Abstract
Antibiotics are used as feed additives for cattle to alter rumen fermentation and increase weight gain. However, this practice can potentially lead to the presence of antibiotic residues in milk and meat and the selection of multiresistant bacteria. Bacteriocins have been suggested as an alternative to antibiotics used in animal production. This work aimed to evaluate the in vitro effects of bovicin HC5 and virginiamycin on ruminal fermentation and on microbial community composition. Ruminal fluid was collected from fistulated cows fed corn silage and incubated with Trypticase (15 g L-1). Cultures treated with bovicin HC5 or virginiamycin decreased (P < 0.05) ammonia accumulation by 47.46% and 66.17%, respectively. Bovicin HC5 and virginiamycin also decreased (P < 0.05) the concentration of organic acids and gas production, but the effects were somewhat distinct. Molecular fingerprinting of the microbial community using PCR-DGGE revealed that community structure varied between treatments and were distinct from the controls. These results demonstrate that bovicin HC5 and virginiamycin have distinct effects on ruminal fermentation and modify differently the microbial community composition. These results also expand the knowledge about the effects of antibiotics and bacteriocins on bacterial and archaeal communities involved in protein metabolism in the rumen.
Highlights
In ruminant livestock, feedstuffs are fermented by rumen microorganisms generating microbial protein, volatile fatty acids (VFAs), ammonia, methane and heat (Rychlik & Russell, 2000; Bach et al, 2005)
Bacteriocins have been traditionally studied as potentially useful biological tools in the food industry (Deegan et al, 2006), but studies demonstrated that these antimicrobials are effective in controlling animal pathogens (Twomey et al, 2000; Wu et al, 2007)
Our results indicated that both bovicin HC5 and virginiamycin reduced (P < 0.05) the concentration of ammonia and total gas production compared to untreated controls
Summary
Feedstuffs are fermented by rumen microorganisms generating microbial protein, volatile fatty acids (VFAs), ammonia, methane and heat (Rychlik & Russell, 2000; Bach et al, 2005). Much of these products are used as protein and energy sources by the host, but dietary losses due to urea excretion and methane production can raise the cost of production of dairy and beef cattle. Ruminant nutritionists have used chemical additives in rations of dairy and beef cattle to decrease dietary losses and increase useful end-products of ruminal fermentation, enhancing the efficiency of feed utilization (Callaway et al, 1997; Shen et al, 2017). Several feeding management strategies and chemical and biological additives are being investigated as potential alternatives to control or manipulate the processing and assimilation of dietary nutrients
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