Infection with Menangle virus in flying foxes (Pteropus spp.) in Australia.

OBJECTIVE: To examine flying foxes (Pteropus spp.) for evidence of infection with Menangle virus. DESIGN: Clustered non-random sampling for serology, virus isolation and electron microscopy (EM). PROCEDURE: Serum samples were collected from 306 Pteropus spp. in northern and eastern Australia and tested for antibodies against Menangle virus (MenV) using a virus neutralisation test (VNT). Virus isolation was attempted from tissues and faeces collected from 215 Pteropus spp. in New South Wales. Faecal samples from 68 individual Pteropus spp. and four pools of faeces were examined by transmission EM following routine negative staining and immunogold labelling. RESULTS: Neutralising antibodies (VNT titres > or = 8) against MenV were detected in 46% of black flying foxes (P. alecto), 41% of grey-headed flying foxes (P. poliocephalus), 25% of spectacled flying foxes (P. conspicillatus) and 1% of little red flying foxes (P. scapulatus) in Australia. Positive sera included samples collected from P. poliocephalus in a colony adjacent to a piggery that had experienced reproductive disease caused by MenV. Virus-like particles were observed by EM in faeces from Pteropus spp. and reactivity was detected in pooled faeces and urine by immunogold EM using sera from sows that had been exposed to MenV. Attempts to isolate the virus from the faeces and tissues from Pteropus spp. were unsuccessful. CONCLUSION: Serological evidence of infection with MenV was detected in Pteropus spp. in Australia. Although virus-like particles were detected in faeces, no viruses were isolated from faeces, urine or tissues of Pteropus spp.

Re-challenge of pigs following recovery from proliferative enteropathy.

An experimental challenge model was developed to demonstrate Lawsonia intracellularis colonization and reproduction of proliferative enteropathy (PE) in naïve weaner pigs. Groups of pigs were orally dosed with between 10(10) and 10(5)L. intracellularis extracted from haemorrhagic PE affected mucosa. Pigs were monitored for clinical signs and intestinal lesions of PE and evidence of bacterial colonization by serology and faecal polymerase chain reaction (PCR). One group of challenged pigs were necropsied after 21 days to confirm the reproduction of PE. L. intracellularis colonization and seroconversion was delayed in pigs dosed with lower numbers of L. intracellularis. When faecal shedding of L. intracellularis ceased to be detected in all of the challenged pigs, they were re-dosed orally with approximately 10(10)L. intracellularis and monitored for evidence of re-colonization and clinical disease. This study demonstrated that pigs previously challenged with L. intracellularis were protected from re-colonization and clinical disease on subsequent exposure 10 weeks later, regardless of the initial dose of L. intracellularis.

Skeletal and neurological malformations in pigs congenitally infected with Menangle virus.

OBJECTIVE: To describe the pathological findings in stillborn piglets and fetuses delivered by sows naturally infected with Menangle virus, a recently recognised Paramyxovirus. DESIGN: Observations of the gross and microscopic pathology of natural disease. PROCEDURE: Postmortem examinations were performed on 49 stillborn piglets, 35 mummified or semi-mummified full-term fetuses and 6 aborted fetuses from 20 litters at a 2600-sow intensive piggery in New South Wales during an outbreak of reproductive disease from June to September 1997. Body weights, crown-rump lengths and gross pathological changes were recorded. Tissues, including brain and spinal cord, were processed for histopathological examination. RESULTS: Litters with reduced numbers of live born piglets had mummified fetuses and stillborn piglets. Affected stillborn and aborted piglets frequently had arthrogryposis, craniofacial and spinal deformities, pulmonary hypoplasia and degeneration of the brain and spinal cord. Intranuclear and intracytoplasmic inclusion bodies were observed in neurones and other cells in the brain and spinal cord in association with extensive degeneration, necrosis, infiltration of macrophages and gliosis. CONCLUSIONS: In utero infection of piglets with Menangle virus is associated with severe skeletal and neurological malformations.

Flow and mixing by small intestine villi.

