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PubMed1987

Distribution and number of spermatozoa in the oviduct of the golden hamster after natural mating and artificial insemination.

A group of female hamsters was mated with males of proven fertility either several hours before or during ovulation. Another group of females was artificially inseminated several hours before ovulation. Females were killed at various times after the onset of mating or artificial insemination, oviducts were fixed and sectioned serially, and spermatozoa were counted individually as to their location in the oviduct. Regardless of the type or time of insemination, the vast majority of spermatozoa that entered the oviduct remained in the lower segments of the isthmus (the intramural and caudal isthmus) without ascending to the ampulla. The lower segments of the oviduct, particularly the caudal isthmus, appeared to be acting as a "sieve" and/or "sperm reservoir." In females mated or artificially inseminated prior to ovulation, virtually no spermatozoa reached the cephalic isthmus or ampulla until the commencement of ovulation. Although a few spermatozoa reached the ampulla by 1 h after the onset of mating, they were the exception rather than the rule. When females were mated during ovulation, spermatozoa spent a minimum of about 3 h in the caudal isthmus before ascending to the ampulla. The number of spermatozoa that entered the oviduct after artificial insemination was considerably lower than in naturally mated animals, but this low number was apparently large enough to ensure complete fertilization.

Animals↗
PubMed1989

Fertility of fresh and frozen rabbit semen inseminated at different times is indicative of male differences in capacitation time.

Some reports indicate that sperm from different males differ in capacitation time, and other reports suggest that freezing sperm may affect their capacitation time. These two variables were specifically studied in rabbits in a fertility trial with 96 does inseminated with approximately 1.6 million motile fresh or frozen sperm from three different bucks at 15, 10, 5, and 0 h before expected ovulation. Fresh semen averaged 84% live (unstained) sperm and 88% had normal acrosomes; corresponding values for frozen sperm were 44% and 54%. On the basis of does that became pregnant, average litter size with fresh semen was 5.5 and with frozen semen was 4.8 (p greater than 0.05), but overall, does bred with frozen semen produced fewer young (p less than 0.05). On the basis of total does and total semen, average litter size from insemination at 15, 10, 5, and 0 h was 2.8, 4.2, 3.8, and 1.7, and average litter size for the three bucks was 4.0, 1.8, and 3.6. There was no interaction of type of semen (fresh or frozen) with the other variables in the model (p greater than 0.05). Bucks and time of insemination affected both the proportion of does that were pregnant and litter size (p less than 0.01). A major interaction between buck and time of insemination (p less than 0.01) was due apparently to both differential sperm survival and probable capacitation time among bucks. This major interaction should be considered in designing in vitro and in vivo fertility studies, and for selecting males for use in artificial insemination.

Acrosome↗
PubMed1994

Fate of fluorescent stained sperm following insemination: new light on oviducal sperm transport and storage in the turkey.

A novel approach was used to evaluate the distribution of sperm in the oviduct of turkey hens inseminated before or after the onset of egg production. Prior to insemination, sperm were stained with the nuclear fluorescent stain bisbenzimide. Sperm distribution in the sperm storage tubules (SST) of the uterovaginal junction and the infundibular tubular glands was determined by use of simultaneous differential interference contrast and fluorescence microscopy. In hens inseminated and examined prior to the onset of egg production, 94% of the SST contained sperm (21% were filled). In contrast, in hens inseminated initially before the onset of egg production and examined after the onset of lay, only 73% of the SST contained sperm (5% were filled); and in hens inseminated initially after the onset of lay and then examined, 78% of the SST contained sperm (4% were filled). Sperm were sparsely distributed in the infundibular tubular glands. Therefore, lower percentages of filled SST were associated with the onset of egg production, an indication that the sperm storage capacity of the SST is diminished with the onset and continuation of egg production. Physical events associated with the daily ovulatory cycle, such as rotation of the egg mass during shell formation, may both displace sperm residing in the SST and diminish the efficacy of sperm entry into the SST.

