Silent Oestrus Research Articles

Induced Early Estrus in Penned White-Tailed Deer Does

Estimated mean breeding date for adult white-tailed deer (Odocoileus virginianus) does confined continuously with individual bucks in 20x 20-m pens since early autumn was 9 November compared to 18 November for does in a forested 252-ha enclosure. Approximately 30% of the penned does were judged to have bred by 4 November vs. <4% of the enclosure herd by that date. We hypothesize that the constant presence of a rutting buck in close confinement with penned does resulted in biostimulation which induced an overt estrus and successful breeding in what otherwise would have constituted an early but silent estrus at onset of the rut. J. WILDL. MANAGE. 51(1):54-56 The white-tailed deer is a seasonally polyestrous breeder with a reproductive cycle cued to photoperiod, which varies according to latitude. Most adult (_1.5 years old) does confined in Upper Michigan at Shingleton (46*25'N) breed in November (Verme 1965, 1969, 1977; Ozoga and Verme 1982, 1984) and give birth in late May-early June. We, therefore, were puzzled to find that a sizeable proportion of the does penned at our downstate Houghton Lake facility (44*20'N) must have bred considerably earlier in the rutting season, as evidenced by fawns being born in late April-early May. This paper describes the circumstances associated with these notable differences and provides a hypothesis to explain the phenomenon. This paper is a contribution from Fed. Aid Wildl. Restor. Proj. W-127-R, Houghton Lake and Cusino Wildl. Res. Stns. We thank R. K. Clute, L. J. Perry, and R. Shellenbarger for assistance; G. F. Lehman drafted the figure. A. B. Bubenik, R. D. Earle, and E. D. Plotka provided helpful criticisms of the manuscript; C. M. Wemmer supplied some pertinent refer-

Plasma concentrations of progesterone in female red deer (Cervus elaphus) during the breeding season, pregnancy and anoestrus.

Concentrations of progesterone in peripheral plasma of red deer hinds were basal (less than 1 ng/ml) during lactation/seasonal anoestrus, but increased abruptly at the onset of the breeding season. Lactating hinds (N = 19) started ovarian cycles 10 days later (P less than 0.01) and conceived 16 days later (P less than 0.001) than did 13 weaned hinds. There was no evidence, from plasma progesterone values, of silent oestrus at the start of the season. Progestagen/PMSG treatment induced early ovulations in 8 anoestrous hinds but fertility was low, only 2 conceiving and giving birth. Pregnant hinds (N = 42) had high plasma concentrations of progesterone (mean 3-5 ng/ml) which declined just before parturition.

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

Serum estradiol-17β concentrations were determined during silent estrus in the mare. Relationships between serum estradiol-17β 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-17β secretion during the periovulatory period. When compared to normal estrous cycles, silent estrus was accompanied by a significantly lower maximum serum estradiol-17β concentration (47.8 vs 34.6 pg/ml), a significantly longer interval from maximum estradiol-17β 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-17β secretion and to the pattern of its secretion as related to regression of the corpus luteum. There appeared to be not only less estradiol-17β 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-17β concentration whenever behavioral estrus occurred [follicle diameter in mm = 0.96 (serum estradiol-17β in pg/ml) + 6.08 and 0.73 (serum estradiol-17β + 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-17β concentration were observed.

Hormonal changes in post-partum blood plasma and milk of buffaloes (Bubalus bubalis)