Flow and mixing in the small intestine are multi-scale processes. Flows at the scale of the villi (finger-like structures of ≈500 µm length) are poorly understood. We developed a three-dimensional lattice-Boltzmann model to gain insight into the effects of villous movements and the rheology of digesta on flow, mixing and absorption of nutrients at the periphery of the intestinal lumen. Our model simulated the hydrodynamic consequences of villi movements that resulted from folding of the mucosa during longitudinal contractions. We found that cyclic approximation and separation of groups of villi generated laminar eddies at the edges of the group and augmented mass transfers in the radial direction between the inter-villous space and the intestinal lumen which improved the absorption of nutrients and mixing at the periphery of the lumen. This augmentation was greater with highly diffusible nutrients and with high levels of shear-thinning (pseudoplasticity) of the fluid. We compared our results with bulk flows simulations done by previous workers and concluded that villous movements during longitudinal contractions is a major radial mixing mechanism in the small intestine and increases mixing and absorption around the mucosa despite adverse rheology.

Synergy of sibutramine and low-dose leptin in treatment of diet-induced obesity in rats.

Tachyphylaxis to the effects of anorexigenic agents, such as sibutramine (S), may be due, in part, to counterregulatory decreases in energy expenditure (EE) and increases in hunger that result from reduced circulating leptin (L) due to loss of body fat and lowered L production/adipocyte. The present study was conducted to test the hypothesis that L administered at low doses sufficient to restore ambient L to preweight loss concentrations would enhance the intercurrent efficacy of S by reducing the strength of physiologic counterregulation to weight loss. Forty male Sprague-Dawley rats were fed a high-fat (HF) diet (45% energy) to induce obesity. After 8 weeks, the obese rats (600 +/- 58 g) were weight-matched into 4 groups (N = 8/group) and implanted subcutaneously (SC) with 2 mL, 7-day Alzet mini-pumps that provided: vehicle (V, saline), L (0.5 mg/kg/d), S (3 mg/kg/d), or L+S. Food intake (FI) on the HF diet was measured daily. On day 7, 24-hour EE was measured by indirect calorimetry, and the animals then killed for body composition analysis. Compared with vehicle, treatment with S alone, but not L alone, produced significant weight loss (-23 +/- 26 v -6 +/- 16 g, P <.01). L alone, or with S, increased fat oxidation (decreased respiratory quotient [RQ]) compared with V (P <.05). The lack of decline in EE with S may be due to its documented effect to stimulate thermogenesis. Administration of L with S synergistically decreased FI and increased weight loss and fractional fat loss. A reduction in plasma L concentration may contribute to the "plateau phenomenon" observed in studies of weight loss therapies. Replacement doses of L during S administration increased weight loss and fractional fat loss by (1) decreasing food intake and (2) by increasing fat oxidation. Such drug combinations may be useful in the treatment of human obesity.

Serological evidence for swine hepatitis E virus infection in Australian pig herds.

Hepatitis E virus (HEV) is an enterically transmitted human pathogen, with some similarities to caliciviruses. A variant of HEV was recently identified in pigs in the USA, infecting almost 100% of animals in commercial herds. Phylogenetic analysis suggests that this is a true 'swine HEV' distinct from the human virus, but the swine virus may also infect man. Using an in-house ELISA based on a highly conserved, recombinant HEV protein, we have examined collections of sera from Australian pigs for evidence of HEV infection in local pig herds. Sera from one research herd (n = 32) were uniformly non-reactive, and this was used to establish an assay cut-off (= mean + 3 SD of reference pig serum reactivities). Screening of sera from other herds demonstrates that swine HEV is present in Australia, with reactivity observed in 30% (12/40) of random samples from two piggeries, 92-95% of pigs by the age of 16 weeks in two other piggeries (n = 45), and 17% (15/59) of wild-caught pigs. Further studies are required to examine whether HEV causes disease in pigs and to determine the risk of swine HEV transmission to man.

Effects of active and passive gonadotrophin-releasing hormone immunization on recognition and establishment of pregnancy in pigs.

