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PubMed2001

Reproductive performance of ewe lambs from ewes from different selection practices with or without induced estrus.

Three groups of ewe lambs born in May (experiment 1; n=211) or April (experiment 2; n=174) were used to evaluate the effects of selection line and induction of estrus on pregnancy rate. Experiment 1 was a single factor experiment with induction of estrus as the main effect. In early December, May-born Targhee (n=82) and Rambouillet x Targhee (n=129) ewes were randomly assigned within body weight to one of two treatment groups: control or induction of estrus. Experiment 2 was designed in a 2x2 factorial array with the main effects of induction of estrus or selection line. In early November, April-born Targhee lambs (n=174) from two distinct selection lines were either treated as controls or received an estrus induction treatment. The two lines included an unselected control line of randomly bred ewes and a line that had been selected since 1976, based on the weight of lamb weaned. Ewes from each line were randomly assigned within body weight to one of the treatment groups. In experiments 1 and 2, estrus was induced using MAP pessaries. Pessaries were inserted for 12 days. At the time of pessary removal, ewe lambs received 400 IU eCG i.m. All ewe lambs were bred in multi-sire pens. Pregnancy rate and fetal numbers were determined either by lambing data or real-time ultrasound. Body weight, lambing date and fetal numbers were analyzed by GLM, and remaining variables were analyzed by CATMOD. For experiment 1, estrus induction increased (P<0.01) pregnancy rates (61 versus 31%) and number of fetuses estimated by real-time ultrasound (79 versus 35%) compared to control ewe lambs. Pregnancy rate and fetal number were increased (P<0.01) for the 1st year compared to the 2nd year. For experiment 2, estrus induction tended to increase (P<0.07) pregnancy rate, and pregnancy rate differed (P<0.01) between selection lines. Estrus induction increased (P<0.05) fetal numbers (0.96) compared to controls (0.77). Fetal numbers were greater (P<0.01) for the selected line (1.06) compared to random bred controls (0.67). Average date of lambing was earlier in both experiments for the estrus-induced ewe lambs compared to controls. These results indicate that induction of estrus can be recommended if increased reproduction is desired for ewe lambs.

Administration, Intravaginal↗
PubMed2000

Evidence for spontaneous postlactational estrus in gray short-tailed opossums (Monodelphis domestica).

Previous studies of the gray short-tailed opossum have shown that ovarian activity and estrus are induced by male pheromones, but we recently documented urogenital sinus (UGS) estrus in postlactational females despite their isolation from the male stimuli known to be associated with induced estrus. Body weights and UGS smears were collected after removal of pups in midlactation (19-37 days postpartum), after weaning (55-61 days postpartum), or after pheromone exposure. Estradiol was measured by RIA in plasma samples collected from dams during lactation, after separation from pups, and at estrus. Average days to UGS estrus from pup removal or initial pheromone exposure differed (P<0.05) only between the midlactation and pheromone exposure groups. Postlactational females showed a decrease in body weight from the time of pup removal or weaning to estrus, which contrasts with the increase seen in pheromonally stimulated females. Plasma estradiol was elevated at estrus in all groups, and females that were paired with males at postlactational estrus mated and produced litters. This study demonstrates that gray short-tailed opossums consistently experience estrus within 2 wk of weaning their young and that postlactational estrus appears to be hormonally and behaviorally equivalent to estrus induced by direct exposure to male pheromones.

Animals↗
PubMed1992

Steroids and plasminogen activator concentrations in follicular fluid of gilts at first and third estrus.

An experiment was conducted to determine whether morphological and functional characteristics of follicles differed at a similar stage of pubertal (first) and third estrus in the same gilts. Nine prepubertal gilts were checked three times daily for estrus and laparotomized 6 h after detected first and third estrus. Samples of vena cava and ovarian venous blood were collected, follicle numbers and diameters were recorded, and follicular fluid (FF) was aspirated from all follicles 8 to 12 mm in diameter. Sera and(or) FF were analyzed for progesterone (P4), estradiol-17 beta (E2), testosterone (T), androstenedione (A4), 5 alpha-dihydrotestosterone (DHT), plasminogen activator (PA), and plasmin (PLM). Overall mean number of follicles > or = 8 mm in diameter did not differ between gilts at first and third estrus (P > .05) but gilts at first estrus had more follicles 4 to 8 (P < .05) and 8.1 to 10 mm in diameter (P < .01) and fewer 10.1 to 12 mm in diameter (P < .07) than at third estrus. Mean FF concentrations of E2, T, and A4 at third estrus were significantly greater than at first estrus, whereas FF concentrations of P4, DHT, PA, and PLM were similar at first and third estrus (P > .05). Mean concentrations of E2 in systemic and ovarian venous sera were also greater in gilts at third than at first estrus (both P < .05). Systemic concentrations of P4 in gilts at first and third estrus did not differ (P > .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Androstenedione↗
PubMed1998

