Pretanned leather shavings in a supplement mixture for steers: I. In situ and in vitro disappearance, ruminal fermentation, and organic matter, nitrogen, and fiber digestion.

Two digestion studies were conducted to evaluate the use of pretanned leather shavings as a component of a protein supplement. In Exp. 1, the in situ and in vitro disappearance of pretanned leather shavings and soybean meal was evaluated. Results revealed that less than 18.4% of the pretanned leather shavings was solubilized and disappeared when exposed to McDougall's buffer for 48 h, but there was 90.0% disappearance with 48-h exposure to a .1 N HCl/pepsin treatment and 97.0% disappearance with exposure to a two-stage digestion. In situ disappearance following 72 h in the rumen allowed 6.8% disappearance. Thus, leather shavings seem to be relatively indigestible in the rumen, but postruminal digestion may be possible. In Exp. 2, six Angus x Holstein steers, fitted with ruminal and duodenal cannulas, were used in a replicated 3 x 3 Latin square to evaluate ruminal and digestion effects of the following supplements combined with fescue hay at 1.7% of BW (DM basis): no supplementation (control); supplementation intraruminally with soybean meal at .07% of BW (as-fed basis); and supplementation intraruminally with a combination of soybean meal and pretanned leather shavings (17:8 ratio) at .05% of BW (isonitrogenous to soybean meal; as-fed basis). Ruminal fluid passage rate was greater and fluid turnover time was shorter in steers fed leather shavings than in those fed soybean meal (P = .10). Ruminal pH was lower (P = .04) for supplemented steers than for control steers and ruminal NH3 N concentration was greater (P = .01) in steers fed soybean meal than in those fed leather shavings. Total VFA concentration was increased (P = .02) by supplementation. Supplementation with soybean meal increased (P < .05) ruminal molar proportions of butyrate, valerate, and isovalerate compared with leather shavings. Duodenal OM flow and OM disappearing in the intestines were increased by supplementation (P < .10), but not by the type of supplement fed (P > .10). Ruminal digestion of OM and total tract OM digestion were unaffected (P > .10) by supplementation and the type of supplement fed. Flow and digestion of NDF were unaffected (P > .10) by the treatments. Flow of N and the quantity of N disappearing in the intestines were increased (P < .05) by supplementation but did not differ (P > .10) between supplementation groups. Microbial N flow, N utilization for net microbial protein synthesis, and ruminal N disappearance were unaffected (P > .10) by supplementation and the type of supplement provided. Combining pretanned leather shavings with soybean meal seemed to have no deleterious effects on digestion or fermentation and to allow for escape of some N to the lower tract.

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.