Evaluation of a blend of organic acids and essential oil in the drinking water during a Salmonella Heidelberg challenge in broilers

Acidification of drinking water of broilers prior to processing is commonly used to reduce Salmonella entering into the plant, via crop contamination. This study evaluated an organic acid and essential oil product (OEP), when provided in the drinking water (3 ml/gallon) early and/or late in production, for reduction in S. heidelberg (SH) colonization in broilers. Eight hundred Ross x Ross day-old male chicks were assigned to 4 treatments in 32 floor pens, with 8 replicates per treatment and 25 chicks per pen. The treatments were: control, none (T1); OEP from 0-14 days of age (T2); OEP from 014 days of age plus the last 96 hours before end of trial (T3); OEP during last 96 hours before end of trial (T4). On day 7, a nalidixic acid-resistant SH was orally gavaged at 4.3 x 10⁷ CFU/chick to 13 marked seeder chicks in each pen. Environmental bootsocks collected on days 14 and 42 and cloacal swabs collected from 5 non-seeder (horizontal exposed; HE) chicks on day 36 were tested for Salmonella. Feed withdrawal was performed 8-10 hours prior to termination. On day 42, 10 birds per pen (5 seeders and 5 HE) were euthanized and cecal contents were collect, as well as, crop contents from 5 HE birds. Birds were weighed and feed intake recorded on days 14, 35 and 42. All statistical testing assumed a two-sided alternative hypothesis, and P < 0.05 was considered significant. Birds in T2 had numerically larger 14 day (P = 0.22) and 42 day (P < 0.1) body weight gain than T1, with other two treatments being intermediate. Birds in T2 also had the lowest feed conversion through day 14 (P < 0.05). A reduction (P = 0.05) in crop Salmonella prevalence was observed in birds from T2 vs. T1, with T3 and T4 being intermediate. No treatment differences were observed in Salmonella most probable number (MPN) in bootsock and cloaca samples. In seeder chicks, a 40% and 35% reduction in cecal SH MPN was observed in T2 and T3 birds as compared to T1. When a Tobit regression was applied to crop data (0 MPN are censored to -0.5 log₁₀ MPN/g), T2 and T4 had a numerical reduction of SH vs. T1 (P = 0.16). Acidifying the water with the product containing organic acid and essential oil may improve animal performance and reduce SH colonization.

Key Words: Salmonella Heidelberg, organic acid, essential oil, drinking water.