Development of a progestin-based estrus synchronization program: I. Reproductive response of cows fed melengestrol acetate for 20 days with an injection of progesterone.

We designed two experiments to determine the efficacy of an estrus control system in cows that combined long-term progestin exposure (20 d) with an acute increase in progesterone concentration. In Exp. 1, cows (n = 30) were fed either melengestrol acetate (MGA; .5 mg x cow(-1) x d(-1)) or ground ear corn (MGA carrier) for 20 d. On d -15 (last day of MGA feeding = d 0), cows were administered 25 mg of PGF2alpha to regress the corpus luteum (CL) and establish an environment conducive to the development of persistent follicles. To synchronously regress persistent follicles, cows fed MGA (n = 15) were injected with 200 mg of progesterone on d -2 (MGA-P), and the cows fed the MGA carrier were not treated (CONT; n = 15). Cows in the CONT group were artificially inseminated 12 h after detection of spontaneous estrus from d -20 to d 8. Estrus was observed, and all cows in the MGA-P group were artificially inseminated during the period of estrus synchronization (SYNC; d 1 to 8). No difference in conception rate was observed between treatments. In Exp. 2, postpartum cows (n = 113) received either the MGA-P (n = 56) or CONT (n = 57) treatment. More (P < .05) cows were observed in estrus during SYNC in the MGA-P (50%) than in the CONT (28%) group. Of the cows in the MGA-P group that were not observed in estrus during SYNC, 50% were in estrus for the first time 23 to 29 d after MGA withdrawal (SYNC2), suggesting that these cows ovulated without observable estrus during SYNC. Estrus was observed for the first time during SYNC2 in more (P < .05) cows in the MGA-P (25%) than in the CONT (7%) group. Conception rate at the synchronized estrus, pregnancy rate, and interval to first service and pregnancy were similar between treatments. We conclude that administration of MGA-P results in the synchronization and(or) induction of a fertile estrus in cows.

Administration, Oral↗
PubMed2000

The strategic use of estradiol to enhance fertility and submission rates of progestin-based estrus synchronization programs in dairy herds.

Two experiments were performed to evaluate the efficacy of a progestin-based estrus synchronization program that incorporated the use of estradiol at the initiation of progestin treatment and at 48 h after progestin withdrawal (Exp. 2). In Exp. 1, cyclic, lactating dairy cows (n = 112) were assigned to receive either 1 (1mg) or 2 (2mg) mg of estradiol benzoate via an i.m. injection on d -9 (d 0 = initiation of the breeding season). All cows received an intravaginal progesterone-releasing insert (IPI; CIDR-B) on d -9. On d -2, the IPI was withdrawn and all cows were administered 500 microg of cloprostenol sodium. Beginning on d 0, cows were bred by AI upon detection of estrus. Estrus was observed in similar proportions of cows in each treatment during the first 6 d of AI (90% across treatments), but the interval to estrus was shorter (P < .05) in 1mg (1.26 +/- .18 d) than in 2mg (1.77 +/- .18 d). Conception and pregnancy rates did not vary among treatments; however, cows in estrus on d 0 tended to be less fertile (P = .11) than those in estrus on d 1. In Exp. 2, 408 cyclic cows from three herds were assigned to receive either no synchrony treatment (Control, n = 214) or the treatments described in Exp. 1 (1mg, n = 100; 2mg, n = 94). Anestrous cows from all herds received an IPI from d -9 to -2 (n = 143; Anestrus). All cows in the 1mg, 2mg, and Anestrus groups, with the exception of those detected in estrus between d -1 and 0, also received 1 mg of estradiol benzoate on d 0. Greater than 90% of cows that received an IPI were in estrus between d -1 and 3, and 92.1% of cows in the Control group were in estrus by d 21. Conception rate to first service in 2mg (61.7%) was similar to Control (57.0%), tended to be higher (P = .06) than 1mg (49.0%), and was greater (P < .05) than Anestrus (39.9%). The mean day of conception was earlier (P < .05) in the 2mg (d 13.1 +/- 2.0) than the Control (d 23.2 +/- 1.6) and Anestrus (d 22.4 +/- 1.9) groups. Conception occurred earlier in 1mg (d 17.4 +/- 2.1) than in Control. The proportion of cows that were pregnant at the end of the breeding season tended (P = .09) to be greater in the 2mg and Anestrus groups. This regimen of estrus synchronization improved reproductive competence in cyclic cows and resulted in similar reproductive performance in anestrous cows and untreated cyclic cows inseminated at a spontaneous estrus.

