Low Concentration of Antibiotics Modulates Gut Microbiota at Different Levels in Pre-Weaning Dairy Calves

Abstract

The aim of this study was to investigate the effect of feeding milk replacer (MR) with two different antibiotics treatments on the gut microbiota of pre-weaning calves. Twelve (12) Holstein male calves at 1-day-old were randomly assigned to: milk replacer without antibiotics (CON), milk replacer plus low cocktail of antibiotics (LCA) concentration (penicillin 0.024 mg/L, streptomycin 0.025 mg/L, tetracycline 0.1 mg/L, ceftiofur 0.33 mg/L), and milk replacer plus a low concentration of single antibiotic (LSA; ceftiofur 0.33 mg/L). All the calves were harvested at 35-day-old, and the digesta from the ileum and colon was collected in addition to fecal samples. Samples were analyzed by 16S rRNA gene using Illumina MiSeq platform. Results showed that there were significant differences among treatments in the ileum, where LCA significantly reduced the relative abundance of Enterobacteriaceae (P = 0.02) especially Escherichia-coli (P = 0.02), while LSA significantly reduced the relative abundance of Comamonas (P = 0.02). In the colon and rectum, LSA treatment was significantly enriched with the class Bacilli, whereas the control group was significantly enriched with Alloprevotlla (P = 0.03). However, at the family level in the rectum LCA and LSA significantly reduced the relative abundance of Acidaminococcaceae (P = 0.01). Moreover, at the genera level in the colon, LSA significantly increased Prevotellaceae_Ga6A1_ group (P = 0.02), whereas in the rectum both of treatments reduced the relative abundance of Phascolarctobacterium (P = 0.01). In conclusion, the overall low cocktail of antibiotics concentration induced changes at different taxonomic levels; specifically the decrease in Escherichia-coli which might subsequently reduce the incidences of diarrhea in calves.

Dynamic changes of the fecal bacterial community in dairy cows during early lactation

“…In addition to studies on the rumen, reports on the microbial composition of the feces in dairy calves are abundant. Previous studies have found an association between fecal microbiota and age (Song et al 2018 ), diet (Dill-McFarland et al 2019 ; Wang et al 2019 ), antibiotic therapy (Behr et al 2018 ; Oultram et al 2015 ; Yousif et al 2018 ), and health (Gomez et al 2017 ) in dairy calves. For lactating cows, the core fecal microbiota was identified from ten farms across Northern and Central California, USA (Hagey et al 2019 ).…”

The Effects of Feeding Waste Milk Containing Antimicrobial Residues on Dairy Calf Health

“…Yousif and colleagues investigated the effects of feeding milk replacer both with and without antimicrobials added. The control was unmedicated, while the LCA (“low cocktail of antibiotics”) milk replacer had penicillin (0.024 mg/L), streptomycin (0.025 mg/L), tetracycline (0.1 mg/L) and ceftiofur (0.33 mg/L) added; ceftiofur (0.33 mg/L) was added to the LSA (“low concentration of a single antibiotic”) milk replacer [ 36 ]. The concentrations of antimicrobials added to the milk replacer were based on the authors’ analyses of waste milk on this farm; the median amount was then added to the milk replacer.…”

“…The LCA diet significantly reduced ( p = 0.02) the level of Enterobacteriaceae (including E. coli ) found in the intestines compared to the intestines of calves fed unmedicated milk replacer. The authors concluded that feeding a low cocktail of antimicrobials in milk replacer led to a shift in the bacterial taxa of intestinal microbiome, including a reduction in E. coli , which might have a positive effect on calf health by reducing the occurrence of diarrhoea in young calves [ 36 ].…”

“…Deng and colleagues described an increased occurrence of pathogenic bacteria through the feeding of waste milk, although the composition and distribution of bacterial genera are similar in all feeding regimes up to 21 days of age in that study [ 23 ]. In contrast, Yousif and colleagues reported a decrease in pathogenic bacteria after feeding milk replacer containing antimicrobials at residual levels, and Li and colleagues could not detect any difference in the composition of the microbiome on days 15, 25 and 35 of medicated milk replacer feeding [ 28 , 36 ]. Feng and colleagues could not determine any significant differences in bacterial functional profiles or resistance genes, and Maynou and colleagues found only minor differences [ 25 , 32 ].…”

“…It is important to note that these studies differ with regard to feeding management, sampling frequency, detection method and bacteria examined, making direct comparisons challenging. While some of these studies used “natural” waste milk obtained from antimicrobially treated cows [ 23 , 32 , 37 ], others experimentally “spiked” milk or milk replacer with antimicrobials [ 25 , 28 , 33 , 36 ]. Both types of feed trial have merit: the artificially spiked milk obviously allows for a more exact comparison between feed groups, as the precise concentration of antimicrobials is known; however, spiked milk does not necessarily recreate real world conditions or allow for the possible pharmacokinetic changes, which may occur between treatment of the cow and the subsequent inclusion of antimicrobial residues in waste milk in the udder.…”