Confinement of lactating sows in crates for 4 days after farrowing reduces piglet mortality

To reduce mortality among suckling piglets, lactating sows are traditionally housed in farrowing crates. Alternatively, lactating sows can be housed in farrowing pens where the sow is loose to ensure more behavioural freedom and consequently a better welfare for the sow, although under commercial conditions, farrowing pens have been associated with increased piglet mortality. Most suckling piglets that die do so within the first week of life, so potentially lactating sows do not have to be restrained during the entire lactation period. Therefore, the aim of the current study was to investigate whether confinement of the sow for a limited number of days after farrowing would affect piglet mortality. A total of 210 sows (Danish Landrace × Danish Yorkshire) were farrowed in specially designed swing-aside combination farrowing pens measuring 2.6 m × 1.8 m (combi-pen), where the sows could be kept loose or in a crate. The sows were either: (a) loose during the entire experimental period, (b) crated from days 0 to 4 postpartum, (c) crated from days 0 to 7 postpartum or (d) crated from introduction to the farrowing pen to day 7 postpartum. The sows and their subsequent litters were studied from introduction to the combi-pen ∼1 week before expected farrowing and until 10 days postpartum. Confinement period of the sow failed to affect the number of stillborn piglets; however, sows that were crated after farrowing had fewer live-born mortality deaths (P < 0.001) compared with the sows that were loose during the experimental period. The increased piglet mortality among the loose sows was because of higher mortality in the first 4 days after farrowing. In conclusion, the current study demonstrated that crating the sow for 4 days postpartum was sufficient to reduce piglet mortality.     

Some Factors Influencing Pregnancy Rate and Subsequent Litter Size in Primiparous Sows

The pregnancy rate and the subsequent litter size were studied in 332 Swedish Yorkshire primiparous sows, fed according to a commercial Swedish feeding regime during lactation. The sows were weighed and backfat depth was recorded at the first farrowing, at weaning, and at mating. Oestrous detection was performed once daily after weaning, and the interval from weaning to first oestrus (IWO) was recorded. Blood samples for determination of plasma progesterone were drawn regularly after the first weaning. Statistical analyses were only performed on sows with an IWO of 3-8 days. Of these 206 sows were mated on their first (OE1 sows) and 87 sows on their second (87 OE2 sows) oestrus after weaning. The pregnancy rate was 85.4% for OE1 sows and 75.9% for OE2 sows (p=0.048). There was no significant difference in pregnancy rate between OE1 sows with an IWO of 3-5 days and OE1 sows with an interval of 6-8 days. OE2 sows with an IWO of 6-8 days, on the other hand, had a significantly lower pregnancy rate compared with OE2 sows with an interval of 3-5 days. The pregnancy rate in sows that lost more than 30 kg during the first lactation period did not differ from that of sows losing less than 30 kg. In sows with a first litter size of more than 9 piglets alive at birth, the pregnancy rate decreases significantly if mating is delayed until the second oestrus after weaning. OE2 sows had a significantly larger second litter size at birth than OE1 sows (+ 2.0). The litter size at six weeks did not, on the other hand, differ significantly (+ 0.4). There was a positive correlation between the IWO and 2nd litter size, although significant only for OE1 sows between the IWO and litter size alive at birth. In the OE1 group, sows losing 20 kg or less during lactation had significantly larger second litters at birth than the sows losing 21-30 kg, but not significantly larger than the sows losing more than 30 kg. One piglet more, at birth, in the first litter resulted in 0.25 piglet more in the second litter. For sows with a large first litter there was a low probability of also having a large second litter.     

