Ruminal and post-ruminal protein disappearance of various feeds originating from Iranian plant varieties determined by the in situ mobile bag technique and alternative methods

Ruminal, post-ruminal and total tract protein disappearance of various feeds originating from Iranian plant varieties classified as grains (barley and maize), by-products (sugar beet pulp and wheat bran), protein sources (soybean and cottonseed meals), forages [alfalfa hay and maize silages treated with 16 (MS16) or 24 (MS24) g of urea per kg dry matter (DM)] and halophytes (Atriplex sp., Sauda sp. and Kochia sp.) were evaluated using the in situ mobile bag technique, an in vitro enzyme procedure and a three-step in situ/in vitro enzyme procedure. Linear regression equations were determined between results from the mobile bag technique and the two other procedures. Mean ruminal protein disappearance of grains, by-products, protein sources and forages were higher (P < 0.05) than halophytes [0.50, 0.62, 0.54, 0.54 and 0.41 (S.E.M. = 0.05), respectively]. There was an effect (P < 0.05) of feed classification on post-ruminal protein disappearance (grains = 0.63, by-products = 0.52, protein sources = 0.66, forages = 0.43, halophytes = 0.41, S.E.M. = 0.06). Total tract protein disappearance of grains, by-products and protein sources were also higher (P < 0.05) than forages and halophytes (0.81, 0.83, 0.84, 0.74, 0.65, S.E.M. = 0.03, respectively). Procedures did not have an effect (P > 0.05) on rates of ruminal, post-ruminal and total tract protein disappearance of the various feeds originating from Iranian plant varieties. The best correlation was observed when results of total tract protein disappearance determined by the in vitro method were plotted against the three-step procedure (r2 = 0.66). The coefficient of determination (r2) for the relationship of total tract protein disappearance between the mobile bag technique and in vitro, and three-step procedures were 0.61 and 0.55, respectively.