The Impact Of Antibiotics On The Intestinal Microbiome, Feed Intake And Growth Of Calves With Diarrhoea

Specifically, this field study evaluated the impact of three distinct oral antibiotic treatments - paromomycin (Parofor®), apramycin (Apravet®) and neomycin - compared to a non-treated control group.

Understanding the ramifications of antibiotic use in this context is critical for developing effective treatment protocols that optimise the health and productivity of affected calves.

Diagnostic confirmation of Cryptosporidium infection was performed using immunochromatography quick tests.

Materials and methods

The study was conducted in Spain over a 42-day period with 24 calves aged 1-2 weeks old and diagnosed with history and clinical signs of diarrhoea attributable to Cryptosporidium infection, confirmed via immunochromatography. 

Calves were divided into four homogenous groups of size calves each: 

• Group 1: Paromomycin
• Group 2: Apramycin
• Group 3: Neomycin
• Group 4: Control (no antibiotics)

Key measurements for assessing microbial changes included:

• Alpha diversity: variety of microbial species within each calf
• Beta diversity: differences in microbial composition between groups
• Feed intake: total dry matter consumed over the study period
• Weight gain: total body weight change over 42 days

These metrics provided a comprehensive view of the treatment-induced microbial dynamics. Faecal samples were collected on days 2, 5, 15, 23 and 42.

Results

The findings demonstrated distinct impacts of the antibiotic treatments on the intestinal microbiota of calves suffering from Cryptosporidium-induced diarrhoea. In terms of alpha diversity, both the control group and the paromomycin-treated group maintained higher diversity levels, particularly by the end of the study period (day 42). This outcome suggests that paromomycin exerted minimal disruptive effects on the microbiota, allowing for a healthier and more stable microbial community. 

Conversely, the neomycin group exhibited a significant alteration in bacterial composition, indicating a more pronounced disruption of the microbiota. The beta-diversity analysis corroborated this observation, revealing substantial differences in microbial profiles between the neomycin-treated group and the others.

The abundance of beneficial bacteria, crucial for maintaining a healthy intestine, was significantly higher in both the control and paromomycin groups, particularly following the initial treatment phase (day 7). 

The evolution of feed intake was a critical aspect of this study. The paromomycin group accounted for a total feed intake of 239.5 kg, displaying a stable and consistent feeding pattern throughout the experimental period. This consistency indicates effective recovery and good digestive efficiency, resulting in the highest feed efficiency among the groups studied. 

Despite experiencing diarrhoea during the initial week, the control group achieved the highest total feed intake at 244.6 kg. However, their feed efficiency was lower compared to the paromomycin group. This finding suggests that high feed intake does not inherently correlate with optimal growth performance, particularly when compounded by diarrhoea. The neomycin group recorded the lowest feed intake at 158.8 kg, indicating potential issues with digestibility or palatability associated with this treatment, leading to decreased overall intake.

The apramycin group reported a total feed intake of 212.7 kg, demonstrating intermediate performance in feed consumption but exhibiting less consistency compared to the paromomycin and control groups. 

Weight gain metrics were highly indicative of the overall effectiveness of the treatments. The paromomycin group showed the highest average weight gain at 27 kg, with minimal variability among individuals. Notably, only one calf in this group experienced diarrhoea, highlighting the treatment's effectiveness in controlling the clinical signs of infection. 

In contrast, the control group, despite initial diarrhoea, attained an average weight gain of 23.25 kg with significant variability likely attributed to individual health factors and responses to infection. The neomycin group revealed the poorest performance, achieving an average weight gain of only 16.5 kg which underscores the adverse effects on growth associated with this antibiotic treatment.

Calves treated with apramycin displayed intermediate growth performance, with an average weight gain of 23.25 kg, though they exhibited greater variability in results compared to the paromomycin group. 

Conclusion

This study shows the significant effectiveness of paromomycin in preserving microbiota diversity and promoting growth in calves suffering from Cryptosporidium-induced diarrhoea. The findings emphasise the critical need for clinicians to select antibiotic treatments not only for their clinical efficacy but also for their ability to maintain microbiota balance, which is essential for both short- and long-term health and productivity in calves. Positive outcomes during the suckling phase are likely to have beneficial effects on subsequent growth phases, thereby improving the overall efficiency of calf rearing practices.