Effects of Olive Leaf Extract on Growth Performance and Immunobiochemical Parameters in Turkey Poults

Olive leaf extract (OLE) is known to have numerous bioactivities attributed to its high phenolic compound content. This study aimed to investigate the impact of OLE and Ceftriaxone on Escherichia coli (E. coli) in turkey poults. A total of 150 cloacal swabs were taken from turkey poults for isolation and identification of E. coli. Fifty-one-day-old turkey poults were divided into five equal groups. The first group served as the control, and the second group orally received 400 mg/kg body weight OLE daily for 35 days. The third, fourth, and fifth groups were infected with a culture suspension of E. coli O78 (0.3 ml, 3×107 organism/ml) via the nasal route. The third group was infected untreated. The fourth group was treated with 50 mg/Kg body weight of Ceftriaxone for 5 consecutive days. The fifth group received 400 mg/kg body weight of OLE from day to day 35 of age. Bacteriological examination revealed positive swabs in 18.18%, 46.67%, and 53.33% of healthy, diseased, and recently deceased poults, respectively. Serological identification of E. coli isolates included O157 (2), O78 (2), and O11 (1). Poults of the third group showed typical clinical signs, gross pathological changes such as congestion in various organs, and a 30% mortality rate. Additionally, significant reductions in body weight, weight gain, catalase (CAT), and superoxide dismutase (SOD) were observed, alongside anemia, hypoproteinemia, and hypoalbuminemia. Conversely, significant increases were noted in the phagocytic index, killing percentage, total globulin, immunoglobulins, and the albumin/globulin ratio. Furthermore, significant increases were observed in FCR, leukocytic counts, lysosome, tumor necrosis factor α (TNF-α), interleukin-10, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), uric acid, creatinine, and malondialdehyde (MDA) levels. Poults in the fourth and fifth groups showed fewer clinical signs, lower lesion scores, and reduced mortality rates. Additionally, there was a decrease in E. coli re-isolation, modulation of altered parameters, and improvement in pathological lesions compared to the infected, untreated poults. Both OLE and Ceftriaxone were found to modulate the haematological, biochemical, and immunological parameters, as well as mitigate performance changes and pathological lesions induced by E. coli infection in turkey poults.