Administration, Intravaginal↗
PubMed2006

Conception rates to artificial insemination in primiparous, suckled cows exposed to the biostimulatory effect of bulls before and during a gonadotropin-releasing hormone-based estrus synchronization protocol.

The objective of these studies was to evaluate whether exposing primiparous, suckled beef cows to the biostimulatory effect of bulls alters breeding performance associated with an estrus synchronization protocol that included GnRH followed 7 d later by PGF(2alpha) and fixed-time AI (TAI). This was a composite analysis of 3 experiments that evaluated (1) the effects of bull exposure at different days after calving (yr 1); (2) the biostimulatory effects of bull excretory products (yr 2); and (3) the biostimulatory effects of familiar and unfamiliar bulls (yr 3) on the resumption of ovarian cycling activity. In all studies, cows were exposed (biostimulated; n = 94) or not exposed (nonbiostimulated; n = 67) to bulls or excretory products of bulls for at least 60 d before the beginning of the estrus synchronization protocol. Average calving day did not differ among years and was 52 +/- 5 d. Year did not affect the proportions of biostimulated and nonbiostimulated cows that were cycling at the beginning of the estrus synchronization protocol; however, a greater (P < 0.001) proportion of biostimulated than nonbiostimulated cows were cycling at this time. In each year, cows were given GnRH followed by PGF(2alpha) 7 d later. Cows were observed for estrus twice daily (am and pm) after PGF(2alpha). Cows that exhibited estrus before 54, 60, and 64 h after PGF(2alpha) were inseminated by AI 12 h later in yr 1, 2, and 3, respectively. Cows that failed to show estrus were given GnRH and TAI at 62, 72, and 72 h after PGF(2alpha) in yr 1, 2, and 3, respectively. Conception rates were determined by transrectal ultrasonography 35 d after TAI in each year. The percentages of cows that exhibited estrus after PGF(2alpha) and before TAI, the interval from PGF(2alpha) to estrus, and the percentages of cows inseminated 12 h after estrus or at TAI did not differ between biostimulated and nonbiostimulated cows and were 51%, 54.7 +/- 7.3 h, 35%, and 65%, respectively. Conception rates for cows bred by AI 12 h after estrus did not differ between biostimulated and nonbiostimulated cows; however, the TAI conception rate was greater (P < 0.05) for biostimulated cows (57.6%) than for nonbiostimulated cows (35.6%). We conclude that TAI conception rates in an estrus synchronization protocol that includes GnRH followed 7 d later by PGF(2alpha) may be improved by the biostimulatory effect of bulls in postpartum, primiparous cows.

Animals↗
PubMed1986

Nonpuberal estrus in beef heifers.

