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PubMed1981

Interval to estrus in sows and performance of pigs after alteration of litter size during late lactation.

The effects of altering litter size during the 5 days before weaning on interval to estrus of sows and postweaning performance of pigs were examined. Litters averaged 8.3 +/- .7 pigs from parturition until 5 days before weaning. Litters were then adjusted so that sows (five per group) nursed small- (three pigs), average- (eight pigs) or large-sized (13 to 14 pigs) litters during the last 5 days of lactation. Weaning occurred 27.4 +/- .7 days postpartum. Interval from weaning to estrus (days) and duration of estrus (hours) for sows that weaned small-, average- and large- sized litters averaged 1.1 +/- .4 and 38 +/- 4, 4.1 +/- .4 and 60 +/- 4, an 4.0 +/- .4 and 61 +/- 4, respectively. Interval to estrus and to ovulation and duration of estrus were decreased (P less than .01) in sows that nursed only three pigs before weaning. Pigs weaned from foster sows weighed less (P less than .05) at weaning than pigs weaned from their dams. However, by 3 weeks after weaning, body weights were similar. Body weight at weaning and at 3 weeks postweaning and average daily gains during the 3 weeks after weaning were similar for pigs weaned from small-, average- and large-sized litters. Reducing the litter size before weaning resulted in earlier postweaning estrus and ovulation and had no adverse effects on the performance of weanling pigs.

Animals↗
PubMed1985

Breed differences in return to estrus after PGF2 alpha-induced abortions in swine.

Fifty-seven Duroc, 41 Landrace and 38 Yorkshire purebred sows in d 10 to 53 of pregnancy were aborted to synchronize estrus by using prostaglandin F2 alpha (PGF2 alpha). Breed differences in time between injection of two 10-mg doses of PGF2 alpha and return to estrus were observed in these three breeds of pregnant sows during two breeding seasons. Duroc sows returned to estrus .9 d faster (P less than .01) than Yorkshire and 1.3 d faster (P less than .01) than Landrace sows. Seasonal differences were also observed. The mean days from injection to estrus were 1.8 d fewer (P less than .01) for the spring season than in the fall season. All sows expressed estrus 5 to 11 d after injection. Normal gestation, parturition and piglet survival were observed in the sows after the treatment. Genetic differences in response to induced abortion and return to estrus could have implications in planned breeding and farrowing systems.

Abortifacient Agents↗
PubMed1987

Progesterone concentrations in beef heifers bred at puberty or third estrus.

Peripheral serum progesterone concentrations were evaluated in beef heifers following breeding collected on d 6 +/- 1, 9 +/- 1 collected on d 6 +/- 1, 9 +/- 1 and 12 +/- 1 (estrus = d 0) after the puberal estrus of all heifers and after the third estrus of E3 heifers. Progesterone concentrations were higher (P less than .05) for heifers in E1 compared with heifers in E3 on d 6, 9 and 12 after breeding to a fertile bull. Progesterone concentrations on d 6, 9 and 12 did not differ (P greater than .10) between pregnant heifers in E1 and E3; however, non-pregnant heifers in E1 had higher (P less than .05) concentrations of progesterone compared with non-pregnant heifers in E3 on each day. Concentrations of progesterone did not differ (P greater than .10) between non-pregnant heifers in E1 and heifers of E3 during their puberal cycle. Pregnant heifers in E1 and E3 had higher (P less than .05) concentrations of progesterone on each day than non-pregnant heifers in their respective treatments. There were no interactions (P greater than .10) between treatment, pregnancy status and day-of-estrous cycle for concentrations of progesterone. Results of this study indicated that luteal function differed between heifers that failed to conceive at their puberal estrus and heifers that failed to conceive at third estrus. However, concentrations of progesterone did not differ between heifers that conceived at puberal or third estrus. The relationship of changes in luteal function from the puberal through the third estrous cycle and pregnancy is not clear.

Animals↗
PubMed1988

Postpartum reproductive performance in crude protein-restricted beef cows: return to estrus and conception.

