scholarly journals Comparison of Single, Fixed-Time Artificial Insemination in Gilts Using Two Different Protocols to Synchronize Ovulation

Animals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 306 ◽  
Author(s):  
Lima Rodrigues ◽  
Rocio Amezcua ◽  
Glen Cassar ◽  
Terri L O’Sullivan ◽  
Robert Friendship
Keyword(s):  
Artificial Insemination ◽  
Fixed Time ◽  
Treatment Groups ◽  
Gonadotropin Releasing Hormone Agonist ◽  
Group 3 ◽  
Group 2 ◽  
Equine Chorionic Gonadotropin ◽  
Triptorelin Acetate ◽  
Timing Of Estrus ◽  
Group 1

In order to efficiently have a consistent supply of service-ready gilts available to incorporate into each batch of breeding sows, it is necessary to manipulate the timing of estrus and possibly the timing of ovulation of gilts. Estrus can be synchronized by the withdrawal of altrenogest after at least 14 days of treatment. It is possible that protocols developed to induce ovulation, and therefore allow fixed-time artificial insemination (FTAI), can improve the predictability of gilt breeding. This study investigated the effect of two FTAI protocols in gilts on reproductive performance and timing of farrowing and piglet weaning weight compared to gilts bred based on signs of estrus after cessation of altrenogest. Puberty was induced in gilts, followed by treatment with altrenogest. Following altrenogest withdrawal, 180 gilts were assigned to one of three treatment groups. Group 1 gilts (LUT, n = 62) were treated with 600 IU equine chorionic gonadotropin 24 h after altrenogest withdrawal and 5 mg porcine luteinizing hormone (pLH) 80 h later, followed by a single FTAI 36 h after pLH. Group 2 gilts (TRI, n= 61) received 2 mL of a gonadotropin-releasing hormone agonist, triptorelin acetate, intravaginally 6 d after altrenogest withdrawal and were bred by a single FTAI 24 h later. Group 3 gilts (CON, n = 57) were observed for estrus and bred twice by AI, 24 h apart. LUT and TRI gilts farrowed closer together (2.4 ± 1.6 and 2.9 ± 1.2 d(days), respectively) compared to CON gilts (4.5 ± 3.3 d). Piglets in LUT were 80 g (p < 0.001) heavier and piglets in TRI were 64 g (p < 0.05) heavier at weaning than CON piglets, when controlling for birth weight. Results indicate that FTAI might be useful as a means of minimizing the time from the first to the last gilt farrowing in a breeding batch of gilts. However, modifications of the protocols may be required to ensure optimum farrowing rates and litter size.

scholarly journals Different estrus induction protocols and fixed time artificial insemination during the anoestrous period in non-lactating Kivircik ewes

2018 ◽  
Vol 69 (1) ◽  
pp. 801 ◽  
Author(s):  
I. DOGAN ◽  
Z. NUR ◽  
B. KILINC
Keyword(s):  
Artificial Insemination ◽  
Fixed Time ◽  
Breeding Period ◽  
Detection Rates ◽  
Mean Values ◽  
Group 3 ◽  
Group 2 ◽  
Equine Chorionic Gonadotropin ◽  
Fresh Semen ◽  
Group 1

The efficiency of medroxyprogesterone acetate (MAP) sponges or norgestomet ear implants (half or entire) for synchronizing and inducing the estrous cycle in non-lactating Kivircik ewes was investigated during the natural non-breeding period. Ewes were treated for 11 days either with 60 mg MAP sponges (group 1, n=27) or with 1.5 mg norgestomet (group 2, n=25) or with 3 mg norgestomet (group 3, n=27) ear implants. In addition, each ewe received an intramuscular injection of 500 IU of equine chorionic gonadotropin (eCG) and 125 μg cloprostenol (PGF2α), 48 h prior to progestagen removal. Double Cervical Artificial Insemination (AI) with diluted fresh semen was performed at a fixed time (36 and 48 h) following progestagen withdrawal. Mean values for estrous detection rates at the first 12 ± 6 h and within 72 h, the time from progestagen removal to the onset of estrous, the duration of the induced estrous and pregnancy rate were found to be 46.8%, 86.1%, 26.1 ± 7.3 h, 27.0 ± 10.7 h and 27.8%, respectively. There were significant differences between groups 2 and 3 in the time of induced estrous onset (P<0.05). These results indicate that, each of the three protocols was equally efficient in inducing and synchronizing estrus in non-lactating Kivircik ewes during the natural non-breeding period.

