Fertility trial in Zebu cattle after a natural or controlled estrus with prostaglandin F2 Alpha, comparing natural mating with artificial insemination

With the object of comparing reproductive efficiency obtained by natural mating and by artificial insemination (AI), not only following a natural estrus but also after an induced estrus with PGF2Alpha in Zebu cattle in the tropics, 244 adult cows were divided into 4 groups. Group I (N = 69) and Group III (n = 62) were injected with 25 mg of PGF2Alpha when a functional CL was found on rectal examination. Group I was inseminated and group III was served by natural mating, both groups within five days after injection. Groups II (n = 57) and IV (n = 56) were left untreated, group II being AI and group IV ran with a fertile bull for 22 days. Estrus detection was carried out only in the injected groups (I and III) for 15 minutes every three hours between 0600 and 1800. All information was analyzed by linear trigonometric models. The onset of estrus occurred on average 68.7 h after injection in group I and 59.5 h in group III. However only 46.3% and 54.8% of animals were detected in estrus in group I and III respectively, the difference being significant (P < 0.10). Conception rates were 18.6%, 29.8%, 19.3% and 33.9% for groups I, II, III, and IV respectively. A significant difference (P < 0.10) existed between the injected groups and the untreated ones.     

Induction of estrus in cows by a new analogue of PGF2α(alfaprostol)

A new analogue of PGFα, alfaprostol, was used to induce estrus in normally cycling and anestrous cows.Five groups of six animals were treated with single injections of different doses of the drug (4, 5, 6, 7 or 8 mg/animal) on day 10–11 of the estrous cycle. Six cows in anestrus, with palpable corpora lutea, were treated i.m. with 8 mg/animal. The luteolytic properties of alfaprostol were assessed by measuring milk progesterone by RIA for 96 h after treatment and by checking for the subsequent signs of estrus. The dose of 4 mg caused a slight fall in progesterone but did not induce heat; the 5 and 6 mg doses induced estrus in animals and the 7 mg dose was effective in animals. The 8 mg dose produced a sharp reduction in milk progesterone within 24 h, followed by estrus in both the normally cycling and the anestrous groups in animals. No clinical signs of drug intolerance were seen. The present results show that alfaprostol might be of great use for both cycle synchronization in normally cycling cows and for treatment of anestrus caused by a persistent corpus luteum.     

Estrus synchronization and conception rate in dairy cattle treated with progestin-impregnated vaginal sponges.

Twelve Israeli-Friesian heifers and cows were treated for estrus synchronization with intravaginal sponges impregnated with 250 mg. medroxyprogesterone acetate (MAP) for a period of 14 days. All sponges were retained throughout the treatment period and 100% of the animals came into estrus 3–7 days after sponge removal. Conception rate from insemination at the synchronized estrus was 60%. It is concluded that further investigation is justified regarding the value of progestin-impregnated sponges as a practical means of estrus synchronization in cattle.     

A new progestin (Sa 45.249) for cycle control in pigs communication III: Confirmation of effectiveness in field trials

A novel progestin, Sa 45.249 was tested for its estrous cycle synchronization effects in field trials in more than 300 animals. Gilts treated orally with 6 mg Sa 45.249/day (as a top dressing on feed) for 12 to 14 days showed complete inhibition of clinical signs of estrus. 95 to 98% of these animals were in heat after treatment. In single fed animals, synchronization was better than in group fed animals. This was partly the result of the dosage form employed in these trials, which allowed exact dosing only in single fed animals. Nevertheless, the synchronized commencement of estrus after all treatments differed significantly from the random distribution of heat in the control population. Conception rate from A.I. or natural breeding at the first heat ranged from 80 to 88% and from 76 to 78% in treated and control populations, respectively. These differences, and the somewhat larger litter sizes in treated animals, were not statistically significant. In a last trial, the daily dose of Sa 45.249 was blended into the daily ration (as a medical feed supplement) and fed for 12 days. Heats were suppressed during treatment and commenced synchronized thereafter.     