A study was conducted to evaluate the effect of a deficiency in dietary crude protein intake on postpartum reproductive performance of first-calf beef cows. Forty primigravid Hereford heifers were randomly assigned to two groups that were fed isocaloric (100% NRC requirements) diets containing .96 (adequate) or .32 (deficient) kg crude protein per head daily. Animals were individually fed from 150 d prepartum to 40 d postpartum and then were group-fed until the end of the experiment at 110 d postpartum. Total nutrient intake was increased by 33% at time of parturition to meet lactation requirements. Animals were artificially inseminated between 45 and 110 d postpartum when they showed estrus. Eighty-nine percent of those fed adequate protein showed estrus, whereas only 63% of protein-restricted heifers exhibited estrus (P less than .05). First-service conception (P less than .05; 71 vs 25%) and overall pregnancy rates (P less than .05; 74 vs 32%) were lower in protein-restricted heifers. Compared with those fed adequately, protein-restricted heifers had a tendency for longer intervals to first estrus (P less than .08; 75 vs 86 d), to first service (P less than .09; 76 vs 87 d) and to conception (P less than .09; 81 vs 92 d). Regardless of diet, weight at first estrus, weight at first service and average daily gain to 40 d postpartum were negatively correlated (P less than .01) with length of intervals from parturition to first estrus and first service.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Effects of GnRH administered to cows at the onset of estrus on timing of ovulation, endocrine responses, and conception.

Two experiments examined effects of GnRH administered within 3 h after onset of estrus (OE) on ovulation and conception in dairy cows. In experiment 1, 46 cows received either saline, 250 microg of GnRH, or 10 microg of the GnRH analogue, Buserelin. Cows were observed for estrus, blood samples were collected, and ovulations were monitored by ultrasound. In controls, 76% of cows had intervals from estrus to ovulation of < or = 30 h and 24% had intervals > 30 h. Treatment with either GnRH or GnRH analogue (data combined) increased magnitude of LH surges and decreased intervals from estrus to LH surge or to ovulation. Treated cows all ovulated < or = 30 h after OE. Among control cows, plasma estradiol concentrations before estrus correlated positively with amplitudes of LH surges. Higher plasma progesterone was observed in the subsequent estrous cycle in GnRH-treated cows compared to control cows with delayed ovulations. Experiment 2 included 152 primiparous and 211 multiparous cows in summer and winter. Injection of GnRH analogue at OE increased conception rates (CR) from 41.3 to 55.5% across seasons. In summer, GnRH treatment increased CR from 35.1 to 51.6%. Across seasons, GnRH increased CR from 36.0 to 61.5% in cows with lower body condition at insemination and GnRH increased CR (63.2 vs. 42.2%) in primiparous cows compared to controls. Use of GnRH eliminated differences in CR for cows inseminated early or late relative to OE and increased CR in cows having postpartum reproductive disorders. In conclusion, GnRH at onset of estrus increased LH surges, prevented delayed ovulation, and may increase subsequent progesterone concentrations. Treatments with GnRH increased conception in primiparous cows, during summer, and in cows with lower body condition.

Animals↗
PubMed2006

Endocrine alterations associated with extended time interval between estrus and ovulation in high-yield dairy cows.