This study investigated the effects of a reduction in gonadotrophins, by means of differently timed active and passive gonadotrophin-releasing hormone (GnRH) immunization at various stages, on the maintenance of early pregnancy in pigs. In the first experiment crossbred sows (n = 11) were immunized against GnRH using a commercial vaccine on the day of farrowing, mated at the first oestrus, and a booster immunization was administered 10 days (n = 7) or 20 days (n = 4) after mating. Plasma samples were collected every second day and assayed for GnRH antibodies and progesterone. Pregnancy testing was carried out by real time ultrasound. None of the sows receiving the booster immunization 10 days after mating were pregnant on Day 18 after mating. All sows receiving the booster on Day 20 after mating aborted, with a mean vaccination-to-abortion interval of 10.0 +/- 1.5 days. In the second experiment, crossbred gilts (n = 6) were passively immunized by infusing (i.v.) GnRH immune pig serum on Day 12 after mating. Luteinizing hormone profiles were determined on the day before immunization and one day afterwards. Daily plasma samples were assayed for GnRH antibodies and progesterone. None of the gilts were pregnant 18 days after mating, compared with 5 of 6 non-immunized controls. Booster immunization 10 days after mating resulted in failure of embryonic development and establishment of pregnancy before the corpora lutea (CL) regressed, according to progesterone profiles, whereas immunization 20 days after mating resulted in regression of CL followed by abortion. Passive immunization 12 days after mating had a similar effect to the active immunization 10 days after mating. These results demonstrate two different outcomes of active GnRH immunization depending on the timing of immunization, and indicate that loss of pregnancy between Days 12 and 18 may occur due a reduction in progesterone rather than complete failure of the CL, as occurs at later stages. The findings may provide an explanation for the reduced fertility of pigs in the summer-autumn period.

Effect of a gonadotrophin-releasing hormone antagonist on luteinising hormone secretion and early pregnancy in gilts.

The aims of the present study were: (1) to determine the duration of suppression of luteinising hormone (LH) following a single treatment with a gonadotrophin-releasing hormone (GnRH) antagonist (BIM-21009; Biomeasure) at a dose of 100 microg kg(-1); (2) to block LH pulses only for certain days of pregnancy; and (3) to determine the period of early pregnancy most susceptible to suppression of LH. Three groups of gilts were injected with 100 microg kg(-1) on Day 16 (n = 5), 14 (n = 6) or 19 (n = 4) of pregnancy. Blood for LH analysis was collected at 20-min intervals for 12 h on the day before treatment and during varying stages of early pregnancy. Blood for progesterone analysis was collected daily and development of pregnancy was followed using real-time ultrasound. Prior to treatment, gilts had 2.6 +/- 0.7 LH pulses per 12 h. The GnRH antagonist abolished LH pulses for a period of 2.7 +/- 1.8 days and, thereafter, suppressed the resumed LH pulses (P < 0.05). Pregnancy was disrupted in three pigs (20%) with a mean treatment-to-abortion period of 4.7 days concurrent with a mean treatment-to-progesterone decline interval of 4.3 days. In a proportion of pigs, short-term LH suppression may cause early disruption of pregnancy.

Factors effecting reproduction in the pig: seasonal effects and restricted feeding of the pregnant gilt and sow.

Recent advances in research on seasonal infertility are discussed with a special focus on implications of the generally recommended restricted post-mating feeding strategy of the early pregnant gilt and sow for the physiology of seasonal infertility. The endocrinological basis of seasonal breeding of the wild and domestic pig is being clarified: as in other seasonal breeders, melatonin is relaying photoperiodic information about season to the pituitary-gonadal axis. Earlier confusion on this matter appears to have been caused by a lack of specificity of the melatonin assays employed. Group housing of the pregnant sow is becoming a common practice and, as an important environmental risk factor for seasonal infertility, may lead to an increase in the incidence of seasonal infertility in the future. After an initial progesterone-mediated beneficial effect on embryonic survival, a restricted post-mating feeding strategy may have a negative effect on maintenance of early pregnancy in the gilt and sow in the summer-autumn period. The endocrinological mechanism of seasonal disruption of pregnancy is yet to be determined. However, it is proposed that LH is reduced in the summer-autumn period and this reduction is amplified by the commonly applied restricted post-mating feeding strategy. These changes in LH secretion, although not as such inducing CL regression, may exert a progesterone-mediated detrimental effect on the capability of embryos to produce adequate embryonic signaling. This may lead to a seasonal disruption of pregnancy and a return to oestrus 25-30 days after mating.

Effect of feed restriction and season on LH and prolactin secretion, adrenal response, insulin and FFA in group housed pregnant gilts.

