EFFECTS OF ABOMASAL SLAFRAMINE INFUSION ON RUMINAL DIGESTA PASSAGE AND DIGESTION IN STEERS

Slaframine was infused intra-abomasally once daily 3 h after feeding t o four ruminally and abomasally cannulated Jersey steers (586 +/-: 88. 6 kg) at 0 (saline control), 10, 20, or 30 mu g kg(-1) BW in a 4 x 4 L atin square design experiment. Periods were 14 d in length. On a DM ba sis, diets were a 38:62, sorghum silage:concentrate offered at 125% of the net energy required for maintenance. Ruminal, abomasal, and fecal samples were collected at 2-h intervals on days 10-12, and ruminal co ntents were completely evacuated and sampled at 3, 6, 12, and 24 h aft er feeding on days 13 and 14. Ruminal volume and pH increased (linear; P < 0.05) from 1.6 to 8.9% and from 0.10 to 0.22 units, respectively, with SF. Total ruminal VFA and ammonia concentrations decreased (line ar; P < 0.05) with SF from 4.1 to 9.4% and from 5.3 to 10.2%, respecti vely. Apparent ruminal DM and starch digestion increased at the lowest dosage and decreased at higher dosages of SF (quadratic; P < 0.05). R uminal NDF digestion decreased with SF (linear; P < 0.1). Totat tract DM digestion was not affected by SF. Fractional turnover rate of rumin al DM increased (linear; P < 0.05) from 1.6 to 11.3% with SF. During t he first 8 h after SF administration, liquid dilution rate increased a s much as 18.5% with the highest dosage of SP(linear; P < 0.05). Durin g the 10- to 21-h period after SF administration, dilution rate decrea sed with the 10- to 20-mu g kg(-1) BW dosages of SF (quadratic, P < 0. 05). Outflow of AA tended to decrease at 10 and 20 and increased at th e 30 mu g kg(-1) BW dosages of SF (quadratic, P < 0.05). Abomasal infu sion of SF alters digesta passage and the site of digestion of nutrien ts between the rumen and the lower digestive tract. The highest level shifted the site of digestion to the lower tract while lower dosages e nhanced ruminal digestion.