Short fertile half-lives of the male and female gametes in the female tract necessitate accurate timing of artificial insemination. We examined the possible association between extension of the estrus to ovulation (E-O) interval and alterations in concentrations of estradiol, progesterone, and the preovulatory LH surge before estrus and ovulation. High-yielding Holstein cows (n = 74 from a total of 106) were synchronized and were examined around the time of the subsequent estrus. They were observed continuously for estrual behavior. Blood samples were collected before and after estrus, and ultrasound checks for ovulation were made every 4 h. About three-quarters of the cows exhibited short (but normal) E-O intervals of 22 to 25 h (25%) or normal intervals of 25 to 30 h (47%); 17% of them displayed a long (but normal) E-O interval of 31 to 35 h, and about 10% exhibited a very long E-O interval of 35 to 50 h. Extended E-O interval comprised estrus-to-LH surge and LH surge-to-ovulation intervals that were both longer than normal. Pronounced changes in hormonal concentrations were noted before ovulation in the very long E-O interval group of cows: progesterone and estradiol concentrations were reduced, and the preovulatory LH peak surge was markedly less than in the other 3 groups. Postovulation progesterone concentrations during the midluteal phase were lesser in the very long and the long E-O interval groups compared with those in the short and normal interval groups. Season, parity, milk yield, and body condition did not affect the estrus to LH surge, LH surge to ovulation, and E-O intervals. The results indicate an association between preovulatory-reduced estradiol concentrations and a small preovulatory LH surge, on the one hand, and an extended E-O interval, on the other hand. Delayed ovulation could cause nonoptimal timing of AI, a less than normal preovulatory LH surge that may be associated with suboptimal maturation of the oocyte before ovulation, or reduced progesterone concentrations before and after ovulation. All may be factors associated with poor fertility in cows with a very long E-O interval.

Animals↗
PubMed1986

Indicators of estrus in Holstein cows housed in tie stalls.

Fourteen lactating Holstein cows were observed between 40 and 150 d postpartum to identify physiological and behavioral changes associated with the day of estrus. Ovulation was predicted on 29 occasions from changes in concentrations of progesterone in milk. Estrus was detected by casual observation by the herdsperson 22 times, but only 13 were detected during a daily 30-min exercise period with an androgenized heifer. Morning milk yield and daily feed intake decreased on the day of estrus. Rectal temperature, afternoon milk yield, and number of changes in postural position during the previous night increased on the day of estrus. When an increase greater than one standard deviation from the within-cow mean was considered evidence of estrus, all measures indicated more false positives than true positives. A combination of elevated temperature, increased changes of postural position at night, and depressed feed intake accurately predicted estrus, but only on 6 occasions out of 29.

Animals↗
PubMed1990

Effectiveness of rump-mounted devices and androgenized females for detection of estrus in dairy cattle.

Detection of estrus was evaluated in 1124 estrous cycles for the effectiveness of rump-mounted devices and androgenized females equipped with chin-ball markers. Estrous number, location, type of detection method (compared with visual observation of estrus), and milk progesterone influenced standing behavior. Rates of disagreement with visual observation of estrus were 13.2, 17.0, and 18.5% for Kamar, Hot Flash, and the two devices used simultaneously. Frequency of observed standing behavior was greater with fourth and subsequent estrous periods. Percentage of high milk progesterone during suspected estrus for cows inseminated was 3.8% for controls, 11.0% for Kamar cattle, 18.5% for Hot Flash cattle, and 12.6% when both devices were used. Androgenized cattle equipped with chin-ball markers marked 47% of the cattle observed in estrus but no cows with high milk progesterone. Combination of rump-mounted devices and androgenized females increased the percentage of estrous detection by 1.3 to 6.2% compared with device or androgenized female used alone. Loss rates of rump-mounted devices exceeded 40%. High milk progesterone at estrus was associated with lower fertility.

Androgens↗
PubMed1993

Automated electronic activity measurement for detection of estrus in dairy cattle.

Two trials were conducted to characterize the performance of an automated electronic activity tag system as an aid for detection of estrus in dairy cattle. In trial 1, activity tags were attached to the rear leg of 24 cows at approximately 35 d postpartum and remained attached until pregnancy. Data collection included 66 periods of predicted estrus (cyclic periods of 18 to 24 d prior to the date of pregnancy). A summary of the data recorded in the activity tags was transmitted telemetrically to a personal computer at each milking via stationary antenna in the milking parlor. An electronic flag used an increased activity ratio to determine the ratio of activity in a test period of the previous 12 h to activity in the same 12 h during the 2 d previous to the test period, thus indicating estrus. Activity patterns were characterized from data recorded on the tags at 2-h intervals. The tag detected 74% of predicted periods of estrus versus 58% reported by herders. An increased activity ratio for at least 4 consecutive h reduced false-positive designations. In trial 2, activity tags were attached to front and rear legs on five cows, and activity patterns from the two sites were compared for 2 mo. Patterns of activity were similar from tags attached at either site, and the sites were not different in their discrimination between periods in which estrus did or did not occur. The activity tag system was an effective practical tool to detect estrus.

