Resumption of ovarian function in autumn lambing Dorset, Rambouillet and Finnish Landrace ewes

The establishment of ovarian activity during lactation was studied in the postpartum period of Rambouillet, Dorset and Finnish Landrace ewes following lambing during the month of October (1981). The mean postpartum intervals to first ovulation and first estrus were 22.7 and 53.0 for Rambouillets, 25.2 and 51.0 for Dorsets, and 22.5 and 49.7 days for Finnish Landrace ewes. Estrus was not associated with the first ovulation postpartum in any breed. The number of silent ovulations prior to the first estrus was highest in the Rambouillet and lowest in Finnish Landrace breeds. Of the 18 ewes in the project, 14 had normal luteal phase lengths, 1 had a possible short luteal phase and 3 had prolonged luteal phases following the first ovulation postpartum. The first service conception rate of all ewes bred was 82% (14 17 ) at an average of 52 days postpartum. The lambing rate following the autumn breeding was higher (2.14 +/- 0.14) than the lambing rate which followed the previous spring breeding (1.28 +/- 0.11).     

Follicular dynamics and dominance in Booroola x Finnish Landrace and Booroola x Suffolk ewes heterozygous for the F gene

To study the influence of the F gene on follicular dynamics and dominance, 2-year-old Booroola x Finnish Landrace (BFL, N = 17) and Booroola x Suffolk (BS, N = 18) ewes were compared with contemporary purebred Finn (FL, N = 18) and Suffolk (S, N = 18) ewes. In Exp. 1, oestrous cycles of ewes were synchronized during the breeding season with progestagen-impregnated sponges. At sponge removal (Day 0), 14 days after insertion, ewes of each of the 4 genetic groups were assigned to Group 1 in which all follicles visible on both ovaries were destroyed by electrocauterization except for the largest (F1) which was marked, Group 2 in which all visible follicles on both ovaries were destroyed, or Group 3 in which the 3 largest follicles of both ovaries were identified as F1, F2 and F3 and marked. At 48 h after treatment (Day 2), follicular growth was evaluated. At Day 0, the mean number of small follicles (1-3 mm) was higher (P less than 0.05) for BS, S and BFL (35.8, 35.1 and 32.9) than FL (24.9) ewes. Large follicles (greater than or equal to 4 mm) were more numerous (P less than 0.05) in FL (3.5) than in BS (2.1) ewes, BFL and S ewes being intermediate. Diameter of the F1 follicle was larger (P less than 0.05) for S (7.6 mm) than FL, BS and BFL (5.8, 5.1 and 5.1 mm) ewes. In Group 1, all F1 follicles marked at Day 0 ovulated at oestrus after sponge removal for BFL, BS and S ewes while in FL ewes, 2 of 6 F1 follicles regressed. In ewes ovulating, only the F1 follicle ovulated except for one S ewe which shed one more ovum. In Group 2, there were no follicles greater than or equal to 4 mm at Day 2 and no ewes ovulated after treatment. In Group 3, the proportion of marked follicles that ovulated was higher for S ewes than in those of the prolific genotypes. The number of follicles not marked at Day 0 but ovulating (compared to the total number of ovulations) was higher in BFL, BS and FL (8/11, 9/13 and 9/13) than S (3/10) ewes. In Exp. 2, prolific (BFL + BS) and non-prolific (S) ewes were compared following destruction of follicles greater than or equal to 3 mm with the F1 left intact (Treatment 1) or destroyed (Treatment 2), 12 days after sponge insertion.(ABSTRACT TRUNCATED AT 400 WORDS)     

Role of photorefractoriness in onset of anoestrus in Rambouillet x Dorset ewes

An experiment was conducted to determine the extent to which refractoriness to short daylength is involved in the onset of anoestrus in Rambouillet x Dorset ewes. Ovary-intact ewes (N = 36) were exposed to ambient photoperiod (C) or to a photoperiod equal to the winter solstice (S) beginning on 21 December 1986 and continuing until 21 April 1987. Samples of serum were obtained at weekly intervals and assayed for progesterone to assess ovarian activity, and for prolactin to assess response to photoperiod treatment. In addition, ovariectomized (ovx) ewes with implants containing oestradiol were housed with C(Covx) and S (Sovx) ewes (N = 4 per treatment). The concentration of LH was determined in serum collected biweekly from all ovariectomized ewes throughout the treatment period as an index of reproductive status. Time-trends for concentrations of LH differed (P less than 0.005) for ewes in Groups Covx and Sovx with LH decreasing on the order of about 8-fold in Group Covx through the treatment period, while not changing appreciably in Group Sovx. Intact ewes in both treatments began to become anoestrous by the 9th week of treatment (about the last week in February). However, fewer Group S than Group C ewes were anoestrous at 13 and 14 weeks of treatment (P = 0.09). Time-trends for concentrations of prolactin also differed for the Group C and S ewes (P less than 0.005), probably reflecting the divergence in duration of photoperiod between the two treatments by the end of the study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Control of gonadotrophin release in Scottish Blackface and Finnish Landrace ewes during seasonal anoestrus