Monitoring blood plasma leptin and lactogenic hormones in pregnant sows

The mechanism of action of leptin in pregnant breeding sows, in which hyperphagia is managed through dietary strategies, is yet to be clarified. The aim of this study was to monitor leptin concentrations and their interactions with lactogenic hormones in Large White×Landrace breeding multiparous sows (n=15). All sows showed a normal body condition (mean body condition score: 2.96). Blood samples were collected the day after weaning the litters, at insemination, every 15 days up to day 45 of pregnancy and every 7 days from day 46 to farrowing. At delivery, the placenta was collected for the analysis of leptin and leptin receptor expressions. Plasma leptin levels increased from the end of mid gestation (day 72) and remained high until farrowing (P<0.05). As expected, plasma prolactin (PRL), low during most of pregnancy, increased during the 2 weeks before farrowing (P<0.05), whereas progesterone levels reached plateau at 30 days of gestation and decreased at farrowing (P<0.05). Cortisol levels peaked close to farrowing (P<0.05). Leptin was expressed in the placenta, where the receptor expression analysis showed the presence of the short form but not of the long form. A positive correlation was found between leptin and PRL concentrations during mid (r=0.430; P<0.001) and late (r=0.687; P<0.001) pregnancy, and with progesterone in early pregnancy (r=0.462; P<0.05). During late gestation, a positive correlation was observed between leptin and cortisol (r=0.585; P<0.001). Our results suggested that, in restrictively fed pregnant sows, the leptin levels increased from the end of mid pregnancy to delivery, confirming the presence of leptin resistance. We showed a correlation between leptin and lactogenic hormones during different stages of pregnancy in sows. Lactogenic hormones show pregnancy-specific changes in their secretion and all may become involved in modulating leptin signal.     

Control of parturition in the sow using progesterone and prostaglandin

The effect of progesterone and prostaglandin administration on the timing of farrowing was studied in three groups of 25 sows each. Progesterone treatment (100 mg/day) on days 112, 113 and 114 of gestation (group I) significantly prolonged the gestation length to 116.4 +/- 0.4 (mean +/- s.e.) days compared to the control sows (group III; 115.5 +/- 0.2; P less than 0.05). Administration of prostaglandin (200 micrograms Cloprostanol intramuscularly) on day 115 of gestation following progesterone treatment (group II) resulted in a gestation length of 116.0 +/- 0.1 days, with the sows farrowing 25.4 +/- 1.0 h after the prostaglandin injection. 80% of the sows farrowed between 0800 and 1700 h of day 116 of gestation. Plasma progesterone levels were maintained by the exogenous progesterone during treatment. At farrowing, higher levels of progesterone were observed in groups I and II compared to controls. Prostaglandin treatment did not significantly alter withdrawal of progesterone in progesterone treated sows, suggesting that the actions of exogenous prostaglandin is primarily on the myometrium and the cervix. Hormonal treatment in late pregnancy did not have any adverse effects on piglet viability and growth rate, or subsequent reproductive performances of sows. Lactation was initiated normally, and the concentrations of lactose, protein, fat, IgG, Na+, Ca2+ and K+ in colostrum and milk were similar in all groups during the first 5 days of lactation.     

Plasma Thyroxine in the Sow During Pregnancy and Lactation and During Resumption of Ovarian Activity After Weaning

Total thyroxine in plasma was studied during pregnancy, lactation and during the post weaning period. The ovarian activity was monitored by progesterone determinations, and oestrous symptoms were recorded. In the two sows studied during pregnancy there was a distinct decrease in total thyroxine values in the last month of pregnancy, reaching a minimum about the time of farrowing. Total thyroxine values stayed low during lactation, but from about the time of weaning and during the following two weeks the concentrations increased rapidly. There was no difference in the thyroxine pattern in sows resuming ovarian activity within normal time (10 days) after weaning (72 sows) compared with sows with delayed resumption of ovarian activity (19 sows). The thyroxine level after weaning did not differ between sows with “silent 11631” and sows with overt oestrus. Primiparous and pluriparous sows had also similar thyroxine values after weaning. Sows weaned in January—June had a little higher thyroxine concentrations after weaning than sows weaned in July—December. There was a significant negative correlation between number of suckling piglets and thyroxine concentrations before weaning. Free thyroxine index was calculated in some selected samples. The results suggested that the changes observed in total thyroxine reflect changes in the free thyroxine concentrations.     