350 EFFECT OF DIFFERENT SUB-DOSES OF EQUINE CHORIONIC GONADOTROPIN ON PREGNANCY AND TWINNING RATES OF CYCLIC ZEBU COWS SUBMITTED TO FIXED-TIME ARTIFICIAL INSEMINATION

2015 ◽  
Vol 27 (1) ◽  
pp. 263 ◽  
Author(s):  
R. H. Alvarez ◽  
F. L. N. Natal ◽  
R. M. L. Pires ◽  
K. M. R. Duarte ◽  
C. A. Oliveira
Keyword(s):  
Artificial Insemination ◽  
Ovarian Response ◽  
Fixed Time ◽  
Sao Paulo ◽  
São Paulo ◽  
Chi Square ◽  
Group 3 ◽  
Group 2 ◽  
Twin Pregnancies ◽  
Group 1

The injection of a low dose of eCG has the potential to induce multiple ovulation and pregnancies in cattle. The present study aimed to evaluate the ovarian response, conception rate and incidence of twin pregnancies of cyclic cows receiving 1 of 2 low doses of eCG. Multiparous Nellore (Bos t. indicus) cows with plasma progesterone levels >1 ng∙mL–1 on at least one of 2 blood samples collected at 10-day intervals (Day –10 and Day 0) received an intramuscular (IM) injection of 2 mg of oestradiol benzoate (EB; Estrogin®, AUSA, São Paulo, Brazil) and a vaginal device (DIP) containing 1 g of progesterone (Primer®, Tecnopec, São Paulo, SP, Brazil) on Day 0. On Day 8, the DIP was removed and cows received an IM injection of 150 μg of cloprostenol (Veteglan®, Hertape Calier, Juatuba, MG, Brazil). At this time, the animals were randomly distributed into 3 groups. Group 1 (n = 30) received an IM injection of 2 mL of saline, whereas groups 2 (n = 41) and 3 (n = 23) received 600 IU and 900 IU of eCG (Novormon® MSD Saude Animal, São Paulo, Brazil), respectively. Twenty-four hours later (Day 9), all groups received 1 mg of EB and were submitted to fixed-time artificial insemination (FTAI) 30 h later (i.e. 54 h after DIP removal). Oestrus observation was performed daily from the time of the withdrawal of the DIP until the day of FTAI. Ovaries were examined ultrasonically at the time of FTAI, the following day and 7 days after FTAI. Pregnancy diagnosis was done by ultrasonography 30 days after FTAI and the incidence of twin or single calves was recorded at birth. Data were analysed by chi-square test. The rate of expression of oestrus was 70.0% (group 1), 82.9% (group 2), and 78.2% (group 3; P = 0.25). Cows that had 2 or more large follicles at the time of FTAI was 0% (group 1), 14.6% (group 2), and 34.8% (group 3; P < 0.05). The ovulation rate of cows in group 1 (80.0%) was higher than cows in groups 2 (48.8%) and 3 (52.2%; P < 0.05). The conception rates for groups 1, 2, and 3 were 50.0, 26.8, and 39.1%, respectively (P < 0.05). Two animals in group 3, one in group 2, and none of group 1 had twin pregnancies on Day 30 after FTAI. Only one of these cows (group 3) had a twin calving. It was concluded that the injection of 600 or 900 IU eCG, in an oestradiol/progestogen FTAI protocol does not result in an increase in the rate of twin calvings, but may negatively affect pregnancy rates of cyclic Nellore cows.Financial support was provided by FAPESP (proc. 2011/13096–0).

