The effect of a selected yeast fraction on the prevention of pullorum disease and fowl typhoid in commercial breeder chickens

A selected yeast fraction (SYF) was tested for the purpose of preventing pullorum disease and fowl typhoid in breeder chickens. In a challenge-protection experiment, commercial Three-Yellow breeder chicks were initially divided into groups A, B (challenged, treated), C (challenged, untreated), and D (unchallenged, untreated). The group A diet was supplemented with SYF and group B was supplemented with Acidipure via drinking water. At 7 D, birds of groups A, B, and C were divided into 2 equal subgroups (A1-A2, B1-B2, and C1-C2). Subgroups A1, B1, and C1 were challenged with Salmonella pullorum (SP), while subgroups A2, B2, and C2 were challenged with Salmonella gallinarum (SG). Clinical signs and mortality were recorded daily. At intervals, antibodies against SP and SG were detected by a plate agglutinate test (PAT). At 42 D, all birds were weighed and necropsied, lesions were recorded and challenge pathogens were isolated. Results showed that SP and SG isolation positive rates of groups A1-A2 were significantly lower (P < 0.05) than those of B1-B2 and C1-C2, respectively. The average body weight (BW) of groups A1-A2 was significantly higher (P < 0.05) than that of B1-B2 and C1-C2, respectively. In the field trial, chicks were randomly divided into 3 groups. Group 1 birds were fed a diet supplemented with SYF, group 2 diet was supplemented with Acidipure via drinking water, and group 3 was fed the same but un-supplemented diet as the control group. Antibodies against SP and SG were detected by PAT at 120 D. The antibodies positive rate of group 1 was significantly lower (P < 0.05) than those of groups 2 and 3, while no significant difference (P > 0.05) was found between groups 2 and 3. The results demonstrated that SYF supplementation could significantly decrease SP and SG infection rates, improve the BW of birds challenged with SP and SG, and was more effective than Acidipure via drinking water.