Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2002
Publication Date: N/A
Technical Abstract: Previously we have shown in separate experiments that resistance in broilers to Eimeria acervulina (EA) was reduced by vitamin A deficiency and enhanced by a probiotic (Lactobacillus-based, Primalac®). In the present 2 x 2 factorial study, a broiler starter ration was amended for vitamin A (control, C, or deficient, A) and probiotic status (-, P). One hundred eighty day-old broilers were randomly assigned to battery cages (11/cage, 4 cages/treatment). At 21 d, 24 birds per treatment were inoculated orally with 104 oocysts of EA. Feces were collected from 27-30 d (6-9 days post infection, dpi), and shed oocysts were enumerated. Sera and intestinal secretions were sampled at 3, 6, 9, and 12 dpi and tested by ELISA for interferon-g (IFN-g) and anti-EA antibodies (Ab). Fecal oocyst shedding was highest (P £ 0.05) in A- birds (1.9 x 109 oocysts/kg body wt), followed by AP, C- and CP, respectively. Feeding the probiotic reduced shed oocysts by about 20% in A fed birds and by 26% in C fed birds. Intestinal IFN-g was relatively constant in all treatment groups except for A-. In those birds, IFN-g declined steadily and was lower (P £ 0.05) from day 6 on. Serum IFN-g levels fluctuated within each treatment, and over time were not revealing. Secretory Ab level against a recombinant Eimeria antigen was constant (P > 0.05) in AP birds, but increased (P £ 0.05) in A-, C- and CP birds. Serum Ab levels were also constant in A- and CP, but increased (P £ 0.05) in AP. Between treatments, A- birds had higher (P £ 0.05) Ab level than AP. At 12 dpi, CP had the lowest serum Ab level and A- the highest. AP birds were not different (P > 0.05) than C-. At this time period, serum Ab level is indicative of a higher invasion by EA in A- birds, and that probiotic treatment reduced this internal challenge. The data demonstrate that this Lactobacillus-based probiotic had an immunostimulatory effect even in birds compromised by a dietary deficiency of vitamin A. Further, this effect occurs at the level of the mucosal immune system of chickens and is best manifested by apparent lower internal invasion by EA, based on lower serum antibody, and lower EA oocyst production.