scholarly journals Effect of two prostaglandin F2α injections administered 24 hours apart on the pregnancy rate of Simmental cows subjected to the Ovsynch or Ovsynch + Controlled internal drug release (CIDR) protocols

2020 ◽  
Vol 76 (10) ◽  
pp. 6451-2020
Author(s):  
MUSHAP KURU ◽  
CIHAN KACAR ◽  
HASAN ORAL ◽  
SEMRA KAYA ◽  
NEBI CETIN ◽  
...  
Keyword(s):  
Drug Release ◽  
Pregnancy Rate ◽  
Artificial Insemination ◽  
Pregnancy Loss ◽  
Prostaglandin F2α ◽  
Fixed Time ◽  
Group 4 ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

The aim of the present study was to determine the effects of one or two doses of prostaglandin F2α (PGF) on the pregnancy rate (PR) in Simmental cows subjected to the Ovsynch or Ovsynch + Controlled internal drug release (CIDR) protocols. On d 0, 100 µg gonadorelin diacetate tetrahydrate (GnRH) was injected into cows in group 1 (n = 50) and group 2 (n = 40) and CIDR was intravaginally inserted. On d 7, 25 mg dinoprost tromethamine (PGF2α, PGF) was administered, and GnRH was injected 56 h later. Fixed-time artificial insemination (TAI) was performed 16 h after GnRH injection. In group 3 (n = 62) and group 4 (n = 63), PGF was administered 7 d following GnRH treatment, and GnRH was injected 56 h later. TAI was performed 16 h after GnRH injection. In groups 2 and 4, a second dose of PGF was injected 24 h after the first dose. Pregnancy was determined by transrectal ultrasonography on d 30 and 60 post-TAI. The pregnancy rate (PR) on d 30 post-TAI was significantly different among the groups: 46%, 55%, 29%, and 36.5%, in groups 1, 2, 3, and 4, respectively (P = 0.048). In addition, the PR was 36.3% and 43.7% in the single PGF and double PGF injection groups, respectively. There was no statistical difference in the PR on d 60 post-TAI (P > 0.05). Pregnancy loss was between 4.34% and 11.11% (P > 0.05). The highest PR in the primiparous cows was observed in group 3 (57.7%). The PR was not significantly different among multiparous cows (P > 0.05). In conclusion, two injections of PGF administered 24 h apart in Simmental cows may increase the PR in the Ovsynch or Ovsynch + CIDR protocols.

scholarly journals Combining Fixed-Time Insemination and Improved Catheter Design in an Effort to Improve Swine Reproduction Efficiency

Animals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 748 ◽  
Author(s):  
Matthew McBride ◽  
Rocio Amezcua ◽  
Glen Cassar ◽  
Terri O’Sullivan ◽  
Robert Friendship
Keyword(s):  
Dose Group ◽  
Fixed Time ◽  
Reproductive Efficiency ◽  
Group 4 ◽  
Catheter Design ◽  
Group 3 ◽  
Group 2 ◽  
Equine Chorionic Gonadotropin ◽  
Group 1 ◽  
Reproduction Efficiency

