Purpose: This study reveals the role of animal age and environmental factors influencing the shedding of Shiga Toxin-producing E. coli (STEC) in beef cattle.
Methods: Several animal factors like breed, age, sex were investigated to determine their influence on STEC shedding. A cohort of 300 beef calves from a multi-breed beef calf population derived from Brahman and Angus cattle was sampled four times every three months after birth. This study utilized a combination of culture-based and nucleic acid-based methods for the detection and enumeration of Shiga Toxin-producing Escherichia coli (STEC) from the fecal samples. Data were analyzed by regression methods and McNemar's test for matched pairs using STATA software.
Results: The herd prevalence of STEC in March was 59.8%, which was significantly higher compared to any of the other sampling times (39.5% in June, 20.3% in August and 20.7% in December). The stx2 genotype was predominant in the herd, whereas stx1/stx2 was the lowest in all samplings. There was no significant association between breed group, sex of the calf and average weight gain with the STEC shedding. However, we observed STEC shedding was significantly affected by animal age. Furthermore, seasonal variation of STEC shedding was observed.
Significance: This study provides insight that animal age is a significant factor that influences the prevalence of STEC; therefore this finding has implications for the development of on-farm mitigation strategies.