A Long Term Study on the Health Status and Performance of Sows on Different Feed Allowances during Late Pregnancy

Thirty nine pairs of full sibs were investigated over 6 parities in a long term study on the effects of late pregnancy feed allowance on the occurrence of agalactia post partum and on the performance of sows and piglets. A careful examination of all sows with a rectal temperature exceeding 39.5°C was performed by a veterinarian within the first 48 h after farrowing. Milk-samples were taken from sows with elevated rectal temperatures and showing clinical symptoms of agalactia. During the last 15 days of gestation the sows in the control group were fed 3.4 kg daily and the sows in the experimental group 1.0 kg daily of a commercial type of diet. In 26.6 % of the farrowings in the control group the sows were agalactic whereas the corresponding figure in the experimental group was 14.4%. On clinical examination udder changes were observed in a majority of the diseased sows in both groups. However, the agalactic sows in the control group were generally more affected, with lower water and feed consumption than in the experimental group. No effects of age of the sow (parity number) or length of the gestation period on the incidence of agalactia were demonstrated. The rectal temperature of agalactic sows was significantly higher than in the healthy sows already 1 day before farrowing. The agalactic sows farrowed a larger number of stillborn piglets, which indicates an early establishment of the disease. The number of weaned piglets at 6 weeks did not differ between agalactic and healthy animals. The interval from weaning to first oestrus was not influenced by agalactia in the preceding lactation.     

Comparison of three different farrowing systems: skin lesions and behaviour of sows with special regard to nursing behaviour in a group housing system for lactating sows

While group housing (GH) is mandatory in the European Union for the greater part of pregnancy, single housing in farrowing crates (FCs) during lactation that restrict sows in most of their natural behaviour patterns is still practised on a large scale. Research is urgently needed to develop alternative farrowing systems that improve sows’ welfare. Therefore, sows in three different farrowing systems – pens with FC, loose housing (LH) pens and GH for six sows – were compared regarding the level of skin injuries and their active and resting behaviour. A skin injury score was assessed for 15 body parts of 102 sows in six batches on 3 days (days 1, 14 and 34). In total, the active and resting behaviour of 77 sows in six batches was examined on 3 days (days 18, 25 and 32) between 0700 h and 1900 h by means of a scan sampling method. The suckling behaviour and the level of cross-suckling were analysed in GH by means of direct observation in four batches during three 4-h sampling periods (days 17, 24 and 31). No significant differences were found in total skin injuries when the sows entered the systems (day 1), but GH sows showed significantly higher total skin injuries compared to FC and LH sows in the middle (day 14) and at the end (day 34) of the lactation period. A significant difference between FC and LH sows was never seen. Differences were found for the proportion of different body postures between the three systems. The odds for lying in lateral recumbency versus standing and sitting versus standing were significantly higher for FC and LH sows compared to GH sows. Additionally, sows were significantly more likely to be standing as opposed to lying in lateral recumbency as the lactation period progressed. Cross-suckling was a frequent behaviour in GH, seen in 35.0% of all successful suckling bouts. However, only an average of 0.56 piglets per successful suckling bout was observed cross-suckling, suggesting only a few piglets were engaged in cross-suckling. In conclusion, the skin injury score was only moderately increased in GH compared to FC and LH and comparable to pregnant group-housed sows, both free farrowing systems seemed to be an environmental enrichment for lactating sows and good management cannot prevent the occurrence of cross-suckling in a GH system, but can probably reduce it.     

The effect of farrowing environment and previous experience on the maternal behaviour of sows in indoor pens and outdoor huts

Outdoor farrowing huts facilitate a less restricted maternal behaviour in sows compared with sows kept indoors in farrowing pens. The aim of our study was to investigate whether there are behavioural differences between primiparous sows kept outdoors in farrowing huts and indoors in pens, and whether the maternal behaviour during the second parity, when all sows were kept outdoors in farrowing huts, would differ between sows that have experienced the indoor or the outdoor environment, respectively, during their first parturition. A total of 26 Yorkshire×Swedish Landrace sows were studied. Of these, 11 sows were housed outdoors in farrowing huts during both parturitions (group=OUTOUT). The other 15 sows were kept indoors in a barn with single farrowing pens during their first parturition. During their second parturition, sows were kept outdoors in farrowing huts (group=INOUT). The behaviour was video recorded from 2 h prepartum to 48 h postpartum. The sows’ responsiveness to playbacks of a piglet’s screams was tested on days 2 to 3 postpartum. Parity 1: during the last 2 h prepartum, OUTOUT sows had a higher proportion of observations in the sternal lying position (P<0.01). During parturition, OUTOUT sows changed posture more often (P<0.05) and were lying less (P<0.05) than INOUT sows. All sows in both groups responded with ‘lifting head’ towards the playback of piglet scream, whereas 100% of OUTOUT sows and only 43% of INOUT sows thereafter were ‘getting up’ (P <0.01). Parity 2: There were no behavioural differences between INOUT and OUTOUT sows. In conclusion, it is not problematic for a second parity sow with initial maternal experience from an indoor farrowing pen to be kept outdoors in farrowing huts during its following farrowing.     

