Effects of a return chewing gum/packaging material mixture on in situ disappearance and on feed intake, nutrient digestibility, and ruminal characteristics of growing steers

In situ and in vivo digestibility experiments were conducted to determine t he acceptability, digestibility, and safety of a return chewing gum/packagi ng (G/P) material mixture when fed to steers. In the in situ experiment, bo th ruminal and intestinal disappearances were measured. Two ruminally and d uodenally cannulated steers, which were given free access to alfalfa hay (A H), were used in this study. Duplicate Dacron bags containing the G/P were incubated in the rumen for 0, 3, 6, 12, 24, and 48 h. After ruminal incubat ion, the 12-, 24-, and 48-h bags were placed in the duodenum and collected in the feces to determine intestinal disappearance. In situ ruminal DM disa ppearance was greater than 70% for all substrates tested at 0 h, indicating high solubility of the substrates in water, and began to reach a plateau a fter 12 h of incubation. Intestinal in situ disappearance was not different (P > .25) from zero. In the digestion trial, four ruminally cannulated ste ers (337 +/- 21.3 kg BW; mean +/- SD) were used in a 4 x 4 Latin square des ign with the following treatments: 0) 50% corn (C), 50% AH; 10) 45% C, 45% AH, 10% G/P; 20) 40% C, 40% AH, 20% G/P; 30) 35% C, 35% AH, 30% G/P. Steers fed G/P-containing diets had greater (P < .01) DMI than the control steers . Increasing the G/P resulted in a linear (P < .05) increase in DMI. Appare nt DM digestibility tended to be higher (P < .10) for the G/P-containing di ets than for the control. A quadratic effect (P < .05) on digestible DMI wa s observed, with greater (P < .01) digestible DMI values for G/P-containing diets (4.8 vs 5.8 kg/d). Digestible organic matter and total nonstructural carbohydrate intakes followed trends similar to those of DM. Apparent alum inum digestibility of G/P-containing diets was not different (P > .13) from zero. The level of G/P in the diet had no effect (P > .2) on total VFA con centration or ruminal pH. There was a linear decrease (P < .01) in the mola r percentage of isobutyrate and isovalerate in addition to a linear increas e (P < .01) in butyrate and valerate with increasing levels of G/P. There w as a quadratic effect (P < .01) on molar proportions of acetate and propion ate and on the acetate:propionate ratio. Results of both experiments sugges t that G/P may be fed to safely replace up to 30% of corn-alfalfa hay diets for growing steers with advantages in improving DMI and digestibility.