Fertility Of Ewes Research Articles

Comparison of 6-day progestagen treatment with Chronogest® CR and Eazi-breed™ CIDR® G intravaginal inserts for estrus synchronization in cyclic ewes

The aim of this study was to compare the efficacy of two different short-term progestagen treatments for estrus synchronization in cyclic ewes. A total of 292 ewes of 3 flocks (A–C) on different farms were treated for 6 days with Eazi-breed™ CIDR® G (n=145) or Chronogest® CR (n=147) vaginal inserts in combination with 0.125mg Cloprostenol and 300IU eCG at device removal. Blood samples were taken for progesterone (P4) determination at insert application and removal as well as 14 days later. One day after insert removal rams fitted with marking harnesses were joined to ewes for 35 days and marked ewes recorded daily. Lambing data were recorded and fertility to first service period and overall assessed. Results show that 24–96h after insert removal 98.8% and 89.4% of the synchronized ewes in the flocks B and C were in estrus. Estrus response was not affected by the type of progestagen treatment and was lower (P<0.05) in nulli- (82.1%) than in pluriparous (97.5%) ewes. Type of progestagen treatment did not affect fertility, but flock and parity influenced the percentage of ewes that lambed as well as the lambing rate. Overall more ewes (P<0.001) lambed in flock A compared to flocks B and C (93.0 vs. 72.5 and 59.1%). In nulliparous animals the percentage of ewes that lambed was higher to the first service (P<0.05) period but lower (P<0.001) to the overall service period compared to pluriparous animals (51.5% vs. 49.3% and 64.7% vs. 84.2%). Lambing rates were higher in flock A than in flocks B and C to first service period and overall (1.3±1.4, 0.9±1.0, and 0.7±1.0, P<0.01 and 1.9±1.1, 1.3±0.9, and 1.0±1.0, P<0.001) and in nulliparous overall lower than in pluriparous ewes (1.1±1.1 and 1.6±1.1, P<0.01). Serum P4 concentrations measured 14days after insert removal were higher in the Chronogest® CR than in the Eazi-breed™ CIDR® G group (6.8±4.1ng/mL vs. 5.7±3.3ng/mL). Ewes of flock A had higher P4 values compared to ewes of flocks B and C (8.3±4.1ng/mL vs. 4.5±1.5ng/mL and 3.8±1.7ng/mL) and nulliparous lower P4 concentrations than pluriparous ewes (4.5±2.2ng/mL vs. 6.7±4.0ng/mL). In conclusion, a 6-day treatment with Chronogest® CR and Eazi-breed™ CIDR® G with prostaglandin and eCG at insert removal resulted in high estrus response and similar fertility in cyclic ewes.

Evaluation of Columbia, USMARC-Composite, Suffolk, and Texel rams as terminal sires in an extensive rangeland production system: I. Ewe productivity and crossbred lamb survival and preweaning growth1,2

