Improved techniques for dissociating particle-associated mixed ruminal microorganisms from ruminal digesta solids.

Combinations of physical and chemical methods were evaluated for their ability to remove particle-associated microorganisms (PAM) from saline-washed ruminal digesta solids (SWRDS). Physical methods included chilling and storage, homogenization, multiple extraction, and agitation with marbles. Chemical methods included use of low pH, Tween 80, formaldehyde, methanol, tertiary butanol, and methylcellulose. Microbial removal from SWRDS was determined directly by using epifluorescence microscopy and indirectly by measuring removal of diaminopimelic acid and total purines. Different combinations of methods resulted in removals of 46 to 82% for particle-associated bacteria (PAB), 52 to 98% for particle-associated protozoa (PAP), and 60 to 83% for PAB plus PAP. Two methods were considered most effective, based on microscopy; both removed similar amounts of PAB (79 to 82%) and PAB plus PAP (80 to 83%). In one method, SWRDS were stored for 24 h at 4 degrees C in a solution of pH 2 saline, .1% Tween 80, 1.0% methanol, and 1.0% tertiary butanol. In the other method, SWRDS were incubated for 30 min in .1% methylcellulose before storage for 24 h at 4 degrees C in pH 2 saline, .1% Tween 80, and 1.0% methanol. Common to both treatments was subsequent homogenization of the suspensions for 15 s followed by washing the digesta solids seven times with the treatment solutions. Both methods resulted in values that exceeded those reported previously for removal of PAM from ruminal digesta solids.

Amino acid limitation and flow to the duodenum at four stages of lactation. 2. Extent of lysine limitation.

Four multiparous Holstein cows with ruminal and duodenal cannulas were assigned to 4 x 4 Latin squares at peak (wk 4), early (wk 14 to 16), mid (wk 21 to 23), and late (wk 29 to 31) lactation to determine, in the presence of supplemental Met, the extent of Lys limitation and its required contribution to total essential AA in duodenal digesta. Treatments were duodenal infusions of 1) water alone or water with 2) 10 g/d of DL-Met plus 10 g/d of L-Lys, 3) 10 g/d of Met plus 20 g/d of Lys, and 4) 10 g/d of Met plus 30 g/d of Lys; quantities were reduced by 20% in late lactation. Rations were corn based (corn and grass-legume silages, corn meal, wheat middlings, soybean meal, and distillers dried grains with solubles) and most limiting in Lys and Met. Intakes of ruminally degraded and undegraded intake protein (percentage of NRC requirements) were (peak) 115, 97; (early) 112, 83; (mid) 113, 87; and (late) 127, 96. Contribution of Lys to passage of total essential AA to the duodenum without infusions were 13.2, 12.4, 13.8, and 14.8% at the four respective stages of lactation. Extent of Lys limitation determined from responses in content and yield of milk protein approximated 25, 20, and 10 g/d during peak, early, and midlactation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of five cycle rapid freeze-thaw treatment in conjunction with various chemicals for the reduction of Salmonella typhimurium.

A five cycle rapid freeze-rapid thaw process was used in conjunction with chemicals to reduce numbers of Salmonella typhimurium cells on poultry meat. The second portion of chicken wings consisting of ulna and radius with attached skin and muscle was inoculated with 400 to 900 colony forming units (CFU/g) of a nalidixic acid resistant strain of S. typhimurium. Chemicals used were 20 ppm chlorine, 5% potassium sorbate, 5% lactic acid, and 5% calcium propionate. The wings were either sprayed with or dipped into all chemicals before the freeze-thaw process. Wings were also chemically treated and not subjected to the freeze-thaw process. Numbers of S. typhimurium were determined by the most probable number procedure. The relative effectiveness of combinations of chemicals and the freeze-thaw process was compared to a control with the following percentage reductions of numbers of S. typhimurium cells: lactic acid, 98%; calcium propionate, 96%; potassium sorbate, 96%; chlorine, 95%; and freeze-thaw process without chemicals, 95%. There were no statistically significant differences among the treatments. In pilot plant study simulating commercial conditions, a carbon dioxide freezer was used for the rapid freeze and a microwave oven was used for the rapid thaw. Treatment of wings with 5% lactic acid plus freeze-thaw process resulted in statistically significant fewer numbers of S. typhimurium cells when compared to the freeze-thaw process without chemical treatment or to wings chemically treated without the freeze-thaw process.