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PubMed2005

Relationship between in vitro fertilisation of ewe oocytes and the fertility of ewes following cervical artificial insemination with frozen-thawed ram semen.

No laboratory test exists that can reliably predict differences among rams in field fertility after artificial insemination (AI) with frozen-thawed semen. In vitro fertilisation (IVF) has been proposed as a method of predicting these differences. The objectives of this study were to evaluate whether IVF system could discriminate among rams of different fertility in vivo after AI using frozen-thawed semen. Also, to examine effects of lowering sperm concentration on discrimination power between rams used for IVF. The aim of Experiment 1 was to evaluate the effect of altering the sperm concentration from 2 x 10(6) to 0.03125 x 10(6) spermatozoa/mL on subsequent cleavage rate and blastocyst rate in vitro. In Experiment 2, six rams (three High and three Low in vivo fertility; average pregnancy rates of 37.6% and 21.8%, respectively) were compared for their fertilising ability in IVF. Spermatozoa from each of the six rams were added to ewe oocytes using a concentration of either 2 x 10(6) or 0.0625 x 10(6)/mL. There were six replicates with 25 oocytes per well and two wells per ram per replicate. Cleavage rate was monitored at 48 h post-insemination (p.i.) and blastocyst rate determined on Days 6-8 p.i. In Experiment 1, cleavage rate increased with increasing sperm concentration and blastocyst rate was not affected by sperm concentration on any day. When the six rams were tested using 2 x 10(6) spermatozoa/mL, no significant differences were found between High and Low fertility groups for cleavage rate or blastocyst rate on Days 6, 7, or 8 p.i. (P>0.05). When the experiment was repeated using 0.0625 x 10(6) spermatozoa/mL, no differences were found between High and Low group rams for blastocyst rate on any of Days 6, 7 or 8 p.i. (P>0.05). However, there was a significant difference between High and Low fertility rams for percentage of oocytes cleaved (16.4, S.E. 2.02%; P<0.01) and the correlation between fertility in vivo and cleavage rate in vitro was significant (P=0.013). Replicate of IVF was a source of significant variation for both cleavage rate and blastocyst rate and conditions need to be further controlled. However, we suggest that using a low concentration of spermatozoa (0.0625 x 10(6)/mL) for IVF may be a useful method for predicting field fertility of frozen-thawed ram semen.

Animals↗
PubMed2001

Timed artificial insemination in beef cattle using GnRH agonist, PGF2alpha and estradiol benzoate (EB).

The present work evaluated low-cost protocols for timed artificial insemination (TAI) in beef cattle. In Experiment 1, cycling nonlactating Nelore cows (Bos indicus, n=98) were assigned to the following groups: GnRH-PGF (GP) and GnRH-PGF-GnRH (GPG), whereas cycling (n=328, Experiment 2) or anestrus (n = 225, Experiment 3) lactating (L) cows were divided into 3 groups: GP-L, GPG-L and GnRH-PGF-Estradiol benzoate (GPE-L). In Experiment 4, lactating cows (n=201) were separated into 3 groups: GP-L, GPE-L and G/2PE-L. Animals from Experiment 1, 3 and 4 were treated (Day 0), at random stages of the estrous cycle, with 8 microg of buserelin acetate (GnRH agonist) intramuscularly (i.m.), whereas in Experiment 2 half of the cows received 8 and the other half 12 microg of GnRH (i.m.). Seven days later (D 7) all animals were treated with 25 mg of dinoprost trometamine (PGF2alpha, i.m.) except those cows from the G/2PE-L group which received only 1/2 dose of PGF2alpha (12.5 mg) via intravulvo-submucosa (i.v.s.m.). After PGF2alpha injection the animals from the control groups (GP and GP-L) were observed twice daily to detect estrus and AI was performed 12 h afterwards. The cows from the other groups received a second GnRH injection (D 8 in GPG-L and d9 in GPG groups) or one injection of estradiol benzoate (EB, 1.0 mg, D 8 in GPE-L group). All cows from GPG and GPG-L or GPE-L groups were AI 20 to 24 or 30 to 34 h, respectively, after the last hormonal injection. Pregnancy was determined by ultrasonography or rectal palpation 30 to 50 days after AI. In the control groups (GP and GP-L) percentage of animals detected in heat (44.5 to 70.3%) and pregnancy rate (20 to 42%) varied according to the number of animals with corpus luteum (CL) at the beginning of treatment. The administration of a second dose of GnRH either 24 (Experiment 2) or 48 h (Experiment 1) after PGF2alpha resulted in 47.7 and 44.9% pregnancy rates, respectively, after TAI in cycling animals. However, in anestrus cows the GPG treatment induced a much lower pregnancy rate (14.9%) after TAI. The replacement of the second dose of GnRH by EB (GPE-L) resulted in a pregnancy rate (43.3%) comparable to that obtained after GnRH treatment (GPG-L, 47.7%, Experiment 2). Furthermore, the use of 1/2 dose of PGF2alpha (12.5 mg i.v.m.s., Experiment 4) resulted in pregnancy rate (43.5%) similar to that observed with the full dose (i.m.). Both protocols GPG and GPE were effective in synchronizing ovulation in cycling Nelore cows and allowed approximately a 45% pregnancy rate after TAI. Additionally, the GPE treatment is a promising alternative to the use of GPG in timed AI of beef cattle, due to the low cost of EB when compared to GnRH agonists.

