An evaluation was made of an interdigital skin test to assess cutaneous basophil hypersensitivity (CBH), mediated by thymic (T) cells, in chickens less than 2 wk of age. Hubbard-by-Hubbard roosters 3, 5, 7, 10 and 14 days of age were injected intradermally in the interdigital skin between Digits 3 and 4 of the right foot with 100 micrograms or 200 micrograms of phytohemagglutinin-P (PHA-P) in .10 mL of physiological saline solution (PSS). The left foot was injected with PSS and served as a control. The CBH response elicited by the PHA-P was evaluated by determining interdigital skin thickness before injection and at 12 and 24 h after injection. The effect of treatment with the T-cell suppressing drugs dexamethasone and cyclosporin on the CBH response was determined in chickens treated daily for 4 or 5 days prior to skin testing at 5 or 10 days of age. Significant increases (P less than .005) of .64 to .88 mm occurred in the mean, interdigital skin thickness for all age groups of chickens at 12 and 24 h after injection of 100 or 200 micrograms of PHA-P. The PHA-P-elicited. CBH response was significantly suppressed by treatment with dexamethasone (P less than .005) or cyclosporin (P less than .05). The results indicated that the interdigital skin test is a rapid and simple means of assessing normal and suppressed immune responses in chickens at 3 to 14 days of age.

Broiler chickens can be contaminated by Salmonella typhimurium, which is a food safety concern. It has been previously shown that D-mannose blocks S. typhimurium adherence to chicken intestine in vitro. One-day-old broiler chickens were fed normal drinking water or drinking water supplemented with 2.5% mannose for 10 days. On Day 3, both groups were challenged orally with 1 x 10(8) S. typhimurium [ST-10 (Animal Diagnostics Laboratory, Ames, IA)] resistant to Nal and Nov (Sigma, St. Louis, MO). On Day 10 the birds' caecal contents were examined for the antibiotic-marked S. typhimurium. Two additional groups of birds were provided normal drinking water or mannose but were not challenged with the bacteria. Salmonella-challenged control chickens were 78, 82, and 93% colonized whereas Salmonella-challenged mannose-treated chickens were only 28, 21, and 43% colonized. Moreover, the mean log10 counts of control and mannose groups were significantly (P less than .001) reduced by at least 99%. Mannose-supplemented drinking water had no effect on weight gains. Certain carbohydrates may provide a means to reduce S. typhimurium contamination in broilers.

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We have previously shown that increased resistance to Salmonella enteritidis organ infectivity in day-old chicks was conferred by the immunoprophylactic administration of S. enteritidis-immune lymphokines (ILK). This resistance was associated with a significant increase in the number of circulating heterophils 4 h after ILK injection. The objective of the present study was to evaluate heterophil function following the administration of ILK in day-old chicks. Significant increases (P < 0.001) in adherence, chemotaxis, and phagocytosis of S. enteritidis were found with heterophils isolated from ILK-injected chickens compared to the heterophils isolated from birds injected with either pyrogen-free saline or lymphokines from non-immune T cells. After phagocytosis, the heterophils from the ILK-injected chickens were also able to kill significantly greater numbers of S. enteritidis more rapidly than did the heterophils from the saline-injected control birds (within 30 min, control cells killed 21.89% of the bacteria whereas ILK-treated cells killed 88.22%). We also found that the heterophils from the ILK-injected birds were more efficient killers of S. typhimurium, S. gallinarum, and E. coli. These results strongly suggest that the protection against S. enteritidis organ invasion induced by the prophylactic treatment of day-old chicks with ILK involves activated heterophils which migrate rapidly to the inflammatory stimulus where they phagocytize and kill the bacteria.