Artificial insemination of subtropical commercial beef cattle following synchronization with cloprostenol (ICI 80996): I. Fertility

Two trials were conducted over a two-year period with 519 cycling Bos taurus x Bos indicus heifers and cows. The objectives of these trials were: 1) To compare fertility of artificial insemination at the cloprostenol-induced estrus and the naturally occurring estrus, 2) To evaluate the fertility of artificial insemination at a predetermined time (Timed AI) following an estrous synchronization regime with cloprostenol (CLP) and 3) To define the optimum interval from a second CLP treatment for Timed AI. In Trial I, 128 animals were assigned to four treatments: 1) Controls, which were inseminated at the natural occurring estrus; 2) timed AI at 72 hr and again at 96 hr post-second CLP; 3) Timed AI at 72 hr post-second CLP and 4) AI at the CLP-induced estrus. Trial II included 391 heifers distributed among six treatments; 1) Timed AI between 70 and 90 hr post-second CLP; 2) Sham AI between 70 and 90 hr post-second CLP, 3) Chute Stress between 70 and 90 hr post-second CLP; 4) AI at the CLP-induced estrus; 5) Control-AI at the naturally occurring estrus and 6) Non-treated and exposed to fertile bulls. The fertility of the animals artificially inseminated at the CLP-induced estrus was similar to that of insemination at the naturally occurring estrus in Trial I and Trial II (30 vs 46%; 37 vs 38%, respectively). The first service pregnancy rates of the animals bred at a predetermined time were similar to those bred at the CLP-induced estrus in Trial I, but lower in Trial II (P < .01).     

Clinical evaluation of a new prostaglandin analog in pigs: 2. Prophylaxis and therapy of anestrus after weaning in sows and first litter gilts

Alfaprostol, a new prostaglandin F(2alpha) (PGF) analog was given in a first trial at two dose levels known to be luteolytic (1 and 2 mg) to 200 sows and first litter gilts at the day of weaning after a 21-day lactation period; 189 controls received saline only. The treatment with alfaprostol shortened the interval to heat (6.0 vs 11.3 days; p<0.01) and increased the percentage of animals coming into heat within 10 days (84.0 vs 65.5%; p<0.01). Fertility to a.i. and litter size at the subsequent parturition were normal. In a second trial, 100 first litter gilts and 100 sows received alfaprostol, 1 or 2 mg, respectively, during July and August when high environmental temperatures tend to increase the rate of anestrus. Again, treatment with alfaprostol shortened effectively the interval to heat (5.9 vs 17.4 days in gilts, p<0.001; 5.6 vs 9.7 days in sows; p<0.01) and greatly increased the number of animals in heat (81 vs 47% in gilts, 83 vs 62% in sows; p<0.001). The effect on the seasonal incidence of clinical anestrus was marked; it was more pronounced in gilts than in sows, expressed by the length of time it took to resume cyclic functions and the lower percentage of animals coming into heat (p<0.001). The effect of alfaprostol was equally well expressed in first litter gilts and sows. In a third trial, 295 anestrous sows and gilts were treated on day 22 after weaning with either 2 mg alfaprostol, or 400 I.U. PMSG+200 I.U. hCG, or saline. Within five days after weaning, 38% of the alfaprostol treated, and 78% and 23% of the animals treated with PMSG/hCG and saline came into heat.     

Synchronization of estrus in cyclic beef heifers with the prostaglandin analog alfaprostol

Seventy-eight Hereford-Angus crossbred heifers were injected intramuscularly twice with 6 mg of alfaprostol^b in 6 ml of propylene glycol. On each representative day of a 20-day estrous cycle (estrus = Day 0), either three or four heifers received their first injection. The second injection was given 12 days after the first, regardless of the response to the first injection. Thirty-nine heifers were not treated. The first alfaprostol injection reduced serum progesterone to less than 1 ng/ml in all heifers injected after Day 4. A total of 79.5% ($\text{62}\text{78}$) of the heifers exhibited estrus by five days after the first injection. Average interval from injection to estrus was 63 hours. The second injection occurred on Days 6 through 16 for all but one heifer, with 75.6% ($\text{59}\text{78}$) falling on Days 8 through 11 of the estrous cycle. Estrus was detected in 93.6% ($\text{73}\text{78}$) of the heifers within five days after the second injection, with an average interval to estrus of 66 hours.Day of cycle at second injection did not affect the interval to estrus. Conception occurred in 79.4% ($\text{58}\text{73}$) of the heifers inseminated in the five days after the second injection. Occurrence of estrus and conception was no different in treated heifers after five days of the insemination period than in nontreated heifers after 21 days of the insemination period, where 94.9% ($\text{37}\text{39}$) were observed in estrus and 83.8% ($\text{31}\text{37}$) conceived. Overall percent conception for a 55-day insemination period was 89.7 ($\text{70}\text{78}$) for treated and 87.2 ($\text{34}\text{39}$) for nontreated heifers. Day of cycle at first or second injection did not affect conception after the second injection. Some signs of estrus were observed in 11 of the 16 heifers injected before Day 5.A second trial to determine if alfaprostol induced luteolysis early in the cycle was conducted. Twenty purebred Angus, Hereford, or Simmental heifers received either one or two injections of alfaprostol on either Day 1, 2, 3, or 4. Only five heifers showed any signs of estrus, and the three that were inseminated did not conceive. Subsequent cycle length indicated that luteolysis occurred in only one heifer.Data suggest that alfaprostol is an effective luteolytic agent in cyclic beef heifers after Day 4 and that two injections 12 days apart will effectively synchronize estrus in heifers when distributed throughout the cycle at the first injection without affecting conception rate.     