Animals↗
PubMed1994

Heritabilities for duration of fertility traits in brown Tsaiya female ducks (Anas platyrhynchos) by artificial insemination with pooled muscovy (Cairina moschata) semen.

1. Fertility traits in 348 Brown Tsaiya female ducks were analysed following intergeneric crossbreeding by artificial insemination (AI) with pooled Muscovy semen. The females descended from 18 sires and 107 dams. At 50 weeks of age, the ducks were intra-vaginally inseminated once with 0.03 ml of pooled Muscovy semen. Subsequently eggs were collected for 15 d and set for incubation up to candling 10 d later. 2. Average fertility decreased from 87% at day 2 after AI to 53% at day 6 and less than 7% from day 10 onwards. 3. The best criterion of selection for duration of fertility seems to be the number of fertile eggs from 2nd day up to the 15th day after AI. Heritability estimates for this trait were hs2 = 0.29 +/- 0.18., hD2 = 0.38 +/- 0.22.

Animals↗
PubMed1994

Inherited Treacher-Collins syndrome in twins after artificial insemination.

We present two cases of the Treacher-Collins syndrome and one case of plagiocephalus in a trigeminus childbirth resulting from artificial insemination. The mother, although affected with the Treacher-Collins syndrome, was not diagnosed before the birth of her children. Genetic counseling did not occur. Medical and forensic problems resulting from modern techniques of reproduction are briefly discussed.

Adult↗
PubMed1982

Sex ratio of births resulting from artificial insemination.

A survey of available data has shown that the sex ratio of births is significantly affected both by the practice of artificial insemination (AI) and by the cryostorage of semen. Comparison of the sex ratio of all infants born in England, Scotland and Wales between 1969 and 1978 (51.5% males) with that of British births after AI showed that the prevalence rate of male births after AI with either fresh or cryostored semen was lower than that for the general population: fresh semen (47.8%); cryostored semen (42.9%). When data from European countries and the US were combined, AI with fresh semen significantly increased the prevalence rate of male infants to 57.7%, whereas AI with cryostored semen significantly decreased the rate to 49.7%. The mechanism/s whereby the cryostorage of spermatozoa affects the secondary sex ratio remains to be determined.

Female↗
PubMed2004

Sperm distribution in the genital tract of the bitch following artificial insemination in relation to the time of ovulation.

In the present study, sperm distribution in the genital tract of the bitch following artificial insemination (AI) in relation to the time of ovulation was investigated by histology, scanning electron microscopy (SEM) and flushing. Ten bitches were inseminated intravaginally with 500 x 10(6) spermatozoa: three dogs before ovulation, four dogs during ovulation and three dogs after ovulation. Ovariohysterectomy was performed 24 h after AI. Half of the genital tract was divided into nine segments (cervix, corpus uteri, caudal, middle and cranial uterine horn (UTH), utero-tubal junction (UTJ), isthmus, ampulla and infundibulum), which were processed for histology and SEM. The contralateral UTH and uterine tube (UT) were flushed, and several sperm characteristics were assessed. Histology revealed that the spermatozoa were mainly located in the uterine glands and at the UTJ, while very few spermatozoa were detected in the UT. Insemination during ovulation resulted in higher percentages of glands with spermatozoa in the different parts of the uterus (P < 0.05). Evaluation by SEM showed higher numbers of spermatozoa in several parts of the uterus for bitches inseminated during ovulation (P < 0.05). The mean number of spermatozoa flushed from the UTH and the UT was low. No significant differences in the evaluated sperm quality parameters were found between the flushings of the UTH and the UT. In conclusion, based on our findings, the uterine glands and the UTJ might act as sperm reservoirs in the bitch and sperm transport in the genital tract is affected by the time of AI in relation to ovulation.