ABSTRACTPost-partum changes in the concentration of progesterone, oestradiol-17β and prolactin were measured by radioimmunoassay in the blood plasma and milk of 28 buffaloes. The mean concentration of progesterone in the plasma of normal animals was 0·24 ± 0·04 μ.g/1 on the day of calving and decreased linearly during the post-partum period, until the complete regression of the residual corpus luteum of pregnancy occurred, when the plasma concentration was recorded as 0μ05 to 0μ08 μg/l. The concentration at a silent oestrus was 0μ17 ± 0·02 μ.g/1. The milk progesterone profile was parallel to that of plasma but the level was 2 to 4 times higher.The mean concentration of oestradiol-17β in plasma was 41·0 ± 2·34 ng/1 on the day of calving; it declined significantly by day 1 post partum (P &lt; 0·001) and fluctuated between 8 and 16 ng/1 until oestrus, when the concentration was approximately 25 ng/1. The oestradiol-17β concentration in milk was significantly higher than that of plasma on the day of calving. During the first 20 days post partum, a similar concentration of oestradiol-17β was maintained in both fluids but thereafter the concentration in milk was 2 to 3 times that of plasma.The mean concentration of prolactin in plasma was 212·6± 19·08 μg/1 on the day of calving and then declined and fluctuated between 70 and 270 μg/1 during the rest of the period. A minor elevation occurred around oestrus. The prolactin concentration for the first 2 days post partum in milk was significantly higher than that in plasma but during the rest of the period it was similar to that in plasma.The progesterone concentrations were slightly lower in anoestrous animals than in those cycling. The concentration of prolactin was significantly higher in multiparous animals (P &lt; 0·001), whilst the progesterone and oestradiol values were similar in primiparous and multiparous animals.

Ovarian hemangioma in swine.

Eighteen (3.9%) ovarian hemangiomas were diagnosed in a survey of reproductive disorders in 460 sows from two to eight years of age during a three-year study. Ovarian hemangiomas only were observed in sows aged over 30 months, and no such neoplasms were found in 42 gilts. The incidence of ovarian hemangioma was highest at five to eight years of age. Of the 18 sows with ovarian hemangioma, one was purebred and 17 were crossbred pigs; of these, twelve had farrowed 12 to 15 litters, four had farrowed six to 11 litters and two had farrowed three litters. All 18 sows with ovarian hemangioma had one or more clinical signs related to reproductive disorders including small litter size, agalactia, fertilization failure, fetal death, silent estrus, anestrus, abortion, and stillbirth. The pathological features of the neoplasms in sows were similar to those described previously in swine and in man. Spontaneous ovarian hemangioma might provide a model for investigation of the etiology and pathogenesis of ovarian hemangioma in man.

Use of Lutalyse® Sterile Solution in Lactating Dairy Cows with Silent Estrus

Prostaglandin F2a (PGF2a) has been reported to be luteolytic in the bovine. As a result of the luteolytic activity, PG F2a has been reported in both scientific and clinical journals to be effective in cattle for treatment of unobserved estrus, abortion, parturition, pyometra, termination of pathological gestation and cystic ovaries. The data support a conclusion that Lutalyse sterile solution was effective for the treatment of unobserved (silent) estrus as measured by pregnancy rates within five (5) days after treatment.

Alteration of the estrous cycle of gilts by movement to a confinement housing system

Thirty-six crossbred gilts were maintained in outside dirt lots for 2 or more estrous periods. Eighteen of the gilts were moved to another outside dirt lot (non-confined) and the other eighteen were moved to a single pen in a confinement finishing building (confined). A blood sample was collected on the day of movement and every 7 days thereafter for 12 weeks and quantitated for progesterone to verify the occurrence of each ovulation. Any estrous cycle shorter than 18 days or longer than 23 days was classified as abnormal. The duration of estrous cycles of non-confined gilts were not different before, during or after movement, whereas the duration of estrous cycles were greater (P=.005) during movement than before movement in the confined gilts. The duration of estrous cycles of confined gilts were greater (P=.020) than those of non-confined gilts during movement. The percentage of abnormal estrous cycles were greater during movement than before (P=.007) or after (P=.052) movement for the confined gilts, whereas the percentage age of abnormal estrous cycles were greater (P=.050) during movement than before movement in non-confined gilts. Therefore, the greatest percentage of abnormal estrous cycles occurred during movement in both groups. A single incident of silent estrus followed by normal estrous cycles was observed. In addition, an estrus occurred while plasma progesterone concentration was elevated (51 ng/ml) and was followed by normal estrous cycles.

Remote temperature sensing of oestrous cycles in cattle

Radio transmission of deep-body temperature changes in cattle was found to be a feasible method of collecting information for husbandry decisions. Oestrous cycles were plotted and ovulations detected so that cattle were effectively bred artificially. Abnormalities of the cycle pattern accurately indicated abnormal reproductive phenomena. The presence of febrile illness was also detectable. The occurrence of silent oestrus was clearly demonstrated.

