Pretanned leather shavings in a supplement mixture for steers: II. Digestakinetics, 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 st eers/treatment) to evaluate the use of pretanned leather shavings as a comp onent of a protein supplement for steers grazing dormant intermediate wheat grass (Thinopyrum intermedium Host). Steers were allotted to one of three t reatments: 1) no supplement (control); 2) supplementation intraruminally at 0700 with soybean meal at .2% of BW (as-fed basis); 3) supplementation int raruminally with soybean meal and pretanned leather shavings (17:8 ratio, r espectively) at .16% of BW (as-fed basis). Supplements were formulated so t hat 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 sup plement 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 onl y 25% degradable within the rumen. Forage OM intake (control = 12.7, soybea n meal = 12.7, and leather shavings = 13.4 g/kg of BW), grazing time, and g razing efficiency were not altered (P > .10) by supplementation or type of supplement provided but did increase between the February and March samplin gs. Total intake was increased (P = .09) with supplementation and reflected the addition of the protein supplements. Particulate and fluid passage est imates were unaffected (P > .10) by the supplements; however, gastrointesti nal fill increased (P = .01) between the February and March samplings. Rumi nal 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 increase d (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 supplementatio n types. Nonetheless, supplementation increased molar proportions of butyra te (P = .04), valerate (P = .02), and isovalerate (P = .05), and leather sh avings supplementation increased (P = .10) isobutyrate proportions over tho se in steers supplemented with soybean meal. Combining pretanned leather sh avings with soybean meal seemed to have no deleterious effects on forage in take, digesta passage, grazing behavior, or ruminal fermentation and seemed to provide effects similar to those of soybean meal alone.