A trial was designed to determine the effect of season and feed restriction on LH and prolactin secretion, adrenal response, insulin and FFA in the early pregnant gilt. Groups of cross bred gilts (n = 24) were mated and allocated to two feeding levels; a non-restricted group received close to ad libitum feeding of 3.6 kg whereas, the restricted group received 1.8 kg as recommended by the NRC. The trial was carried out in winter-spring and repeated in summer-autumn to investigate the effects of season. The feeding regimen were fed to the group housed animals for the first two weeks of pregnancy. A 12 h period of blood sampling every 15 min thereafter revealed higher amplitude LH pulses with larger area under the curve in winter compared with summer (1.17 +/- 0.03 vs. 0.69 +/- 0.03 ng ml(-1) and 65.09 +/- 1.46 vs. 33.60 +/- 1.25, P < 0.05). Overall, feed restriction reduced LH pulse frequency (2.5 +/- 0.1 and 1.6 +/- 0.1 pulses/12 h for high and low feeding levels, P < 0.05), but the difference was large in winter and no difference was detected in summer. An ACTH challenge test carried out the day after the frequent sampling revealed greater response to the ACTH challenge in winter in comparison with summer. Plasma prolactin values were generally very low and ranged from 1 to 4.5 ng/ml with highest values detected in the feed restricted group in summer. Plasma FFA and insulin concentrations showed greater pre- versus post-prandial variation in the feed restricted groups. It was concluded, that feed restriction and season affected LH secretion and those effects appeared to be related to the metabolic changes in the early pregnant group housed gilt.

Early disruption of pregnancy as a manifestation of seasonal infertility in pigs.

All gilts and sows in production from which the detailed production information was available in a 160-sow unit were included to the study. In winter-spring, there were complete data available from 47 animals and in summer-autumn from 64 animals. The farm had a consistent history of the seasonally reduced farrowing rate in summer-autumn. Success of inseminations was monitored during a 4-month breeding period in winter-spring and in summer-autumn. Each animal was bled twice a week for 6 weeks starting a day before insemination and the blood samples were assayed to determine serum progesterone concentration. The blood samples were also assayed for cortisol to detect any acute infectious response. Starting on day 18, animals were pregnancy tested by transcutaneous real time ultrasound twice a week. In winter-spring, the farrowing rate was 72% (58 inseminations, 1.2 inseminations/sow) and in summer-autumn 63% (81 inseminations, 1.3 inseminations/sow). In winter-spring, there was only one detected case of early disruption of pregnancy (EDP), whereas nine such cases were recognised in summer-autumn. Five out of those nine animals returned to oestrus with a mean insemination to oestrus interval of 25.8+/-1.6 days. One sow returned to oestrus 35 days after insemination and three sows did not return to oestrus within 45 days. However, two of these sows had progesterone profiles that indicated an undetected oestrus around day 25. In those nine animals, no acute phase infectious response as indicated by a rise in serum cortisol was evident. Serum progesterone concentrations in the animals eventually loosing the pregnancy tended to be lower on day 13 (no significant difference) and were significantly lower on day 20 when compared with animals remaining pregnant. There was no difference in serum progesterone levels of pregnant animals between winter-spring and summer-autumn. Litter size was not affected by the season. The weaning to oestrus interval tended to be longer in summer-autumn. This study showed that the seasonally decreased farrowing rate is partly caused by EDP. The lowered progesterone concentrations in summer-autumn were demonstrable only in "problem animals".

Changes in feeding level during early pregnancy affect fertility in gilts.

Modified feeding combining the benefits of restricted feeding after ovulation and abundant feeding during implantation in autumn was tested. Three groups of eight gilts were housed with individual feeding stalls and fed 40 MJ per day of a commercial ration. Following insemination gilts were fed 27 MJ per day (LLL) or 54 MJ per day (HHH) for 34 days or 27 MJ per day for 10 days, 54 MJ per day for 7 days followed by 27 MJ per day until day 34 (LHL). Blood for progesterone analysis was collected daily during the week of ovulation and then twice a week until the end of the study. For LH assay, blood was collected from five gilts from each group at 15 min interval for 10 h on the day 15 of pregnancy. Gilts were weighed three times at intervals of 4 weeks. The effect of dietary treatment was significant (P<0.05) on body weight gain from days 0 to 30 of pregnancy, 1201, 287 and 438 g per day for groups HHH, LLL and LHL respectively. The pregnancy rate at day 34 was significantly higher (P<0.005) in HHH-group (100%) compared with LLL (25%) and LHL (38%) although HHH group had significantly lower (P<0.05) progesterone concentration on days 9 and 12. The basal LH level was significantly higher (P<0.01) in HHH group compared to LHL group (mean +/- S.D.) (0.98 +/- 0.22 and 0.60 +/- 0.08, respectively). Gilts in HHH group had a significantly higher mean LH concentration (1.18 +/- 0.24) than those in group LHL (0.7 +/- 0.07) (P<0.05), but not in group LLL (0.93 +/- 0.15) (P=0.09). There was a tendency (P=0.058) for amplitude to be higher for gilts in HHH group. The LHL feeding strategy did not provide the benefits anticipated. Instead, it was the HHH feeding strategy that provided a distinct advantage in pregnancy rate. The mechanism mediating supportive effect of high feeding level on the maintenance of early pregnancy is yet to be determined.