Abnormal patterns of ovarian activity in dairy cows and their relationships with reproductive performance

ABSTRACTProgesterone profiles were obtained from 533 dairy cows during the interval from calving to the re-establishment of pregnancy by twiceweekly radioimmunoassay of milk progesterone. The importance of abnormal patterns of ovarian activity on herd fertility was determined. Animals were divided into five categories based on profile analysis: A, normal; B, delayed start to ovarian cycles; C, cessation of cycles; D, prolonged luteal activity; and E, silent oestrus. Animals in categories B to E were subdivided into treatment groups: categories B and C either (i) untreated controls, (ii) single injection 0·5 mg luteinizing hormone-releasing hormone (Hoechst) or (iii) progesterone-releasing intravaginal device (Abbott Laboratories Ltd) inserted for 14 days; categories D and E either (i) untreated controls or (ii) single injection 0-5 mg cloprostenol (Imperial Chemical Industries).The proportion of cows in each category was: A 77·5%; B 4·9%; C 5·1%; D 1·9%; and E 10·7%. The incidence of ‘normal’ cows was 75% (first lactation), 80% (2nd to 5th lactations) and 69% (5th to 11th lactations). For normal cows (no. = 413) the interval to the start of cyclicity varied significantly with season but was not correlated with either the intervals to first insemination or to conception. In categories B to E the open period, the number of services per conception, and the days from first insemination to conception were greater than in category A, but only in category C were any differences significant. None of the treatments reduced calving-toconception intervals.

The use of progesterone and oestrogen concentrations in the diagnosis of pregnancy, and in the study of seasonal infertility in sows

Plasma concentrations of progesterone and oestrogen in sows 18 days after mating were examined, firstly, as a method of pregnancy diagnosis, and secondly, for indication of any abnormal endocrine patterns that may have been involved in the aetiology of seasonal infertility in sows. Progesterone levels were the most relevant indicator of ovarian function. For the diagnosis of pregnancy, progesterone levels were accurate (97 %), but for the diagnosis of non-pregnancy, especially where a high degree of early embryonic death and/or cystic follicles was suspected, as in this trial, progesteronc levels were not as accurate (60%). Oestrogen levels were of use only in confirming the type of infertility suffered by non-pregnant sows. This study shows that seasonal infertility in mated sows is a complex of several forms of infertility, each manifest in a common physical symptom of delayed return to oestrus after a normal mating to a fertile boar. The forms of infertility involved appear to be early embryonic death, luteinized ovarian cysts, small ovarian cysts and silent oestrus.

Combined Use of Milk Progesterone Profiles, Clinical Examination and Oestrus Observation for the Study of Fertility in the Post-Partum Period of Dairy Cows

Three different criteria were used to study the fertility of 50 cows: 1. Clinical investigation of ovaries and uterus at two-weekly intervals. 2. Daily observation of oestrus, three times a day. 3. Determination of milk progesterone every second or every third day. From the combination of clinical data and progesterone profiles it was found that 26% of the animals were abnormal according to both criteria. This group could be subdivided into three categories: delayed start (later than day 30 after parturition) of luteal activity (12%), prolonged (lasting longer than 20 days) luteal activity (6%) and irregular luteal activity (8%). Three animals (6%) which were clinically diagnosed to be abnormal (retained placenta or peritonitis) had normal progesterone profiles. On the other hand, one animal (2%) which appeared to be clinically normal had an abnormal progesterone profile. Two animals with follicular cysts were treated with Nymfalon (progesterone + HCG), one with a pyometra was treated with Cloprostenol (PGF2α) and one cow showing anoestrus was treated with GnRH. In all these cows the effectiveness of the treatment was confirmed by the corresponding progesterone profile. From the combined data of oestrus observations and progesterone profiles it was found that 48% of the animals showed at least one silent oestrus (the start of the first progesterone rise was not taken into consideration). 27% of a total of 110 oestrous periods, as expected from the progesterone profiles (excluding the start of the first progesterone rise), were apparently silent, since they were not observed despite frequent oestrus observations. One animal was never seen in oestrus, although there was some (delayed) luteal activity. Although 88% of the animals had started luteal activity earlier than day 30 after parturition, only 36% had shown oestrus at that time.