The frequency of occurrence of behavioral estrus without subsequent development of functional luteal tissue (termed nonpuberal estrus, NPE), was determined in 43 Simmental X Hereford-Brahman heifers. Blood samples were collected weekly from the start of the study to first behavioral estrus and then daily from d 1 (d 0 = estrus) through d 14 following first and subsequently observed estrous behaviors. All blood samples were analyzed for serum progesterone (P4) concentrations by radioimmunoassay. More heifers (62.8%) exhibited NPE than had luteal development after their first behavioral estrus (37.2%). There was a tendency for fewer light-weight heifers (less than or equal to 240 kg at the start of the experiment) to exhibit a puberal first estrus compared with the heavy-weight (greater than 240 kg at the start of the experiment) heifers (31.2% vs 68.8%, respectively; P = .12). Heifers that had a puberal first estrus were older (376 +/- 12 d vs 334 +/- 9 d, P less than .05) compared with heifers that had NPE. Weight at first behavioral estrus was similar between heifers that had a puberal first estrus and those that had NPE (298 +/- 8 kg and 289 +/- 6 kg, respectively). More heifers that had a puberal first estrus also had an elevation in serum P4 concentrations before that first estrus (64.3% vs 20.0%, P less than .05), and the serum P4 elevation was greater (2.5 +/- .4 ng vs 1.2 +/- .1 ng, P less than .05) than heifers that had NPE. We have concluded from these results that NPE is a common occurrence in heifers approaching puberty.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Timing of preovulatory endocrine events, estrus and ovulation in Brahman x Hereford females synchronized with norgestomet and estradiol valerate.

The purpose of these studies was to investigate the pattern and timing of preovulatory endocrine events, estrus and ovulation in Brahman X Hereford (F1) heifers synchronized with norgestomet and estradiol valerate. In Exp. 1, 66 nulliparous and 191 primiparous Brahman X Hereford (F1) heifers were used to estimate the interval from norgestomet implant removal to onset of estrus. The mean interval from implant removal to onset of estrus was 29.8 +/- .5 h, with 80.9% exhibiting estrus within 48 h. Endocrine and reproductive characteristics were examined in detail during Exp. 2 with 37 primiparous heifers. Continuous observation for estrus, 6-h or 2-h blood sampling and ovarian palpation per rectum were employed. All animals were artificially inseminated 48 h after implant removal. Mean interval from implant removal to onset of estrus and to onset of the luteinizing hormone (LH) surge were closely related (r = .91; P less than .0001). Mean intervals from implant removal to ovulation, onset of estrus to ovulation and onset of LH surge to ovulation were 59.1 +/- 2.5 h, 23.3 +/- 1.4 h and 23.1 +/- 1.6 h, respectively. Approximately 73% of heifers exhibited estrus within 54 h after implant removal (optimal timing); conception rate was 59.3% in this subgroup. Conception rate of heifers that did not exhibit estrus within 54 h after implant removal or exhibited an LH surge later than 12 h after estrus (delayed timing) was 10%. Assessment of plasma estradiol-17 beta concentrations suggested that retarded selection and(or) maturation of the preovulatory follicle following implant removal delayed estrus and lowered conception in up to 28% of females timed-inseminated at 48 h.

Animals↗
PubMed1989

Relationship between body fat and postweaning interval to estrus in primiparous sows.

Twenty-two primiparous Yorkshire sows were used to determine whether a minimal threshold of body fat exists below which the return to estrus is delayed. A second objective was to examine the relationship between body fat and interval from weaning to estrus in restricted-fed sows. During lactation (28 d), sows received 7, 9, 11 or 13 Mcal of ME daily to produce a range of sow body fatness at weaning. Intake of all dietary essentials except ME was similar for all sows. Litter size was adjusted to 10 pigs for all sows by d 3 postpartum. Each day from weaning to estrus, sows received 110 kcal ME per kg metabolic body weight plus 1,359 kcal ME per sow. Body fat was estimated at weaning and at first postweaning estrus by deuterium oxide dilution. Last rib backfat depth was determined ultrasonically 24 h postpartum and at weaning. Irrespective of dietary ME intake, percentage body fat at weaning (R2 = .24; P less than .05) and first postweaning estrus (R2 = .03; P greater than .50) accounted for only a small portion of variation in interval from weaning to estrus. Likewise, loss of backfat depth during lactation was not an accurate predictor of interval from weaning to estrus (R2 = .24; P less than .05). The low coefficients of determination (less than .25) suggest that body fat is a minor controller of postweaning interval to estrus. In contrast, dietary ME intake during lactation accounted for the largest portion of the variation (R2; = .48; P less than .01) in postweaning interval to estrus. We conclude that timing of postweaning estrus in primiparous sows is not dependent on a minimal threshold of body fat. Furthermore, effects of lactational ME intake on the postweaning interval to estrus are more pronounced than the effects of body fat.