Conventional practice is to breed sows by artificial insemination (AI) at least twice using approximately three billion sperm per insemination upon estrus at standing heat. This research explored the use of combined technologies, including fixed-time insemination (FTAI) and an alternative catheter design that reportedly reduces semen backflow, in order to reduce the number of inseminations and the semen dosage and maintain reproductive efficiency. The FTAI technique used in this study was to inject I.M. 600 IU equine chorionic gonadotropin (eCG) at weaning and 5 mg porcine luteinizing hormone (pLH) to stimulate ovulation 80 h later, followed by a single insemination 36 h after the pLH injection. The two catheters used in this study were a conventional foam-tipped insemination catheter and a Gedis catheter. The Gedis catheter is designed to be completely inserted into the vagina. The semen is enclosed along the length of the rod and held in place by a gel cap that melts when inserted into the cervix. Sows were assigned to the following treatments: Group 1 (n = 135), bred twice with a conventional catheter and a standard semen dose of approximately three billion sperm in 80 mL; Group 2 (n = 123), FTAI with conventional catheter and a standard semen dose; Group 3 (n = 127), FTAI with Gedis catheter and a standard semen dose; Group 4 (n = 126), FTAI with Gedis catheter and a reduced semen dose with one billion sperm. The farrowing rates were 81.6%, 77.7%, 74.0%, and 62.7% for Groups 1 to 4, respectively. The likelihood of farrowing was lower for Group 3 and Group 4 compared to Group 1 (odds ratio (OR) = 0.57; p = 0.08 and OR = 0.35; p = 0.001, respectively). Likewise, litter size of Group 3 and Group 4 was smaller than Group 1 (p = 0.006 and p = 0.04, respectively). Overall, the combination of Gedis catheter and FTAI resulted in decreased reproductive performance that outweighed the value of using less semen.

scholarly journals Pengaruh Monoklonal Antibodi Bovine Zona Pelusida 3 (bZP3) terhadap Diameter dan Atresia Folikel Ovarium Mencit (Mus musculus)

2018 ◽  
Vol 24 (1) ◽  
pp. 37
Author(s):  
Annisa Trissatharra ◽  
Sri Ratna Dwiningsih ◽  
Ratna Sofaria Munir
Keyword(s):  
Mus Musculus ◽  
Ovarian Follicles ◽  
Observation Time ◽  
Control Group ◽  
Control Group Design ◽  
Treatment Groups ◽  
Group 4 ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

Objectives: To identify the effect of monoclonal antibody bZP3 at ovarian follicles that undergo atresia and diameter of various ovarian follicles.Materials and Methods: This is a true experimental research with post only control group design. Samples were 36 female mices (Mus musculus) which is divided into 6 groups, there are 3 control groups (group 1, 2, and 3) injected by Phospatase Buffer Saline (PBS) 50µl and 3 treatment groups (group 4, 5, and 6) injected by Mab bZP3 50µl. Group 1 and 4 terminated at 5th day, group 2 and 5 terminated at 10th day, and group 3 and 6 terminated at 20th day. Evaluation of atretic ovarian follicles and diameter of ovarian follicles performed by hematoxylin eosin (HE) and the data processed by parametric statistic.Results: There are no significant in different among groups in the aspect of atretic follicles and diameter of folicles (p>0.05), but descriptively, number of follicles undergo atresia of the follicle primary, secondary, and tertiary treatment group was higher than the control group, except on the 20th day of observation time.Conclusion: administration of Mab bZP3 had no effect to amount of atretic follicles and diameter of folicles during observation time.

207 INFLUENCE OF THE INTERVAL BETWEEN THAWING TO TRANSFER ON PREGNANCY RATES OF FROZEN - THAWED DIRECT-TRANSFER EMBRYOS

2007 ◽  
Vol 19 (1) ◽  
pp. 220
Author(s):  
G. A. Bo ◽  
L. C. Peres ◽  
D. Pincinato ◽  
M. de la Rey ◽  
R. Tribulo
Keyword(s):  
Bos Taurus ◽  
Body Condition Score ◽  
Bos Indicus ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Direct Transfer ◽  
Condition Score ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