A 3-yr study was conducted to comprehensively evaluate Columbia, Suffolk, USMARC-Composite (Composite), and Texel breeds as terminal sires in an extensive rangeland production system. The objective was to estimate breed-of-ram effects on ewe fertility, prolificacy, and dystocia, and sire breed effects on lamb survival and growth until weaning at approximately 132 d of age. Data were from 22 Columbia, 22 Composite, 21 Suffolk, and 17 Texel rams with 957 exposures to 574 adult Rambouillet ewes (3- to 7-yr-old at lambing), 908 lambings, and 1,834 lambs. Ram breed did not affect ewe fertility (mean = 94.9%; p = 0.73), total number born per ewe lambing (mean = 2.02 lambs; p = 0.20), number born alive per ewe lambing (mean = 1.90 lambs; p = 0.24), or number weaned per ewe lambing (mean = 1.45 lambs, p = 0.94). Dystocia rates were different (p = 0.01) for ewes mated to Columbia (12.2%), Composite (13.5%), Suffolk (25.7%), and Texel rams (31.9%) during 1 yr of the study, but differences among ram breeds were not repeatable (p ≥ 0.38) during the other 2 yr. Suffolk-sired lambs were heavier (p ≥ 0.02) at birth (5.5 kg) and weaning (40.3 kg) than lambs sired by the other breeds, which did not differ (p ≥ 0.34) for birth weight (mean = 5.3 kg). Texel-sired lambs (37.4 kg) were lighter (p ≥ 0.02) at weaning than Columbia- (38.8 kg) and Composite-sired (38.4 kg) lambs, which did not differ (p = 0.40) for weaning weight. Sire breed effect approached significance (p = 0.06) for lamb survival to weaning; estimated survival probabilities were 0.87 (Columbia), 0.89 (Composite), 0.93 (Suffolk), and 0.86 (Texel) for lambs reared by their birth dam. Interaction between sire breeds and birth weight affected (p < 0.001) lamb survival and revealed that lightweight Columbia- and Suffolk-sired lambs had a greater risk of death than lightweight lambs sired by Composite and Texel rams, but risk of death did not increase substantially for heavyweight lambs from any of the breeds. When mated to adult Rambouillet ewes in an extensive rangeland production system, the use of Suffolk rams is warranted to improve preweaning growth of market lambs and is not predicted to affect ewe fertility, ewe prolificacy, dystocia, or lamb survival compared with the other sire breeds we tested.

Effects of GnRH administration on ovulation and fertility in ewes subjected to estrous synchronization

The objective of this study was to verify the effects of GnRH on ovulation and pregnancy of ewes subjected to a short-term synchronization of estrus. Santa Ines and crossbred Santa Ines/Dorper ewes received 60 mg MAP sponges during 6 days plus 300 IU eCG and 30 μg d-cloprostenol 24 h prior to sponge withdrawal (SW). Ewes were assigned to receive 0.9% NaCl solution (T control ; n = 32) or 25 μg GnRH (licerelin, T GnRH ; n = 34) 24 hours after SW. Each group was assigned to intrauterine insemination by laparoscopy (n = 25) or to natural mating (n = 41). Artificial insemination was performed with a single dose of fresh semen. For controlled mating, females were exposed to males 12, 24, 36 and 48 hours after SW. Ten females per treatment were subjected to transrectal ultrasound examination at 12-hour intervals (SW to 60 hours after). Estrous response (100.0% vs 95.2%), interval from SW to estrus (32.9±7.4 vs 29.8±6.9 hours), estrous length (37.4±9.0 vs 31.5±10.4 hours), pregnancy rates (57.0% vs 41.0%), ovulation rate (100.0% vs 90.0%), number of ovulations/ewe (1.1±0.3 vs 1.2±0.4), maximum follicular diameter (6.4±0.7 vs 6.1±0.6 mm), interval from SW to ovulation (59.1±3.5 vs 58.4±3.5 hours) did not differ between T control and T GnRH , respectively. Administration of GnRH 24 hours after SW does not improve ovulation or pregnancy rate in estrous synchronization in ewes.

Effects of stress on reproduction in ewes

Stressors, such as poor body condition, adverse temperatures or even common management procedures (e.g., transport or shearing) suppress normal oestrus behaviour and reduce ewe fertility. All these events are co-ordinated by endocrine interactions, which are disrupted in stressful situations. This disruption is usually temporary in adult ewes, so that, when prevailing conditions improve, normal fertility would resume. Imposition of an experimental stressor (shearing, transport, isolation from other sheep, injection of endotoxin or insulin or cortisol infusion) suppresses GnRH/LH pulse frequency and amplitude. Part of the cause is at the pituitary, but effects on GnRH/LH pulse frequency and the GnRH/LH surge are mediated via the hypothalamus. It is not yet clear whether delays in the surge are caused by interruption of the oestradiol signal-reading phase, the signal transmission phase or GnRH surge release. Stressors also delay the onset of behaviour, sometimes distancing this from the onset of the pre-ovulatory LH surge. This could have deleterious consequences for fertility.

