection, followed by ovulations 72 to 96 hours after PG-2 was injected. None of the treated heifers ovulated, and the resulting follicular cysts (14 to 18 mm diameter) persisted for 7 to 21 days. In all treated heifers, serum cortisol concentrations increased (4- to 10-fold) during the first 2 hours after each infusion and then decreased gradually until the next infusion. Luteinizing hormone concentrations remained at baseline values throughout the treatment period in all treated heifers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1978

Controlled breeding of sheep for studies in fetal physiology.

A supply of fetal sheep of known gestational age was ensured after synchronizing estrus in the ewes, by means of an intravaginal pessary impregnated with a progestagen. Estrus occurred approximately 2 days after the pessary was removed. Conception rates at different times of the year and for a period of 4 years were described.

Animals↗
PubMed1993

Drug needs of the sheep industry.

Two areas of drug needs in the sheep industry are reviewed. The first is the need for prolificacy drugs such as those used outside the country. These drugs would encourage out-of-season lambing, increased lambs/per ewe during the traditional lambing season and synchronize estrus for easier management of lambing and increased use of artificial insemination for faster genetic improvement. The other area is drugs to treat or prevent major causes of disease, specifically abortion, neonatal diarrhea, pneumonia and internal parasitism. Efficacious drugs for these diseases are either not now cleared for use in sheep at all; a safe, easy to administer product is not available; or not cleared for sheep at a dosage level which is effective. These are drugs which will have a positive impact on the industry by increasing production, reducing expenses, and helping the U. S. to be able to compete with other sheep producing countries in the U. S. markets.

Abortion, Veterinary↗
PubMed1998

Reproductive performance of lactating dairy cows treated with gonadotrophin-releasing hormone (GnRH) and/or prostaglandin F2a (PGF2a) for synchronization of estrus and ovulation.

The objective of this study was to determine the reproductive performance of lactating dairy cows treated with GnRH and/or PGF2a for synchronization of estrus and ovulation. Between Days 43 and 57 post partum, a total of 374 dairy cows was divided into 4 groups. Cows in Group 1 (n = 62) were treated with 25 mg, i.m. PGF2a on Days 43 and 57; cows in Group 2 (n = 65) were not treated at this time; cows in Group 3 (n = 118) were treated with 100 ug, i.m. GnRH on Day 50, 25 mg, i.m. PGF2a on Day 57, 100 ug, i.m. GnRH on Day 59, and time-inseminated 16 h later; cows in Group 4 (n = 129) were treated with 25 mg, i.m. PGF2a once on Day 57. Cows in Groups 1 and 4 were inseminated at an induced estrus within 7 d after the last PGF2a treatment, and cows in Group 2 were inseminated at a noninduced estrus within a corresponding period of time. Conception rate, estrus detection rate and pregnancy rate were analyzed using logistic regression, and controlled for lactation number, body condition score and time of year. Days from calving to conception were analyzed using the GLM procedures of SAS, and the model included group, body condition score, lactation number, time of year, and their interactions. Cows in Group 3 had a significantly higher pregnancy rate than cows in Groups 1, 2 and 4. Orthogonal contrasts of mean days from calving to conception showed that cows in Group 3 had significantly (P < 0.01) less days from calving to conception than cows in Group 1 and Group 4. There was a significant effect of time of year on pregnancy rate and days from calving to conception, but there was no interaction between time of year and these reproductive characteristics. There was no effect of body condition score and lactation number on the reproductive characteristics evaluated. From the results of this study, it was concluded that better reproductive performance was observed in cows inseminated at a synchronized ovulation than in those inseminated at a synchronized estrous period.

Animals↗
PubMed1979

[Synchronization of estrus in heifers using Chlorsuperlutin (CSL) vaginal tampons].

A pilot experiment with heifer heat synchronization with chlorsuperlutin-soked intravaginal tampons was conducted with 254 heifers in six herds in the North Moravian region. The rubber-foam tampons, cylindrical in shape (diameter 70 mm, height 70-90 mm), were introduced into the cranial part of the vagina, using an applicator and a vaginal speculum. Sixteen days after introduction, the tampons were removed by pulling the silon thread with which the tampons were cross-stitched. The heifers were inseminated on the second to fifth day after the removal of the tampons. The average performance in the application of the tampons was 38.5 tampons per hour, and in their removal 20.7 tampons per hour. The retention rate of the tampons was 97.6%; out of this, 79.8% of the tampons were pulled out by the silon thread. The signs of heat were good, 87.9% of the heifers could be inseminated intrauterinally. All the heifers with retained tampons were inseminated. The conception rate after the first insemination was 32.7%, after the second insemination 56.4%, and after two inseminations 68.1%. Out of the synchronized heifers, 8.1% were culled for slaughter. The drawbacks of this treatment include the low conception rate of the synchronized heifers, a high requirement for repeated insemination in the synchronized oestrus, and, consequently, a high sperm consumption.

Animals↗