Activity Cycles↗
PubMed1994

The estrus detection problem: new concepts, technologies, and possibilities.

The single most important problem limiting high reproductive efficiency in the national dairy herd is poor detection of estrus. Failure to detect estrus or erroneous diagnosis of estrus results in an estimated annual loss of over $300 million to the dairy industry in the US. New technologies for the solution of this problem must be more effective than visual observation and aids currently used to detect estrus. Ideally, technologies that provide the solution for detection problems should provide the following: continuous (24 h/d) surveillance of the cow, accurate and automatic identification of cows in estrus, operation for the productive lifetime of the cow, minimized labor requirements, and high accuracy in identifying the appropriate physiologic or behavioral events that correlate highly with ovulation. New approaches are aimed at providing automation of detection of estrus using electronic technology. Pedometry, implantable impedance sensors, and surface-applied and implantable pressure sensors are in various stages of development and use.

Animals↗
PubMed1998

An electronic nose to detect changes in perineal odors associated with estrus in the cow.

Changes in perineal odor as estrus is approached could form the basis of a new method of estrus detection. Perineal odor of cyclic cows was monitored. Estrus was identified using ovarian ultrasound, behavioral observations, and plasma assay for progesterone and estradiol. Samples were taken from the dorsal lateral perineal (perivulval) area using cotton bud swabs and presented to an electronic nose. Twelve conducting polymer sensors were used to quantify odor in terms of a change in sensor resistance. Preliminary data (Experiment 1) indicate that the odor signals between the luteal phase and estrus could be distinguished for a group of five cows. In Experiment 2, samples were obtained daily from eight cows during the midluteal phase and from d -2 to d 8 of the cycle (d 0 = day of estrus, induced using cloprostenol). Seven of the eight cows cycled normally. Of the 12 sensors, 7 showed a significant change in resistance that was dependent on the day of the estrous cycle. Basal values were those taken in the luteal phase; values peaked on d -1, rose transiently on d 3, and returned to baseline on d 5 to 6. This pattern is strongly correlated with plasma estradiol concentration. The use of artificial olfaction could enable more accurate detection of estrus and has the potential to increase fertility in cows.

Animals↗
PubMed1990

[Recovery and light microscopic evaluation of follicular oocytes of swine and relationship between the degeneration rate of oocytes and the estrus phase].

Cumulus-oocyte complexes were recovered from 25 gilts by aspiration of follicular fluid or cutting of follicles from all Graafian follicles of greater than or equal to 3 mm in diameter during diestrus, proestrus or estrus. In 5 gilts the oocytes were collected post ovulation by flushing of oviducts. The recovery rate of follicular oocytes differed between 75.5% during the late diestrus (days 13-17) and 43.5% during the proestrus (days 18-21). During the proestrus and on day 1 of the estrus the recovery of oocytes was more difficult as a result of the higher viscosity of follicular fluid and the mucification of cumulus-oocyte complexes. The degeneration rate of oocytes was high during the diestrus with a peak at the time of regression of corpora lutea. From diestrus to the estrus the degeneration rate decreased. Following degeneration rates were found in the oocytes during the cycle: days 7-12: 38.8%, days 13-17: 50.0%, days 18-21: 29.6%, day 1 of the estrus: 10.8%, day 2 of the estrus ante ovulation: 11.8%, day 2 of the estrus post ovulation: 6.2%. Signs of degeneration were: Loss of cumulus cells (during diestrus and proestrus), damaged zona pellucida, enlargement of perivitelline space, deformation of oocyte, alteration of structure of the ooplasm, diameter of vitellus less than 100 microns. It was concluded that the selection of dominant follicles takes place in pigs during a long time of the cycle, especially during the diestrus. There were not any indications of a 2-wave hypothesis of follicular growth during the cycle in pig.