Progress in exploring genes for high fertility in ewes

Fecundity trait in sheep is regulated by some major genes. Among them, BMPR-IB, BMP-15, and GDF-9 are most distinguishing. The mutant FecB of BMPR-IB has multiplicative effects on ovulation. GDF-9's mutants FecGH, FecI, and BMP-15's mutants FecXI, FecXH, FecXG, FecXB, FecXL, and FecXR increase ovulation rate in the heterozygote but result in sterile phenotypes in the homozygote, while GDF-9's mutant, FecGE, only increases ovulation rate in the homozygote. In addition, Woodlands and Lacaune are known as inheritable major genes. Woodlands gene is an X-linked maternally imprinted gene, and Lacaune is similar to FecB with a multiplicative effect on ovulation rate. The size of the effect of one copy of a mutation on ovulation rate ranges from an extra 0.4 ovulations for the woodlands mutation to an extra 1.5 ovulations for the BMPR-IB and Lacaune mutation. Investigation into these genes will not only help to select breeds with high fertility, but also give a chance to further elucidate the mechanism involved in the phenomenon. This review summaries the source, location, phenotype, and mechanism of the major genes in all breeds of sheep.

Laparoscopic artificial insemination in dairy sheep with chilled semen stored for up to 26 h

Adult East Freisan crossbred (n = 220) and Chios ewes (n = 105) were divided into four groups and inseminated with chilled semen, which had been stored for 7, 13, 20 or 26 h at 5°C. Unilateral intrauterine insemination (50 x 10 6 spermatozoa in 0.25 ml) was performed with the aid of a laparoscope. Inseminations were carried out 48 – 52 h after pessary removal (30 mg FGA) without detecting estrus. The lambing rates after intrauterine insemination with chilled semen were found to be similar in East Fresian crossbred (40%) and Chios ewes (30%). Intrauterine insemination with chilled semen stored up to 26 h resulted in similar lambing rates; whereas, fertility of Chios ewes tended to decline with increased holding time of chilled semen. From this study, it is concluded that decreasing the storage time of chilled semen at 5°C improves pregnancy in Chios ewes and that East Fresian crossbred ewe’s conception rates to intrauterine insemination with chilled semen was relatively higher than Chios ewes. Key words: Dairy sheep, chilled semen, time of insemination, lambing rate.

Parenteral Administration of L-Arginine Enhances Fetal Survival and Growth in Sheep Carrying Multiple Fetuses1–3

The frequency of multiple fetuses has increased in human pregnancies due to assisted reproductive technologies. This translates into a greater proportion of premature and low-birth weight infants in the United States and worldwide. In addition, improvements in sheep breeding have resulted in new breeds with increased litter size but reduced fetal survival and birth weight. Currently, there are no treatments for preventing fetal growth restriction in humans or sheep (an established model for studying human fetal physiology) carrying multiple fetuses. In this work, Booroola Rambouillet ewes (FecB+/-) with 2–4 fetuses were fed a diet providing 100% of NRC-recommended nutrient requirements. Between d 100 and 121 of gestation, ewes received an i.v. bolus injection of either saline solution or 345 μmol arginine-HCl/kg body weight 3 times daily. The arginine treatment reduced (P< 0.05) the percentage of lambs born dead by 23% while increasing (P= 0.05) the percentage of lambs born alive by 59%. The i.v. administration of arginine enhanced (P< 0.05) the birth weights of quadruplets by 23% without affecting maternal body weight. The improved pregnancy outcome was associated with an increase in maternal plasma concentrations of arginine, ornithine, cysteine, and proline, as well as a decrease in circulating levels of ammonia and β-hydroxybutyrate. These novel results indicate that parenteral administration of arginine to prolific ewes ameliorated fetal mortality and growth retardation. Our findings provide support for experiments to assess the clinical use of arginine to enhance fetal growth and survival in women gestating multiple fetuses.