Animals↗
PubMed2003

Repeated inseminations required for natural fertility in a wild bird population.

In most bird species, pairs copulate many times before egg laying. The exact function of repeated inseminations (i.e. successful copulations) is unknown, but several suggestions have been made. We tested the hypothesis that repeated inseminations are required to ensure fertilization of eggs, by using an experimental method where free-ranging male collared flycatchers (Ficedula albicollis) were prevented from inseminating their mates. We show that egg fertility was lower when females had not copulated during the studied part of their fertile period. By counting sperm on the inner perivitelline layer of eggs, we estimated that a minimum of 86 sperm must reach the site of fertilization to ensure average fertility. Using the timing of inseminations and the numbers of sperm on successive eggs, we show that repeated copulations are necessary to achieve an average rate of fertilization of a single clutch. Our results thus provide evidence that repeated inseminations function to ensure fertilization success. We discuss possible constraints on sperm production and utilization that may have contributed to this pattern.

Animals↗
PubMedDate not supplied

Lack of immunization after intraperitoneal insemination of spermatozoa.

Twenty infertile patients with normal tubal patency were inseminated intraperitoneally (11 once, seven twice, and two three times) with spermatozoa (mean 14 x 10(6), range 0.6-48 x 10(6)) prepared by the standard swim-up technique. The occurrence of immunization to spermatozoa was looked for by the Gelatin Agglutination Test (GAT) and Tray Agglutination Test (TAT). Both tests gave negative results for all the controls (10 pregnant and 10 puerperal women). Antisperm antibodies were measured in the serum before, 30 d and 4-7 months after Intraperitoneal Insemination (IPI). The last check was done for only 14 patients, since six became pregnant as a consequence of the first treatment. Of the 14 patients studied after 4-7 months, seven had two, and two had three IPI. In the group of inseminated patients, 18 women with no basal sperm antibody did not show evidence of antibody formation after the treatment and it was not increased after insemination in the two patients who already had low antibody titre (1/32). In conclusion, despite the large number of spermatozoa inseminated and even after several IPI attempts, there was no evidence of de novo production of or increase in already present anti-sperm antibodies according to the methods used for the detection of ASA in this study.

Adult↗
PubMed2004

Prostaglandin F2alpha treatment associated with timed artificial insemination in ewes.

Traditional treatments of two prostaglandin F2 alpha (PGF2alpha) doses at 10-day intervals or more did not result in acceptable pregnancy rates in timed artificial insemination (TAI) programmes in ewes. An explanation might be the undefined time-period of the onset of oestrus and ovulation after the treatment. Recently a consistent interval to oestrus and ovulation was obtained by giving PGF2alpha at day 3 post-ovulation, i.e. when the largest follicle of the first follicular wave of the cycle was still growing. This can be achieved when a second dose of PGF2alpha is given 7 days after a first dose. In this work, we evaluated the synchronization of oestrus and determined which of three different moments of TAI was the most successful using a PGF2alpha (PG-7d) protocol in a large flock. A total of 436 nulliparous and multiparous ewes were treated with two doses of a PGF2alpha analogue (delprostenate 160 microg, i.m.) separated by 7 days. Onset of oestrus was recorded twice a day and a single cervical TAI with fresh undiluted semen was performed either at 42 h (n = 152), 48 h (n = 120), or 54 h (n = 164), after the second PGF2alpha dose without taking into account the oestrous response. Pregnancy rate was determined by transrectal ultrasonography 30 days after insemination. Onset of oestrus was detected in 308 of 328 and 89 of 108 multiparous and nulliparous ewes, respectively (p < 0.001), within 72 h after treatment. The distribution of the onset of oestrus did not differ between multiparous and nulliparous ewes and the highest proportion of ewes in oestrus was detected between 25 to 48 h (313/397) from the second PGF2alpha dose. The pregnancy rate in ewes inseminated at 42 h tended to be higher than those inseminated at 48 h (p = 0.09) and was higher than those inseminated at 54 h (p < 0.05) (56/152, 31/120, 37/164; respectively). Therefore, the use of the PG-7d protocol resulted in a very high synchronization of oestrus with the highest concentration (around 80%) between 25 to 48 h from the end of treatment. The best pregnancy rate (37%) was obtained after a single cervical TAI with fresh semen at 42 h.