Animals↗
PubMed1989

[The appearance of ovarian cysts in young sows after treatment with gonadotropin preparations for estrus induction].

In 72 (46%) of 155 gilts discarded for genetic reasons after performance testing and housed under fattening conditions no heat could have been detected during the first 30 days. The gilts were assigned alternatingly to a control group and four different treatments of delayed puberty. The induction of puberty was carried out by injections of 1000 iu PMSG, 400 iu HCG and 2 mg oestradiol benzoate, 400 iu PMSG and 200 iu HCG and 800 iu PMSG and 400 iu HCG. If there was no estrus gilts were slaughtered 12 days later for examination of the ovaries. Those coming into estrus were slaughtered 8 days after disappearance of estrus. Estrus could be induced in 69 to 94% of the gilts, whereas 40% of the untreated showed estrus signs. After treatment with PMSG and HCG in 40 and 87% of the gilts cysts were found whereas none of the untreated and 26 and 29% of those treated with PMSG und HCG + oestradiol benzoate revealed ovarian cysts. In addition, those gilts that had come into estrus during the first 30 days were given injections of either 1000 iu PMSG or 800 iu PMSG and 400 iu HCG. The injections were made either on the 5th, 10th or 15th day of cycle. In both latter groups significantly more gilts showed standing heat than after treatment at cycle day 5. The results of inspection of the ovaries at slaughter and steroid hormones could not be assigned to a defined stage of the physiological ovarian cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Use of pulsatile intravenous administration of gonadotropin-releasing hormone to induce fertile estrus in bitches.

The pulsatile IV administration of gonadotropin-releasing hormone (GnRH) was evaluated as a method to induce fertile estrus in 8 anestrous Beagle bitches. Bitches received 1.25 micrograms of GnRH every 90 minutes for 11 to 13 days. Gonadotropin-releasing hormone was delivered by use of an automatic pump. Reproductive history was known for all bitches, 4 of which, on the basis of 3 or 4 preceding cycles, had an interestrous interval of 219 +/- 14 days (mean +/- SEM). Estrus induction was attempted during early anestrus in 6 bitches (ie, 148 +/- 10 days since the preceding estrus) and late anestrus in 1 bitch (ie, 260 days since the preceding estrus); another bitch had not had an estrous cycle for nearly 2 years before GnRH administration. Signs of estrus were seen within 16 days after the start of GnRH administration in the bitches with regular estrous cycles (group 1, n = 7), and within 23 days in the bitch (group 2) with prolonged anestrus. All bitches were bred, and 7 of 8 (87.5%) became pregnant, with a mean litter size of 4.5 +/- 0.75. A normal hormonal response pattern was observed in group-1 bitches--a peak increase in plasma estrogen concentration of 22.3 +/- 2 pg/ml immediately before the onset of estrus. Peak plasma progesterone concentration (17.3 +/- 3 ng/ml) was observed 1 to 14 days after the onset of diestrus in the group-1 bitches that ovulated, and adequate plasma progesterone concentration was maintained throughout gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Effect of sex hormones on HL-RH-degrading hypothalamic enzyme system during estrus cycle in rats.

Basal activity of L-cysteine arylamidase, an LH-RH-degrading enzyme, was determined in the hypothalamus of rats at 4 h intervals throughout the 4-day estrus cycle. The activity of the enzyme system fluctuated during the four estrus stages in a circadian rhythm with maximal values in the night and lowest values at noon. The injection of increasing doses of estradiol-17 beta at various estrus stages caused a moderate stimulation of enzyme activity with no relationship to endogenous hormone levels or estrus stage. The highest activation of the hypothalamic enzyme in response to the application of progesterone occurred at such periods of the cycle when endogenous plasma progesterone is known to be low, and vice versa. When luteinizing hormone or prostaglandin E2 were injected i. v. during the various estrus stages maximal stimulation could be observed at diestrus. The LH-RH-degrading L-cystine arylamidase in the hypothalamus of the rat seems to play a modulating role in the regulation of the tonic LH release during the estrus cycle, but apparently does not influence the events governing the preovulatory LH-peak.