A retrospective study on the preserving capacity of a commercial boar semen extender

The objective of this study was to evaluate the preserving capacity of a commercial, long-term boar semen extender beyond 4 days in terms of farrowing failure and total born per litter in sows and gilts. Data from 21 farms were subjected to logistic and linear regression analyses to assess the effect of parity (2-5, > 5 and gilts), wean-to-service interval (/= 6 days) and number of AI (1, 2, or 3) on the association between semen age (/=10 days) and fertility. As the semen age increased, the likelihood of farrowing failure increased and total born per litter decreased in sows and gilts. The effect of semen ageing on farrowing failure was more pronounced in sows than in gilts as in the latter it became significant only after 8 days. The effect of semen ageing on total born per litter was similar in both sows and gilts. A lower parity and wean-to-service interval were associated with a reduction in farrowing failure and increase in total born per litter in sows. Increasing the number of inseminations up to two was beneficial in reducing farrowing failure in sows and gilts. A third insemination increased the likelihood of farrowing failure in sows. The number of total born per litter in sows increased with number of inseminations and the effect was not significant in gilts.     

Evaluation of false ultrasonographic pregnancy diagnoses in sows by measuring the concentration of unconjugated estrogens in feces

On Days 26, 28, and 30 after AI, ultrasonographic pregnancy diagnoses were performed on 207 gilts and sows by using a 3.5 MHz linear-array transducer. Fecal samples were taken from the rectum after each ultrasonographic examination, and the concentrations of unconjugated estrogens in selected samples (n = 73) were measured by RIA. Fecal unconjugated estrogen concentration of 11.7 ng/g feces or higher was indicative of pregnancy. The overall sensitivity and specificity of the ultrasonographic test was 99% for farrowing sows and 73.1% for nonfarrowing sows. With one exception, sows with a false negative diagnosis by ultrasonography on Day 26 were correctly diagnosed pregnant by elevated fecal unconjugated estrogens or repeated ultrasonographic examinations on Days 28 or 30. Return to estrus around the sampling period may cause false positive results in the unconjugated estrogen assay, while early embryonic mortality can result in false positive diagnoses in both the ultrasonographic test and estrogen assay. Although there was a positive correlation between the concentrations of unconjugated estrogens in the feces and litter size at farrowing in the selected sows, it seems very unlikely that fecal estrogens can provide an accurate tool for predicting litter size.     

An interaction between feeding rate and season affects fertility of sows

Trials were conducted in two piggeries in the summer-autumn and winter-spring periods to determine the effects of rate of feeding and type of housing (group or individual stalls) on farrowing rate. Sows were fed a low (1.6–2.0 kg per sow per day), moderate (2.5 kg per sow per day) or high (> 3.6 kg per sow per day) rate for the first 4 weeks postmating and from then until farrowing fed at a moderate (2.5 or 3.2 kg per sow per day) rate. The low level of feeding in the summer-autumn was associated with increased numbers of delayed returns to oestrus and low farrowing rate (< 75%) typical of the infertility that occurs at this time of the year. This same rate of feeding in winter-spring was associated with few delayed returns to oestrus and a high farrowing rate (> 85%). Feeding sows at the high rate during the summer-autumn significantly improved the farrowing rate reducing the adverse effect of season. Litter size was not affected by feeding rate during early pregnancy. The seasonal effect on farrowing rate was not evident in individually stalled sows fed a moderate level during pregnancy. This study demonstrated effects on farrowing rate of interactions between rate of feeding and season and type of accommodation and season. Current practice restricting feed intake postmating, aimed at reducing embryonic mortality and increasing litter numbers, appeared to contribute substantially to the decrease in farrowing rate commonly observed in summer-autumn. The optimal level of feeding to minimise the effect of season on fertility has yet to be defined. Accommodation of sows in individual stalls, rather than in groups, removed the seasonal effect on fertility.     