Identification of a Line of Sheep Carrying a Putative Autosomal Gene Increasing Ovulation Rate in Sheep That Does Not Appear to Interact with Mutations in the Transforming Growth Factor Beta Superfamily1

Sheep lines with mutations in single genes that have major effects on ovulation rate have been very useful in gaining a better understanding of pathways important in controlling follicular development and ovulation rate. To date however, all known mutations are in the transforming growth factor beta (TGFB) superfamily. Ovulation rates were measured in 720 progeny of 20 rams that were descendants of a single prolific ewe. Evaluation of ovulation rates of daughters of closely related sires suggests the presence of a segregating major gene Fecundity Davisdale (FECD) that increases ovulation rate between 0.4 and 0.8 in heterozygous daughters. Key features of mutations in genes of the TGFB superfamily pathway, such as synergistic interactions with other family members, infertility in homozygous carriers, and increased responsiveness to exogenous gonadotropins, were not observed in this line; thus, the mutation does not appear to be acting in the TGFB pathway. Hence, there is likely a novel mutation being carried in this line of sheep that alters ovulation rate. Future identification of the causative mutation may provide new insights into regulation of follicular development and ovulation rate.

Epidemiological Survey of Border Disease Virus among Sheep from Northern Districts of Japan

The first epidemiological survey of Border disease virus (BDV) was undertaken in small ruminants in Japan. Ovine sera, collected from the northern prefectures of Hokkaido, Aomori and Iwate, were examined for the presence of antibodies against BDV using the neutralization peroxidase-linked antibody test. Twenty-nine (17.6%) of one hundred and sixty-five samples were seropositive for BDV. Results were specific, excluding cross-reactions with bovine viral diarrhea virus (BVDV). Only one sample (0.6%) was positive for BVDV, and was negative for BDV. Despite serological evidence of virus circulation, there have been no clinical cases of border disease in sheep in Japan. Although no diagnostic measures were performed, the infection did not appear to be associated with a reduction in ewe fertility nor with lamb mortality.

Effect of subsequent two short-term, short-term, and long-term progestagen treatments on fertility of Awassi ewes out of the breeding season

Bu calismanin amaci, ureme mevsimi disinda Ivesi koyunlarinda PMSG ile birlikte farkli progestagen uygulamalarinin etkinligini arastirmakti. Toplam 48 bas koyun 4 esit gruba bolundu. Grup I, vaginal sungerler (30 mg FGA) koyunlara 7 gun sureyle uygulandi, daha sonra 7. gunde cikarilan sungerin yerine yeni sunger tekrar 7 gun sureyle yerlestirildi. Grup II ve Grup III’de vaginal sungerler sirasiyla 7 ve 14 gun uygulandi. Grup IV, kontrol grubunu olusturdu. Calisma gruplarinin tumunde sungerlerin cikarildigi anda 500 IU PMSG yapildi. Ostrusa gelme orani, gebelik ve kuzulama oranlari, sungerin cikarilmasindan sonra ostrusa gelme araligi ve ostrus suresi ile verimlilik gibi parametreler degerlendirildi. Ostrusa gelme, gebelik ve kuzulama oranlari ile dogurganlik acisindan Grup I, II ve III arasinda onemli bir farklilik bulunmadi. Buna ilaveten, tum gruplarda ostrus suresi istatistiksel acidan farkli olmadi. Ancak, sungerlerin cikarilmasindan sonra ostrusa gelme sureleri acisindan Grup II (53±3,37 saat) ve Grup III (41,5±1.81 saat) arasinda onemli farkliliklar bulundu (p<0.05). Koc katimindan sonra progesteron (P4) seviyesi hafif artti ama bu artisi takiben koc katimindan iki hafta sonra azaldi (p<0.05). Sonuc olarak, sunger uygulama surecinde yuksek progesteron konsantrasyonu olusturmak icin ardisik olarak iki defa sunger kullanilmasi hic bir avantaj saglamadi. Buna ilaveten, ureme mevsimi disindaki Ivesi koyunlarinda kisa sureli (7 gun) sunger uygulamasinin uzun sureli uygulama kadar etkili oldugu bulundu

Effect of the short-term progestagen treatments plus PMSG prior ram introduction on the estrus synchronization and the fertility of Ile de France ewes

