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. 2002. Humoral and cellular immune responses of piglets after castration at different ages. Can. J. Anim. Sci. 82: 519-526. In this study, growth of piglets and their humoral and cellular immune responses were used to evaluate the effect of castration at different ages. Piglets (n = 84) from 14 litters were assigned to one of the six treatments: castration or sham-castration at 3, 10 or 17 d of age. An injection of bovine serum albumin (BSA) was given on the day of castration and a second one 14 d later. Blood samples were taken at different times to evaluate the antibody levels against BSA and lymphocyte blastogenesis responses to concanavalin A (Con A), phytohaemagglutinin (PHA) and pokeweed mitogen (PWM). The age of piglets at the first immunization significantly influenced (P < 0.0001) the ability to raise antibodies to the injected antigen. Three-day-old piglets developed weaker antibody response than those immunized at 10 or 17 d of age. Ten-and 17-d-old castrated piglets tended to develop weaker secondary antibody responses than sham-castrated piglets, while those castrated and sham-castrated at 3 d of age did not differ in their antibody response (interaction castration × age; P < 0.08). The fluctuation in lymphocyte blastogenesis response between days 21 and 35 was numerically greater in castrated than in shamcastrated piglets. Ratios between days 35 and 21 of PWM proliferative indexes were significantly higher (P < 0.05) in piglets castrated at 10 or 17 d of age than in sham-castrated piglets. The results indicate that castration of piglets at 10 d of age or older impairs antibody response to BSA and modulates piglet lymphocyte responses to mitogens. Castration at 3 d of age had no marked effect on antibody response and lymphocyte proliferation. Thus castration appears to be less disruptive to immune response if performed at three days of age compared to 10 d of age or older. Dans cette étude, la croissance et les réponses immunitaires de type humoral et cellulaire ont été les paramètres choisis pour évaluer l'influence de l'âge des porcelets à la castration. Des porcelets provenant de 14 portées (6/portée) ont été assignés à un des groupes suivants: castré ou noncastré à l'âge de 3, 10 ou 17 jours. Une injection d'albumine bovine (BSA) a été donnée le jour de la castration et une seconde 14 jours plus tard. Des prises de sang ont été prélevées à différents temps pour évaluer la production d'anticorps contre BSA et la prolifération des lymphocytes activés avec les mitogènes concanavalin A (ConA), phytohaemagglutinine (PHA) et pokeweed (PWM). L'âge des porcelets à la première immunisation a significativement influencé (P < 0.0001) leur capacité à répondre à l'antigène injecté. Les porcelets immunisés dès l'âge de trois jours ont développé une réponse anticorps secondaire contre BSA plus faible (P < 0.0001) que ceux ayant reçu une première injection à l'âge de 10 ou 17 jours. Les porcelets castrés à l'âge de 10 ou 17 jours avaient tendance à développer une réponse anticorps secondaire inférieure à celle...

A multi-mode cavity constructed of 22-gauge perforated galvanized steel with a horn irradiator was used to expose chicken embryos to microwave (MW) radiation during incubation. The MW exposure system was placed within an environmental chamber. Mean +/- standard error of mean (SEM) power level was 3.6 +/- 0.02 mW/cm2 and mean egg specific absorption rate was 0.8 mW/g per mW/cm2. Mean temperature of the MW-exposed eggs was 37.5 +/- 0.9 degrees C as monitored by a Luxtron fluoroptic thermometer. Non-irradiated eggs were incubated at 37.5 +/- 0.1 degrees C and 55% relative humidity. There was no significant different in percent fertile eggs hatched between eggs exposed to MW radiation during incubation or eggs incubated conventionally (82.9% and 87.7%, respectively).

Twenty-two 1-wk-old broiler chicks (Gallus domesticus) were housed at 16 C and operantly conditioned to activate either a 250-W infrared bulb (control) or a microwave generator delivering 13 mW/cm2 (treated). Plasma corticosterone concentration did not differ between groups (P greater than .05) at 4 wk of age. At that time the birds were killed, and post-mortem examination revealed no treatment differences in gross morphology of the chicks or in weights of spleen and bursa of Fabricius (P greater than .05). Histological study of comparable segments of spleen, bursa, adrenal, and thyroid tissue did not show differences in any of the chosen parameters (P greater than .05). Heterophil:lymphocyte ratios, packed cell volume, and total plasma protein content were similar between groups (P greater than .05). These results suggest that operant exposure to low density microwave radiation did not result in stress or immunological disturbances.