The patterns of LH and FSH secretion were measured in 4 experimental groups of Finnish Landrace and Scottish Blackface ewes: long-term (18 months) ovariectomized ewes (Group 1), long-term ovariectomized ewes with an oestradiol implant, which has been shown to produce peripheral levels of approximately 5 pg/ml (Group 2), long-term ovariectomized ewes with an oestradiol implant for 18 months which was subsequently removed (surgery on Day 0) (Group 3) and short-term ovariectomized ewes (surgery on Day 0) (Group 4). LH and FSH concentrations were monitored in all groups at approximately weekly intervals, before and after Day 0. Finnish Landrace ewes in Groups 1, 2 and 3 had significantly higher mean FSH concentrations than did Scottish Blackface ewes (P less than 0.01). FSH and LH concentrations increased significantly in Groups 3 and 4, but values in Group 4 were significantly lower (P less than 0.01) than those in Group 1 ewes even up to 30 days after ovariectomy. In Group 3, LH concentrations increased to levels similar to those in Group 1. The pattern of LH release was, however, significantly different, with a lower LH pulse frequency (P less than 0.05), but higher pulse amplitude (P less than 0.05). This difference was maintained at least until 28 days after implant removal. We suggest that removal of negative feedback by ovariectomy demonstrates an underlying breed difference in the pattern of FSH secretion and that ovarian factors other than oestradiol are also involved in the negative-feedback control of hypothalamic/pituitary gland function. Furthermore, negative-feedback effects can be maintained for long periods, at least 28 days, after ovariectomy or oestradiol implant removal.     

Response of seasonally anoestrous ewes to six-hour periods of GnRH infusion administered on six consecutive days

Twelve seasonally anoestrous Clun Forest ewes were infused i.v. with either 500 or 1000 ng GnRH/h for 6 h on each of six consecutive days in early or mid-anoestrus. Plasma LH concentrations were elevated during each GnRH infusion but returned to pretreatment levels when infusion ceased. The response to the first infusion was significantly greater (p<0.001) than that to subsequent infusions. In addition, both a GnRH dose and a seasonal influence were evident in the LH response, but these failed to reach statistical significance. Although 7 12 ewes ovulated, only two produced functionally normal corpora lutea.     

Reproductive performance of ewes exposed to vasectomized rams before breeding and forced exercise before lambing

Twenty days before a regular fall breeding season, 93 mature Rambouillet ewes were randomly allotted to one of two groups to examine the response of cycling females exposed to sterile rams. Six vasectomized rams were joined with 46 ewes during the 20-day period while 47 ewes remained separate from the rams. All ewes were judged to have been cycling either by paint marks from rams on treated animals or by the cyclic nature of progesterone (sampled at four-day intervals) profiles in control ewes. After removal of sterile males, fertile Debouillet rams remained with the ewes during a 34-day breeding season. Approximately six weeks before beginning the lambing season, one-half the females in each sterile ram treatment group were forced to walk 0.8 km per day to examine the influence of exercise on subsequent reproductive performance. Presence of sterile males did not alter (P>0.10) lambing rate, average lambing date or percentage of ewes lambing during thirds of the lambing season suggesting that prebreeding exposure of cycling ewes to vasectomized rams does not enhance lambing rate or shorten the lambing season. Forced exercise resulted in increased daily feed consumption which was reflected in heavier (P<0.05) lamb birth weights. Percentage of ewes experiencing either dystocia or pregnancy toxemia was similar (P>0.20) in exercised and unexercised animals. Moderate exercise during late gestation may increase lamb birth weight without increasing lambing difficulty.     