The photophase light intensity does not affect the scotophase melatonin response in the domestic pig.

This study investigated the effects of the photophase light intensity on the scotophase melatonin response. Twelve, 8-month-old crossbred gilts were allocated to three groups of four and housed in temperature- and lighting-controlled climate rooms. The rooms had a light intensity of 40, 200 or 10,000 lx and a light-dark cycle of 12 L:12 D. The gilts were allowed to acclimatize to a new lighting regimen for 1 week before being sampled at 2h intervals for 24h. Following the sampling, pigs were transferred under a different light intensity, allowed to adjust for 1 week and sampled again. The procedure was repeated three times so that all the groups went through all three lighting regimens (light intensities). All the gilts exhibited a clear circadian serum melatonin rhythm under each lighting regimen with high melatonin concentrations occurring during the scotophase. There was no difference in the scotophase melatonin response in terms of mean concentrations or duration of increased melatonin levels within or between the groups under different lighting regimens. There was considerable inter-individual variation in the dark phase melatonin response but the individual profiles were consistent under the different lighting regimens. It is concluded that when a certain threshold light intensity (<40lx) is exceeded, the photophase light intensity has no effect on the scotophase melatonin response. These results imply that extremely high light intensities during the photophase would provide no additional benefits compared with normal comfortable light intensity, if artificial lighting programs were introduced to commercial piggeries in order to reduce seasonal effects on reproduction.

Seasonal and management effects on fertility of the sow: a descriptive study.

This study was undertaken to determine management and seasonal effects on fertility in 1298 Finnish sow units over a 4-year period in 1992-1996. A multivariate analysis of the herd record data was undertaken to study the effect of various management factors on rebreeding rate. Factors found to have an effect were further subjected to time series plotting for seasonal effects. In addition, seasonal effects on the farrowing rate, age of gilts at first mating and littersize as well as the 3-week litterweight were studied. Year and month caused the most significant variation in the rebreeding rate. Moreover, geographical area, herd and way of breeding (mating vs. artificial insemination) were found to be significant determinants of rebreeding rate. Dry sows loosely housed were more likely to be rebred than sows housed in individual stalls. Sows receiving roughage feed (hay, straw) or bedding (straw) were less likely to require rebreeding. A significant seasonal fluctuation in farrowing rate was found with a nadir of 72.6% in August and a high of 80.9% in January. The average farrowing rate for the 4-year period was 77.7%. The age of gilts at first mating showed seasonal variation of 11 days (229.9 +/- 0.5 days in March and 241.4 +/- 0.5 days in November). In conclusion, this study indicates that group housing of dry sows increases the risk of rebreeding. In group housed sows, rebreeding more often occurs after an irregular oestrus-to-oestrus interval in summer-autumn whereas a not-in-pig seems to be a more common finding at late gestation in individually housed sows.

Altered secretion of LH does not explain seasonal effects on early pregnancy in gilts.

This work was undertaken to study the effects of energy intake and gut fill on LH secretion in the early pregnant gilt to investigate the role of the hypothalamo-pituitary-gonadal axis in the seasonal disruption of pregnancy. Four groups of mated gilts (N = 23 in total) were individually housed and fed four different energy levels (23, 46, 47 and 55 megajoules digestible energy per day, MJ DE day-1) for two weeks after mating during the season identified as a period of increased rate of early pregnancy failures from January till April (summer-autumn). The energy content of base feed (13 MJ kg-1) was increased by means of adding a fat supplement (soybean oil) to the feed of two groups of gilts, while the other two groups were given different levels of the basic feed. The groups gained weight and backfat according to energy intake levels during the two-week period. Frequent blood samples (15-min interval) collected on day 14 revealed a significant treatment effect on LH pulse amplitude: the group on the highest energy intake level (55 MJ DE day-1) had higher LH pulse amplitude compared with the other groups (1.01 +/- 0.04, 0.74 +/- 0.04, 0.72 +/- 0.08 and 0.66 +/- 0.05 ng ml-1 in the descending order of energy intake, P < 0.01). There was no effect of energy intake on LH pulse frequency, mean level, area under the curve or mean nadir (P > 0.10). Plasma insulin concentrations tended to increase (P < 0.08) in each group with time after feeding, but no significant differences between the treatment groups were found. Plasma free fatty acid (FFA) concentrations were decreased 1 h after feeding (P < 0.05) in all but the group on 55 MJ DE day-1. This group also had higher postprandial FFA concentrations in comparison with other groups (P < 0.05). In conclusion, these results show that energy density of feed and energy intake have little effect on LH secretion in the early pregnant gilt. Protective effect of high feeding level against seasonal disruption of pregnancy appears to be mediated by mechanisms other than an alteration in LH secretion.