Estrous cycle synchronization in dairy heifers with the prostaglandin analog alfaprostol (II)

Over a two year period, 276 dairy heifers (German Black Pied x Holstein Friesian) received one or two injections i.m. of 1.5 mg/100 kg body weight of the PGF analog alfaprostol. Only animals not showing heat after the first injection were treated twice, with the same dose, 11 days apart. Before treatment, 71% of the heifers were cycling regularly, 12% were cycling irregularly and 17% were not observed in heat prior to treatment. Animals in heat were inseminated once or twice, 18 to 24 h apart. In response to the first injection, 60.5% of all treated animals came into heat; 38% showed heat after the 2nd treatment. Three of the six non-responding animals were later diagnosed as freemartins. Heat was well synchronized. Twenty seven percent, 60% and 9% of all first inseminations occurred on days two, three and four after treatment (s), respectively; 65% of all heifers conceived from the first insemination. Pregnancy rates after one or two inseminations were 66.0% and 63.8%, respectively. At the second a.i., 45% of all animals had already ovulated. Pregnancy rates from first a.i. after one or two treatments with alfaprostol were 60.1% and 72.2%, respectively. Years had no influence on any of the parameters observed. Stage of cycle in which the first treatment occurred had a strong influence on the occurrence of heat and on conceptions as well. Of the animals treated between days 6 and 18% of their cycles, 92.6% responded with heat to the first treatment and 79% conceived. When animals were treated for the first time between days 19 and 5 of their cycles, only 28.8% came into heat and only 23.8% conceived. After the 2nd treatment, 71.2% of the latter group came into heat and 73.1% conceived.     

Treatment of summer anestrous buffalo (bubalus bubalis) with progesterone releasing intravaginal device plus pregnant mare serum go nadotropin

Three experiments were conducted to treat forty-two summer-anestrous buffalo at three different villages. In all the experiments animals were randomly divided into two groups. One group was treated with a progesterone releasing intravaginal device (PRID) plus 800 IU pregnant mare serum gonadotropin (PMSG) at the time of PRID removal. The second group was retained as untreated control animals. All the treated animals were clinically examined and inseminated twice 48 and 72 h post treatment. Ovulation and fertility rates at induced estrus were 88, 90 and 100% and 50, 60 and 50% during Experiments I, II and III, respectively. None of the controls exhibited estrus during the course of the study.     

Estrus synchronization with melengestrol acetate in cyclic ewes. Insemination with fresh or frozen semen during the first or second estrus post treatment

A total of 540 cyclic ewes were randomly allocated to 1 of 6 groups according to synchronization or not with melengestrol acetate (MGA), insemination with fresh or frozen semen, and insemination during the first or second estrus post treatment. The MGA was effective in synchronizing estrus, since the percentage of ewes showing estrus during the first 6 days after treatment was significantly higher (P<0.05) for treated (79.5%) than for nontreated ewes (33.5%); 74% of the treated ewes showed estrus during a 72-h period. Progesterone concentrations in plasma samples obtained at random from 34 treated ewes on Day 8 post estrus revealed that 94% of them ovulated and formed a functional CL. Synchronization was maintained during the second estrus post treatment, since 71.9% of the ewes showed the second estrus during a 72-h period. Treatment with 0.22 mg of MGA/head/d for 14 d had a detrimental effect on fertility when insemination was carried out during the first estrus post treatment. Delaying insemination until the second estrus post treatment caused a less marked reduction in conception rates. Thus, MGA can be a useful alternative for estrus synchronization of a large number of ewes. Artificial insemination can be delayed until the second estrus post treatment, improving fertility without loosing the advantages of estrus synchronization.     