Ovarian and endocrine responses and reproductive performance following GnRH treatment in early postpartum dairy cows

At calving forty-eight Holstein and Guernsey cows were assigned according to age and breed to one of six postpartum periods (1 or 2, 3 or 4, 5 or 6, 7 or 8, 12 or 13 and 18 or 19 days postpartum). Thirty-six of the cows (6 cows per postpartum period) received a single intramuscular injection of 100 μg GnRH. The other twelve cows (2 cows per postpartum period) served as controls and received a single intramuscular injection of the carrier vehicle for GnRH. Four of 36 cows administered GnRH and three of the 12 control cows ovulated by the day following treatment. Four of the cows were 12 or 13 days postpartum (1 control and 3 GnRH treated) and three were 18 or 19 days postpartum (2 controls and 1 GnRH treated). Six of the seven cows that ovulated the day following treatment had a follicle > 1.0 cm the day prior to treatment. Follicular growth was detected in the earlier postpartum periods but ovulation the following day was not detected for either control or GnRH treated cows. Following estrus or silent estrus, plasma progesterone concentrations increased to about 4 ng/ml on day 13. However, in cows ovulating the day following GnRH treatment, plasma progesterone declined from about 3 ng/ml on day 9 to approximately 1 ng/ml on day 13 postestrus. In addition, LH in plasma was higher (P < .01) ł through 13 days following estrus or silent estrus in cows ovulating the day after GnRH treatment in comparison to cows during the first or subsequent postpartum estrous cycles. In summary, in addition to days postpartum other factors including follicular development and maturity are probably involved in GnRH induced ovulation.

Oestrus synchronisation with a prostaglandin analogue III. Special aspects of synchronisation

Abstract Two groups of lactating dairy cows in each of 4 dairy herds were injected with either 0.5 mg (219 cows) or 0.3 mg (118 cows) of Ooprostenol (I.C.I.) The first group of cows were injected from Day 6 to Day 17 of the oestrous cycle (Day 0 — oestrus) and the second group from Day 6 to Day 12. The four herds were selected specifically because oestrus-detection procedures were thorough and reliable. Of the cows receiving the 0.5 mg dose rate, 54.3% were observed in oestrus within 4 days of treatment. The remainder were in groups which were: (i) in oestrus from 5 to 10 days post-treatment (20.5% with prolonged response intervals), and 11 to 20 days post-treatment (15.5% with unaltered cycle lengths); or (ii) experienced a “silent oestrus” in the immediate post-treatment period and either did not show oestrus for a further 3 weeks (6.4% in oestrus from 21 to 29 days post-treatment) or conceived to a single set-time insemination 72 h after treatment (0.9%). Use of the lower dose rate resulted in fewer co...

Tail painting — a simple form of oestrus detection in New Zealand dairy herds

Abstract Tail painting could be a satisfactory, convenient, and economical aid to oestrus detection in many dairy herds in New Zealand. A strip of enamel paint 20 cm × 5 cm running posteriorly from the first coccygeal vertebra was used as a method of oestrus detection in 4 herds of lactating dairy cows during the premating period. Occurrence of oestrus activity was accurately identified in 335 of 350 cycling cows and lack of oestrus activity was identified in 40 of 49 anoestrous cows. Only 4 cows correctly identified in oestrus by the herd owners were not detected by tail painting. In contrast, 24 cows not observed in oestrus by the herd owners were correctly identified by painting. The technique was used in 4 herds as well as 2 larger herds to identify groups of cycling cows which were subsequently treated with a prostaglandin analogue as part of an oestrus synchronisation programme. The interval from treatment to behavioural oestrus and the incidence of silent oestrus were conveniently monitored by observation of the paint strip.