Animals↗
PubMed2005

The effect of post-ovulatory insemination on the subsequent embryonic loss, oestrous cycle length and vaginal discharge in sows.

The aim of present study was to study the effect of post-ovulatory insemination on the subsequent embryonic loss, oestrous cycle length and vaginal discharge in sows. Ten Large White multiparous sows were divided into two groups. Group A sows were inseminated once at 15 h after ovulation. Thereafter, they were ovariohysterectomized on day 11 (n = 5, first day of standing oestrus = day 1) and flushed for recovery of embryos. Group B sows were also inseminated once at 15 h after ovulation. They were further observed for return to oestrus and vaginal discharge (n = 5) after insemination. The endometrium tissues were biopsied from sows with vaginal discharge, embedded with paraffin, stained with haematoxylin and eosin and examined under light microscope. Only two embryos were observed in one of four sows from group A. All embryos had a spherical shape but differed in size (range 1-2 mm). In group B, only one sow had a regular return to oestrus (i.e. on day 23) and another sow had an irregular return to oestrus (i.e. on day 27). The other two sows in this group had shown vaginal discharge on days 20 and 38 after standing oestrus. For the number of leucocytes in the endometrium of sows with vaginal discharge, a large number of lymphocytes and plasma cells were observed in the connective tissue of the subepithelial layer. In conclusion, post-ovulatory insemination resulted in early embryonic loss, a subsequent prolonged oestrus interval and also vaginal discharge (i.e. endometritis) in sows.

Animals↗
PubMed2005

Factors affecting pregnancy rate in artificial insemination with frozen semen during non-breeding season in Murciano-Granadina goats: a field assay.

An artificial insemination programme was carried out to study the effect of factors such as depth of semen deposition, inseminator skill, farm, sire and expression of oestrus on pregnancy rate in Murciano-Granadina (MG) goats during non-breeding season and using frozen semen. Frozen-thawed semen from six males was applied by three technicians to inseminate a total of 551 goats in 17 farms distributed throughout the Mediterranean area of Spain. Pregnancy rate was determined at 6 weeks after insemination by transabdominal ecography. Overall pregnancy rate was 57%. Farm and depth of semen deposition affected pregnancy rate, whereas the sire and the technician had no effect. The deeper the semen was deposited in the genital tract, the higher was the rate of pregnancy obtained, being greater when the catheter reached the uterus. In spite of the relevant difference observed (48.2% vs 59.0%), pregnancy rate of females not coming into oestrus until 30 h after sponge removal was not significantly different, compared with those showing oestrus during the OD procedure. In conclusion, our field assay data on AI in MG goat with frozen-thawed semen showed that post-cervical insemination presented significantly greater pregnancy rate in comparison to when semen is deposited in the vagina or in the caudal part of the cervix.

Animals↗
PubMed1991

Conception rates in European fallow does (Dama dama dama) following intrauterine insemination with frozen-thawed semen from Mesopotamian fallow (Dama dama mesopotamica) and crossbred (Dama dama dama x Dama dama mesopotamica) bucks.