Adipose Tissue↗
PubMed1977

Variation in physical activity as an indication of estrus in dairy cows.

Pedometers were used to measure daily physical activity of cows to determine if variation related to estrus was great enough to be useful in estrus detection. Forty cows in free stalls and 28 cows in comfort stalls were studied during the breeding period after calving. Pedometers were enclosed in specially designed cases and attached to a cow's lower rear leg with a plastic ankle strap. Readings were taken twice daily when the cows were milked in a milking parlor. Data from free stalls were available for 5163 intervals between milkings, 87 of which were periods of estrus. Activity definitely increased at the time of estrus; cows were about four times as active during estrus as they were when not in estrus. Data from comfort stalls were available for 2433 intervals between milkings, 39 of which were periods of estrus. Cows in comfort stalls were about 2.75 times as active during estrus as when not in estrus. There was relatively little variation within cow in activity from day to day among cows not in estrus. Activity monitoring appears to have potential as an aid in estrus detection.

Animals↗
PubMed1985

Serum estradiol-17beta concentrations during spontaneous silent estrus and after prostaglandin treatment in the mare.

Serum estradiol-17beta concentrations were determined during silent estrus in the mare. Relationships between serum estradiol-17beta concentration, corpus luteum regression, follicular development, ovulation, prostaglandin treatment and behavioral estrus were investigated. The expression of behavioral estrus was found to be related to the patterns of progesterone and estradiol-17beta secretion during the periovulatory period. When compared to normal estrous cycles, silent estrus was accompanied by a significantly lower maximum serum estradiol-17beta concentration (47.8 vs 34.6 pg/ml), a significantly longer interval from maximum estradiol-17beta concentration to ovulation (1.7 vs 4.0 days), and a significantly shorter interval from corpus luteum regression to ovulation (5.3 vs 2.8 days). Silent estrus following prostaglandin treatment was related to a significantly shorter interval from prostaglandin treatment to ovulation (3.6 +/- 0.4 days) than from normal corpus luteum regression to ovulation (5.3 +/- 0.3 days). Silent estrus appeared to be related to changes in follicular estradiol-17beta secretion and to the pattern of its secretion as related to regression of the corpus luteum. There appeared to be not only less estradiol-17beta present, but also less time available after luteal regression for it to interact with the central nervous system to elicit the changes necessary to cause behavioral estrus. There fore, unusual relationships between luteal function and folliculogenesis can result in one type of silent estrus. Significant correlations (P<0.05) were found between follicle size and serum estradiol-17beta concentration whenever behavioral estrus occurred [follicle diameter in mm = 0.96 (serum estradiol-17beta in pg/ml) + 6.08 and 0.73 (serum estradiol-17beta + 13.32 for control and normal estrus following prostaglandin treatment groups, respectively]. During silent estrus, however, no significant correlations between follicle size and serum estradiol-17beta concentration were observed.

Journal Article↗
PubMed1985

Insemination management for a one-injection prostaglandin F(2)alpha synchronization system. II. One versus two inseminations following detection of estrus.

Following detection of estrus in an estrus synchronization system, 216 dairy heifers were inseminated (A.I.) randomly either soon after detected estrus (1X) or soon after detected estrus and again 10 to 12 h later (2X). Average h from detection of estrus to A.I. was 1.8+/-0 for 1X and 1.1+/-0 and 11.1+/-0.4 for 2X. During the regimen, heifers were checked visually for estrus daily for five consecutive days with 16.0 and 17.3% showing estrus and receiving A.I. in the 1X and 2X groups, respectively. Those not seen in estrus were injected with 25 mg PGF(2)alpha with observations for estrus and A.I. continuing for five more days. Response rates as indicated by estrus following prostaglandin F(2)alpha (PGF(2)alpha) were 74.7 and 75.8% for 1X and 2X, respectively. Percentages of heifers in estrus <24, 25 to 48, 49 to 72, 73 to 96 and >96 h after PGF(2)alpha were 3.7, 22.8, 47.1, 15.4 and 11.0, respectively. Based on rectal palpation for pregnancy between 45 and 60 days after A.I., conception rates of 70.2% for 1X and 68.6% for 2X did not differ significantly (P>0.05). Progesterone concentrations at injection for heifers not responding to PGF(2)alpha were lower than was seen in responding heifers (2.7 vs 5.8 ng/ml) (P<0.01). Data from the present experiment supports the conclusion of an earlier experiment that satisfactory conception can be achieved with a single, established daily insemination period.

