Effects of genetic group selection against mortality on behavior and peripheral serotonin in domestic laying hens with trimmed and intact beaks.

Severe feather pecking is a maladaptive behavior in laying hens that may result in cannibalism and ultimately death of the victims. Selection methods in which the genetic effect of an animal on the survival of its group members is taken into account, i.e. 'group selection', have been shown to be very effective in reducing mortality due to feather pecking and cannibalism in laying hens. It has been suggested that fearfulness and serotonergic functioning are involved in the causation and development of feather pecking. We investigated effects of selection based on survivability in non-beak trimmed groups on fear-related behavior and peripheral 5-HT concentration and uptake in hens with trimmed or intact beaks, in a 2 x 2 factorial arrangement. Hens from the second generation of the low mortality line showed less fear-related behavior than control line hens. In addition, they displayed higher whole blood 5-HT concentrations and a lower platelet 5-HT uptake, indicating differences in functional activity of the 5-HT system. Beak trimming resulted in lowered levels of fear, and in a reduction of feather damage. Hens with trimmed and intact beaks did, however, not differ in peripheral 5-HT. The results imply that fearfulness and 5-HT activity are related to feather pecking without distinguishing between cause and effect. However, given that selection altered fear-related behaviors and peripheral 5-HT concentration and uptake, whereas beak trimming affected fearfulness and feather damage, but not 5-HT parameters, we suggest that peripheral 5-HT activity might reflect the predisposition to develop severe feather pecking under adverse conditions in laying hens.

Response to LPS in female offspring from sows treated with cortisol during pregnancy.

Prenatal stress has been shown to program responsiveness of the hypothalamus-pituitary-adrenal axis (HPA-axis) and behavior in offspring. In pig husbandry, sows are exposed to stressful conditions during gestation. Previously, cortisol treatment of pregnant sows has been shown to alter stress responsiveness and immunological parameters in their piglets. In the present study, we explored whether cortisol treatment of pregnant sows affects the offspring's response to an inflammatory stimulus. Sows were treated orally with cortisol either during the first, second, or third period of gestation, or received a placebo during this period. At 8 weeks of age, female offspring were injected intravenously with lipopolysaccharide (LPS). Offspring of sows that received cortisol during the first and third period of gestation showed a higher fever response to LPS. Cortisol treatment of sows during gestation did not affect offspring's response to LPS with regard to their cortisol response. LPS-induced sickness behavior, which was measured as the latency time in a human approach test, appeared to recover more quickly in offspring from sows that received cortisol during the second period of gestation. These results suggest that prenatal cortisol exposure programs responsiveness to inflammatory stimuli in female piglets.

Age, gender and litter-related variation in T-lymphocyte cytokine production in young pigs.

The capacity of farm animals to produce cytokines could be an important determinant of robustness and health. From research in rodents and humans it appears that the production and the balance of T helper 1 (Th1) and T helper 2 (Th2)-type cytokines influences susceptibility to autoimmune and infectious diseases. It is known that pigs show a large variation in many immune response parameters. So far the extent of individual variation in the production of Th1- and Th2-type cytokines in commercial outbred pigs has not been reported. In the current experiment we determined mRNA expression, as well as protein production of cytokines in 32 pigs from eight litters. From each litter two male and two female pigs were tested at 2, 5 and 8 weeks of age. Two Th1-type cytokines, interleukin (IL)-2 and interferon (IFN)-gamma, and two Th2-type cytokines, IL-4 and IL-10, were measured after phytohaemagglutinin (PHA)-stimulation of blood mononuclear cells. Cytokine production and the Th1/Th2-ratio were highly variable. The variation in cytokine protein production was moderately consistent across ages, i.e. pigs that produced high levels of cytokine at 2 weeks of age tended to do so as well at 5 and 8 weeks of age. Cytokine production tended to increase with age, and gilts and boars differed in their IL-2/IL-4 ratio. Unexpectedly, age, gender and litter effects often differed for mRNA and protein production data. We hypothesize that cytokine production is a consistent trait in pigs, especially at the protein production level. Future investigations in more animals and across a wider age range are necessary.

Evaluation of oral administration of cortisol as a model for prenatal stress in pregnant sows.

OBJECTIVE: To design a treatment that increases plasma corticosteroid concentrations to mimic prenatal stress in pregnant sows. ANIMALS: 24 pregnant sows. PROCEDURE: Sows were assigned to 1 of 4 treatment groups; treatment consisted of twice-daily oral administration of a placebo or 20, 60, or 180 mg of hydrocortisone acetate (HCA)/sow from 7 to 11 weeks of gestation. Blood and saliva samples for determination of cortisol concentrations were obtained hourly on treatment days 3 and 25 and twice weekly for the remainder of the treatment period. The WBC, neutrophil, and lymphocyte counts and concentrations of interleukin (IL)-2 and IL-4 were determined on 4 days during treatment. Litter characteristics were recorded. RESULTS: Plasma and salivary cortisol concentrations were significantly increased in sows that received 60 or 180 mg of HCA (0.30 to 0.37 mg/kg and 0.95 to 1.15 mg/kg, respectively), compared with control sows. Except for the second day of treatment, the number of WBCs and the IL-2:IL-4 ratio did not differ among treatment groups. The neutrophil-to-lymphocyte ratio was significantly higher in sows that received 180 mg of HCA. Gestation duration was significantly shorter in sows that received 180 mg of HCA. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of 60 mg of HCA is suitable to increase plasma and salivary cortisol concentrations in pregnant sows in a controlled manner to concentrations comparable to concentrations detected after psychologic stressors. This model seems to be suitable to study the effects of increased maternal corticosteroid concentrations on young pig behavior, physiologic variables, and development.

Social stress in male mice impairs long-term antiviral immunity selectively in wounded subjects.

An important property of the antiviral immune response is its time-dependent character. Beginning with a few antigen-specific cells upon infection, it evolves to a stage where there is an abundance of antigen-specific cells and antibodies that are needed to clear the pathogen, and ends with circulating antibodies and a population of virus-specific memory cells to protect the animal from reinfection. Short-term effects of stress on the immune system have been investigated extensively, showing that stress acutely changes many aspects of immunity. However, relatively little is known about the consequences of stress for the quality and quantity of long-term immunological memory. In the present study, we have investigated the effect of social stress, applied in mice at Days 1, 2 and 3 after inoculation with a herpes virus, on long-term antibody and memory cytokine responses to the virus. Male mice were subjected to three 5-min confrontations with an aggressive conspecific. Approximately half of the mice was wounded by bites of the aggressor during this stress procedure, and these mice were analyzed separately from nonwounded mice. It appeared that wounded mice showed suppressed protective antibody responses and impaired memory for virus-specific IL-4 and IL-10 production, whereas mice that were not wounded showed intact long-term immune responses and memory. It is concluded that the combination of wounds and the social stress of repeated confrontations is associated with impaired protective immunity as a consequence of suppressed antibody levels and impairment of some aspects of antiviral immunological memory.