Seasonal infertility in pigs.

A retrospective study of a seasonal infertility problem in a large intensive piggery showed that during the periods of infertility there was a significant increase in the numbers of sows returning to oestrus in the periods 22 to 37 and 44 to 53 days after mating. A prospective study showed that the majority of sows affected by the seasonal infertility problem returned to oestrus during the fourth of fifth week after mating. However, some sows did not exhibit a normal behavioural oestrus at this time and so the oestrus was undetected until and sow completed another oestrous cycle accounting for the second period of increased returns at 44 to 53 days. Some sows failed to exhibit behavioural evidence of oestrus at this second to exhibit behavioural evidence of oestrus at this second oestrus and so had very prolonged mating to detectable oestrus intervals.

Definition of a seasonal infertility problem in pigs.

A summer infertility problem was investigated on a large intensive piggery in a warm temperate climatic zone in Eastern Australia. The period of infertility correlates with the period of summer heat stress. The infertility problem was manifest as a delayed return of sows to oestrus after mating and an increase in the number of sows found non-pregnant when due to farrow. Litter size was apparently not adversely affected. Gilts and first parity sows were most frequently involved. The subsequent breeding performance of sows affected by this infertility problem was quite normal. There was no apparent effect of heat stress on the boars. It is proposed that the infertility is caused by heat stress imposed more than seven days after mating causing whole litter loss and the return of the sow to oestrus.

Reproductive performance of first parity sows.

An investigation of the reproductive performance of first parity sows is described. In a retrospective study it was found that the size of the second litter was significantly greater in those sows with a prolonged weaning to oestrus interval of more than 15 days. Deliberately delaying mating until at least 12 days after weaning produced a similar increase in second litter size. This improvement was not associated with an increase in ovulation rate.

Proliferative haemorrhagic enteropathy in pigs.

An outbreak of proliferative haemorrhagic enteropathy (PHE) occurred in two epidodes and affected 372 adult pigs in the breeding units of a minimal disease piggery; 186 pigs died. In the initial episode breeding sows and boars of all ages were affected, suggesting infection of a fully susceptible population. Animals involved in the first episode of the disease did not show clinical symptoms at a later date and further clinical cases occurred only in animals introduced into the breeding population. Antibiotic feed medication was an effective method of prophylaxis. Bacteria resembling Campylobacter sputorum subspecies mucosalis were isolated from the intestinal mucosa of affected animals.

Seasonal effects on reproduction in the domestic sow in Finland--a herd record study.

Seasonal effects on fertility of the domestic sow were assessed by retrospective analysis of the Finnish national computerised data management system covering 1081 herds in 1993. Multivariate analyses were used, where the reproductive parameter of interest (repeat breeding, weaning to oestrus interval, age of gilts at first farrowing, litter size, culling due to anoestrus or no conception) was designed as the response variable. The months of the year (each month compared with January) and all herds and breed were included in the models as explanatory variables. The study demonstrated clear seasonal effects on various aspects of fertility in the domestic sow. The poorest reproductive performance was consistently observed in late summer and autumn and was demonstrated in a number of ways. Firstly, the gilts born between December and April were older (> 5 days) at farrowing than those born during the rest of the year (p < 0.01). Secondly, the risk that a culled sow would be culled due to anoestrus was significantly increased during the autumn months (Odds Ratio (OR) ranged from 1.10 to 1.36). Thirdly, the risk of a repeat breeding was higher from July to November (OR = 1.16). Risk of a prolonged weaning-to-oestrus beyond day 10 was the highest from August to October (OR ranged from 1.70 to 1.77). Risk of a sow to be culled due to no conception was the highest in January and February (weaned in October-November). In addition, descriptive data gathered in a slaughterhouse in 1993 (a subpopulation of the sows included in the herd records) suggest that incidence of inactive ovaries is increased in summer-autumn (p < 0.05). In conclusion, a marked reduction in fertility of the domestic sow in Finland is reported between July and November.