An experiment was designed to evaluate the effect of the interval between thawing to deposition of the embryo into the uterine horn on pregnancy rates of in vivo-produced frozen–thawed embryos in 1.5 M ethylene glycol (direct transfer). Data were collected from 1122 embryo transfers performed in the same farm (Estancia El Mangrullo, Lavalle, Santiago del Estero, Argentina) during the spring and summer of 2004/05 and 2005/06 (6 replicates, ambient temperature between 20 and 40�C). Recipients used in all replicates were non-lactating, cycling, multiparous Bos taurus � Bos indicus crossbred cows with body condition score between 3 and 4 (1 to 5 scale) that were synchronized using fixed-time embryo transfer protocols. Briefly, the synchronization treatments consisted of the insertion of a Crestar ear implant (Intervet, Sao Paulo, Brazil) or a progesterone-releasing device (DIB; Syntex SA, Buenos Aires, Argentina), plus 2 mg of estradiol benzoate (EB; Syntex) intramuscularly (IM) on Day 0, and 400 IU of eCG (Folligon 5000; Intervet, or Novormon 5000; Syntex) IM plus 150 �g d-cloprostenol IM (Preloban; Intervet, or Ciclase; Syntex) on Day 5. Progestin devices were removed on Day 8 and all cows received 1 mg of EB IM on Day 9. All cows were examined by ultrasonography on Day 16 and those with a luteal area &gt;76 mm2 (by calculating the area of the CL minus the area of the cavity) received, on Day 17, frozen–thawed embryos by nonsurgical transfer. All embryos were Grade 1, and all were frozen in 1.5 M ethylene glycol at the Embryo Plus Laboratory (Brits, South Africa). After being stored in liquid nitrogen, the embryos were plunged directly (no air thawing) in a 30�C water bath for 30 s, and then transferred to the recipient cows by either one of two technicians. Based on the interval between thawing and transfer, the transfers were classified as being in one of 3 groups: Group 1: &lt;3 min; Group 2: 3 to 6 min; and Group 3: 6 to 16 min. The main reason for delayed transfers beyond 6 min was the replacement of one recipient for another because of difficulty in threading the cervix (1% of the total transfers) or a recipient falling down into the chute or with very bad disposition and behavior. Pregnancy was determined by ultrasonography 28 to 35 days after fixed-time embryo transfer, and data were analyzed by logistic regression. There were no effects of replicate, technician, CL area, recipient body condition score, embryo stage, and time from thawing to transfer on pregnancy rates. Pregnancy rates in the 3 thawing to transfer intervals were: Group 1: 215/385, 55.8%; Group 2: 372/655, 56.8%; Group 3: 42/82, 51.2%; P &gt; 0.6. These results may be interpreted to suggest that there is no significant effect of time from thawing to transfer (up to 16 min) in direct transfer embryos using Bos taurus � Bos indicus recipients transferred at a fixed time.

scholarly journals The Effect of the Model of Eradication of Dengue Fever Vector Movement of Housewives Monitoring Larva in Efforts to Prevent Dengue Fever in Mojolangu Village, Lowokwaru District Malang

2020 ◽  
Author(s):  
Fiashriel Lundy ◽  
◽  
Prima Soultoni Akbar ◽  
Keyword(s):  
Dengue Fever ◽  
Health Workers ◽  
Viral Disease ◽  
Control Group ◽  
Self Awareness ◽  
Treatment Groups ◽  
Intervention Models ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