Comparison of pregnancy rates with two estrus synchronization protocols in Italian Mediterranean Buffalo cows

The aim in this study was to compare two estrus synchronization protocols in buffaloes. Animals were divided into two groups: Group A (n=111) received 100 microg GnRH on Day 0, 375 microg PGF(2alpha) on Day 7 and 100 microg GnRH on Day 9 (Ovsynch); Group B (n=117) received an intravaginal drug release device (PRID) containing 1.55 g progesterone and a capsule with 10mg estradiol benzoate for 10 days and were treated with a luteolytic dose of PGF(2alpha) and 1000 IU PMSG at the time of PRID withdrawal. Animals were inseminated twice 18 and 42 h after the second injection of GnRH (Group A) and 60 and 84 h after PGF(2alpha) and PMSG injections (Group B). Progesterone (P(4)) concentrations in milk samples collected 12 and 2 days before treatments were used to determine cyclic and non-cyclic buffaloes, and milk P(4) concentrations 10 days after Artificial insemination (AI) were used as an index of a functional corpus luteum. Cows were palpated per rectum at 40 and 90 days after AI to determine pregnancies. All previously non-cyclic animals in Group B had elevated P(4) (>120 pg/ml milk whey) on Day 10 after AI. Accordingly, a greater (P<0.01) relative percentage of animals with elevated P(4) 10 days after AI were observed in Group B (93.2%) than in Group A (81.1%). However, there was no difference in overall pregnancy rates between the two estrus synchronization protocols (Group A, 36.0%; Group B 28.2%). When only animals with elevated P(4) on Day 10 after AI were considered, pregnancy rate was higher (P<0.05) for animals in Group A (44.4%) than Group B (30.3%). The findings indicated that treatment with PRID can induce ovulation in non-cyclic buffalo cows. However, synchronization of estrus with Ovsynch resulted in a higher pregnancy rate compared with synchronization with PRID, particularly in cyclic buffalo.     

A model for economic comparison of swine insemination programs

Optimal artificial insemination schedules are those that result in a high farrowing rate and litter size, while minimizing costs of semen and labor by avoiding unnecessary inseminations. A simulation model programmed in a commercial spreadsheet was developed to permit comparison of alternative schedules. Farrowing rate and litter size for a particular schedule were dependent on the timing of insemination relative to the time of ovulation. Economic return was calculated by multiplying the number of pigs born per bred sow by $33.00 and subtracting the cost of producing a litter of pigs and raising them to weaning ($222.88 per sow plus $2.44 per pig born) and the cost of detection of estrus and breeding. Seven insemination schedules combined with once versus twice per day detection of estrus were simulated in 500 herds of 100 sows each. Inseminations were simulated to occur on schedules of: 1) 0, 12, 24 and 36 h; 2) 12, 24 and 36 h; 3) 0 and 24 h; 4) 12 and 36 h; 5) 12 h; 6) 24 h; and 7) 36 h after first detection of estrus. Schedule 1 was predicted to yield the highest farrowing rate and litter size. Economic return was highest for Schedule 2 with twice per day detection of estrus followed closely by Schedule 1 with once per day detection of estrus at $14.90 and $13.75 per bred sow, respectively. High performance was dependent on insuring that inseminations occurred at an optimum time in as great a proportion of sows as possible.     

