Environmental enrichment in early life affects cortisol patterns in growing pigs.

Effects of environmental enrichment at different stages of life on stress physiology of pigs were investigated in a trial with 63 groups, each of four siblings. In each of the three growing phases (suckling 0 to 4 weeks of age, nursery 5 to 9 weeks, fattening 10 to 24 weeks) pens either were (=E) or were not (=0) enriched. Accordingly, the treatments were (i) 000, (ii) E00, (iii) EE0, (iv) 00E, (v) 0EE and (vi) EEE. The enrichment material, renewed twice daily to leave a thin layer, consisted of wood shavings and chopped straw. Salivary cortisol was sampled hourly from 0700 to 1900 h at the age of 9 and 21 weeks. The presence of a circadian secretion rhythm was evaluated by an intra-assay coefficient of variation-based method. An adrenocorticotropic hormone test was performed at 21 weeks. Treatment effects on the odds of a physiological cortisol rhythm were assessed by logistic regression, and effects on cortisol concentrations with a repeated measures GLM. Substrate-enrichment from 0 to 9 weeks of age increased the odds of a rhythm as compared to barren housing (odds ratio (OR) = 30.0, P < 0.01). A flat cortisol secretion pattern may indicate chronic stress and/or delayed maturation of the rhythm. Barren as compared to enriched rearing (0 to 4 weeks of age) seemed to cause a blunted secretion rhythm at 21 weeks of age. Although behavioural and tail lesion observations provided support to the assumption that a blunted rhythm indicates chronic stress, the biological significance of these cortisol results needs confirmation in future studies.

Fertility of sows fed ad libitum with a high fibre diet during pregnancy.

The effect of ad libitum (ADLIB) feeding strategy on the fertility of the group housed sow was studied in a prospective field trial during 1.5 years. All study animals farrowed under standard farrowing circumstances in crates, and they were provided with an ad libitum feeding throughout the 30-day lactation. After weaning, animals were randomly allocated to one of the two dry sow feeding strategies (AD LIB or CONT). After oestrus detection in groups, they were artificially inseminated and moved into pregnancy pens with partially slatted floor, in groups of 40 sows each. The ADLIB sows (n = 447) were loose housed and provided with ad libitum access to 7.7 MJ/kg feed high in fibre from two feeders per group. The control sows (n = 479; CONT) were also loose housed and given a standard dry sow feed in feeding stalls once a day (2.5 kg/day. The energy content of the feed was 9.3 MJ/kg NE). The feeding strategy (ADLIB vs CONT) had no effect on pregnancy rate (85.8 vs 90.9, p > 0.05), weaning to oestrus interval (7.7 vs 7.3 days, p > 0.05), piglets born alive (11.5 ± 3.5 vs 11.6 ± 3.3, p > 0.05), stillborn piglets (1.2 ± 1.8 vs 0.9 ± 1.5, p > 0.05) nor on progesterone concentration (p > 0.05). CONT sows weaned more piglets (9.7 ± 2.2 vs 9.4 ± 2.0, p < 0.01), whereas the piglets of AD LIB sows were heavier at weaning (8.8 ± 0.9 vs 8.0 ± 1.3 kg, p < 0.05). In conclusion, ad libitum feeding with a high in fibre diet during pregnancy did not affect the reproductive performance.

Re-modelling the piggery breeding unit may affect the farrowing rate.

The objective of this retrospective cohort study was to clarify the effect of re-modelling the breeding unit on farrowing rate. The original study population included 63 sow herds that participated in the Finnish herd surveillance system. In these herds, the breeding units were re-modelled between 1995 and 2002. Information about the production system and other herd data for the last year before and the second year after re-modelling were available for 47 herds. The herds had an average of 68.5 (SD 45) sows per herd. Data were collected during one farm visit per herd. Initially, all herds had individual cages in their breeding units. The piggeries had either re-modelled their cages or switched to a group housing system with deep-litter, solid or slatted (partly or totally) floors. Farrowing rates were gathered from the national database, and data were tested with a linear regression model. Re-modelling did not have an effect on farrowing rate if initial reproductive performance of the herd was neglected. However, when farms were stratified according to performance prior to the beginning of study, namely into 'farms with initially high farrowing rate' (HF) and 'farms with initially low farrowing rate' (LF), the re-modelling had a significant effect on farrowing rate. In the HF farms, re-modelling caused a decrease in farrowing rate. Correspondingly, farrowing rate increased after remodelling in the LF farms. Farrowing rate was also influenced by mean parity of sows and by proportion of sows culled because of leg problems. This study could not show a profound impact of the design of the breeding unit on the fertility of the sow in the modern commercial production environment if the farm's reproductive performance before re-modelling was neglected. However, when initial performance was taken into account, re-modelling revealed significant, although varying effects on farrowing rate.