The aim of the present study was to evaluate the effect of the short-term progestagen treatments plus PMSG prior ram introduction on the estrus synchronization and the fertility of Ile de France ewes in the beginning of mating season. The study was carried out with 36 pure-bred ewes (aged 4-6 years) during April 2009. The ewes were divided in 3 groups (n=12 for each group): group I - vaginal sponge impregnated with 30mg FGA for six days, as at the time of placement of sponge 125 ?g cloprostenolum was put i.m At the time of removal of the sponge 250 UI PMSG was put i.m.; group II- the same as the I group, but without cloprostenolum treatment: III group - control. The teasers were introduced to ewes 24h after the sponge removal and ewes in estrus was inseminated artificially. The following parameters were studied: effect of estrus synchronization (EES) ewes in estrus was recorded twice daily for the first 6 days after sponge removal; onset, end and duration of estrus for group I and II, fertility (at first estrus) and fecundity (calculated after lambing). The data for fertility and fecundity for the control group was obtained as ewes were fertilized during 30 days from the begging of the breeding. A significant effect of both schemes to estrus synchronization was determined F=33,33, P&lt;0,001). The EES, fertility and fecundity for group I, II and III were - 91,66%, 63,64% and 142,0%; 91,66%, 45,45% and 140,0 %; 8,33%, 91,66% and 140,0% respectively. The mean onset, end and duration of estrus was 51,27 h, 77,45 h and 27,27h for the I group and 57,82h, 87,27h and 29,45 h respectively for the II group. We conclude that the scheme applied for the first group is better to use for estrus synchronization in the beginning of mating season.

Heterozygous Inverdale ewes show increased ovulation rate sensitivity to pre-mating nutrition

This study aimed to determine whether ewes heterozygous (I+) for the Inverdale mutation of the bone morphogenetic protein-15 (BMP15) gene with high natural ovulation rate (OR) show similar sensitivity to nutritional manipulation as non-carriers (++). Increasing pre-mating nutrition results in OR increases in sheep, but whether this effect occurs in ewes with naturally high OR is unknown. Over 2 years, I+ or ++ ewes were given high (ad libitum) or control (maintenance) pasture allowances for 6 weeks prior to mating at a synchronised oestrus, with OR measured 8 days later. The high group increased in weight compared with controls (+5.84kg; P<0.01), accompanied by increased OR (+19%; P<0.01). As well as having higher OR (+45%; P<0.01), I+ ewes responded to increased feed with a larger proportional increase in OR (+27%; P<0.01) compared with the response in ++ ewes (+11%; P<0.05), suggesting an interaction between BMP15 levels and nutritional signals in the follicle to control OR. Although litter size increases only tended to significance (+12%; P=0.06), extra feed resulted in over 50% of I+ ewes giving birth to more than three lambs, compared with 20-31% of I+ ewes on maintenance rations. This information can guide feed management of prolific Inverdale ewes prior to breeding.

Improvement studies on mutton sheep for Marmara region conditions: I. fertility, lamb survival, and growth traits of lambs

The present study was conducted to compare the fertility of ewes, the survival rates, and the growth performance of lambs that were crossbred by mating German Black-Headed Mutton (GBM) rams with Kıvırcık ewes. The average lambing rates of the GBM × K(F1), Bandırma-I and Bandırma-II genotype, and Kıvırcık ewes were 80.00%, 75.73%, 76.78%, and 83.72%, respectively. The differences in lambing rates between the genotypes were significant (P < 0.01). The genotypes had a significant effect on litter size at birth, but not on fecundity. The differences in lambs' survival rates between the genotypes were significant (P < 0.05). The birth weight (BW), weaning weight (WW), and yearling live weight (YLW) of the lambs were 3.77 kg, 34.11 kg, and 43.71 kg for the GBM × K (F1); 3.74 kg, 32.98 kg, and 44.91 kg for the Bandırma-I; 3.73 kg, 33.18 kg, and 45.71 kg for the Bandırma-II; and 3.45 kg, 30.92 kg, and 42.22 kg for the Kıvırcık lambs. The results of this study showed that crossbreeding between the GBM and Kıvırcık breed did not significantly increase lamb production. However, crossbred lambs did not have significant survival problems when compared to native Kıvırcık lambs and had higher growth performance than purebred Kıvırcık lambs.