Journal Article↗
PubMed1993

Effects of work and diet on progesterone secretion, short luteal phases and ovulations without estrus in postpartum F1 crossbred dairy cows.

The effects of work and diet supplementation on progesterone secretion and on incidence of short luteal phases and ovulations without estrus was investigated in 40 postpartum F(1) crossbred dairy cows. These cows were allocated to 1 of 4 treatment groups: Group SPNW, supplement-nonworking; Group SPW, supplement-working; Group NSNW, nonsupplement-nonworking; and Group NSW, nonsupplement-working. After calving, working cows pulled sledges with a load of 300 to 450 Newtons(N); 4 hours per day 4 days per week, for a total of 100 days over a 1-year period. All cows were fed natural grass hay ad libitum while the supplemented cows were fed 3 kg of concentrate per head per day. The proportion of cows which showed behavioral estrus by 1 year post partum was 100, 100, 60 and 20% for Group SPNW, SPW, NSNW and NSW cows, respectively. Based on plasma progesterone concentrations, ovulation started 62 days earlier than onset of behavioral estrus. A total of 73 ovulations occurred by 1 year post partum. Forty-nine (67.1%) and 26 (32.9%) ovulations occurred in the supplemented and nonsupplemented cows while 33 (45.2%) and 40 (54.8%) ovulations occurred in the working and nonworking cows, respectively. Of the total ovulations, 26 (35.6%) were not associated with behavioral signs of estrus and occurred in 13 (32.5%) cows. The incidence of ovulation without estrus was higher (P<0.05) in working (42.4%) than in nonworking (30%) cows and in nonsupplemented (41.7%) than in supplemented (32.7%) cows. Short luteal phases occurred in 32.5% of the cows before the establishment of normal estrous cycles. In working cows, diet supplementation off-set the negative effect of work on the onset of estrus and conception. However, a relatively higher number of cows in Group SPW had ovulations without estrus before a normal estrous cycle was established. The incidence of short luteal phases or ovulations without estrus did not influence the pregnancy rate in subsequent normal estrus periods. In conclusion, in the supplemented cows, work did not influence the proportion of cows showing estrus and conceiving, but it significantly delayed the postpartum anestrus interval. In the nonsupplemented cows, reproductive activity was impaired in both working and nonworking cows, but was pronounced in working cows. However, once pregnancy was established there was no effect of work on the maintenance of pregnancy. Our study shows that with appropriate feeding regimens lactating crossbred cows could be used for draught purposes without any detrimental effects on fertility, but calving intervals would be extended. Finally, the physiological mechanisms involved in anestrus and ovulations without estrus and the significance of such phenomena in affecting postpartum reproductive performance and fertility in working cows require further investigation.

Journal Article↗
PubMed2002

Reproductive performance of early-weaned female swine according to their estrus profile and frequency of artificial insemination.

We determined the estrus profile (weaning-to-estrus interval (WEI), estrus duration (ED), and frequency of estrus per detection period) in 184 female swine and estimated the effect of the WEI, ED and frequency of artificial insemination (AI) on farrowing rate (FR) and litter size. Estrus detection was done at 8:30 a.m. and 5:00 p.m. The WEI was categorized as short (<100 h), medium (100-120 h) and long (>120 h). The ED was categorized as short (<60 h), medium (60-72 h) and long (>72 h). Mean lactation length was 14.6 days, mean WEI was 124.5 h and mean ED was 69 h. In each weaning group, females received either one or two AI, following a breeding schedule based on the estrus profile. In single-mated females, Al was performed 36 h after the beginning of estrus. In double-mated females, the first AI was done 24 h after the beginning of estrus and the second AI occurred 12 h later. The period of estrus detection had no effect (P > 0.05) on WEI, ED, FR, total born (TB) and live born litter size (LB). Mean FR was 82.6%, mean TB was 10.0% and mean LB was 9.2%. Mean ED was shorter (P < 0.03) for females having medium and long WEI (67.0 and 65.4 h, respectively) than for those having short WEI (72.2 h). A linear regression analysis identified a weak (R2 = 0.02) but significant negative association between ED and WEI (P = 0.05). The WEI did not influence FR (P > 0.05). Total litter size for females having short WEI (9.4) was lower (P < 0.03) than for those having long WEI (10.4). Also, LB for females having medium and long WEI (9.7-9.8) was higher (P < 0.05) than for those having short WEI (8.7). AI frequency had no effect on FR (P > 0.05). TB and LB litter size were lower (P < 0.05) for single-mated females (9.6 and 9.0, respectively) than for double-mated females (10.7 and 9.6, respectively). Double Al was associated with higher subsequent litter size. However, breeding schedules based only on estrus profile may not be precise in determining ideal breeding time, since females having short WEI had the longest ED and produced the lowest litter size.

