Effect of Distillers Feedstuffs and Lasalocid on Campylobacter Carriage in Feedlot Cattle

Campylobacter bacteria are foodborne pathogens that can colonize the gut of food animals. Limited in their ability to ferment sugars, Campylobacter can derive energy for growth via amino acid catabolism. The objectives of the present studies were to test whether supplemental distillers grains containing high amounts of rumen-undegradable intake protein or supplemental lasalocid may, by promoting amino acid flow to the lower bovine gut, increase intestinal carriage of Campylobacter. In study one, 10 steers (5 per treatment) were adapted to diets formulated to achieve 0 or 30% dried distillers grains. After an initial 14-day adaptation to the basal diet, control and treated steers were fed their respective diets for 23 days, after which time they were fed supplemental lasalocid for an additional 8 days, followed by a 5-day withdrawal. In study two, 24 steers preacclimated to a basal diet were adapted via 3-day periodic increases to dietary treatments formulated to achieve 0, 30, or 60% wet corn distillers grains with solubles. Analysis of Campylobacter bacteria cultured from duodenal and fecal samples in study one and from fecal samples in study two revealed no effect of dried distillers grains or wet corn distillers grains with solubles on the prevalence or concentrations of duodenal or fecal Campylobacter. The results from study one indicated that colonized steers, regardless of treatment, harbored higher Campylobacter concentrations when transitioned to the basal diet than when coming off pasture. Campylobacter carriage was unaffected by lasalocid. These results provide no evidence that feeding distillers grains high in rumen-undegradable intake protein or supplemental lasalocid contributes to increased intestinal carriage of Campylobacter in fed cattle.

Effect of undegradable intake protein supplementation on urea kinetics and microbial use of recycled urea in steers consuming low-quality forage

We evaluated the effect of undegradable intake protein (UIP) on urea kinetics and microbial incorporation of urea-N in ruminally and duodenally fistulated steers (n4; 319 kg) providedad libitumaccess to grass hay in a 4 × 4 Latin square. Casein was continuously infused abomasally in amounts of 0, 62, 124 and 186 mg N/kg body weight per d to simulate provision of UIP. Periods were 13 d long with 7 d for adaptation and 6 d for collection. Jugular infusion of [15N15N]urea followed by determination of urinary enrichment of [15N15N]urea and [14N15N]urea was used to measure urea kinetics. Forage and N intake increased (quadratic,P < 0·02) with increasing UIP. Urea synthesis was 27·1, 49·9, 82·2 and 85·8 g urea-N/d for 0, 62, 124 and 186 diets, respectively (linear,P < 0·01). The proportion of urea synthesis that entered the gastrointestinal tract was 0·96 for steers receiving no UIP and decreased linearly (P = 0·05) to a low of 0·89 for steers receiving 186. The amount of urea entering the gastrointestinal tract was least for 0 (26·3) and increased (linear,P < 0·01) to 48·7, 77·2 and 76·6 g urea-N/d for 62, 124 and 186 diets, respectively. Microbial incorporation of recycled urea-N increased quadratically (P = 0·04) from 13·9 for 0 to 47·7 g N/d for 124. The proportion of microbial N derived from recycled urea increased (quadratic,P = 0·05) from 0·31 to 0·58 between 0 and 124 and dropped to 0·44 for 186 mg N/kg body weight per d. UIP increased intake of hay and provided a N source for ruminal microbes via urea recycling.