Circulating immune complexes in bovine leukemia virus (BLV)-infected cattle.

Circulating immune complexes (ICs) were detected in the sera of bovine leukemia virus (BLV)-seropositive cattle. Immune complexes were precipitated in 2.5% polyethylene glycol (PEG) and further dissociated. Bovine leukemia virus antigens, IgG and IgM molecules were detected after solubilization in the presence of sodium dodecyl sulphate, and quantitated by enzyme-linked immunosorbent assay (ELISA) assays. Mean values of IgG and IgM in BLV-containing ICs did not significantly differ from those obtained from ICs originating from BLV-seronegative animals. However, differences were found in the composition of ICs from older BLV-positive animals as compared to those obtained from young animals. The ratio of IgG/IgM was 5.02 in animals aged 5-10 years, while this ratio was 11.66 in animals of less than 5 years of age and 10.19 in controls. This might indicate a possible increase in the contribution of IgM molecules to the structural composition of ICs in BLV-infected cattle as related to age or stage of infection.     

Circulating immune cells and immune complexes in peripheral blood of healthy and of bovine leukemia virus-infected cows and lymphosarcomatous calves

The peripheral blood (lymphocytes and immune complexes (IC)) from 20 healthy cows, 5 healthy calves, 10 bovine leukemia virus-infected cows and 4 lymphosarcomatous calves was investigated using 4 different immunological techniques. A highly significant increase in the percentage of surface immunoglobulin (SIg)-bearing peripheral blood lymphocytes of persistent lymphocytosis-cows could be demonstrated while the percentage was decreased in the lymphosarcomatous calves. Percentages of spontaneous sheep red blood cells (SRBC)-rosettes (E-rosettes) were not elevated. Antibodies to bovine leukemia virus-antigen were detected in the sera (immuno-diffusion test) of all the leukotic cows but not of the lymphosarcomatous calves. Although there seems to be an increased level of IC in the advanced stage, as compared to the beginning of the disease, there was no statistically significant difference in comparison with the control individuals. In the lymphosarcomatous calves as well as in the leukemic cows there was no statistical difference in the IC values between diseased animals and controls.     

Controls of feeding in pigs

The physiological controls of feeding behavior in pigs are reviewed. Feeding patterns, central nervous system integration of the control systems and the influence of taste and olfaction are briefly considered, but the emphasis of the review is on the specific control systems that determine meal size. The glucostatic mechanism of stimulation of eating operates in the pig, but is probably an emergency control in response to a severe deficiency of glucose available to the central nervous system. The effective controls determining meal size are predominantly inhibitory signals initiated within or near the gastrointestinal tract by the presence of food. There is evidence that a rise in osmoconcentration caused by the arrival of foodstuffs in the duodenum during a meal can inhibit feeding behavior to a degree proportional to the hypertonicity of the duodenal content. Arrival of chyme in the duodenum will also trigger the release of cholecystokinin (CCK). Exogenous CCK injected by various routes inhibits feeding, suggesting that endogenous CCK acts as a satiety or inhibitory signal during meals. Gastrointestinal distention during meals probably also acts as an inhibitory signal, but only preliminary studies have been made to delineate the role of this factor in feeding behavior. It is concluded that although considerable research has been conducted to reveal what control mechanisms operate in pigs, even the mechanisms already investigated are not firmly established as operating in normal meals. The osmoreceptive, CCK and gastrointestinal distention control systems are promising hypotheses worthy of further study, and the search for other control systems that may also participate continues.     