Effect of one spontaneous estrus cycle (after synchronization with PGF2alpha) on reproductive performance in dairy cows

The objective of the study was to analyze the effect of a spontaneous estrus cycle after synchronization of estrus with prostaglandin F2alpha (PGF2alpha) in dairy cows on the degree of synchronization and reproductive performance. We assigned 557 Holstein cows to two treatment groups. In Group 1 estrus was synchronized by two treatments with 25 mg of Dinoprost-Trometamol in 14-day intervals. Cows were treated 27 to 33 days postpartum (dpp) and 41 to 47 dpp, respectively. Cows in Group 2 were treated with 25 mg of Dinoprost-Trometamol three times in 14-day intervals, starting at 34 to 40 dpp. The second and third injections were administered at 48 to 54 dpp and 62 to 68 dpp, respectively. All cows were inseminated on observed estrus after a voluntary waiting period of 65 days post partum. Thus cows in Group 1 were inseminated on spontaneous estrus and cows in Group 2 on induced estrus. Cows not inseminated at 80 days post partum were palpated per rectum and treated according to a predefined protocol. Herd reproductive performance measures did not differ significantly between groups. The proportion of cows with low serum progesterone levels was significantly higher 3 days after synchronization than 24 days after synchronization (97% vs 39%). The first-service conception rate was 34.8% in Group 1 and 30.7% in Group 2 (P > 0.05). Days open were 113.5 in Group 1 and 110.9 in Group 2 (P > 0.05). It is concluded that postponing artificial insemination for one spontaneous estrus cycle after synchronization decreased the degree of synchronization. This procedure, however, had no effect on herd reproductive performance compared to insemination on first observed estrus after synchronization.     

The development and marketing of estrus synchronization in cattle in Australia using prostaglandins

Estrus synchronization using prostaglandins was applied to a well-developed system of AI in beef cattle. Cows and heifers were selected to be free from infectious disease. Cows were run at pasture in a single group and estrus was detected visually twice a day without the use of any aids. Estrous cows were removed from the group each morning. Cows detected in estrus in the morning were inseminated that afternoon and cows detected in the afternoon were inseminated the next morning. The AI program ran for 25 to 42 days and was evaluated by rectal pregnancy palpation about 42 days after the last insemination. Calves were produced at an average cost of $26. The only management systems of synchronization using prostaglandins that could match this cost was the 10 day program with one treatment of 10 or 12.5 mg prostaglandin F2α on day 5. Management systems using two treatments of PGF2α, 12 days apart, increased calf costs to $160, $100, and $45, respectively, with two or one timed insemination or insemination after detection of estrus.The most significant efficiency factor was the ratio of the number of cows inseminated to the number of cows put into the AI program and this ratio was statistically the same in normal AI (72%) and AI with synchronization and detection of estrus (74%). About half of the cattle not inseminated had ovarian activity, palpable follicles or corpora lutea but had not yet come into estrus. Pregnancy rates per insemination and the number of cows pregnant per 100 cows in an AI program were the same but the labor input was reduced by synchronization.Responses to prostaglandin F2α treatment were the same over the range of dose rates from 8 to 20 mg. The 10 day AI program with a single treatment of 10 or 12.5 mg PGF2α has been used commercially in Australia for 6 years with other management systems being tailored to particular needs.     

Artificial insemination of subtropical commercial beef cattle following synchronization with cloprostenol (ICI 80996): II. Estrous response

Data collected from two controlled breeding field trials involving 561 Bos indicus x Bos taurus cows and heifers were analyzed for estrous and fertility response following a cloprostenol ICI-80, 996 (CLP) synchronization regime. Fertility data were discussed in a companion paper (1). In Trial 1, 128 animals were assigned to four treatments: 1) controls which were inseminated at the naturally occurring estrus; 2) Animals artificially inseminated at approximately 72 hr and 96 hr following a second CLP; 3) Animals artificially inseminated at approximately 72 hr following a second CLP; and 4) Animals artificially inseminated approximately 12 hr after detection of estrus post-second CLP. Trial II included 391 heifers distributed among six treatments: 1) Artificially inseminated between 70 and 90 hr post-second CLP; 2) Sham inseminated between 70 and 90 hr post-second CLP; 3) Processed with no manipulation of the genital tract between 70 and 90 hr post-second CLP; 4) Artificially inseminated approximately 12 hr after the detection of estrus following a second CLP; 5) Artificially inseminated at the naturally occurring estrus and 6) Non-treated heifers exposed to fertile bulls. Cloprostenol ICI-80996 was effective (P < .01) in synchronizing estrus in comparisons of treated vs non-treated controls in Trials I and II (82 vs 29%; 57 vs 19%, respectively). However, a significant reduction in the expression of estrus was observed following Timed AI when compared to heifers bred 12 hr after detection of CLP-induced estrus in Trial II (37 vs 54%, P < .05). The authors conclude that a single timed insemination of Brahman crossbred heifers suppresses the behavioral expression of estrus. Other evidence (1) indicates that the fertility during this period is similarly reduced.     