Expression of seasonality in Merinos d’Arles ewes of different genotypes at theMT1melatonin receptor gene

Spontaneous ovulatory activity (SOA) in spring has been used to study the out-of-season breeding ability of Merinos d’Arles (MA) ewes. Within this breed, an association was found between more intense seasonality and genotype −/− at aMnlI restriction site (allele − for its absencev.+ for its presence) in Exon II of theMT1receptor gene. This study was designed to ascertain whether this association results in a direct effect of theMT1genotype on the expression of seasonality in MA ewes. In the first year of the study, genotyping of 314 MA ewes at locusMnlI was carried out and resulted in frequencies of 43.0%, 44.9% and 12.1% for genotypes +/+, +/− and −/−, respectively. The SOA of these ewes was determined in early April of two consecutive years by assaying plasma progesterone concentrations in two blood samples taken 9 days apart. Groups of 30 ewes of each homozygous genotype (+/+ and −/−) were identified from this population and their SOA was followed by taking blood samples at regular intervals between January and mid-April of the second and third year of the study. In the second year, groups of ewes were managed together on rangelands, whereas in the third year each group was split into two subgroups given differential feed levels. The results clearly showed that genotype had no significant effect on SOA during the 2- to 3-month period preceding the introduction of rams for spring mating. In the second year of the study, in which the experimental procedure allowed a fair comparison of the fertility of ewes in spring mating, fertility was similar for both genotypes. The reciprocity of the association was not demonstrated and theMnlI polymorphic site could not be used as a genetic marker of selection for out-of-season breeding ability, at least not in the MA breed. The percentage of cycling ewes significantly decreased between January and April, and older ewes (5 or 6 years old depending on the year of the study) were more cyclic than younger ones (2 and 3 years old, respectively). The differential feeding level of ewes from early February did not significantly affect their SOA during the time period studied in the third year of the study.

Effect of season and mating system in Awassi ewes superovulated with FSH on fertilization rate and embryo recovery

The aim of the present study was to evaluate the contribution of laparoscopic intrauterine insemination to the improvement of fertilization and embryo recovery in Awassi ewes superovulated with FSH in breeding and non-breeding season. Twelve nonpregnant and cycling Awassi ewes of 3-4 years of age were randomly allocated in equal numbers (n = 6) to two groups. Each ewe was treated with a progesterone impregnated intravaginal sponge for 12 days. All ewes were superovulated with FSH in eight reducing doses for four days in the morning and evening from two days prior to sponge withdrawal. Ewes of group 1 were mated naturally at least two times with Awassi rams of proven fertility. Ewes of group 2 had intrauterine insemination and were conducted 44-46 h after sponge removal, under laparoscopic visualization of uterine horns, depositing 1 ml of semen in the distal portion of each uterine horn. Ovarian response was assessed by determining number of corpora lutea by laparoscopy on day 6 after mating. Embryo recovery was performed by hand assisted laparoscopy and by flushing both uterine horns. Ovarian response of the ewes superovulated with FSH was decreased to half in the non-breeding season. High number of unfertilized ova (P

Effects of Melatonin Implants During Non‐Breeding Season on Sperm Motility and Reproductive Parameters in Rasa Aragonesa Rams

The effect of melatonin implants administered during non-breeding season in Rasa Aragonesa rams on sperm motility parameters and other reproductive traits was assessed. In a first experiment, two Rasa Aragonesa rams were implanted (with melatonin group M), remaining other two males as control group (C). Semen of each group was collected from 1 May to 23 June, twice or three times a week, and motility parameters were assessed using a computer-assisted sperm analysis system. Melatonin increased the percentage of progressive motile spermatozoa, particularly during 46-75 days after melatonin implantation (p < 0.01). In experiment 2, M and C in vitro fertilization ability had been determined by zona-pellucida binding assays, using spermatozoa from experiment 1, obtained 60-70 days after melatonin was implanted. A significantly higher number of spermatozoa attached per oocyte was observed in frozen-thawed immature ovine oocytes incubated with sperm from M animals than in those incubated with sperm from the C group (p < 0.01). Finally, a field assay (experiment 3) was performed. In this case, five Rasa Aragonesa rams were implanted with melatonin and three remained as control group. Sperm doses from those animals were used for artificial insemination of 2608 Rasa Aragonesa ewes from 39 different farms at non-breeding season. Fertility, litter size and fecundity were studied. Semen from melatonin implanted rams seemed to increase both fertility and fecundity in ewes inseminated with spermatozoa obtained 46-60 days after implantation (p < 0.1). Thus, melatonin treatment in rams during non-breeding season modifies sperm motility parameters and seems to improve the fertilization parameters obtained.