Floor temperature preference of sows at farrowing

A preference testing apparatus was used to provide sows with continuous access to three identical farrowing crates, each with a different floor temperature. The concrete floor under each crate contained copper pipe through which temperature-controlled water was circulated to achieve unoccupied floor temperatures of 22 degrees C (+/-3.5), 29 degrees C (+/-1) and 35 degrees C (+/-1). Eighteen sows were tested in the apparatus. Video recording was used to determine sow position from 7 days before farrowing (Days -7 to -1) to 14 days after (Days 1 to 14). On Days -7 to -1, sows showed no significant preference among the three temperatures when selecting a resting area. Once farrowing had begun, there was a significant increase (P<0.01) in the use of the 35 degrees C floor and it became the most preferred resting area for Days 1 to 3. After this interval, use of the 35 degrees C floor declined significantly (P<0.01), and use of the cooler floors increased, resulting in no significant thermal preference during Days 4 to 6. There was a further decline in the use of the 35 degrees C floor after Days 4 to 6 (P<0.01) to the extent that the coolest floor (22 degrees C) became the most preferred from Days 7 to 14. In summary, sows showed a pronounced increase in preference for a warm floor during the 3 days after the start of farrowing. This change in preference may explain how free-living sows select a suitable thermal environment for their young, and why sows try to avoid metal flooring at the time of farrowing.     

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".     

Effect of the environment on the physiology of the sow during late pregnancy, farrowing and early lactation

We investigated the effect of two types of housing on the duration of farrowing and the physiology of sows before and after farrowing. We assigned 20 sows (PEN) to farrowing pens (210 cm x 335 cm) enriched with straw bedding and 18 sows (CRATE) were placed in farrowing crates (80 cm x 210 cm) with no bedding material. We sampled the animals during period A (from day -5 before farrowing to day +1 of lactation) and during period B (from days +2 to +5 of lactation). We took daily venous blood samples for progesterone measurements and four salivary samples per day (at 09:00, 11:00, 13:00 and 15:00) for cortisol determination. In addition, intensive blood sampling was performed in 18 catheterised sows (9 PEN and 9 CRATE) to determine the level of oxytocin during farrowing. The treatment had no effect on litter size, piglet mortality at birth and weaning, growth of the piglets between days 1 and 5 of life. We found no significant difference in the cortisol concentration between the two groups during period A (p=0.36). Significant difference was found in period B, where the CRATE group had a higher concentration of cortisol than the PEN group (p=0.03). Progesterone concentration did not differ between the two groups (p=0.80). The duration of farrowing was on average 93 min longer in the CRATE sows (n=15), with a mean of 311+/-35 min (mean+/-S.D.), than in the PEN sows (n=19), with a mean of 218+/-24 min (p=0.03). In addition, the mean interval between each piglet expulsion was longer in the CRATE group (n=11), with a mean of 25+/-4 min, than in the PEN group (n=15) with a mean of 16+/-2 min (p=0.05). During farrowing, the post-expulsion oxytocin pulses average tended to be higher in the PEN group (77.6+/-47.6 ng/ml) than in the CRATE group (38.1+/-24.6 pg/ml) (p=0.08). The concentration of oxytocin strongly affected the duration of farrowing (p<0.001). In conclusion, this study showed that the environment influences the physiology of the sow during farrowing and early lactation.     

Supplying sows energy on the expected day of farrowing improves farrowing kinetics and newborn piglet performance in the first 24 h after birth