Aminopeptidases↗
PubMed1986

Pregnancy diagnosis in swine: a comparison of the accuracies of mechanical and endocrine tests with return to estrus.

The relative accuracies of various commercially available detection procedures in the evaluation of pregnancy status were evaluated in 51 sows of mixed parity. Sows were mated 1 to 3 times during estrus to one or more boars. A blood sample was obtained from each sow between 19 and 23 days after estrus (first day of estrus = day 1) and again between 26 and 30 days and was analyzed by radioimmunoassay for content of progesterone and estrone sulfate, respectively. Sows were considered pregnant if progesterone concentrations were greater than 5 ng/ml and if estrone sulfate concentrations were greater than 0.5 ng/ml. At daily intervals, sows were exposed to mature, sexually aggressive boars and observed for signs of estrus. Between 31 and 35 days of gestation, sows were evaluated for pregnancy by use of the following mechanical devices: a Doppler ultrasound pregnancy detector fitted with an abdominal probe, the Doppler detector with a rectal probe, an amplitude-depth ultrasound pregnancy detector (diode ruler), and another amplitude-depth ultrasound detector from a different manufacturer (oscilloscope). Relative to the proportion of sows that farrowed, the overall accuracies of the techniques were returns to estrus, 98%; estrone sulfate, 92%; progesterone, 92%; Doppler with rectal probe, 86%; Doppler with abdominal probe, 86%; diode ruler amplitude-depth ultrasound, 73%; and oscilloscope amplitude-depth ultrasound, 86%. Estrus detection resulted in the lowest prevalence of sows that were predicted to farrow, but did not subsequently farrow (false-positive diagnoses) and the lowest prevalence of sows that were not predicted to farrow, but subsequently did farrow (false-negative diagnoses).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

The influence of transportation on the induction of estrus in gilts of different ages.

Six series of experiments, involving 72 gilts in groups of 4 were carried out to investigate the effects of transportation, vibration and noise, and proximity of sexually mature adult breeding stock on attainment of first estrus in gilts of different ages. The animals grew normally during the periods of observation. Gilts aged 120 days (n = 12) at the start of the observations did not display estrus in response to exposure to vibration and noise or a 2 hr road journey. Similarly aged groups housed near adult breeding stock, but not exposed to vibration and noise, displayed estrus during the first 30 days of observation. All gilts aged 140 days (n = 12) displayed estrus within 5 days of being housed adjacent to adult breeding stock. Others, not housed near adult stock, but exposed to vibration and noise, or a road journey, did not consistently display estrus. When the observations were repeated on gilts aged 160 days (n = 12), the observations were similar. It was concluded that proximity of adult breeding stock and not transportation per se was the critical factor in inducing estrus behavior in normally growing gilts.

Animals↗
PubMed1984

Postpartum and lactational estrus: a comparative analysis in rodentia.

Virgin rodents exhibiting cycling estrus have traditionally been used for comparative studies of reproductive behavior. However estrus occurs in other life-history contexts, some of which differ from cycling estrus (CE) in that (a) the female is disposed to behave both maternally and sexually and (b) they result in litter overlap (i.e., the simultaneous gestation and lactation of two litters). In this report, two of these other modes of estrus are examined, with emphasis on their evolutionary and ecological implications. By means of a literature search of the order Rodentia, postpartum estrus (PPE) and lactational estrus (LE) were documented in 15 families, 71 genera, and 141 species. Analysis of these data showed that PPE and LE were nonrandomly distributed across taxa. They were statistically overrepresented in the family Cricetidae and underrepresented in squirrels (Sciuridae) and in pocket mice and kangaroo rats (Heteromyidae). Analysis of the phenotypes by which PPE and LE are achieved suggests important differences between them and CE in several parameters of female reproductive effort and breeding strategy, including maternal and copulatory behavior, optimal timing of litters, and hormonal control of heat and lactation.

Animals↗