Ninety eight parous fallow does received laparoscopic intrauterine insemination of frozen-thawed semen at one of 2 fixed intervals following oestrus synchronisation treatment. Semen was collected from a Mesopotamian (Dama dama mesopotamica) and a crossbred (F1) (Dama dama dama x Dama dama mesopotamica) fallow buck. Does were inseminated at either 56 or 66 hours after the removal of an intravaginal controlled internal drug releasing device. Eighty eight does received a single straw of frozen-thawed semen containing a total of 50 x 10(6) spermatozoa, while the remaining 10 received split straws containing 25 x 10(6) spermatozoa. Overall, the use of F1 semen containing 50 x 10(6) spermatozoa resulted in a 68% (17/25) conception rate compared with the Mesopotamian semen, which resulted in a 41% (26/63) conception rate. Conceptions were also achieved using 25 x 10(6) spermatozoa of either Mesopotamian or F1 semen (3/8 versus 2/2, respectively). Overall, the conception rate was higher for F1 than Mesopotamian semen (P less than 0.025) and there was a significant interaction with time of insemination (P less than 0.05); for F1 semen there was no difference in conception rate at the 2 insemination times, but for Mesopotamian semen conception was significantly higher (P less than 0.005) following insemination at 66 hours than at 56 hours.

Animals↗
PubMed2002

Effect of deposition site and sperm number on the fertility of sheep inseminated with liquid semen.

The effect of the deposition site and the numbers of sperm on the fertility of sheep was tested in a field trial in which 1292 Norwegian crossbred ewes aged between six months and five-and-a-half years from 52 farms were inseminated with liquid semen after natural oestrus. Cervical insemination with 150 x 10(6) and 75 x 10(6) spermatozoa resulted in 25-day non-return rates of 63.7 and 56.1 per cent, and vaginal insemination gave non-return rates of 63.3 and 56.6 per cent, respectively. There was no significant difference between the cervical and vaginal inseminations, but the inseminations with 150 x 10(6) spermatozoa gave significantly higher non-return rates (P=0.004). There were significant differences between the non-return rates for different rams (P<0.0001) and farmers (P=0.0002) but the age of the ewe had no significant effect.

Administration, Intravaginal↗
PubMed2005

Effect of vaginal and cervical deposition of semen on the fertility of sheep inseminated with frozen-thawed semen.

The effect of vaginal and cervical deposition of frozen-thawed semen on the fertility of sheep was tested in a field trial in which 543 Norwegian crossbred ewes aged between six months and five-and-a-half years from 10 farms were inseminated after natural oestrus. Cervical insemination with 200 x 10(6) spermatozoa resulted in 25-day non-return and lambing rates of 75.4 and 72.7 per cent, respectively, and vaginal insemination gave rates of 71.3 and 67.4 per cent; the cervical inseminations produced significantly higher lambing rates (P=0.04). There were significant differences between the lambing rates for different rams (P=0.006) and different farmers (P=0.003), and there was a significant interaction between farmer and deposition site (P=0.03). After vaginal insemination fertility was encouragingly high, but the results varied with the farmer, and different flock and management conditions.

Animals↗
PubMed2004

Human chorionic gonadotropin administration is associated with high pregnancy rates during ovarian stimulation and timed intercourse or intrauterine insemination.

BACKGROUND: There are different factors that influence treatment outcome after ovarian stimulation and timed-intercourse or intrauterine insemination (IUI). After patient age, it has been suggested that timing of insemination in relation to ovulation is probably the most important variable affecting the success of treatment. The objective of this study is to study the value of human chorionic gonadotropin (hCG) administration and occurrence of luteinizing hormone (LH) surge in timing insemination on the treatment outcome after follicular monitoring with timed-intercourse or intrauterine insemination, with or without ovarian stimulation. METHODS: Retrospective analysis of 2000 consecutive completed treatment cycles (637 timed-intercourse and 1363 intrauterine insemination cycles). Stimulation protocols included clomiphene alone or with FSH injection, letrozole (an aromatase inhibitor) alone or with FSH, and FSH alone. LH-surge was defined as an increase in LH level > or =200% over mean of preceding two days. When given, hCG was administered at a dose of 10,000 IU. The main outcome was clinical pregnancy rate per cycle. RESULTS: Higher pregnancy rates occurred in cycles in which hCG was given. Occurrence of an LH-surge was associated with a higher pregnancy rate with clomiphene treatment, but a lower pregnancy rate with FSH treatment. CONCLUSIONS: hCG administration is associated with a favorable outcome during ovarian stimulation. Awaiting occurrence of LH-surge is associated with a better outcome with CC but not with FSH treatment.

