Major histocompatibility (B) complex-associated differences in the delayed wattle reaction to staphylococcal antigen.

The influence of the major histocompatibility (B) complex on the delayed wattle reaction (DWR) to Staphylococcus aureus was studied in 109 segregants (B2/B2, B2/B5, and B5/B5) of a fourth generation cross between inbred Regional Poultry Research Laboratory lines 6(1) and 15(1). Chickens were sensitized at 6 weeks of age with S. aureus antigen. One week later, DWR was evaluated by injecting the right wattle with S. aureus antigen. Thickness measurements were taken 4, 24, 48, 72, and 96 hr after injection. A quadratic equation model was used for each bird to calculate maximum wattle thickness, hour of maximum response, and rate of response development and decline. In males, the maximum wattle thickness in response to S. aureus antigen was significantly greater in B2/B5 heterozygotes (1.77 +/- .07 mm) than in either homozygote, B2/B2 (1.36 +/- .13 mm) or B5/B5 (1.39 +/- .08 mm). Heterozygous males reached maximum response sooner and recovered more quickly than homozygous males but these differences were not statistically significant. In females, response developed later than in males but no B complex effect was detected in either rate of development or maximum response.

Major histocompatibility (B) complex and sex effects on the phytohaemagglutinin wattle response.

The influence of the major histocompatibility (B) complex and sex on the phytohaemagglutinin (PHA) wattle response was studied in 136 segregants (B2/B2, B2/B5 and B5/B5) of a fourth generation cross between inbred lines 6(1) and 15(1). At 6 weeks of age, chickens were injected with 100 micrograms purified PHA-P. Wattle thickness measurements were taken 4, 24, 48, 72 and 96 h after injection. Analysis of variance showed that 4 h after injection, males had a significantly higher response than females but the sex-genotype interaction was also significant. Females had higher responses than males 24 and 48 h after injection as a consequence of more rapid development and earlier resolution of the reaction in males. B2/B2 chickens had significantly lower responses than B5/B5 chickens 72 and 96 h after injection, signifying a faster late resolution phase in the B2/B2 genotype. The developmental and early resolution phases of the PHA wattle response were influenced by sex while the late resolution phase was influenced by B genotype.

The effect of bile acids and lipase on absorption of tallow in young chicks.

White leghorn chicks were fed diets with 4% tallow supplemented with one of the following bile acids at .04%: cholic acid, chenodeoxycholic acid, dehydrocholic acid, deoxycholic acid, or sodium taurocholate. Cholic acid improved the absorption of tallow but not significantly; chenodeoxycholic acid significantly improved tallow absorption during days 0 to 7 but decreased it during days 14 to 21. The bile acids, dehydrocholic acid, deoxycholic acid, and sodium taurocholate had no significant effect on absorption of tallow. In a 2 x 3 factorial design involving cholic acid and lipase, .04% cholic acid and/or .10% lipase significantly improved the absorption of tallow by 8 and 4% in chicks 1 and 3 weeks of age, respectively. Dry matter digestibility and efficiency appeared to be improved with the improvement of lipid absorption.