Animals↗
PubMed2000

Evaluation of reproductive performance in lactating dairy cows with prostaglandin F2alpha, gonadotropin-releasing hormone, and timed artificial insemination.

Nine hundred and twenty Holstein cows from 16 commercial dairy herds to evaluate three systematic breeding protocols: 14-d PGF2alpha, timed artificial insemination (AI), and GnRH-PGF2alpha, relative to AI following estrus detection without hormone intervention. The timed AI protocol involved GnRH, followed by PGF2alpha 7 d later and GnRH again 2 d after PGF2alpha, with AI 6 to 18 h after the second GnRH. The GnRH-PGF2alpha protocol consisted of GnRH followed by PGF2alpha 7 d later. Eight herds relied on visual observation to detect estrus, and eight herds utilized the HeatWatch estrus detection system. The average interval to first postpartum AI was shortest for the timed AI protocol (77.1 d) followed by the 14-d PGF2alpha protocol (81.6 d). There was no difference in days to first AI between the control (86.1 d) and GnRH-PGF2alpha (89.5 d) protocols. Percent pregnant per first AI did not differ among control (45.6%), 14-d PGF2alpha (43.7%), or GnRH-PGF2alpha (44.0%) protocols, but all protocols had a higher percent pregnant per first AI than the timed AI protocol (30.1%). Response to the GnRH-PGF2alpha protocol was limited because 44.0% of the cows submitted to the protocol were not detected in estrus < or = 10 d post-PGF2, administration and had an interval to first AI of 103.8 d. Cumulative percent pregnant by 120 d postpartum did not differ between control cows (53.1%) and hormonally treated cows (50.6%). Visual observation herds had a shorter interval to first postpartum AI (82.8 d) than the HeatWatch herds (84.8 d), with a higher overall rate of estrus detection across all protocols (75.3 and 67.6%, respectively).

Animals↗
PubMed2006

Economic comparison of timed artificial insemination and exogenous progesterone as treatments for ovarian cysts.

The objective of this study was to compare the economic benefits of timed artificial insemination (AI) and a progesterone insert as therapeutic treatments for cows diagnosed with cystic ovarian disease (COD). A secondary objective was to illustrate the use of a stochastic dynamic simulation model to fully account for all changes in revenues and costs affected by differences in treatments. First, 4 herds of 1,000 cows each were simulated until steady state. These cows were free from COD and inseminated based on estrus only. Herds differed by probability of estrus detection (46 or 70%) and days in milk (DIM) when nonpregnant cows were culled (330 or 400 d). Second, 3 herds were created with 1,000 nonpregnant cows at 90, 170, or 250 DIM. These cows were considered diagnosed with COD at the start of the simulation (d 0); no new cases of COD developed after d 0. Cows spontaneously recovered or were treated. Treatments were either timed AI or intravaginal device containing progesterone followed by PGF(2alpha) and then AI if estrus was detected. Effects of treatments were evaluated in 48 scenarios based on compliance of timed AI (82 or 100%), probability of estrus detection (46 or 70%), and DIM when nonpregnant cows were culled (330 or 400 d). As cows became pregnant or were replaced, the herd evolved into the associated steady-state herd. Seven scenarios resulted in less than 50% of cows conceiving before they were culled. The percentage of cows diagnosed with COD that calved again ranged from 14.0 to 74.4% and was significantly reduced when COD was diagnosed later in lactation. Treatments in all cases were more valuable than waiting for spontaneous recovery. The average values of timed AI (82 or 100% compliance) and the progesterone insert were 83.29 dollars, 86.83 dollars, and 71.89 dollars, respectively, compared with waiting for spontaneous recovery. Treatments were least beneficial at 90 DIM. The benefits of timed AI (82 or 100% compliance) compared with the progesterone insert, adjusted for DIM and days to culling, were 14.98 dollars and 21.53 dollars when the probability of estrus detection was 46%. At 70% probability of estrus detection, the benefits were 7.81 dollars and 8.34 dollars, respectively. Overall benefit of treatment by timed AI was 11.39 dollars greater than by progesterone insert.