Effects of Progestagen and Pmsg on Estrous Synchronization and Fertility in Kivircik Ewes during Natural Breeding Season

An experiment was conducted using indigenous Kivircik ewes to evaluate the effect of intravaginal progestagen sponges, containing 30 mg of fluorogestone acetate (FGA), followed by administration of pregnant mare serum gonadotrophin (PMSG) on inducing synchronized oestrus in the season and fertility. Three times of PMSG administration relative to sponge withdrawal (24 h before (n = 30), at (n = 29) or 24 h after (n= 29)) and two routes of PMSG administration (intramuscular (n = 46) and subcutaneous (n = 42) were compared for estrous response, number of multiple births and fecundity rates. There were no significant differences in terms of estrous response, due to differences in the time and route of PMSG administration. Lambing percentage, proportion of multiple births and fecundity were 75.6, 51.6 and 114.6%, respectively. The administration had a significant effect on lambing (p<0.05), multiple birth and fecundity rates (p<0.01). The subcutaneous administration of PMSG resulted in a significantly higher lambing rate (p<0.05) and fecundity rate (p<0.01), compared to the intramuscular injection of the PMSG.

Factors Affecting the Fertility of Ewes after Intrauterine Insemination with Frozen-Thawed Semen During the Non-Breeding Season

In this study, two successive field trials were conducted during the non-breeding season to investigate various factors affecting on fertility of Suffolk ewes after intrauterine insemination with frozen-thawed semen. In the first year (Experiment 1), three sperm numbers per insemination dose (0.25, 0.5 and 1 million sperm) and five sheep farms were used, and in the second year (Experiment 2), parity, age, body weight, body condition score (BCS) and postpartum days were investigated to compare pregnancy and lambing rates. High pregnancy and lambing rates (70.6 and 70.6%, respectively) were obtained with 0.25 million sperm per dose. There were no significant differences in the pregnancy and lambing rates among the five farms, but there was a tendency for one farm to have higher pregnancy (75.8%, P=0.065) and lambing (72.7%, P=0.077) rates than those (46.7-53.3% and 45.2-53.3% for the pregnancy and lambing rates, respectively) of the other farms. In Experiment 2, ewe age significantly affected both the pregnancy and lambing rates. Nulliparous ewes had a higher lambing rate (72.0%) than that (44.2%) of multiparous ewes, but a significant difference was not revealed. Regardless of body weight, BCS tended to be an important factor influencing on fertility of ewes. Body weight and the postpartum days did not affect the fertility of ewes. It was concluded from these results that the fertility of Suffolk ewes after intrauterine insemination with frozen semen was significantly influenced by sperm number per dose and ewe age. Nulliparous ewes at less than three years of age and with a BCS of more than 3.0 are expected to have higher fertility than other ewes.

33 TIMING OF OVULATION AND ESTRUS IN LONG PROTOCOLS WITH OR WITHOUT CIDR REPLACEMENT IN Santa Inês SHEEP DURING BREEDING SEASON

