Pretanned leather shavings in a supplement mixture for steers: II. Digesta kinetics, ruminal fermentation, and grazing behavior in steers grazing dormant wheatgrass pasture.

Twelve ruminally cannulated steers (Angus x Holstein; average initial BW = 533 +/- 3.28 kg) were randomly allotted to one of three treatments (four steers/treatment) to evaluate the use of pretanned leather shavings as a component of a protein supplement for steers grazing dormant intermediate wheatgrass (Thinopyrum intermedium Host). Steers were allotted to one of three treatments: 1) no supplement (control); 2) supplementation intraruminally at 0700 with soybean meal at .2% of BW (as-fed basis); 3) supplementation intraruminally with soybean meal and pretanned leather shavings (17:8 ratio, respectively) at .16% of BW (as-fed basis). Supplements were formulated so that intakes were isonitrogenous and were placed intraruminally once daily (0700). Sampling periods were conducted February 3 to 16 and February 17 to March 5, 1995. In situ organic matter disappearance of the soybean meal supplement was greater (P > .05) than that of the leather shavings supplement at all incubation times (1, 3, 6, 9, 12, 24, and 48 h). Data suggested that pretanned leather shavings within the leather shavings supplement were only 25% degradable within the rumen. Forage OM intake (control = 12.7, soybean meal = 12.7, and leather shavings = 13.4 g/kg of BW), grazing time, and grazing efficiency were not altered (P > .10) by supplementation or type of supplement provided but did increase between the February and March samplings. Total intake was increased (P = .09) with supplementation and reflected the addition of the protein supplements. Particulate and fluid passage estimates were unaffected (P > .10) by the supplements; however, gastrointestinal fill increased (P = .01) between the February and March samplings. Ruminal pH was lower (P = .04) and ruminal NH3 N concentration was greater (P = .02) for supplemented steers than for control steers, and supplementation treatments did not differ (P > .10). Total VFA concentrations were increased (P = .01) by supplementation but were not affected by type of supplement provided (P > .10). Ruminal molar proportions of acetate and propionate and the ratio of these two VFA did not differ (P > .10) between supplementation types. Nonetheless, supplementation increased molar proportions of butyrate (P = .04), valerate (P = .02), and isovalerate (P = .05), and leather shavings supplementation increased (P = .10) isobutyrate proportions over those in steers supplemented with soybean meal. Combining pretanned leather shavings with soybean meal seemed to have no deleterious effects on forage intake, digesta passage, grazing behavior, or ruminal fermentation and seemed to provide effects similar to those of soybean meal alone.