Cervical versus intrauterine insemination of ewes using fresh or frozen semen diluted with aloe vera gel

This study was conducted at Belen de Escobar, Argentina, in March and April 1987. Experimental work on synchronization of estrus, deep-freeze conservation of ram semen and small fertility trials involving cervical and intrauterine (i.u.) insemination methods was undertaken. A total of 80 Corriedale ewes were used in seven insemination trials. Insemination trials were grouped into two experimental groups for comparison of 1) frozen semen diluted with an experimental extender and a control diluent inseminated cervically or i.u. in synchronized/superovulated ewes and 2) cervical insemination of fresh diluted or frozen semen in ewes inseminated at natural estrus or in ewes that were synchronized/superovulated. An overall ovulation rate of 8.7 +/- 0.5 was obtained by using a superovulatory regimen consisting of 3 mg Norgestomet implants and a total dose of 18 mg follicle stimulating hormone-pituitary (FSH-P). Numbers of ova recovered per ewe following superovulation ranged from 4.3 to 5.4. In experimental Group I, fertilization rates improved when laparoscopic intrauterine AI was used compared with cervical insemination (P<0.05). Fertility rates of i.u. and cervical insemination of frozen semen diluted with the experimental extender showed satisfactory fertilizing capacity. In experimental Group II, a lower number of fertilized ova were recovered from ewes inseminated with frozen semen (P<0.02), irrespective of their estrus manipulation.     

Induced puberty in prepuberal zebu heifers treated with norgestomet and pregnant mare serum gonadotropin

Three experiments were conducted to examine the progestogen plus PMSG treatment for its effectiveness in inducing synchronous puberty in prepuberal zebu heifers in three different seasons. In Experiment 1, ten Ongole heifers (age 21 months) were treated with Norgestomet implants for nine days and an intramuscular injection of 400 IU of PMSG two days before implant removal. Ten heifers (age 25 months) were kept as untreated controls. Animals were inseminated 12 h after detection of cyclic estrus (not bred at induced estrus) until all animals conceived. The proportion of treated animals showing estrous, ovulatory, and cyclic activity were 100%, 75% and 25% respectively, while the average age at first conception was significantly less (P < 0.05) than in the control group. In Experiment 2, 18 Ongole heifers (age 22 months) were divided into treatment and control groups. Fixed-time inseminations were done 48 and 72 h after implant removal and 12 h after being detected in heat at other times. Estrus was seen in all while 63% became pregnant (P < 0.05). At the end of the 100-day experiment, the percent pregnant were 33 and 63 in the control and treatment groups, respectively. In the third study, twenty-six Ongole heifers (age 22 months) were assigned to treatment and control groups. Eighty-eight percent of the animals exhibited estrus, 75% ovulated (P < 0.01) and 25% conceived to fixed-time insemination. The pregnancy rate at the end of the experiment was 10 and 56% (P < 0.01) respectively in control and treated groups. Estrous response and fertility were better in the cooler month (February) and the treatment imposed in the hotter month (May) resulted in a significantly higher (P < 0.05) age and body weight at conception.     

Strategies to improve pregnancy per insemination using sex-sorted semen in dairy heifers detected in estrus

The objective was to improve pregnancy per artificial insemination (P/AI; 35–42 d after AI) in virgin Jersey heifers bred by AI of sex-sorted semen after being detected in estrus. Giving 100 μg of GnRH at first detection of estrus, with AI 12 h later, did not affect P/AI in Experiment I [GnRH = 47.2% (100/212) vs. No GnRH = 51.7% (104/201); P = 0.38] or Experiment II [GnRH = 53.1% (137/258) vs. No GnRH = 48.6% (122/251); P = 0.43]. In these two experiments, estrus detection was done with tail-head chalk or a HeatWatch^® system, respectively. In Experiment III, a single insemination dose (2.1 × 10⁶ sperm) 12 h after estrus detection (n = 193), a double dose at 12 h (n = 193), or a double dose involving insemination 12 and 24 h after estrus detection (n = 190) did not affect P/AI (87/193 = 45.1%, 85/193 = 44.0%, and 94/190 = 49.5%, respectively; P = 0.51). However, P/AI was influenced by the number of AI service (First, 115/208 = 55.3%^a; Second, 94/204 = 46.1%^a; and Third, 57/165 = 34.8%^b; P = 0.004). In Experiment IV, the P/AI of heifers inseminated from 12 to 16 h after the onset of estrus (40/106 = 37.7%) was less (P = 0.03) than those inseminated from 16.1 to 20 h (85/164 = 51.8%), and 20.1 to 24 h (130/234 = 55.6%). However, the P/AI for heifers inseminated from 24.1 to 30 h (61/134 = 45.5%) did not differ from that of any other interval. In conclusion, in Jersey heifers inseminated with sex-sorted semen, P/AI was not significantly affected by giving GnRH at detection of estrus or a double insemination dose, but it was higher with AI 16.1 to 24 h vs. 12 to 16 h after the onset of estrus.     