Ovarian antral follicular dynamics and their associations with peripheral concentrations of gonadotropins and ovarian steroids in anoestrous Finnish Landrace ewes

Daily transrectal ultrasonography of ovaries was done in seven Finn ewes during three 17-day periods from May to July. Blood samples were collected each day for estimation of the serum follicle-stimulating hormone (FSH), oestradiol and progesterone concentrations, and also every 15 min for 6 h, halfway through each period of ultrasonographic examination, to determine the patterns of gonadotropic hormone secretion. Four ewes ceased cycling from March to mid-April (ewes entering anoestrus early) and three in May (ewes entering anoestrus late). In all ewes cyclicity resumed during the period from mid-August to mid-September. The growth of ovarian antral follicles to periovulatory sizes of >/=5 mm in diameter was seen at all stages of anoestrus. An average of four waves of follicular development (follicles growing from 3 to >/=5 mm in diameter before regression) with a periodicity of 4 days were recorded during each of the three scanning periods. There was a close temporal relationship between days of follicular wave emergence and peaks of successive FSH fluctuations. Ewes entering anoestrus late exceeded ewes that became anoestrus early in numbers of large (>/=5 mm in diameter) ovarian antral follicles and maximum follicle diameter. Peak concentrations of transient FSH increases were higher (P<0.05) in ewes entering anoestrus late than in ewes entering anoestrus early. The secretion of luteinising hormone, (LH; mean and basal level, and LH pulse frequency, but not amplitude) was lowest during the month of June in all ewes. Oestradiol production was markedly suppressed throughout anoestrus. Peaks of progesterone secretion appeared to occur at regular intervals and were associated with the end of the growth phase of the largest follicles of sequential waves. In conclusion, the growth of ovarian follicles to ostensibly ovulatory diameters is maintained throughout anoestrus in Finn ewes and periodic emergence of follicular waves is correlated with an endogenous rhythm of FSH secretion. The present study also provides evidence for the inverse relationship between the time of the onset of seasonal anoestrus and the number and size of antral follicles developing throughout anoestrus in Finn ewes, and indicates that differences exist in both the secretion of and ovarian responsiveness to gonadotropic hormones among early and late anoestrous ewes.     

Coat growth in Red deer (Cervus elaphus) exposed to a day-length cycle of six months duration

Four male Red deer were subjected to artificial light giving a shortened annual cycle of six months. Moulting and colour changes, coat length, and histological changes in the activity of hair follicles were studied in samples taken at three-weekly intervals for 20 months.     

Estradiol increases multiunit electrical activity in the A15 area of ewes exposed to inhibitory photoperiods

Seasonal anestrus in ewes results from an increase in response to the negative feedback action of estradiol (E(2)). This increase in the inhibitory effects of E(2) is controlled by photoperiod and appears to be mediated, in part, by dopaminergic neurons in the retrochiasmatic area of the hypothalamus (A15 group). This study was designed to test the hypothesis that E(2) increases multiunit electrical activity (MUA) in the A15 during inhibitory long days. MUA was monitored in the retrochiasmatic area of 14 ovariectomized ewes from 4 h before to 24 h after insertion of an E(2)-containing implant subcutaneously. In six of these ewes, MUA activity was also monitored before and after insertion of blank implants. Three of the 14 ewes were excluded from analysis because E(2) failed to inhibit LH. When MUA was recorded within the A15, E(2) produced a gradual increase in MUA that was sustained for 24 h. Blank implants failed to increase MUA in the A15 area, and E(2) did not alter MUA if recording electrodes were outside the A15. These data demonstrate that E(2) increases MUA in the A15 region of ewes and are consistent with the hypothesis that these neurons mediate E(2) negative feedback during long photoperiods.     

Mineral status and mechanical properties of cancellous bone exposed to hydrogen peroxide for various time periods

Processed cancellous bone has been regarded as one alternative for the treatment of bone defects. In order to avoid immunogenic effects and preserve the natural properties of the bone, the optimal processing method should be determined. To observe the influence of hydrogen peroxide on the mineral status and mechanical properties of cancellous bone for various time periods and find the optimal processing time. Cancellous bone granules from bovine femur condyles were treated with 30% hydrogen dioxide for 0, 12, 24, 36, 48, 60 and 72 h separately. The microstructure and mineral content of the granules were evaluated by ash analysis, Micro-CT, scanning electron micrograph and energy dispersive X-ray. The biomechanical properties were analyzed by applying cranial-caudal compression in a materials testing machine. With increasing exposure to hydrogen peroxide, the BMD and BMC of granules gradually decreased, and the Ca/P molar ratios clearly increased (P < 0.05). Meanwhile, the mineral content of the granules increased from 48.5 ± 1.3 to 79.5 ± 2.1%. Substantial decreases in the strength of the granules were observed, and after 48 h severe decreases were noted. The decrease in strength was also evident after normalizing the parameters to the cross-sectional area. Granules of bovine cancellous bone matrix should be processed by hydrogen peroxide for 12 to 36 h to fulfill the basic requirements of a bone tissue engineering scaffold. These granules could potentially be useful during orthopedic operations.     