Animals↗
PubMed1982

Estrous synchronization and fertility in gilts after 14- or 18-day feeding of altrenogest beginning at estrus or diestrus.

A synthetic progestogen (altrenogest) was used to synchronize estrus in 160 Yorkshire and Duroc x Yorkshire gilts (6 to 11 mo old) in four trials. Gilts were fed 15 mg altrenogest for 14 or 18 d beginning either at or near estrus (d -1, 0, +1 or +2) or at diestrus (d +3 to +21). Mean intervals to estrus after treatment did not differ between 14- and 18-d treatments (5.4 +/- .1 vs 5.3 +/- .1 d, respectively), but were slightly longer (P less than .01) in gilts beginning treatment at or near estrus than in diestrus (5.6 +/- .1 vs 5.2 +/- .1, respectively). Average intervals to estrus were similar between treatment groups and among stages of the cycle even though more gilts (P less than .01) beginning treatment at estrus had serum progesterone concentrations greater than 2 ng/ml at the end of progestogen treatment. Although more 18- than 14-d treated gilts (P less than .05) were in estrus on d 5 post-treatment, proportions in estrus from 3 to 10 d post-treatment were similar (greater than 98%). Neither stage of estrous cycle at onset of treatment nor duration of progestogen treatment affected percentages of gilts farrowing (greater than 73%), average gestation length (116.5 d), or total (10.3), live (9.7) and dead (.6) pigs at birth after artificial insemination at the post-treatment estrus. We concluded that 14-d feeding of altrenogest effectively synchronized fertile estrus in gilts regardless of stage of estrous cycle at the onset of progestogen treatment. Although 18-d treatment of gilts with altrenogest improved estrous synchronization precision compared to 14-d treatment, there was no advantage of the 18-d treatment for subsequent farrowing responses.

Administration, Oral↗
PubMed2006

Serum estradiol-17beta, vaginal cytology and vulval appearance as predictors of estrus cyclicity in the female collared peccary (Tayassu tajacu) from the eastern Amazon region.

This report describes the characteristics of estrus in the female collared peccary (Tayassu tajacu) from the eastern Amazon. Two consecutive experiments were performed. The objective of the first experiment was to assess the efficacy of estrus diagnosis by serum estradiol-17beta measurements, vaginal cytology and vulval appearance. The second experiment was designed to evaluate the effectiveness of these features for predicting the period of mating acceptance. In Experiment 1, we monitored 56 presumptive estruses in 14 captive females. Estrus was characterized by the reddish and tumescent appearance of the vulva, the presence of vaginal mucus and vaginal opening, which persisted for 4, 4, 2, and 2 days, respectively. In vaginal smears, superficial plus intermediate cells became predominant (accounting for 60% of all cells) for a 4-day period, from 2 days before the estradiol-17beta peak. Superficial cells did not attain their maximum density (45% of all cells) until approximately 1 day before the serum estradiol-17beta peak. Following estrus, superficial and intermediate cells were notably reduced and the appearance of the vulval appearance was characterized by a pale, non-tumescent vulva and vaginal closure. A complete concordance in estrus diagnosis by the 3 methodologies was observed in 35 (62.5%) of the total 56 estrus predictions. In Experiment 2, mating was confirmed in 10 out of the 14 cyclic females. Sexual receptivity was observed in the last third of the period during which secondary estrus signs were shown. In conclusion, examining the vulval appearance and taking a vaginal smear constitutes a useful method of detecting estrus and predicting the period of male acceptance of the collared peccary female. Estrus was indicated by a predominance of superficial cells, and a proportion of superficial plus intermediate cells higher than 60% in the vaginal smear.