ABSTRACT Background: In recent years, the incidence and geographic distribution of dengue fever have greatly increased. Dengue fever is an acute viral disease transmitted by mosquitoes and is characterized by fever, headache, muscle and joint pain, skin rash, nausea and vomiting. The Mosquito Nest Eradication Program (PSN) through 3M Plus needs to be carried out continuously throughout the year, especially in the rainy season through the movement of housewife who monitor larvae. This study aimed to determine the effect of the dengue fever vector eradication model through the housewife movement of larva monitoring in the efforts of dengue fever prevention in Mojolangu Village, Malang City. Subjects and Method: This was a quasi-experiment using 2 treatment groups and 1 control group conducted at Mojolangu village, Lowokwaru district, Malang. A sample of 90 respondents divided into three groups was selected by purposive sampling. The dependent variable was DHF Prevention Efforts (Larva Monitoring). The independent variables were Dengue Fever Vector Eradication Model. The data were collected by questionnaire and observation. The data was analyzed by Kruskal-Wallis. Results: After being given treatment in group 1 (educated by health workers) and group 2 (trained cadres) the ability increased to be very good by 83% and 53%. In group 3 (control) his ability improved by 37%. Group 1 has the most effective influence in increasing knowledge and skills. Then group 2 with a significance value of <0.001 (p <0.005). Conclusion: Housewife are a resource in Family Empowerment and Intervention models. The eradication of dengue vectors needs regular monitoring and monitoring so that self-awareness and independence from the family can increase so that the degree of health can be achieved optimally. Keywords: Model, eradication, vector, dengue fever, larva Correspondence: Fiashriel Lundy. School of Health Polytechnics, Ministry of Health Malang. Jl. Besar Ijen No 77, Oro-oro Dowo, Klojen sub-distric, Malang, East Java. Email: [email protected]. Mobile: 0811367446 DOI: https://doi.org/10.26911/the7thicph.05.16

scholarly journals The Clinicopathological Evaluations of the Efficacy of Incorporation of Amantadine Hydrochloride in the Treatment of West African Dwarf Goats Experimentally Infected with Peste des Petits Ruminants Virus

2019 ◽  
Vol 11 (4) ◽  
pp. 379-386
Author(s):  
Iniobong C.I. UGOCHUKWU ◽  
Sunday I. IDOKO ◽  
Jacinta N. OMEKE ◽  
Chioma I. ANEKE ◽  
Nuhu A. SANI ◽  
...  
Keyword(s):  
Clinical Signs ◽  
West African ◽  
Peste Des Petits Ruminants ◽  
Treatment Groups ◽  
West African Dwarf ◽  
West African Dwarf Goats ◽  
Group 3 ◽  
Group 2 ◽  
Dwarf Goats ◽  
Group 1

Peste des petits ruminants poses a major threat to the development of small ruminant production. The objective of this study was to determine the comparative efficacy of amantadine hydrochloride (HCl), oxytetracycline long acting (LA) and levamisole in West African dwarf (WAD) goats experimentally infected with PPR. In addition to the presence of the characteristic clinical signs, complement ELISA and haem agglutination inhibition (HI) tests were used to confirm PPR infection in the West African dwarf goats, then treatment was instituted in the different groups namely, group 1 which was treated with amantadine HCl orally, oxytetracycline LA intramuscularly (IM) and levamisole per os. Group 2 was treated with oxytetracycline LA IM and levamisole. Group 3 was treated with levamisole while group 4 served as untreated control. The physiological parameters namely rectal temperature, pulse rate and respiratory rates of the different groups were recorded. The mortality rates in the different treatment groups were also recorded. The respiratory rates of the WAD goats increased as the infection progressed, but the increase was not significant (P>0.05). The treatment helped reduce the respiratory rates in the treated WAD. The rectal temperatures of all the animals in the different treatment groups increased only slightly as the infection progressed and was not significant (P>0.05). The percentage mortalities were 0% in Group 1, 25% in the Group 2, 50% in the treated group 3 and highest (75%) in the untreated group respectively. In conclusion, incorporation of specific antiviral agents like amantadine hydrochloride in the treatment regimen with oxytetracycline and levamisole particularly during the early stages of the infection can reduce morbidity and mortality of the disease to the barest minimum.

scholarly journals Parasitemia of Male White Mice (Mus musculus L.) DDY Strain Infected with Trypanosoma evansi Pidie and Pemalang Isolate