Adult↗
PubMed2003

Effect of intrauterine insemination with spermatozoa or foreign protein on the mechanism of action of oestradiol in the rat oviduct.

Previously, we showed that oestradiol accelerates oviductal egg transport through a non-genomic action involving oviductal protein phosphorylation in non-mated rats, and through a genomic action in mated rats. Thus, sensory stimulation, seminal fluid or sperm cells may be the source of signals that switch the mechanism of action of oestradiol in the oviduct to a genomic pathway. The present study examined the ability of spermatozoa to switch the mode of action of oestradiol in the absence of the sensory stimulation and seminal fluid provided by mating. Pro-oestrous rats were inseminated in each uterine horn with epididymal spermatozoa and 12 h later were injected subcutaneously with oestradiol and intrabursally with the mRNA synthesis inhibitor alpha-amanitin. The number of eggs in the oviduct, assessed 24 h later, showed that alpha-amanitin blocked the oestradiol-induced egg transport acceleration, indicating that the interaction of spermatozoa with the genital tract shifts the action of oestradiol from non-genomic to genomic. Other rats were inseminated with live or dead spermatozoa and then treated with the protein kinase inhibitor H-89, and oestradiol. Treatment with H-89 did not block the oestradiol-induced acceleration of egg transport in these rats, although dead spermatozoa did not enter the oviduct, indicating that the mere presence of spermatozoa in the uterus abrogated the non-genomic action of oestradiol in the oviduct. Treatment with H-89 also failed to prevent the acceleration of oviductal egg transport induced by oestradiol in rats inseminated with hamster spermatozoa or with BSA, whereas in rats inseminated with their own serum (autologous proteins), H-89 was able to prevent the effect of oestradiol. This finding reveals that the effect of insemination on the mode of action of oestradiol is neither species-nor sperm-specific and it is produced by foreign organic material. It can be concluded that the presence of spermatozoa or foreign protein in the uterus is one of the components of mating that is capable of switching the action of oestradiol in the oviduct from a non-genomic to a genomic mode.

Amanitins↗
PubMed1977

[Artificial insemination in the mouse with special reference to the effect of sperm numbers on the conception rate and litter size (author's transl)].

Mature female mice (ICR-JCL), 8 to 12 weeks of age, were artificially inseminated at 8:30-9:30 a. m. on the day of estrus vaginal smear (about 3-7 hr after ovulation) with 3.18 X 10(6), 1.83 X 10(6) and 1.15 X 10(6) sperms from four, two and one cauda epididymidis, respectively, of adult males which were suspended in 50 microliter of a modified Krebs-Ringer-bicarbonate solution and incubated at 37 degrees C was under 5% CO2 in air for an hour. Immediately after insemination, pseudopregnancy induced by an artificial penis and a vaginal tampon. Out of 13 females inseminated with 3.18 X 10(6) sperms, 9 females showed placental signs and 8 of them gave birth to the mean 10.5+/-2.20 (M+/-S.D.) young at term. Four of 13 females having received 1.83 X 10(6) sperms became pregnant giving birth to the mean 4.3+/-2.1 (M+/-S.D.) young at term. On the other hand, 5 out of 6 females failed to become pregnant following insemination with 1.15 X 10(6) sperms, and only one showed a placental sign and gave birth to twelve young at term. It is concluded that the conception rate and litter size are both dependent on the number of sperms inseminated and that more than 3 X 10(6) sperms are necessary to get the conception rate and the litter size comparable to those in natural mating.

Animals↗
PubMed2000

Synchronizing estrus and(or) ovulation in beef cows after combinations of GnRH, norgestomet, and prostaglandin F2alpha with or without timed insemination.