Short or long day light regimes may not affect reproductive performance in the sow.

The objective of this study was to evaluate the effect of short or long day light regimes on the reproductive performance in the sow. The study comprised approximately 1300 sows and their 3400 breedings in three commercial sow pools, in which a batch farrowing of 40 sows was employed. Each batch remained in the farrowing unit for 8 weeks under either a short day (10 h light, 14 h dark) or a long day (14 h light, 10 h dark) light regime. After weaning and transportation to the central unit, all sows were kept under the long day regime until they were moved back to the farrowing unit. Production results for each individual sow were recorded. The effect of the two different light regimes on the farrowing rate (FR) and on the weaning-to-oestrous interval was evaluated using logistic and Poisson regression models, respectively. The light regime affected none of the parameters significantly. The FR in June, July and August did, however, drop below that in December, January and February (OR 0.7, p < 0.05). The FR was affected by the sow pool (p < 0.01). Parity two sows exhibited a lower FR (OR 0.5, p = 0.05) and higher incidence of delayed first oestrus (IRR 2.7, p < 0.01) than did older sows. This study indicates that despite an artificial light regime, sows may still react to changes in season. In conclusion, use of simple light regime to obtain complete control over reproductive performance appears to be difficult.

Housing during early pregnancy affects fertility and behaviour of sows.

From 1.1.2013 EU legislation will permit stall-housing of dry sows for only 4 weeks post-service. Stalls are associated with compromised animal welfare, but group housing comes with risks from social confrontations. Studies on housing effects on fertility have produced contradictory results as systems are inconsistently defined. Effects of housing on pregnancy rate 28 days post-service (P28), early disruption of pregnancy (EDP) and behaviour were investigated in 12 replicates of 40 sows. Half of the animals were stalled (treatment S, mean parity 2.4) and half group-housed adjacent on 5.1 m(2) deep litter per sow (treatment G, mean parity 2.3). Pregnancy was detected using real-time ultrasound. An EDP-diagnosis required a drop of salivary progesterone concentration from >15.9 to <15.9 mmol/l in a series of samples taken on days 17, 20, 24 and 27 post-service. Behaviour was scan sampled on day 27 for 120 min with 10-min intervals. Data was analysed using mixed regression models in MLwiN. Treatment S increased the odds for P28 with 2.3 and the pregnancy rate of a treatment group with 0.1 compared with G. G increased the odds for EDP with 4.6. Treatment did not affect total exploratory or total passive behaviour. S sows explored floor and fixtures (not bedding) more and performed more passive sitting than G sows. Social stress may have caused the impaired reproductive performance in G sows. S sows showed behavioural signs of decreased welfare, but no corresponding reproductive effects. An interdisciplinary approach is needed when evaluating the appropriateness of housing systems.

Photoperiod and luteinizing hormone secretion in domestic and wild pigs.

During seasonal anoestrus (long-days), oestradiol can effectively inhibit the pulsatile secretion of luteinizing hormone (LH) in sheep. The aim of our trial was to determine whether the same regulatory mechanism exists in the pig. Altogether, 20 ovariectomized and oestradiol-implanted gilts (16 domestic pigs, 4 European wild boars) were randomly allocated to two treatment groups. The first group was kept under a short-day light-dark cycle of 8L:16D, and the second group under a long-day light regime of 16L:8D. After a 6-week treatment period, blood samples were taken at 20-min intervals for 12h. After sampling, the light regimens were switched. Sampling was then repeated following another 6 weeks of treatment. In both treatment groups, 2.3 LH pulses occurred every 12h. The basal LH level was 0.7+/-0.4 ng/ml for the short-day group and 1.0+/-0.5 ng/ml for the long-day group. The mean LH level was 0.9+/-0.4 and 1.3+/-0.6 ng/ml and the LH pulse amplitude 0.5+/-0.4 and 0.6+/-0.5 ng/ml, respectively. The basal and mean LH levels were therefore lower in short-day gilts (P<0.05), while LH pulse amplitude and frequency remained unaffected by treatment. In conclusion, the 6-week period under two different light regimes resulted in higher basal LH concentration in long-day gilts but was not able to produce changes in LH frequency in prepubertal gilts.

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.

Welfare index and reproductive performance in the sow.