2014 ◽  
Vol 10 (2) ◽  
Author(s):  
Febiola Rama Sari ◽  
Yudha Fahrimal ◽  
Ummu Balqis ◽  
Didik T Subekti ◽  
Aprilia Wardana
Keyword(s):  
Treatment Group ◽  
Trypanosoma Evansi ◽  
Rapid Rise ◽  
Treatment Groups ◽  
Parasitemia Level ◽  
Group 3 ◽  
The Difference ◽  
Group 2 ◽  
Short Time ◽  
Group 1

This study aimed to find out the parasitemia of DDY white mice infected with T. evansi of Pidie and Pemalang isolates obtained from Bbalitvet Bogor. A total of 12 mice were divided into 3 treatment groups. Group 1 (K1) without any treatment, group 2 (K2) was inoculated with 104 T. evansi Pidie isolate, and group 3 (K3) was inoculated with 104 T. evansi Pemalang isolate. Parasitemia examination was carried out every two days and the level of parasitemia was observed as well. Parasitemia examination was conducted until all mice died. Parasitemia of mice infected with Pidie isolate was characterized by rapid rise of parasitemia in blood (107-108/mL of blood) in a short time (2-4 days) since first parasitemia was detected and followed by death at day 4. The parasitemia of mice infected with Pemalang isolate increased in the blood (108-109/mL of blood) on day 4 and maintained for a few more days and then fluctuated for a few more days before the animal was dead. In conclusion, there was the difference in parasitemia level between Pidie and Pemalang isolates. Key words: Trypanosoma evansi, parasitemia, Pidie isolate, Pemalang isolate

Effects of progesterone withdrawal on uterine secretion of prostaglandin F2α in response to oxytocin in ewes

1997 ◽  
Vol 9 (2) ◽  
pp. 255 ◽  
Author(s):  
M. A. Kaminski ◽  
S. H. Hayes ◽  
W. J. Silvia
Keyword(s):  
Venous Blood ◽  
Prostaglandin F2α ◽  
Inhibitory Effect ◽  
Treatment Groups ◽  
Group 4 ◽  
Sham Surgery ◽  
Group 3 ◽  
Group 2 ◽  
Ovine Uterus ◽  
Group 1

Two experiments were conducted to determine if withdrawal of progesterone during the luteal phase of the oestrous cycle affected the ability of the ovine uterus to secrete prostaglandin F2α(PGF2α ) in response to oxytocin. In Experiment 1, 18 ewes were ovariectomized on Day 9 and Day 12 after oestrus. Ewes were subdivided into three treatment groups (n= 6 per group): Group-1 ewes underwent sham surgery; Group-2 ewes received oestradiol (OVX + O); and Group-3 ewes received oestradiol + progesterone (OVX + O,P). Oxytocin was administered to each ewe on Days 10, 13 and 15 after oestrus. Concentrations of 13,14-dihydro-15-keto-PGF2α (PGFM) were determined in samples of jugular venous blood for 2 h after oxytocin challenge. The magnitude of the PGFM response 24 h after ovariectomy was greater (P < 0·1) in ewes from which progesterone had been withdrawn (OVX + O) than in ewes in which progesterone was maintained (intact controls and OVX + O,P). Therefore, progesterone appears to exert an inhibitory effect on uterine secretory responsiveness to oxytocin which is removed by progesterone withdrawal. In Experiment 2, ewes were ovariectomized on Day 11 and assigned to 1 of 4 treatment groups (n = 6 per group): Group 1, no steroid replacement (OVX); Group 2, oestradiol replacement (OVX + O); Group 3, progesterone replacement (OVX + P); or Group 4, progesterone+oestradiol replacement (OVX + O,P). Ewes received oxytocin on Day 12 and Day 15. On Day 12, uterine secretory responsiveness to oxytocin was greatest in ewes in the OVX + O group (P < 0 · 1). Responsiveness was low in ewes in the OVX group, as it was in ewes in both groups that received progesterone replacement. Therefore, the increase in uterine secretory responsiveness to oxytocin following progesterone withdrawal is dependent on oestradiol replacement.

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