Effects of red clover and maize silages on the carriage of gut pathogens in steers

An experiment investigated the effects of increasing proportions of red clover (RC) (Trifolium pratense) silage relative to maize (M) (Zea mays) silage in the diet of steers on the pathogenic microflora of gut digesta and faecal samples. The experiment consisted of 3 periods of 21 d. Eight Hereford x Friesian steers were used, with 4 maintained on a 90 % maize: 10 % red clover (90M:10RC) silage diet throughout and 4 receiving 90M:10RC silage in period 1 then 50M:50RC, 10M:90RC in periods 2-3, respectively. Populations of Listeria monocytogenes and E. coli were enumerated at time points in each period. L. monocytogenes data showed disparity between periods. In the latter part of period 2, L. monocytogenes populations were higher in the rumen, duodenum and faeces of steers offered 50M:50RC but in period 3, L. monocytogenes populations were lower in the faeces of steers fed the higher level of red clover silage (P <0.05). Despite negligible E. coli levels in the diets, populations of E. coli, including E. coli 0157, were detected in the steers throughout the trial. Diet effects on E. coli levels were not apparent at any of the three sites examined. Further research is needed to elucidate the effects of red clover and dietary pathogen load on gut and faecal pathogen populations.