The Use of Milk Progesterone Radioimmunoassay in the Diagnosis and Treatment of Subfertility in Dairy Cows

Milk progesterone profiles of dairy cows have been developed using a radioimmunoassay of samples of whole milk collected twice weekly. The profiles have been used in three herds to select cows with abnormal progesterone patterns. Fifty percent of the cows had significant rises in milk progesterone prior to 20 days post partum and 93% had commenced ovarian activity by 40 days post partum. Based on an absence of high milk progesterone levels by 50 days post partum, 7% were classified as anoestrus. A further 2% exhibited persistently high milk progesterone levels (persistent corpus luteum) and approximately 7% exhibited unobserved or silent oestrus. Treatment of anoestrous cows with either 0·5 mg GnRH (Hoechst HOE 471) or the insertion of a progesterone releasing intravaginal device (PRID Abbotts) for 14 days initiated oestrous cycles with normal levels of fertility following insemination at the first post-treatment oestrus. Treatment of cows with unobserved or ‘silent’ oestrus during the luteal phase with 0·5 mg ICI 80 996 i.m. to induce luteolysis resulted in overt oestrus and normal levels of fertility following insemination.

THE DURATION OF THE BREEDING SEASON OF FOUR BREEDS OF SHEEP

Three breeds of sheep (Dorset, Leicester, and Suffolk) and a crossbred line from these breeds (DLS) were observed throughout 1 yr to determine their sexual activity by daily exposure of the ewes to vasectomized rams. The DLS and Dorset ewes exhibited their first estrus earlier in the year (P &lt; 0.01) and stopped cycling later than the Leicester and Suffolk ewes (P &lt; 0.01). The duration of the breeding season in the DLS ewes was 20 days (P &gt; 0.05) longer than in the Dorsets and 70 and 115 days (P &lt; 0.01) longer than in the Leicester and Suffolk ewes, respectively. The percentage of Dorset and DLS ewes showing one or more estrous periods increased progressively from June to reach 100% in September for both breeds. The Suffolk and Leicester ewes commenced to cycle in late August and by September almost all ewes had shown an estrous period. The progressive decline in estrous activity became evident first with the Suffolk in January, then with the Dorset and Leicester in February and with the DLS in March. The Dorset, DLS and Leicester ewes had longer estrous cycles than the Suffolk ewes. Within ewes, length of estrous cycles was highly repeatable for all breeds. False estrus and silent estrus occurred in 1.0 and 3.9% of the estrous periods, respectively. Over successive estrous cycles, length of estrous cycles increased significantly.

Estrous Behavior and Ovarian Activity in Prepuberal and Postpuberal Dairy Heifers

The reproductive tracts of 53 Holstein heifers were examined per rectum twice weekly beginning at least 30 days before the first ovulation and continuing until ten days after the third ovulation, to determine pre- and postpuberal ovarian activity. The heifers were observed twice daily for estrus.The mean interval from birth to first ovulation was 42.3 weeks and from first to second ovulation and second to third, 20 days. The first ovulation was accompanied by silent estrus in 74% of the heifers. The occurrence of silent estrus declined to 43% at the second ovulation and to 21% at third ovulation. These differences were highly significant (P<0.005). Estrous behavior did not affect subsequent ovarian conditions.Normal corpora lutea occurred during 79.9% of the cycles, cystic corpora lutea during 12.6%, cystic follicles during 2.5%, and anovulation during 5%. The occurrence of anovulation was significantly greater at first estrus than at subsequent estrous periods (P<0.005).

Seasonal variation in the reactivity to oestrogen of the ovariectomized ewe

Fifteen tests carried out at an average interval of 4 weeks for 14 months showed an annual rhythm in the proportion of spayed crossbred ewes which exhibited oestrus after an injection of 15.6 µg oestradiol benzoate (ODB) following a 12 day period of progesterone treatment. Reactivity was highest in late summer and early autumn and lowest in winter and early spring. The periods of minimum reactivity coincided with the periods of low environmental temperatures and low body weights. The significance of the annual rhythm is discussed with particular relation to the phenomenon of "silent oestrus". No similar rhythm was detected in the 7-aginal response to oestrogen.