Dioxin residues in the edible tissue of finishing pigs after dioxin feeding

The aim of this study was to determine the contamination of finishing pigs with polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) after feeding either uncontaminated feed or feed contaminated with 0.75, 2 or 4 ng/kg toxic equivalents (TEQ; calculated by multiplying individual congener concentrations by congener-specific toxicity equivalency factors). The feed was mixed with pure substances of PCDD/Fs to get the intended contamination. Five groups of six piglets each were fed contaminated feed, one group of five piglets served as control. One group was fed contaminated feed (4 ng TEQ/kg) only for the rearing period (6 weeks), and another group for the first 8 weeks of the fattening period (4 ng TEQ/kg feed). The other groups received the contaminated feed during the 12-weeks fattening period. After slaughtering, the edible parts of the belly, loin and fore-end were collected and homogenized. The samples of group 2 and 4a were investigated uncooked as well as roasted. Fattening yield and feed conversion (kg feed/kg weight gain) of the animals of all groups were in the normal range (final weight 109.7 kg; feed conversion 2.55-2.69 kg). The PCDD/F-content in 1 kg fat of the belly, loin and fore-end in relation to the intake was between 0.016 (4 ng TEQ/kg feed for a 6-weeks rearing period) and 1.39% (fore-end; 2 ng TEQ/kg feed for 12-weeks fattening period). There was a decrease in dioxin residues after a 12-weeks period but not after a 4-weeks period of feeding an uncontaminated feed. When feed contaminated with 0.75, 2 and 4 ng TEQ/kg was given for a 12-weeks fattening period, the residue concentrations of PCDD/F-TEQ in 1 kg belly was 0.455, 1.07 and 1.55 ng, in 1 kg fore-end 0.04 ng, 0.32 ng and 0.34 ng and in 1 kg loin 0.015 ng, 0.07 ng and 0.30 ng respectively. Roasting had no influence on the dioxin-residues. The residues per g belly fat exceed the maximum limits for dioxin in food of 0.6 pg WHO-PCDD/F-TEQ/g fat (EC Recommendations 2002/201/EC), when feed containing 0.75 ng PCDD/F-TEQ/kg is given for 12 weeks. When feed containing 0.4 ng TEQ (maximum content; EC recommendations 2002/201/EC) is given for 12 weeks, approximately 0.55 pg TEQ/g fat can be expected in the food. This value is within the action level of 0.6 pg/g fat of porks. In conclusion, the results of the study allow prediction of dioxin residues in the edible tissue of pork, if the feed contamination is known and the amount of feed intake can be estimated.     

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Energy metabolism and substrate oxidation in pigs during feeding, starvation and re-feeding

Energy metabolism and substrate oxidation was measured in 12 growing pigs by means of indirect calorimetry and nutrient balances. The measurements were carried out during 5 days of feeding followed by 4 days of starvation and 5 days of re-feeding. During the feeding period, dietary carbohydrates were the main energy source, sufficient to cover energy requirements without oxidation of fat. Starvation reduced the total heat production and affected the oxidation pattern by reducing protein oxidation and shifting from carbohydrate to fat oxidation. On the second day of starvation, the main energy source was body fat and there was no oxidation of carbohydrate. On the second day of re-feeding, the heat production reached the same level as during the feeding period. Also, during the second day of re-feeding, the pattern of nutrient oxidation was similar to the feeding period with oxidation of carbohydrate providing 90% and oxidation of protein providing 10% of the total heat production. There was no fat oxidation. The results demonstrated that the growing pigs were able to re-establish oxidative patterns already 2 days after re-alimentation.     

Oxygenated drinking water enhances immune activity in pigs and increases immune responses of pigs during Salmonella typhimurium infection

It has been considered that drinking oxygenated water improves oxygen availability, which may increase vitality and improve immune functions. The present study evaluated the effects of oxygenated drinking water on immune function in pigs. Continuous drinking of oxygenated water markedly increased peripheral blood mononuclear cell proliferation, interleukin-1β expression level and the CD4(+):CD8(+) cell ratio in pigs. During Salmonella Typhimurium infection, total leukocytes and relative cytokines expression levels were significantly increased in pigs consuming oxygenated water compared with pigs consuming tap water. These findings suggest that oxygenated drinking water enhances immune activity in pigs and increases immune responses of pigs during S. Typhimurium Infection.     

The intestinal and mammary immune system in pigs

Evidence exists from studies in other species for a link between the intestinal and mammary immune systems. This was examined in pigs by various methods including analysis of lymphocyte subsets in intestinal and mammary tissues and lymphocyte migration studies. It was concluded that in the pig both a common mucosal immune response and a genuine local immune response exist in the mammary gland.     

