Intermittent Stress in Pigs: Behavioural and Pituitary-Adrenocortical Reactivity

Abstract

Ninetysix pigs, half females and half castrated males from 12 litters, were housed in 24 groups of 4 litter mates (2 females, 2 castrates). The pigs were weaned at 4 weeks of age and from the age of 115 days half of the groups were subjected to a schedule of unpredictable, inescapable electroshocks for 33 days, and half served as control. The adrenocortical reactivity to ACTH stimulation and to an emotional stressor (the procedure associated with initiation of blood collection) was measured in females, whereas the behavioural and pituitary-adrenocortical reactivity to an open field test was measured in castrates, as was the behavioural reactivity in a social test. Intermittent stress increased adrenocortical reactivity to ACTH stimulation significantly. This effect was present within the first week of intermittent stress (p < 0.06), but no difference was found after 4–5 weeks of stress. In contrast, the adrenocortical reactivity to additional emotional stressors was unaffected by stress after one week of intermittent stress, but increased after 4–5 weeks. In the open field test, centre location increased after one week of intermittent stress, whereas exploration decreased and walking and ambulation increased after 4–5 weeks of stress. In addition, 4–5 weeks of intermittent stress decreased aggressiveness in a social test. In conclusion, the change in reactivity to an additional acute stressor during intermittent stress appeared in different variables and contexts at different times during the course of intermittent stress. Thus, assessment of stress based on changed reactivity has to include several distinct measures of behavioural and hormonal reactivity.     

Ability of heifers to discriminate between familiar herdmates and members of an unfamiliar group: preference test and operant conditioning test

Using a preference test and operant conditioning in a Y-maze, this experiment examined the ability of heifers to discriminate between their own familiar herdmates and member(s) of an unfamiliar group. Sixteen Danish Friesian heifers, eight older animals (360.6 ± 24.2 days of age) and eight younger ones (190.1 ± 14.1 days of age) were used. Each age group was further divided into two experimental groups. Members of each of these groups were housed together in small pens before the experiments began. In experiment 1, each of the 16 animals was allowed to approach either a familiar or an unfamiliar individual in the Y-maze. The test was repeated 12 times, with a different unfamiliar subject for each test. In experiment 2, eight heifers were individually tested in a conditioning experiment to examine whether they could learn to discriminate between a group of their three herdmates and a group of three unfamiliar heifers. Test animals were rewarded when they chose their own group. In experiment 1, heifers did not show a preference between familiar and unfamiliar individuals. Interestingly the younger stimulus heifers but not the test animals showed an ability to discriminate between unfamiliar animals by vocalizing. In experiment 2, four of the eight test animals achieved the criterion for successful discrimination between the familiar and unfamiliar group ( P  < 0.003: binomial law). There was no age group difference in the ability to discriminate between familiar and unfamiliar animals. In conclusion, heifers did not show a preference toward familiar or unfamiliar individuals; but after conditioning, some heifers could learn to discriminate between familiar and unfamiliar groups.     

Hybridization between Quercus robur and Q. petraea in a mixed oak stand in Denmark

? Hybridization and mating pattern between Quercus robur and Q. petraea was studied in a 5.8 ha mixed forest stand in Jutland, Denmark which comprises in total 135 Quercus robur and 230 Q. petraea trees. Classification of the oak trees into species was performed using canonical discriminant analysis of a range of leaf morphological traits. Adult trees (365) and offspring (582) were genotyped with eight microsatellite markers. Seedlings were sampled in 2003 and acorns were collected in 2004.

? Mating patterns of Q. robur and Q. petraea are expected to be different in the northern range of the distribution area and a larger hybridization rate is expected. It is further expected, that pollination from outside sources will be relatively less in small fragmented forest management systems compared to large scale oak forest. The conclusions should be verified through repeated year to year analysis of the mating pattern.

? Phenological studies revealed that there was no difference in flowering time between species. Data for the adult trees revealed no significant departures from Hardy-Weinberg proportions and there was weak, but significant spatial genetic structure, which supports the idea that the stand is of natural origin. Spatial genetic structure in the first distance class is stronger for Q. petraea. The genetic composition of the offspring was remarkably consistent from year to year. Paternity analysis revealed that, on average, 85% pollination came from fathers within the stand. The direction of the pollen flow varied from year to year. Inter-specific hybridization was high and ranged from 15–17% and from 48–55% for Q. petraea and Q. robur mothers respectively. Paternity analysis revealed that the population was basically outcrossing and only 3.7% of the analysed progeny were the product of selfing. Over the two years of study, approximately 200 trees contributed to the paternity of the next generations.