Administration, Intravaginal↗
PubMed2003

Neutrophil recruitment and phagocytosis of boar spermatozoa after artificial insemination of sows, and the effects of inseminate volume, sperm dose and specific additives in the extender.

In this study the recruitment of leucocytes and phagocytosis of spermatozoa after artificial insemination of multiparous sows was investigated. In Expt 1, groups of sows received either no inseminate (n = 6) or inseminates with various concentrations of spermatozoa and seminal plasma or different inseminate volumes (n = 9 per group). In Expt 2, groups of sows received inseminates containing no addition, caffeine + CaCl(2), or excess EDTA (n = 6 per group). Leucocytes and spermatozoa were counted in the collected backflow from the vulva, and in the PBS flushings of the genital tract of sows killed at 4 h after insemination. Tissue homogenates were checked for remaining spermatozoa. Leucocyte recruitment did not depend on the presence of seminal plasma or spermatozoa. In the control groups about 43% of the inseminated spermatozoa were found in the backflow and 5% in the genital tract. Many spermatozoa could be recognized inside polymorphonuclear leucocytes. With an inseminate volume of 20 ml instead of 80 ml, fewer spermatozoa were found in the backflow and more (non-phagocytosed) spermatozoa were recovered in the uterus (P < or = 0.05). With a sperm dose of 0.24 x 10(9) instead of 2.4 x 10(9), a higher percentage of the inseminated spermatozoa was recovered in the oviducts (P < or = 0.05). The use of caffeine + CaCl(2) resulted in lower recruitment of leucocytes (P < or = 0.05) and a higher number of non-phagocytosed spermatozoa in the uterus (P < or = 0.01) compared with controls. The numbers of spermatozoa in the oviducts were not different. Insemination with excess EDTA had no positive effects on the number of spermatozoa in the genital tract.

Animals↗
PubMed1984

[Effect of the type of restraint of sheep during artificial insemination on their fertility].

Studies were carried out to establish the effect of the various methods of restraining the sheep at their artificial insemination on the rate of conception. It was found that as a result of the fixing technique practiced up to then with sheep stress conditions developed that varied in number and effect, which led to a lower conception rate. The use of a new technique and technology of fixing and inseminating the sheep, with which all unfavourable stress factors were fully avoided, raised the conception rate by 7 to 14 per cent. A new equipment was used that made unnecessary the driving, seising; and lifting the animals as they themselves passed onto the platform for fixing and insemination. With the employment of the new method the enhanced vaginal contractions, which stood in the way of proper insemination, were lowered from 26 to 8.2 per cent as against the old technology. The new equipment further made it possible to shorten the time of inseminating each animal twice to three times and thus shorten the time for the semen to stay out of the animal body. This, in turn, also produced a favourable effect on the impregnation of sheep.

Animals↗
PubMed1996

[Artificial insemination by donor/in vitro fertilization by donor and quality of the embryo. Federation of CECOS].