Effects of chitooligosaccharide supplementation on growth performance, nutrient digestibility, blood characteristics and immune responses after lipopolysaccharide challenge in weanling pigs

The objective of this study was to determine the effects of dietary supplementation with chitooligosaccharide (COS) on growth performance, nutrient digestibility, blood characteristics and immune response in lipopolysaccharide-challenged weanling pigs. A total of 90 crossbred weanling pigs (5.44 ± 0.50 kg BW) were employed in Exp. 1. The three dietary treatments were basal diets supplemented with 0, 2.5, and 5 g COS/kg, and fed for 28 d. Each treatment had 6 replications with 5 pigs per pen. Increasing the level of supplemental COS tended to linearly (P < 0.10) improve ADG and ADFI during phase 2 and overall period, while there were no differences in G:F. The linear improvement in the apparent DM (P < 0.05) and N (P < 0.10) digestibility in pigs fed COS supplemented diets was noticed. The tested blood characteristics were not influenced under non-challenge conditions. In Exp. 2, a total of 20 pigs (5.22 ± 0.31 kg BW) were initially assigned to two dietary treatments and fed basal diets supplemented with 0 or 0.5 g COS/kg for 28 d. At the end of d 28, half of the pigs in each treatment (n = 5) were injected i.p. with Escherichia coli lipopolysaccharide at a concentration of 100 μg/kg of BW. The other half of the pigs in each treatment were injected with sterile saline solution at a concentration of 100 μg/kg of BW. This arrangement resulted in a 2 × 2 factorial design with diet and LPS challenge as the main effects. Blood sample and rectal temperature data were collected at 0, 2, 4 and 12 h post-challenge. Rectal temperatures increased as the result of LPS injection at 4 and 12 h post-challenge (P < 0.05). Serum cortisol, IGF-1, and TNF-α concentration were also increased as the result of LPS challenge (P < 0.05). The COS treatments resulted in lower cortisol concentrations at 2 h and higher IGF-1 concentrations at 4 h post-challenge (P < 0.05). COS and LPS interactions were also observed on cortisol and IGF-1 when the COS effects were presented (P < 0.05). Haptoglobin concentrations remained unaffected throughout the challenge period. White blood cell counts were increased in the LPS-treated pigs at 2 and 4 h post-challenge (P < 0.01). Lymphocyte count was elevated at 2 h and reduced at 12 h post-challenge as the result of LPS challenge (P < 0.05). However, there were no COS main effects observed on lymphocyte count throughout the challenge period. The comparison between two LPS challenged treatments also indicated that COS treatment has beneficial effects on rectal temperature, cortisol and IGF-1 concentrations. In conclusion, dietary supplementation with COS had little effect on nutrient digestibility and inflammatory stress markers in weanling pigs.     

Breed and age affect baseline immune traits, cortisol, and performance in growing pigs

It was hypothesized in these studies that differences would exist in baseline immune and performance measures among different breeds of pigs, and that these differences would be affected by age of the pig. Baseline immune, plasma cortisol (CORT) concentrations, and performance measures were determined among Berkshire (n = 36), Duroc (n = 18), Meishan (n = 54), Landrace x Yorkshire (White X; n = 36), and Yorkshire (n = 36) pigs at 4, 8, and 12 wk of age. All piglets were weaned at 17 to 21 d of age and moved to a common nursery environment. Total white blood cell (WBC), leukocyte differential, plasma CORT, immunoglobulin G (IgG) concentrations, natural killer cytotoxicity, neutrophil phagocytosis (PHAGO), and chemotaxis (CHTX) were evaluated. At all ages, plasma CORT was greatest in Meishan pigs, and least in Yorkshires (P < 0.05). Plasma IgG increased with age for all breeds (age: P < 0.01; breed x age: P < 0.005), except that in Meishans, IgG decreased. Natural killer cytotoxicity was greatest (P < 0.05) among Meishan pigs. There were breed x age interactions for neutrophil PHAGO (P < 0.001) and CHTX (P < 0.001). Overall, Yorkshire pigs showed the greatest (P < 0.05) percentage of PHAGO but the least (P < 0.05) CHTX. White X pigs had the greatest (P < 0.05) CHTX response. Berkshire pigs had the greatest (P < 0.001) numbers of neutrophils. At 12 wk of age, Meishan pigs had the least BW gain (P < 0.001), and Durocs had the greatest G:F (P < 0.001). There were no significant sex differences for immune (P > or = 0.15), performance (P > or = 0.20), or CORT (P = 0.70) measures. Pig breed and age influenced both baseline immune measures and plasma CORT in growing pigs, suggesting that pig breed and age are important factors influencing the response to various stressors or infectious challenges.     