? The study confirms earlier studies with a greater tendency for Q. robur mothers to produce hybrid seeds than Q. petraea mothers. The rate of hybridization is higher in this Danish stand than in comparable studies elsewhere in Europe. Gene flow from outside sources are relatively low.

     

Cultivars and cultivation systems for organic strawberry production in Norway

Cultivars and cultivating methods for organic strawberry production were studied in experiments in open fields and high plastic tunnels during four cropping seasons in southern Norway. In open fields, flowers and fruits were attacked by grey mould when the flowering and harvest seasons were wet, and marketable yield was reduced by up to 20%. Production in high tunnels showed a potential of high yields of fruits of good quality when strawberry powdery mildew was controlled. Berry size varied significantly among the cultivars. ‘Frida’ had the largest fruits followed by ‘Sonata’ and ‘Florence’, while ‘Polka’, ‘Korona’ and ‘Iris’ had the smallest fruits. All cultivars yielded well, but due to fruit decay caused by grey mould the marketable yield was significantly reduced, especially in open field. Grey mould was the most important factor influencing marketable yields. Fruits from matted rows were largest, while the highest yield was obtained on woven polyethylene. There were no effects of mulching methods on marketable yield or the amount of fruits with grey mould. High tunnels with good control of pests and diseases showed a potential of high and stable yields of good quality.     

Microstructural and chemical investigation of subsurface hardened potatoes (Solanum tuberosum L.)

Summary Microstructural changes related to subsurface hardening of pre-peeled potatoes were investigated using cv. Sava potatoes peeled using an industrial peeler, a laboratory knife peeler or a hand knife peeler. The pre-peeled potatoes were packed in polymer bags and stored at 18°C for six days until cooking. Potato hardness and microstructure of the tissue was investigated. Cellulose and suberin in hard potato tissue increased linearly with increase in mechanical impact in a damage barrel. The area of cell walls and especially cell corners of mechanically damaged potatoes showed white autofluorescence in blue light. The number of layers of bricklike and autofluorescent parenchyma increased significantly with increasing hardness. Subsurface hardening was related to percentage cells with fluorescent gelatinised cell mass and curly cell walls in a depth of the potato tissue corresponding to the depth of maximum hardness.     

Salmonella Typhimurium invasion of HEp-2 epithelial cells in vitro is increased by N-acylhomoserine lactone quorum sensing signals

Background

In Gram-negative bacteria, the most commonly studied quorum sensing signals are the N-acylhomoserine lactones (AHLs). In Salmonella, AHLs are recognized by SdiA, which is believed to be a sensor of AHLs produced by other bacteria, since Salmonella does not produce AHLs itself. It has been speculated that AHLs produced by the gastrointestinal flora may influence the regulation of virulence traits in Salmonella. The aim of the present work was to study the effect of AHLs on epithelial cell invasion by Salmonella in vitro.

Methods

Invasion by Salmonella enterica subspecies enterica serovar Typhimurium (S. Typhimurium) strain and its isogenc sdiA mutant was studied using a conventional gentamycin invasion assay with HEp-2 cells at 37°C. Gene expression was studied using a semi-quantitative PCR.

Results

The S. Typhimurium strain, but not its isogenic sdiA mutant, displayed increased in vitro invasion after addition of both N-hexanoyl-DL-homoserine lactone (C6-AHL) and N-octanoyl-DL-homoserine lactone (C8-AHL). Increased expression of two of the genes in the SdiA regulon (rck and srgE) was observed in the wild type strain, but not in the sdiA mutant.

Conclusions

The results from the present study show that S. Typhimurium can respond to two different AHL quorum sensing signals (C6-AHL and C8-AHL) with increased cell invasion at 37°C in vitro, and that this response most likely is sdiA mediated. These results indicate that if AHLs are present in the intestinal environment, they may increase the invasiveness of Salmonella.     

Production of chips from potato cultivars (Solanum tuberosum L.) with high sugar content using lactic acid fermentation

Summary Tubers of twelve cultivars ofSolanum tuberosum L., with a varying content of reducing sugars (0.49–2.30 g/100 g fresh weight), were sliced and fermented for up to 48 h by lactic acid bacteria in a brine of 1.5% NaCl, prior to frying. The content of reducing sugars decreased by 80 to 100%, depending on the initial sugar level. Colour of chips was measured using the CIE (1976) L^*a^*b^* colour system, where L^* is lightness, a^* is redness and b^* is yellowness of the material and by IBVL colour cards, photographs used for grading the colour of potato chips. L^*-values were the best measurement of chip colour. The scale of the IBVL colour cards was too narrow (scale 1–9) for this study, as chips from eight of the cultivars were scored lighter than IBVL 9 after 48 h of fermentation. Lighter coloured chips significantly correlated with lower contents of reducing sugars. The sugar content decreased as fermentation time increased. Fermentation time can thus be used to control potato chip colour, and all the cultivars tested can be used for production of chips with regard to colour.     