Three experiments were conducted to induce estrus and(or) ovulation in 1,590 suckled beef cows at the beginning of a spring breeding season. In Exp. 1, 890 cows at three locations were allotted to three treatments: 1) GnRH on d -7 + prostaglandin F2alpha (PGF2alpha) on d 0 (Select Synch); 2) GnRH on d -7 + PGF2alpha on d 0 (first day of the breeding season) plus a norgestomet implant (NORG) between d -7 and 0 (Select Synch + NORG); or 3) two injections of PGF2alpha given 14 d apart (2xPGF2alpha). More (P < 0.05) cycling cows were detected to have been in estrus after both treatments that included GnRH, whereas, among noncycling cows, the addition of norgestomet further increased (P < 0.05) the proportion in estrus. Pregnancy rates were greater (P < 0.01) among noncycling cows after treatments that included GnRH. For cows that calved >60 d before the onset of the breeding season, conception rates were greater (P < 0.01) than those that calved < or =60 d regardless of treatment, whereas days postpartum had no effect on rates of detected estrus. When body condition scores were < or =4 compared with >4, rates of detected estrus (P < 0.05) and conception (P = 0.07) were increased. In Exp. 2, 164 cows were treated with the Select Synch + NORG treatment and were inseminated either after estrus or at 16 h after a second GnRH injection (given 48 h after PGF2alpha). Conception and pregnancy rates tended (P = 0.08) to be or were less (P < 0.05), respectively, for noncycling cows inseminated by appointment, but pregnancy rates exceeded 53% in both protocols. In Exp. 3, 536 cows at three locations were treated with the Select Synch protocol as in Exp. 1 and inseminated either: 1) after detected estrus (Select Synch); 2) at 54 h after PGF2alpha when a second GnRH injection also was administered (Cosynch); or 3) after detected estrus until 54 h, or in the absence of estrus, at 54 h plus a second GnRH injection (Select Synch + Cosynch). Conception rates were reduced (P < 0.01) in cows that were inseminated by appointment. An interaction of AI protocol and cycling status occurred (P = 0.05) for pregnancy rates with differing results for cycling and noncycling cows. Across experiments, variable proportions of cows at various locations (21 to 78%) were cycling before the breeding season. With the GnRH or GnRH + NORG treatments, ovulation was induced in some noncycling cows. Conception rates were normal and pregnancy rates were greater than those after a PGF2alpha program, particularly when inseminations occurred after detected estrus.

Animal Husbandry↗
PubMed2003

Effect of boar exposure at time of insemination on factors influencing fertility in gilts.

The effect of boar exposure during artificial insemination (AI) on semen backflow, fertilization, and embryo quality was evaluated. Gilts (approximately 170 d) were induced into estrus with PG600, and ovulation was synchronized using hCG 72 h later. Estrus detection was initiated after PG600 and continued at 12-h intervals. At estrus, gilts were allotted to receive boar exposure (BE, n = 20) or no boar exposure (NBE, n = 20) during AI. Gilts receiving NBE were identified to be in estrus prior to AI and the boar was then removed for 1 h, whereas gilts in the BE group received 15 min of exposure during AI. Insemination occurred in crates at 12 and 24 h after onset of estrus with 3 x 10(9) sperm/80 mL. Backflow was collected continuously with samples taken at time 0, (during AI), and at 0.25, 0.5, 0.75, 1, 2, 4, and 8 h after first and second AI. The effect of treatment was evaluated for time of insemination (min), backflow (mL), and sperm in backflow samples. Oviducts were flushed 2 d after first AI to evaluate the effect oftreatment on fertilization rate, accessory sperm numbers on embryos (scored 1 to 5), and embryo quality. There was no effect of first or second AI; therefore, data were pooled. Average duration of AI was 3.7 +/- 0.2 min and was not influenced by BE (P < 0.10). However, during the initial stage of AI, BE reduced the volume of semen (18.6 vs 32.4 +/- 3 mL) and the number of sperm lost (0.8 vs 1.3 +/- 0.15 x 10(9) sperm) compared to NBE (P < 0.05). There was a treatment x time effect (P < 0.05) for volume of backflow. By 45 min, the BE gilts lost more volume (9.0 vs 3.6 mL) compared to the NBE group, but sperm loss did not differ. Between 1 and 8 h after AI, neither volume nor sperm loss was influenced by treatment. By 8 h, total leakage (65 vs 63 mL) and total sperm loss (1.6 x 10(9) vs 1.8 x 10(9) sperm) were not influenced by BE (P > 0.10). However, more accessory sperm (P < 0.01) were found on embryos for the NBE (> or = 11 sperm/embryo) compared to BE embryos (< or = 10 sperm/embryo). Despite this observation, percentages of fertilized embryos (99.5 +/- 0.5 %) and number of embryos (11.5 +/- 0.1) were not different (P > 0.10). In conclusion, AI in the presence of a mature boar did not affect total semen leakage, sperm loss, fertilized embryos, or embryo quality. The importance of boar exposure during insemination was evident from less leakage during insemination, but had no effect on fertility; this suggests that the elimination of boar exposure during AI may not be deleterious to reproductive performance.