Pathologic changes of the small intestinal mucosa of pigs after feeding Phaseolus vulgaris beans

The jejunal mucosa of pigs fed diets containing Phaseolus vulgaris beans was characterized grossly as mucosal atrophy and microscopically as atrophy and blunting of the villus in association with elongation of crypts with cells with increased mitotic activity. These morphologic findings were most severe in the proximal and middle parts of the jejunum. Compared to controls, goblet cells were significantly decreased in the villus but markedly increased in the crypt region. The activity of aminopeptidase and sucrase-isomaltase in the test animals was also significantly lower than in the controls. The findings in this study suggested that feeding Phaseolus vulgaris beans reduced the digestive and absorptive capacity of the mucosa, resulting in weight loss and diarrhea of affected pigs.     

Early development of immune system in pigs

Prenatal and early postnatal immune system development has been studied in minipigs. First leukocytes were observed in the yolk sac and fetal liver (FL) on the 17th day of gestation, the majority of them being SWC3(+). The colonization of the thymus (TH) with leukocytes was observed 21 days later. Two waves of fetal TH colonization with pro-T cells were deduced from the frequency of thymocyte subsets. Thymic B cells and immunoglobulin-secreting cells (Ig-SC) were studied by flow cytometry and ELISPOT, respectively. When the total numbers of fetal Ig-SC were compared, the TH was identified as the main source of natural antibodies and the only site of IgA and IgG synthesis. In germ-free animals, the TH also represented the major site of IgG and IgA production and the number of Ig-SC was not influenced by colonization with microflora. FL and bone marrow were identified as primary B lymphopoietic sites. The phenotype of B precursors was characterized and pre-B II cells were shown to be the dominant mononuclear fraction between DG50 and DG105. In the periphery, relative proportions of lymphocyte subsets were determined. Studies in gnotobiotic piglets have revealed that the appearance of CD4(+)CD8(+) T cells and CD2(-) B cells is absolutely dependent on the contact of immune system with live viruses and bacteria, respectively.     

Effects of feeding systems on social and feeding behavior and performance of finishing pigs

Two experiments were conducted to study the effects of feeding systems on feeding behavior, aggression, social ranks and average daily gain (ADG) of pigs. In Exp. 1, feed was delivered during the day from 1100 to 1400 and at night from 2300 to 0200. One pen containing 10 barrows and 10 gilts was used. Correlation coefficients were calculated between pairs of traits. In Exp. 2, four feeding systems were tested using similar group composition as in Exp. 1. Two feeding systems were ad libitum, offering either dry or wet feed; the other two used time-restricted feeding from 0900 to 1100 and from 1600 to 1800, but with water supplied either ad libitum or time-restricted. Analyses of variance were used to test feeding system effects; correlation coefficients were calculated for pairs of traits. Results of Exp. 1 indicated that pigs displayed predominantly daytime activities. Frequency of aggressive acts were correlated significantly with feeding frequency (r = .48), time to first feeding (r = -.50) and ADG (r = .56). In Exp. 2, pigs on time-restricted feeding with ad libitum water had significantly depressed ADG and reduced feed intake. A possible association between time-restricted feeding and water intake is postulated. Feeding behavior, aggression and social rank were associated with ADG in time-restricted systems but not in ad libitum systems. There was a tendency in time-restricted-fed pigs for the more aggressive pigs to perform more feeding activities, to rank higher in the social order, and to gain faster.     