Automatic blood sampling in dairy cows

Loose housing systems for dairy cows are becoming increasingly common, raising new questions in the area of animal health and welfare. Some of these questions can be addressed by studying the variation in blood parameters, such as glucocortistioids. However, the traditional manual blood sampling procedure can in itself affect the responses of the animal. To address this issue we have developed a device for automated collection of multiple blood samples. The device is placed on the back of the animal and allows the animal to be kept in all types of environments, either alone or in social groups. The animal can move freely: no restraints and no handling of the animal are necessary during blood sampling.Three experiments were conducted to study the performance of the system and how the blood sampling procedure affected the cortisol responses in dairy cows. In the first experiment the accuracy of sample size and timing were investigated.In the second experiment, automatic samples were collected from six cows kept in tie-stalls, with samples taken at 3-min intervals for 38 min. At 12, 24, 36 and 38 min, a manual sample was taken by vein puncture. None of the cows showed a consistently increased cortisol response to automatic sampling, while two cows showed increased cortisol concentration after vein puncture.In the third experiment automatic blood sampling was conducted with 12 cows kept in a loose housing system. In the morning, over a period of 1.5 h, 14 blood samples were taken at varying time intervals from each cow. In the afternoon, over a period of 2.5 h, a further 14 samples were taken. Cortisol concentrations in the blood samples suggest that the cows were not affected by the blood sampling procedure.On some occasions during these experiments, it was not possible to get a sample. For the manual vein puncture 3 out of 24 samples (12.5%) were not successfully taken within a time limit of 2 min. During the automatic blood sampling process, the catheter occasionally became twisted and blocked by the movement of the cow's head. This occurred in 8 out of 84 samples (9.5%). In four of the manual samples, considerable hemolysis had occurred during the sampling procedure. No hemolysis was observed in the automatic blood samples.Automated blood sampling offers the opportunity to collect a series of samples without disturbing the animal. Data suggest that automatic blood sampling is a superior alternative to manual blood sampling, even in a tie barn.     

Glycaemic index and glycaemic load in relation to blood lipids - 6 years of follow-up in adult Danish men and women

BACKGROUND: Cross-sectional studies have suggested an association between glycaemic index (GI) or glycaemic load (GL) and serum lipids. However, no prospective studies have been performed. OBJECTIVE: To examine whether GI or GL was associated with subsequent changes in serum lipids. DESIGN: Prospective study with 6 years of follow-up. Overall dietary GI and GL of each participant were assessed from diet history interviews. SETTING: Population-based study.Subjects Three hundred and thirty-five healthy men and women aged 35-65 years selected randomly from a larger sample of Danish adults. RESULTS: In men GI was directly related to changes in total cholesterol (DeltaTC), regression coefficient (beta) = 0.0044 (95% confidence interval (CI): 0.0008-0.0081) and GL was positively related to changes in low-density lipoprotein cholesterol (DeltaLDL), beta = 0.1554 (95% CI: 0.0127-0.2982). Furthermore, the relationship between GL and DeltaTC was modified by age, being particularly strong for the younger men (P = 0.02). In women the relationship between GI and DeltaLDL was modified by age and was stronger for younger rather than older women (P = 0.01). A tendency for a similar interaction was seen for GI and DeltaTC (P = 0.09). Associations between GL and DeltaLDL and GL and DeltaTC were inverse for women with body mass index > or = 30 kg m(-2) (P = 0.03 and 0.04, respectively). CONCLUSIONS: This is the first study to demonstrate that dietary GI and GL are related to 6-year changes in serum lipid levels. However, associations were weak and generally confined to subgroups.     

Seasonal and diel effects on the activity of northern pike studied by high‐resolution positional telemetry

Abstract – Temperate lakes can be ice covered for several months each year, yet little is known about the behaviour and activity of the fish during the cold season. As northern pike represents the top of the food web in many northern temperate lakes and may structure the ecosystem both directly and indirectly, a detailed understanding of the behaviour of this species during winter is important. We continuously monitored the activity of adult northern pike (Esox lucius) in a small temperate lake from late summer to winter for two consecutive years using an automatic acoustic positional telemetry system. Four subsample periods representing different temperature regimes from each year were chosen for further investigation. The results revealed that pike activity was similar between seasons. In all periods, a distinct diel pattern, showing increased activity during day as compared to night, was evident. Our findings indicate that the fish component of temperate lentic ecosystems can be more active during the cold season than previously assumed. This may have implications for the structuring effect of pike on the lower trophic levels.