Seroconversion of recipient ewes after transfer of ova exposed to Brucella ovis in vitro

Zona pellucida-intact ova collected from ewes seronegative to Brucella ovis were exposed in vitro to B ovis and washed 10 times in medium that contained no antibiotics. After exposure and washing, nontransferable ova were cultured for isolation of Brucella , and the viable ova were transferred into seven B ovis seronegative ewes. No pregnancies resulted, thus recipient ewes were bred during the next breeding season, and blood samples were collected for bacteriological and serological examination until one month after lambing. Brucella ovis was isolated from all of the nontransferable ova, indicating that the transferred ova had viable organisms adhered to them. Although no recipient was found to be pregnant at Day 45, all seven ewes responded to the transferred ova by producing anti-Brucella antibodies. With the exception of a ewe that was euthanized early in the project due to a traumatic injury, all recipients lambed normally during the following breeding season. Brucella was not found in any sample collected from ewes or lambs. However, ELISA titers for B ovis remained in the suspicious range and a ewe was positive on the CF test within 2 wk of lambing.     

Impulse activity in the CA1 field in animals of various typological groups exposed to emotional stimuli

Hippocampal unit activity in the right and left CA1 fields was studied in rats divided in two groups by the method of "emotional resonance": the animals that did (A) and did not stop (E) crying of rat-partner. The rate of neuron firing was studied in the state of hunger, satiation, and under exposure to intracranial electrical stimulation of the emotional positive and negative structures of the brain. It was shown that the intracranial stimulation, especially positive, increased the rate of firing. Under exposure to emotional stimuli, the neural activity was asymmetric only in the A rats. The activity at the left was more intensive than the right-sided activity and did not depend on the sigh of emotion.     

Interaction of endogenous and exogenous factors controlling locomotor activity rhythms in Carcinus exposed to tidal salinity cycles

The shore crab Carcinus maenas (L.) reported hitherto not to express endogenous circatidal rhythmicity in winter, is shown not to lose the ability to express such rhythmicity. Crabs maintained in constant reduced salinity in winter exhibit circatidal and circadian rhythms similar to the normal endogenous rhythms of summer caught crabs.In sinusoidal changes of salinity of tidal periodicity, reductions of salinity and increases to ambient sea water induced increased locomotor activity. The former were purely exogenous responses but the latter were also observed to entrain the underlying endogenously controlled circatidal pattern of behaviour.The occurrence of separate exogenous and endogenous responses to different phases of imposed salinity cycles has implications when seeking to understand rhythmic locomotor activity of crabs on the shore and in the search for components of the underlying physiological clock mechanism.     

Ovulatory activity and plasma prolactin concentrations in wild and domestic ewes exposed to artificial photoperiods between the winter and summer solstices

Mouflon and domestic Manchega sheep differ in the timing of their reproductive season under natural photoperiod (NP) conditions. This study examines whether they also differ in their reproductive responses to artificial photoperiod cues. For this, mouflons (n=24) and ewes (n=24) were exposed between the winter and summer solstices to artificial long days (LD: 16 h light/day), to short days (SD) simulated via the use of melatonin implants, or to NP conditions (controls), and their ovulatory activity monitored. The effects of these treatments on annual changes in prolactin concentration were also recorded. In the LD mouflon ewes, the offset and onset (7 March ± 5 and 2 October ± 4, respectively) of cyclic ovulatory activity occurred earlier (P<0.001) than in the NP animals (26 April ± 6 and 20 October ± 2, respectively), but no differences were seen (P>0.05) between the SD and NP mouflon ewes in either the onset of anoestrus (12 May ± 6 and 26 April ± 6, respectively) or the onset of subsequent ovulatory activity (13 October ± 8 and 20 October ± 2, respectively); however the duration of the anoestrus period was significantly reduced in the SD. In LD Manchega ewes, the onset of anoestrus was advanced (2 February ± 5 vs 15 March ± 11), but ovulatory activity started at the same time as in NP Manchega ewes (16 July ± 4 vs 5 July ± 8). In the SD Manchega ewes, two animals showed continuous cyclic ovulatory activity over the course of the experiment while the remainder entered anoestrus two months later (16 May ± 6, P<0.001) than their NP counterparts. In these SD ewes, the onset of cyclic ovarian activity was very variable. An annual rhythm of plasma prolactin concentration was seen in both the mouflon and Manchega ewes under all three photoperiod conditions. However, the amplitudes of the changes seen in prolactin concentration were smaller in both the LD and SD animals than in the corresponding NP animals (P<0.001). In conclusion, the results show that these two types of Mediterranean sheep differ in their ovulatory response when subjected to artificial photoperiods. The results also suggest that refractoriness to SDs may be the most important physiological mechanism regulating the onset of anoestrus in highly seasonal breeds, but not in less seasonal breeds.