Circulating cortisol, tumor necrosis factor-alpha interleukin-1beta, and interferon-gamma in pigs infected with Actinobacillus pleuropneumoniae

This study evaluated the time course of systemic cytokine concentrations in an acute model of pneumonia in pigs challenged intranasally with Actinobacillus pleuropneumoniae. Feed intake and serum cortisol were measured as overt clinical and systemic markers of disease onset, respectively, and serum tumor necrosis factor-alpha, interleukin-1beta, and interferon-gamma as representative systemic inflammatory markers. Crossbred barrows (n = 15), approximately 5 wk of age, were used in the study. Pigs were housed in an environmentally controlled facility at 25 degrees C and under continuous illumination in pens measuring approximately 1.5 m2. Pigs had free access to water and an unmedicated diet. Approximately 1 wk prior to disease challenge, pigs were fitted nonsurgically with venous catheters. At challenge, pigs were given 5 x 10(8) CFU Actinobacillus pleuropneumoniae intranasally (n = 8) or a similar volume of sterile growth media intranasally (Control; n = 7). Feed intake was estimated by the change in feeder weight at 12-h intervals from -12 to 72 h relative to the time of disease challenge. Blood sampling began 12 h prior to challenge and continued until 72 h after challenge. Pigs were sampled at -12, -6, and 0 h, then at 90-min intervals until 12-h post-challenge, continuing at 3-h intervals until 24-h post-challenge, then again at 6-h intervals until 72 h after challenge. Serum was harvested and frozen until assayed for cortisol, tumor necrosis factor-alpha, interleukin-1beta, and interferon-gamma. Feed intake was reduced in Actinobacillus pleuropneumoniae pigs during the intervals 0 to 12 h (P < 0.001), 24 to 36 h (P < 0.001), 48 to 60 h (P <0.05), and 60 to 72 h (P < 0.05). TheActnobacillus pleuropneumoniae-challenged pigs had elevated serum cortisol from 180-min to 18-h post-challenge (P < 0.001) and also at 36 (P < 0.05), 42 (P < 0.001), and 60 (P < 0.05) h following infection. Circulating cytokines were not affected by disease challenge. Thus, in this experimental model of pneumonia, weaned pigs demonstrated expected behavioral and endocrine characteristics of disease in the absence of significant changes in circulating inflammatory cytokines.     

Partial inhibition of the humoral immune response of pigs after early postnatal immunization

The ability of young pigs to be immunized during the postnatal period was studied. Eight groups of pigs born on the same day from 3 sows were injected with hen egg-white lysozyme in Freund's incomplete adjuvant at days 0, 1, 2, 3, 4, 5, 7, and 10 after birth. The serum antibody titers were determined each week. Results indicated that pigs injected within the first 3 days of life exhibited a delay of 10 days in the appearance of the humoral antibodies, compared with the antibody response observed in pigs injected later. Serum antibody titers were markedly lower in the early immunized pigs. The secondary immune response was similar in all pigs. This partial inhibition is not directly linked to the corticoids present in the serum at the immunization day. Possible reasons for this impairment of the humoral immune response were reviewed.     

The effect of feeding system at weaning on performance,health and feeding behaviour of pigs of different sizes

Abstract

Pigs weaned at 31 to 34 days of age (n=280) were mixed into groups of 10 and fed from either feeders (2 feeding places per pen) or troughs (10 feeding places per pen). Analyses on performance, diarrhoea scores and feeding behaviour were made separately on small-, medium- and large-sized pigs, defined as their relative size in the group. During the second week after weaning, feed conversion ratio (FCR) was lower for pigs fed from feeders. Trough feeding resulted in lower total diarrhoea scores for small (p=0.002) and large (p=0.04), and higher scores for medium pigs (p=0.03). Small pigs had lower scores on individual days around the peak on day 6. All three size categories of pigs spent a numerically higher amount of time feeding when fed from a trough. Feeding bouts were longer in pigs fed from a trough (p=0.0002 – 0.05).