Animals↗
PubMed2006

The effects of a low dose of cabergoline on induction of estrus and pregnancy rates in anestrous bitches.

This is the first report of successful induction of normal estrus and ovulation in breeder bitches with as a low dose as 0.6 microg/kg/day of cabergoline formulation marketed for use in women. Sixty-one pure breed bitches from various breeds were used in the study at their already determined periods of anestrus. Twenty-four dogs formed the control group, while 37 bitches were administered with two different doses of cabergoline (recommended dose group, n=10, 5 microg/kg/day and low dose group, n=27, 0.6 microg/kg/day). Induced estrus rates and mean treatment and proestrus durations of dogs in these two dose groups were compared. At the second phase of the study, the effects of 500 IU human chorionic gonadotropin (hCG) administered on days 1 and 3 of estrus induced by the low dose of cabergoline, on the duration of behavioral estrus, ovulation rates, pregnancy rates and the number of offspring were investigated. For this purpose, the dogs with signs of proestrus (22/27) following the treatment in the low dose group were assigned into two subgroups. Five hundred IU of hCG (Pregnyl, Organon, Turkey) was intramuscularly administered to eight of these dogs [low dose (hCG+) group] on days 1 and 3 of estrus. The remaining 14 dogs were not treated with hCG [low dose (hCG-) group]. An aqueous solution of cabergoline (Dostinex, Pharmacia, Italy) was orally administered until 2 day after the onset of proestrus or for a maximum of 42 days. Blood samples were taken daily from all treatment and 11 control bitches during the first five days of behavioral estrus to measure progesterone concentrations. In the recommended dose and low dose groups, estrus was induced between days 8-45 and 4-48 (mean: 23.63+/-14.33 and 24.41+/-14.31 days), in the ratio of 80.0 and 81.5%, respectively (p>0.05). In both dose groups, post-treatment interestrous intervals were significantly shorter than both those of the control group and their own pre-treatment interestrous intervals (p<0.05). Ovulation rates, pregnancy rates and mean number of offspring delivered by the dogs in the recommended dose, low dose (hCG-), low dose (hCG+) and control groups were found to be similar (p>0.05). However, the mean duration of behavioral estrus of the dogs in the low dose (hCG+) group was found to be significantly longer compared to dogs in all other groups (p<0.05). In both dose groups, no correlation could be found between the anestrus stages and treatment durations (p>0.05). Shortly, it has been concluded from the study that (1) normal and fertile estrus can be induced more economically in bitches during different stages of anestrus using as a low dose of 0.6 microg/kg of cabergoline formulation marketed for use in women, and that (2) hCG injections on days 1 and 3 of the estrus induced by this method has no positive effects on the ovulation rates, pregnancy rates and the number of offspring per pregnancy.

Anestrus↗
PubMed2000

The time of ovulation in relation to estrus duration in gilts.

The objective of this study was to determine time of ovulation, monitored by transcutaneous ultrasonography, relative to the duration of estrus in gilts. We exposed 92 cyclic gilts, Camborough x Canabrid terminal line, at Day 19 of their third estrous cycle to vasectomized boars every 6 h for the detection estrus. Transcutaneous ultrasonography was performed every 6 h, starting 24 h after the onset estrus, to determine time of ovulation. Estrus duration was, on average, 52.6 h (range: 30 to 72 h), and ovulation occurred between 30 and 60 h after the onset of estrus (mean: 44 h), about 85 % of the way through the estrus period. The time of ovulation during estrus was dependent on the duration of estrus (Time of ovulation = (duration of estrus) x 0.409 + 22.7; r = 0.57, P = 0.0001). Prediction of the time of ovulation in relation to duration of estrus is important for determining the optimal time for inseminating gilts. This knowledge would contribute to an improvement in the fertilization rate and in reproductive efficiency of the breeding herd.

Animals↗