To study the relationship between on-farm welfare and reproductive performance in the sow, the TGI 35L Animal Needs Index was modified for use in Finnish pig production. The modified index had a maximal total score of 100. It was comprised of six categories: 'locomotion' (maximal score 21 for dry sows and 11 for lactating sows), 'social interaction' (12/8), 'floor quality' (16/9), 'stable climate' (16/21), 'feeding' (16/23) and 'health and stockmanship' (19/29). Index scorings were performed separately in farrowing, breeding and gestation units on 28 representative Finnish sow farms. One-year production parameters were collected. Multiple linear regression was used for statistical analysis. Total ANI-points varied between 36.5-68.0 for lactating and 39.5-86.0 for dry sows. Litter size increased with increasing scores for 'feeding' in the dry sow unit. Controlling for breed, high scores for 'health and stockmanship' and 'floor quality' shortened the reproductive cycle, probably because of good leg health. The number of weaned piglets per sow per year (PSY) increased with increasing scores for dry sow 'health and stockmanship', 'floor quality' and an interaction of 'feeding' in the farrowing and mating units. PSY increased with decreasing scores for farrowing pen 'climate'. High-quality floors and stockmanship appear to correlate positively with reproductive performance in the sow. Effects of a welfare-promoting feeding strategy on reproduction are contradictory.

Investigation of a simplified artificial lighting programme to improve the fertility of sows in commercial piggeries.

Two artificial lighting regimens were studied in a commercial unit of 800 sows. The aim was to develop a simplified lighting regimen to overdrive the effects of season on reproduction. A long-day group had a constant 16 hours light and eight hours dark photoperiod in all units during a production cycle. A short-day group had eight hours of light and 16 hours darkness in a farrowing unit for four weeks and in a mating unit for four weeks. After one month of pregnancy the short-day group was transferred to 16 hours light and eight hours dark for the rest of the dry-sow period. Production data were collected for eight months, and the farrowing rate, weaning to oestrus interval, culling rate for fertility problems and the number of live-born piglets were analysed. Seasonal infertility, which had previously affected the herd, was not detected in either group during the follow-up period. The farrowing rate was 90 per cent for both groups. The median weaning to oestrus interval was five days in both lighting regimens with ranges from four to 74 days in the short-day group and three to 55 days in the long-day group. The long-day programme had a positive effect on the weaning to oestrus interval. When the sows were classified as either "normal", with a weaning to oestrus interval of up to 10 days, or "problem" animals, with a weaning to oestrus interval of over 10 days, the short-day programme also had a positive effect. The culling rate for fertility problems was 2.4 per cent for the short-day group and 3.2 per cent for the long-day group (P=0.027). The only significant predictor for the number of live-born piglets was parity (P=0.027).

Seasonal alterations in circadian melatonin rhythms of the European wild boar and domestic gilt.

The aims of the present study were: 1) to determine if the European wild boar exhibits a circadian pattern of melatonin secretion under its natural light environment; 2) to compare this pattern with the pattern in domestic pigs reared under the light environment typical for domesticity; and 3) to determine if there are seasonal alterations in melatonin rhythms. Four to six young, pure-bred, European wild boars and four to six cross-bred (Yorkshire x Finnish Landrace) domestic gilts were sampled at 2-hr intervals for 48 hr at the spring/autumn equinoxes and summer/winter solstices. Samples were obtained via saphenous arterial catheters from the wild boars and via ear vein catheters from the domestic gilts. The ambient light intensity was recorded simultaneously with sampling both outdoors and indoors. Following ether extraction, the serum samples were assayed for melatonin using a commercial RIA (Bühlman). All the experimental animals exhibited a distinct circadian pattern in melatonin secretion, with high concentrations occurring during the scotophase. There was no difference in scotophase melatonin response between the wild boars and domestic gilts in any season in terms of mean melatonin concentration or peak value. The mean duration of increased melatonin secretion (more than two standard deviations over a mean photophase concentration) in 24 hr in the wild boars in spring, summer, autumn and winter, was 10, 6, 11 and 17 hr, respectively, and in the domestic gilts, 9, 8, 12 and 11 hr, respectively. These results demonstrate the existence of circadian rhythm in melatonin secretion in both the European wild boar and domestic pig. In both groups, the duration of secretion is subject to seasonal alterations. The results suggest no difference in photoperiodic-melatonin transduction between the European wild boar and domestic pig whether due to altered genotype or reduced light environment.

A practical method for non-surgically inserting intra-arterial catheters in European wild boars (Sus scrofa).

In endocrinological studies, the usual methods for taking blood samples are impractical because of the need for frequent sampling, and catheterization is required. The catheterization methods described for domestic pigs are not suitable for use with European wild boars (Sus scrofa) under field conditions. We describe a method for inserting an intra-arterial catheter into the European wild boar. The animals were sedated with a combination of medetomidin (Domitor 1 mg/ml, Orion-Farmos, Finland) and zolazepam and tiletamine (Zoletil forte vet 50 mg/ml + 50 mg/ml, Virbac Laboratories, France). Four animals were catheterized and sampled at 2-h intervals for 48 h in March under winter conditions and five in June under summer conditions. In March, all the catheters remained in place for the entire sampling period. In June, one animal managed to displace the catheter from its artery, but it was recatheterized and the rest of the samples were collected without problems. This catheterization method is relatively easy to carry out and requires no special facilities.