The farrowing process is one of the most energy-demanding activities for the modern hyperprolific sow. This study evaluated the effects of supply of energy on the expected date of farrowing on the farrowing kinetics and piglets’ performance during the first 24 h after birth. A total of 80 sows were used. The sows and their respective litters were considered as the experimental unit. On the expected day of farrowing, the sows were allocated to one of the following groups: sows that did not have access to feed from farrowing induction until the end of the farrowing process (CON, n = 40); sows fed 500 g of energetic supplement, which consisted of 250 g of the basal lactation diet plus 250 g of cane sugar, 18 h after farrowing induction (SUP, n = 40). The farrowing duration, farrowing assistance, birth interval, number of total born, stillborn and mummified piglets were recorded for each sow. Piglets were weighed individually at birth and 24 h later. The interval from birth to first suckle was evaluated individually for each piglet in 16 randomly selected litters (eight litters per treatment group). Blood glucose concentrations of six sows were measured shortly after expulsion of the first piglet. Farrowing duration, farrowing assistance and stillborn rate tended to be greater (P = 0.06, P = 0.09 and P = 0.07, respectively) in sows from the CON group compared to sows from the SUP group. However, there was no difference (P > 0.05) between the groups for birth interval. Colostrum intake was greater (P < 0.05) for piglets from the SUP group compared to piglets from the CON group. Additionally, BW gain of the piglets suckling the SUP group was greater (P < 0.05) than those suckling the CON group at 24 h after birth. The blood glucose concentrations during the expulsive stage of farrowing were greater (P < 0.05) in the SUP group than for sows from the CON group. In conclusion, supplying modern hyperprolific sows energy on the expected day of farrowing is a valuable nutritional intervention to improve the farrowing kinetics and piglets’ performance in early life.     

Early piglet mortality in loose-housed sows related to sow and piglet behaviour and to the progress of parturition

The aim of the present study was to identify characteristics of sow behaviour and parturition related to early piglet mortality in loose-housed farrowing sows. Data from 152 farrowings that originated from three different herds with loose-housed sows during parturition were used. Graphical chain models were used to model the relationships between perinatal behaviour, periparturient individual conditions (time of day of parturition, rectal temperature 1–3 days postpartum) and causes of early piglet mortality. Modelling was based on the correlation between variables within herd and farrowing batch.The analysis showed that different causes of mortality were linked to different behavioural variables during the periparturient period and that they grouped into three independent categories. The first category was associated with stillbirth and death due to other causes. Stillbirth was positively related to the variation of the inter-birth interval and negatively related to the percentage of piglets that suckled during the first 8 h after birth of first piglet (BFP). Death due to other causes was negatively related to the suckling activity during the post-partal period (9–24 h after BFP). The second category was associated with piglet crushing, which was positively related to much lateral lying the last 4 h before BFP. Finally, the third category was associated with death due to lack of colostrums ingestion of colostrum, which was linked to the time of parturition and sow rectal temperature on days 1 and 2 after farrowing. Sows that gave birth during the morning compared to evening/night had more dead piglets due to lack of colostrums ingestion. Death due to lack of colostrums ingestion was also higher in sows with high rectal temperature on the day after BFP. The results further showed that litter size not only influenced mortality but also behavioural variables. High litter size was related to high nest building activity before BFP, low but more variable inter-birth intervals, and much lateral lying after BFP. The study points towards several areas of interest for further research that can help understand early piglet mortality. These include causes of variation in the progress of parturition, causes of individual differences in sow activity and responsiveness to piglets, and early management of farrowing. In addition, the study suggests possible indicators of problematic farrowings rendering liveborn piglets at risk. These include prepartum lateral lying in the sow, low suckling activity and rate of stillbirth.     

The importance of farrowing to service interval in sows served during lactation or after shorter lactation than 28 days

In a retrospective study, based on data from the national litter recording system, farrowing rate and litter size of sows served (inseminated or mated) during the lactation period (n = 574) or after a lactation period shorter than 28 days (n = 14,219) were analysed. The results were compared with the corresponding figures for sows with lactation length between 28 and 35 days and weaning to first service interval of 4 or 5 days (reference group; n = 41,741). The farrowing rate of the reference group was 80.9% and subsequent litter size was 13.7 total piglets born. Among sows served prior to weaning, the farrowing rates and litter sizes were significantly lower for those served earlier than 22 days post-farrowing compared to those served later (P < 0.05). Shorter lactations than 28 days and service within 10 days post-weaning led to lower farrowing rates than in the reference group (P < 0.01). Significant differences were seen after different lactation lengths. After correction for weaning to service interval, preceding litter size weaned, parity, breed and the interaction between parity and breed, litter size was significantly and positively associated with the preceding lactation length. The study shows that service within the first 3 weeks post-farrowing results in reduced reproductive performance.     

Reproductive performance of gilts and sows in temperate versus subarctic and arctic zones of Norway

The reproductive performance of gilts and sows from two regions in Norway was investigated in a retrospective analysis of data from the litter recording system. In the Northern region (North; between 65°N and 71°N), there are extreme shifts in natural photoperiod between winter and summer. In the Southern region (South; between 59°N and 60°30′N), photoperiodic changes are less dramatic.