OBJECTIVE: To assess pregnancies and conceptus after artificial insemination (IAD) or IVF with frozen semen donor (IVFD) on sufficiently large study population in order to distinguished minor variations. STUDY DESIGN: From 1987 to 1994 all pregnancies obtained after AID or IVFD where registered prospectively in the French CECOS Federation data base. Different factors were recorded for this study: first menarch age of the recipient women, cycle length, insemination date in the conception cycle, maternal age at delivery, hormonal treatments, donor age, sperm conservation length and follow up of the pregnancy: miscarriage, tubal pregnancy, time at delivery, sex of the fetus, weight, malformation. RESULTS: 21,597 pregnancies obtained after AID and 3381 after IVFD were registered. 2% where lost of follow up. Fetal loss rate is 18% after AID and 21.5% after AID and 1.7% after IVFD (p < 0.0001). 18,128 children were born after AID and 3,313 after IVFD. After AID the twin pregnancy rate is 6.9% and the multiple pregnancy (> or = 3 fetus) rate is 0.7%. After IVDF these rates are respectively 24.8% and 4.2% (p < 0.0001). After AID the mean weight at delivery, sex ratio, premature rate, intra uterine growth retardation rate are not different from national rates published in 1995. The fetus malformation rate (including medical abortions) is 1.9% after AID and 2.7% after IVFD (p < 0.009). After AID the trisomy 21 rate increase with the mother age but also with the donors age if the maternal age is equal. The birth defects rate is not different from those registered in Paris, Strasbourg and Marseille. The birth defects rate observed after IVDF is not different from the rate observed after IVF with husband semen (2.74% versus 2.99%, p = 0.16). CONCLUSION: After AID the miscarriage and tubal pregnancy rate, the children weight, the premature rate is not different from the general French, population. Sex ratio is normal as the global malformation rate. The multiple pregnancy rate (x 7 for twin and by 10 for multiple pregnancies more than 3 fetus) is high showing the influence of ovulation induction treatment. The birth chromosomic abnormalities rate is normal and correlated to the mother age but also to the donor age. This result without clear biological explanation will require further verification in a greater population. Practically speaking, this observations encourages lowering the age limit for the semen donors less than 45 years. IVFD practice instead of AID double the tubal pregnancy rate (0.9% versus 1.7% and increase the twin pregnancy rate by 2.5% and the multiple pregnancy (> or = 3 fetus) rate by 3. It is necessary to promote AID from which the pregnancy rate is very different from one center to another with in the centers with AID low results a too high rate of IVFD. Finally we can say that pregnancy from IVFD or IVF with husband semen are not significantly different. In other words pregnancy outcome is not changed after sperm cryopreservation.

Adult↗
PubMed1976

[Decolorization of methylene blue by bovine spermatozoa and its significance in artificial insemination (author's transly].

The mechanism of action of methylene blue reduction is discussed with special reference to its relationship to the metabolism of bovine spermatozoa. The results of experimental studies of the effect of metabolic inhibitors on decolorization of methylene blue are reported. Attention is also paid to the effect of the addition of methylene blue to semen on the oxygen uptake of bovine spermatozoa. Methods used to determine the decolorization time of methylene blue in artificial insemination are reviewed. One of these methods is described in greater detail. The results of a number of experiments is concerned with the effect of environmental factors on the decolorization times of suspensions of spermatozoa are reported. Finally, the relationship between the decolorization time of methylene blue and a number of other semen characteristics as well as usefulness of this method in artificial insemination are discussed.

Animals↗
PubMed1978

The use of a one-day luteinizing hormone assay for timing of artificial insemination in infertility patients.

A 1-day rapid assay for luteinizing hormone (RLH) was developed by combined alteration of incubation temperatures and immune-complex precipitation of a commercially available LH kit. The RLH assay, compared with the standard 3-day assay, had the following characteristics: standard curve slope values of --2.47 and --2.314; assay sensitivity of 5.5 and 3.8 mIU/ml of serum; average coefficients of variation for the standard curves of 13.6% and 14.1% and for serum controls of 10.6% and 13.1%, respectively. Two consecutive RLH assays of split samples were highly correlated (r = 0.9908; P less than 0.001), as were split aliquots measured by RLH or the 3-day assay (r = 0.993; P less than 0.001). When 52 samples from portions of 5 normal menstrual cycles were assayed in both systems, agreement was again high (r = 0.9871; P less than 0.001). Representative curves of both RLH and standard LH assays, together with other data, are presented to show the feasibility of applying this method for timing of artificial insemination.

Adult↗
PubMed1983

Clitoral stimulation and the effect of age, breed, technician, and postpartum interval on pregnancy rate to artificial insemination in beef cattle.

An experiment was conducted to assess the effect of clitoral stimulation on pregnancy rate to artificial insemination in 1,856 beef females. For unadjusted data, pregnancy rate to first service in nonstimulated females was 61% for cows and 59% for heifers, and that of females receiving clitoral stimulation was 69% for cows and 58% for heifers. After adjusting the data for the influences of age, breed, technician, and postpartum interval, clitoral stimulation increased first service pregnancy rate in cows (74+/-3% vs 59+/-3%, P<0.05), but not in heifers (53+/-5% vs 57+/-5%, P>0.10). Postpartum interval significantly influenced pregnancy rate, regardless of treatment, and clitoral stimulation was beneficial when applied to cows with relatively short postpartum intervals. Variation in the effect of clitoral stimulation on pregnancy rate was observed among technicians. Clitoral stimulation improved pregnancy rate more effectively in 3 to 4 year old cows than in cows 2 years old and cows 5 years of age or older. We concluded that clitoral stimulation at the time of artificial insemination was an effective means of increasing pregnancy rate in cows, but not in heifers.