Strategies to improve pregnancy per insemination using sex-sorted semen in dairy heifers detected in estrus

The objective was to improve pregnancy per artificial insemination (P/AI; 35-42 d after AI) in virgin Jersey heifers bred by AI of sex-sorted semen after being detected in estrus. Giving 100 μg of GnRH at first detection of estrus, with AI 12 h later, did not affect P/AI in Experiment I [GnRH = 47.2% (100/212) vs. No GnRH = 51.7% (104/201); P = 0.38] or Experiment II [GnRH = 53.1% (137/258) vs. No GnRH = 48.6% (122/251); P = 0.43]. In these two experiments, estrus detection was done with tail-head chalk or a HeatWatch^® system, respectively. In Experiment III, a single insemination dose (2.1 × 10⁶ sperm) 12 h after estrus detection (n = 193), a double dose at 12 h (n = 193), or a double dose involving insemination 12 and 24 h after estrus detection (n = 190) did not affect P/AI (87/193 = 45.1%, 85/193 = 44.0%, and 94/190 = 49.5%, respectively; P = 0.51). However, P/AI was influenced by the number of AI service (First, 115/208 = 55.3%^a; Second, 94/204 = 46.1%^a; and Third, 57/165 = 34.8%^b; P = 0.004). In Experiment IV, the P/AI of heifers inseminated from 12 to 16 h after the onset of estrus (40/106 = 37.7%) was less (P = 0.03) than those inseminated from 16.1 to 20 h (85/164 = 51.8%), and 20.1 to 24 h (130/234 = 55.6%). However, the P/AI for heifers inseminated from 24.1 to 30 h (61/134 = 45.5%) did not differ from that of any other interval. In conclusion, in Jersey heifers inseminated with sex-sorted semen, P/AI was not significantly affected by giving GnRH at detection of estrus or a double insemination dose, but it was higher with AI 16.1 to 24 h vs. 12 to 16 h after the onset of estrus.     

Reaginic and homocytotropic IgG antibodies in Schistosoma mansoni infected Mastomys natalensis: time courses in untreated infections and after chemoprophylactic and chemotherapeutic treatment

Mastomys natalensis were infected percutaneously with 250 cercariae of Schistosoma mansoni and treated effectively with 5 X 50 mg amoscanate/kg body-weight 12-16 (I), 28-32 (II), 56-60 (III) and 101-105 days p.i. (IV) respectively. Levels of reaginic antibodies (RAb) and homocytotropic IgG antibodies (GAb) were assessed by passive cutaneous anaphylaxis tests (PCA) and compared with those in infected, untreated animals. In untreated animals RAb were first detected in the 6th week p.i. Maximum titres around 1:80 were reached after 100 days. High levels persisted until the end of the experiment 185 days p.i. RAb did not develop after treatment I. After treatment II only low PCA titres occurred. After treatment III the time course was similar to the controls but levels were reduced. Treatment IV did not interfere with the occurrence of specific RAb. In the case of GAb, independent of any treatment, after a first peak of PCA titres in the 5th week either a negative pattern or only very low titres were found in week 7. In untreated infected Mastomys GAb levels increased thereafter to maximum titres of about 1:80 at day 70. Later than 100 days p.i. relatively constant titres were observed. The second rise of antibody levels did not occur after early treatment. After treatment II only low transient titres developed. Animals treated in the early patency (III) showed reduced PCA titres and were negative at the end of the observation period. Treatment given 101 to 105 days p.i. rather enhanced the development of GAb.