Effect of tylosin on ruminal Fusobacterium necrophorum population and fermentation products in cattle fed a high-grain diet

Tylosin feeding prevented the increase in Fusobacterium necrophorum population normally associated with the feeding of a high-grain diet. Also, tylosin appeared to moderate the ruminal fermentation during initial adaptation to a high-grain diet.


Introduction
Fusobacterium necrophorum, a normal diet and then stepped up rapidly (4-day step inhabitant of the rumen, is the primary up) to an 85% grain diet.Steers were fed a causative agent of liver abscesses in cattle.It 70% grain diet on days 1 to 3 and an 85% has been detected in or isolated from bovine grain diet from days 4 to 32.The intention of ruminal contents and ruminal wall lesions by a rapid step-up was to promote lactic acid provariety of methods.The concentration in the duction and accumulation in the rumen.The rumen is in the range of 100,000 to a grain portion of the diet was composed of 1,000,000 cells per gram of ruminal contents.
cracked corn (87.8%); soybean meal (10.5%); Tylosin is used widely in the feedlot indus-mineral mixture (0.2%); and vitamins A, D, try to prevent liver abscesses.The antibiotic is and E (0.1%).Steers were fed daily at 2% of a macrolide and is primarily effective against BW.gram-positive bacteria.
Although, F. necrophorum is gram-negative, it is suscepti-Ruminal contents were collected on 3 ble to tylosin.However, the effect of feeding consecutive days before grain feeding (days -2, tylosin on the population of F. necrophorum in -1, and 0); after feeding the 70% grain diet the rumen has not been determined.Also, the (days 2, 3, and 4) and 85% grain diet (days 5, antimicrobial activity of tylosin could moderate 6, and 7); and thereafter on 2 consecutive days the rate of ruminal fermentation and, thus, weekly for 4 weeks.Ruminal samples were contribute to a stable fermentation.Therefore, a study was conducted to determine the effect

Experimental Procedures
Six ruminally cannulated Holstein steers in ruminal contents.Treatment groups were control and tylosin-fed (90 mg/head/day).Steers were adapted initially to an alfalfa hay salt (1.0%); dicalcium phosphate (0.3%); trace collected before feeding (time 0), transported to the laboratory, and processed for enumeration of F. necrophorum and analyses of pH and concentrations of lactate, volatile fatty acids (VFA), and ammonia.Also, on days 1 (70% grain diet) and 4 and 11 (85% grain diet), ruminal samples were collected at feeding and 3, 6, 9, 12, and 24 hours after feeding to monitor the effect of tylosin on postfeeding feeding ruminal fermentation products.F. necrophorum was counted by the mostprobable-number (MPN) technique using a selective culture medium.

Results and Discussion
Before grain feeding, F. necrophorum counts in ruminal contents averaged 8.8 and 10.0 x 10 5 /g DM in the control and tylosin-fed groups, respectively.In the control, F. necrophorum counts increased in response to grain feeding (Table 1), possibly because of availability of lactate, an energy substrate for F. necrophorum.The increase peaked at week 2, and counts decreased somewhat following adaptation to the 85% grain diet.Including tylosin in the diet inhibited the increase in F. necrophorum associated with increased grain feeding.
The counts through-out the grain feeding period remained similar to or less than the baseline counts during alfalfa feeding.Apparently, feeding tylosin did not induce resistance in F. necrophorum, because counts did not increase during the feeding period.
We observed a trend (P=0.08) for ruminal pH to be higher in tylosin-fed than in control steers during the initial step-up to the 70 and 85% grain diets.Once the steers were adapted to the 85% grain diet, ruminal pH was similar between both groups.Ruminal lactate VFA and ammonia concentrations were not affected by including tylosin in the feed (Table 2).A 24-hour profile of ruminal fermentation products was obtained on days 1, 4, and 11 to determine whether tylosin moderates ruminal fermentation.On day 1, when steers were switched abruptly to the 70% grain diet, the postfeeding ruminal pH and concentrations of fermentation products were not affected by tylosin (data not shown).However, on days 4 and 11, ruminal pH tended to be higher in tylosin-fed than in control steers (Figure 1).The postfeeding concentrations of ruminal VFA, lactate, and ammonia were not affected by tylosin in the feed.Treatment * sampling days interaction, P < 0.05.

Figure 1 .
Figure 1.Ruminal pH Profile on Days 4 and 11 in Steers Fed High-Grain Diets with or without Tylosin.

Table 1 . Effect of Tylosin on Ruminal Fusobacterium necrophorum abc
c Treatment x sampling days interaction P = .09. d Different from days 1 to 3 at P < .05.