Low levels of progesterone (P4) during synchronization of estrus in ewes can promote excessive growth of the follicles, resulting in large persistent and old ovulatory follicles. Timing of ovulation or the LH surge in relation to onset of estrus is also more variable with lower P4. These findings have been related to reduction in fertility in ewes (Viñoles et al. 2001 Theriogenology 55, 993-1004). To avoid prolonged periods of subluteal P4 concentrations, the aim of this study was to compare long protocols with or without CIDR replacement in Santa Inês sheep during the breeding season. Twenty-three adult ewes were divided into 2 groups (G-1CIDR, n = 11 and G-2CIDR, n = 12). Estrus was synchronized with a P4 device (CIDR™; Pfizer-New Zealand, Auckland, New Zealand) for 14 d. However, in G-2CIDR, the CIDR was replaced by a new one on Day 7. Doses of 2.5 mg of dinoprost, i.m. (Lutalyse™, Pfizer-New Zealand) were administered on Days 0 and 14. All ewes received 300 IU of eCG (Novormon™, Syntex, Buenos Aires, Argentina) on Day 14. Estrus detection was accomplished using a teaser ram starting 12 h after CIDR removal and was repeated 3 times a day for 4 d. Ultrasonographic exam was used every 8 h for 5 d after the end of the treatment to determine the moment of ovulation and the diameter of the ovulatory follicle. Data were analyzed by ANOVA using SAS software (chi-square and Tukey tests). The proportions of treated ewes that were detected in estrus did not differ statistically between groups (G-1CIDR: 90.9% and G-2CIDR: 100%). The interval from onset estrus to CIDR removal differed (P &lt; 0.05), between G-1CIDR (37.80 ± 8.02 h) and G-2CIDR (49.00 ± 9.16 h) groups. The frequency distributions of estrus in G-1CIDR ewes were 10, 70, 10, and 10% at 24, 36, 48, and 54 h, respectively, compared with 8.33, 8.33, 50, 8.33, and 25% at 30, 36, 48, 54, and 60 h after CIDR removal in the G-2CIDR ewes. All ewes ovulated at the end of the synchronization protocols. Ovulation occurred at 69.45 ± 10.00 h and 76.66 ± 15.04 h after the end of the protocols in G-1CIDR and G-2CIDR, respectively (P &gt; 0.05). The ovulation frequency distribution for ovulation time in G-1CIDR was 27.27, 54.54, 9.09, and 9.09% at 60, 68, 84, and 92 h, whereas in G-2CIDR, 8.33, 50, 16.66, 8.33, 8.33, and 8.33% ovulated at 60, 68, 76, 92, 100, and 108 h after the end of treatment. The interval between estrus and ovulation was 29.40 ± 9.97 h in G-1CIDR compared with 27.66 ± 11.71 h in G-2CIDR (P &gt; 0.05). The number of ovulations per animal and diameters of ovulatory follicles were 1.54 ± 0.82 and 6.95 ± 0.75 mm in G-1CIDR and 1.33 ± 0.77 and 7.00 ± 1.22 mm in G-2CIDR, respectively (P &gt; 0.05). These results showed a later onset of estrus in G-2CIDR. However, the treatment with CIDR replacement did not promote an effect on ovulation rate and number of ovulatory follicles. Both protocols showed efficiency. Funding support: FAPESP.

Effect of different dietary energy levels on the reproductive performance of Kivircik sheep under a semi-intensive system in the South-Marmara region of Turkey

The objective of the study was to determine the effects of four dietary energy levels (L 1 - 10.3, L 2 - 11.0, L 3 - 11.6 and L 4 - 12.2 MJ ME per kg DM) on oestrus synchronization and fertility in Kivircik ewes. Eighty Kivircik ewes were randomly allocated in equal numbers to the four dietary energy treatments. The groups were treated with intra vaginal sponges containing 40 mg FGA (fluorogestone acetate) for a period of 14 days and 500 IU pregnant mare serum gonadotropin was injected intramuscularly after sponge withdrawal. The proportion of ewes exhibiting overt oestrus within 96 h after the injection was significantly lower (P<0.05) in the L 1 and L 2 eves (86 and 89 %) than in those on the L 3 (100%) and L 4 (100%) treatments, respectively. Mean litter size and fecundity were higher (P<0.05) in the L 3 (1.95) and L 4 (2.05) compared with the L 1 (1.45 and 1.25) and L 2 (1.63 and 1.55) ewes. It is concluded that shortterm (21 days) in the level of dietary energy supplementation pre-mating can have a beneficial effect on reproductive performance in ewes.