Journal Article↗
PubMed2003

Directional postcopulatory sexual selection revealed by artificial insemination.

Postcopulatory sexual selection comprises both sperm competition, where the sperm from different males compete for fertilization, and cryptic female choice, where females bias sperm use in favour of particular males. Despite intense current interest in both processes as potential agents of directional sexual selection, few studies have attributed the success of attractive males to events that occur exclusively after insemination. This is because the interactions between pre- and post-insemination episodes of sexual selection can be important sources of variation in paternity. The use of artificial insemination overcomes this difficulty because it controls for variation in male fertilization success attributable to the female's perception of male quality, as well as effects due to mating order and the relative contribution of sperm from competing males. Here, we adopt this technique and show that in guppies, when equal numbers of sperm from two males compete for fertilization, relatively colourful individuals achieve greater parentage than their less ornamented counterparts. This finding indicates that precopulatory female mating preferences can be reinforced exclusively through postcopulatory processes occurring at a physiological level. Our analysis also revealed that relatively small individuals were advantaged in sperm competition, suggesting a possible trade-off between sperm competitive ability and body growth.

Animals↗
PubMed1994

Psychosocial aspects of donor insemination. Sperm donors--their motivations and attitudes to artificial insemination.

STUDY OBJECTIVES: To examine sperm donors' motivations and emotional reactions to the role of donors and to measure their willingness to provide information about themselves to recipients and offspring. DESIGN: A prospective trial in which the 26 subjects who were actively functioning as sperm donors in our fertility clinic at the time of investigation were asked to fill in a questionnaire and return it anonymously and voluntarily. MAIN RESULTS: 8% of the donors stated purely altruistic motivation, 32% purely financial and 60% a combination of both. The acceptance rate for providing non-identifying, phenotypic, descriptive information to recipients is 76%, for providing medical information it is 60% and the provision of psychosocial information is accepted by 28% to 40%, depending on the item. 20% of donors are willing to continue donation if the present rules of anonymity are revoked. CONCLUSIONS: Most donors do not seem to feel any close relationship to donor offspring and at least 60% found anonymity to be essential for their further functioning as donors.

Adult↗
PubMed2000

Serum progesterone profiles of zebu cattle (Bos indicus) in relationship to conception and repeat breeding after artificial insemination.

Sixty-four zebu cows, comprised mainly of Bunaji cattle aged between 3 and 7 years old, were involved in an intensive artificial insemination programme. The study was conducted during the breeding period (May-October), and cows were inseminated with freshly prepared Friesian semen when they stood to be mounted by the vasectomised bull or herdmates. Fertility was measured by serum progesterone (P(4)) concentrations and pregnancy diagnosis by rectal examination post-insemination. From the records of oestrus detection and P(4) profiles of cattle following breeding, 39 oestrous cycle lengths were classified into short, normal and long cycles. The mean duration for short, normal and long oestrous cycles were 15.6+/-2.0, 21.5+/-1.5 and 29.5+/-2.5 days, respectively. Mean inter-oestrus intervals between the treatment groups were not different. The percentage frequency distribution was 48.7% for normal oestrous cycles. The short oestrous cycle lengths of 11-17 days were observed in 12.8% of the cases, while 38.5% of the cases of oestrus returns had long luteal phases with oestrous cycle lengths of 26-32 days. Out of the 64 cows, 48.4% conceived to the first breeding while 18.8% conceived to the second breeding. Five and nine cows became acyclic after the first and second breeding, respectively, constituting 22. 0%. Cows that displayed irregular oestrous cycles (repeat breeders) constituted 10.9%. Average number of services per conception was 1.3. Serum P(4) is of practical value in monitoring ovarian activity in cattle and in the identification of acyclic and repeat breeder cows. Repeat breeder cows could be investigated by a combination of radioimmunoassay and clinical examination of the ovaries and reproductive tract. In cattle management, it is economical and profitable to diagnose pregnancy early after insemination so that cows which fail to conceive may be rebred.

Animals↗