Animals↗
PubMed1981

Synchronization of estrus in gilts with allyl trenbolone: fecundity after natural service and insemination with frozen semen.

The synthetic progestogen, allyl trenbolone, was fed daily to 60 gilts at 15 mg/gilt for 18 days. Sixty-eight gilts that came into estrus the same week as treated gilts served as controls. Gilts were checked for estrus twice daily and were artificially inseminated with frozen semen or bred by natural service. All but two treated gilts returned to estrus between 4 and 7 days after withdrawal of allyl trenbolone (mean = 5.6; SD = .82). The farrowing rate among gilts inseminated with frozen semen was significantly lower than that among gilts bred by natural service (52.5 vs 89.6%). The farrowing rate among synchronized gilts was similar to that among untreated gilts (70.7 vs 73.5%). Average total and live litter sizes at birth and litter size at weaning were significantly smaller for untreated gilts inseminated with frozen semen than for synchronized gilts inseminated with frozen semen or those of untreated gilts bred by natural service. Average litter size for synchronized gilts bred by natural service was not significantly larger than that for synchronized gilts inseminated with frozen semen or that of untreated gilts bred by natural service.

Animals↗
PubMed1986

Influence of body weight and number of inseminations on fertility of progestogen-treated ewe lambs raised in controlled environments.

The influence of body weight at breeding on reproductive response to one and two artificial inseminations (AI) of fresh extended semen was assessed in 195 crossbred ewe lambs selected for early breeding and compared with 159 adult ewes, all housed indoors in a controlled environment. In six trials, ewe lambs and adult ewes in progestogen-induced estrus were inseminated 55 to 57 h after sponge removal. One-half of the lambs and one-fourth of the adults received a second insemination at 60 h. Resultant reproductive performance of both groups indicated no advantage in a double insemination. Overall fertility, litter size and fecundity after one and two inseminations were 33%, 1.7 and .6 for ewe lambs and 68%, 2.4 and 1.6 for adult ewes, respectively. Embryonic mortality after the first 2 wk of pregnancy was estimated at 24% for ewe lambs and 9% for adults. The influence of body weight was analyzed by grouping the ewe lambs according to body weight at breeding. The lambs in group 1 weighed 30 to 35 kg; group 2, 36 to 40 kg; group 3, 41 to 45 kg and group 4, 46 to 50 kg. The proportion of ewes lambing in groups 1, 2, 3 and 4 was 16, 34, 39 and 48%, respectively. Corresponding litter sizes were 1.4, 1.6, 1.8 and 2.0. Fecundity increased (P less than 01) from .2 in group 1 to 1.0 in group 4. The results indicate that even when ewe lambs are bred by AI (eliminating a ram behavioral problem), sheep with heavier body weights produce more lambs per ewe bred.

Animals↗