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Ruminal use of undegraded‐feed soluble protein and accuracy of the estimations of the nutrient content in ruminal bacteria
Author(s) -
González Javier,
DíazRoyón Fernando,
Vanegas Jorge L,
Arroyo José M,
Carro María D
Publication year - 2020
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.10169
Subject(s) - rumen , zoology , bacteria , ammonia , chemistry , nitrogen , nutrient , composition (language) , food science , biology , biochemistry , fermentation , genetics , linguistics , philosophy , organic chemistry
BACKGROUND The possible escape from the rumen of undegraded‐feed soluble proteins (SP) was investigated using nitrogen‐15 ( 15 N) infusions (25 mg) in three rumen and duodenum cannulated wethers. Animals were fed three isoproteic diets differing in SP content and including protein concentrates either untreated (control) or treated with solutions of either malic acid (MHT) or orthophosphoric acid (OHT) and heat. RESULTS Compared with control, MHT and OHT diets reduced ruminal concentrations of ammonia‐nitrogen (NH 3 ‐N) by 35.9% ( P = 0.007), non‐ammonia nitrogen (NAN) by 36.8% ( P = 0.007), and SP‐nitrogen (SP‐N) by 45.2% ( P = 0.072) over the post‐feeding period. Both NAN and SP‐N were lower ( P ≤ 0.040) for OHT than for MHT diet. The 15 N enrichment of NAN and SP‐N did not vary either among diets or with time, and both values were closely related ( R 2 = 0.965; P < 0.001). Estimations, either using solid‐associated bacteria (SAB) or liquid‐associated bacteria (LAB) as a reference, indicated that 0.983 and 0.894 of SP‐N (values averaged across diets) was of microbial origin, respectively, which would indicate a practically negligible ruminal escape of feed SP‐N. Values of 15 N‐enrichment in SAB and LAB fitted well to previously published SAB–LAB relationships, indicating a 22% underevaluation of the N supply from SAB when only LAB is used as a reference. CONCLUSION Both the negligible ruminal escape of feed SP and the underevaluation of the bacterial nutrient supply as a consequence of the use of LAB as the only bacterial reference should be considered to improve ruminant protein feeding systems. © 2019 Society of Chemical Industry