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Variations in protein digestibility of blood meal, feather meal, and a rumen-protected lysine prototype within and across laboratories.

K. A. Estes

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06-24-2020

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Abstract:

W117
Variations in protein digestibility of blood meal, feather meal, and a rumen-protected lysine prototype within and across laboratories.
K. A. Estes*1,2, P. S. Yoder1,3, C. Stoffel4, M. D. Hanigan1. 1Virginia Tech Blacksburg, VA, 2Balchem Corporation New Hampton, NY, 3Perdue AgriBusiness LLC Salisbury, MD, 4Papillon Agriculture Company Easton, MD.

The objectives of this work were to (1) compare post-ruminal protein availability estimates from 2 different in vitro procedures (Ross 3-step and pepsin digestibility assays) with in vivo observations for blood meal (BM), feather meal (FM) and a rumen protected lysine prototype (RP-Lys), and (2) to assess the in vitro assays variability for those ingredients within and across laboratories. Three commercial laboratories each received subsamples of BM (n = 14) and FM (n = 22) for assessment of CP, rumen undegradable protein (RUP), and digestible RUP (dRUP). One laboratory received subsamples of the RP-Lys prototype (n = 5). The supply of AA from BM and FM were evaluated within CNCPS v6.55 using a lactating diet and BM and FM inputs derived from the CNCPS feed library, in vivo, or in vitro results. The effect of laboratory on in vitro protein digestibility was assessed using the GLM procedure in SAS 9.3 and post-test comparisons of the means were made using the LSMEANS statement with the HSD option. Across laboratories, differences (P < 0.0001) were observed for BM dRUP where Lab 1 reported a lower estimate (67%) than Lab 2 (93%) or Lab 3 (92%). Also, for FM dRUP, Lab 1 (40%), Lab 2 (34%) and Lab 3 (73%) all reported different values (P < 0.0001). Within laboratories, BM estimates were reported in a narrow range, suggesting low procedural variation. But, when testing multiple subsamples of FM or the RP-Lys prototype within a laboratory, CV values ranged up to 11% and 34%, respectively. In vitro dRUP estimates for BM from one laboratory closely matched those determined in vivo (67 vs. 65%, respectively), but no in vitro estimates for FM were similar to in vivo values. For the RP-Lys prototype, dRUP estimates from the in vitro method were half of that determined by the in vivo methods suggesting poor in vitro and in vivo procedural correlation for these ingredients. In vitro methods should be refined and evaluated for accuracy and precision for all ingredients and standardized across laboratories. This effort will result in more accurate model inputs for ration balancing leading to better animal performance.

Keywords: in vitro, blood meal, feather meal.