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Applicability of Chromogen and Nitrogen as Internal Indicators of Forage Digestibility 1
Author(s) -
Davis L. E.,
Marten G. C.,
Jordan R. M.
Publication year - 1967
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1967.00021962005900060017x
Subject(s) - forage , grazing , zoology , feces , agronomy , organic matter , nitrogen , bromus inermis , biology , chemistry , ecology , organic chemistry
Twelve yearling sheep were fed three forages (alfalfa, bromegrass, and reed canarygrass) cut at various stages of maturity in each of two stall digestion trials during two succeeding years. Four techniques were employed to measure apparent digestibility of forage organic matter in stall trials during each of three 6‐day periods in 1964 and 1965. These included the conventional total collection method (control), the chromogen ratio method, the chromogen fecal‐index using the equation of Reid et al. (18), and the nitrogen fecal‐index using the equation of Lancaster (11). The control mediod indicated that alfalfa and reed canary were significantly more digestible than brome during 1964, but that the three forages were not different in digestibility in 1965. The three indicator methods were also used to estimate digestibility of the same forage species under grazing conditions. Measurements of the digestibility of organic matter consumed by esophageal‐fistulated sheep were made during five 9‐day periods of the 1965 grazing season. None of the indicator methods were useful for predicting absolute values. Also, the chromogen methods gave low relative values for alfalfa, while the fecal nitrogen prediction equation of Lancaster (11) gave low relative values for reed canary. The need for verification of published equations or establishment of local fecal‐ index equations was apparent. The chromogen fecal‐index equation of Reid et al. (18) failed to provide accurate measurements under our conditions primarily because the chromogen ratio technique upon which it is based was apparently invalid, due to low recovery in the feces of alfalfa chromogen and high recovery of grass chromogen.