Gilts were 8 days older at first mating or insemination in the North than in the South (P<0.01). A significantly lower proportion of sows in the North were mated or inseminated within 5 days post-weaning than in the South, a difference present both among primiparous and multiparous sows (P<0.01). Overall farrowing rate in the North was lower than in the South, but litter size (total number born) among those pigs that farrowed was larger. After correction for year, month, breed and age at first service, there were still lower odds of farrowing for gilts in North than in South. Neither for primiparous nor multiparous sows were regional differences in farrowing probability significant when year, month, breed and weaning to service interval were included in the model. Gilts and primiparous sows had a lower probability of farrowing following insemination during summer or autumn months, but service month was not significantly related to the farrowing probability of multiparous sows.

For gilts, litter size was positively related to age at first service. For sows, litter size was lowest at weaning to service intervals between 6 and 10 days. Total numbers of piglets born per litter were estimated to be 0.36, 0.38 and 0.55 larger in the North than in the South (differences in least square means; gilts, primiparous sows and multiparous sows, respectively) (P<0.01). Litter size was lower after service during natural long photoperiod than during the rest of the year.     

Effects of meloxicam (Metacam®) on post-farrowing sow behaviour and piglet performance

Farrowing is an intrinsically risky process for both the sow and the piglets that can cause welfare and economic problems. The effects of the non-steroidal anti-inflammatory drug meloxicam on post-farrowing behaviour of sows, and the performance of piglets were investigated. A total of 48 sows were randomly allocated at the day of farrowing (day 0) into two homogeneous groups regarding parity, and treated with either meloxicam or saline solution as placebo. For each sow, number of position changes, total time lying and standing or sitting, feed intake and rectal temperature (RT) were recorded during 3 days after farrowing. Piglets were individually weighed at farrowing and at weaning. The number of position changes did not show significant differences between treatments (P = 0.79). Sows spent significantly less time lying during day +3 after farrowing in the meloxicam group than in the placebo group (P = 0.04). Feed intake and RT showed a parity effect (P < 0.001 in both cases); however, no treatment effect was observed (P = 0.67 and P = 0.47, respectively). Pre-weaning mortality rate in piglets was not affected by treatment. In litters from multiparous sows, piglets of low birth weight (defined as percentile 15: BW <1180 g) had an average daily gain significantly higher in the meloxicam group than in the placebo group (196.6 ± 7.2 v. 166.6 ± 9.1 g/day; P = 0.03). Although the administration of meloxicam 90 min after farrowing showed a positive effect on the total time lying of the sows, additional investigations are required to better qualify relevant indicators of pain following farrowing in sows and to specify the analgesic effects of meloxicam on piglet performance.     

Ontogeny of the opioidergic regulation of LH and prolactin secretion in lactating sows. II: Interaction between suckling and morphine administration

Administration of morphine to ten suckled and nine zero-weaned (piglets removed immediately after farrowing) sows was used to investigate the apparent absence of opioid regulation of LH and prolactin secretion in early lactation. Blood samples were collected at 10 min intervals at 24-30, 48-54, 72-78 h post partum, and for a 12 h period from 08:00 to 20:00 on day 10 after farrowing. Morphine (0.1 mg kg-1) was administered as three i.v. bolus injections at intervals of 1 h during the last 3 h of each of the 6 h sampling periods, and at 6, 7 and 8 h after the beginning of sampling on day 10. There were significant (P < 0.001) group (zero-weaned versus suckled), time and morphine effects on LH secretion. Plasma LH concentrations increased (P < 0.001) within 48 h of farrowing in zero-weaned sows. Long-term trends of an increase in mean plasma LH in the sampling periods before treatment were attenuated in both groups by morphine treatment. Morphine also significantly inhibited (P < 0.05) prolactin secretion in suckled sows. In zero-weaned sows, plasma prolactin was already low at the start of sampling and did not change with time or in response to morphine treatment. Therefore, the inability to demonstrate an opioidergic involvement in the suckling-induced inhibition of LH secretion during the early post-partum period in sows is not due to a lack of opioid receptors. Furthermore, in suckled sows, morphine is stimulatory to systems that have an inhibitory effect on prolactin secretion.