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Changes in lipids, chlorophyll pigments, hot water insoluble n and ph of alfalfa during ensiling
Author(s) -
Makoni Nathaniel F.,
Shelford James A.,
Nakai Shuryo,
Fisher Lorne J.
Publication year - 1993
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.2740630303
Subject(s) - wilting , forage , chlorophyll , chlorophyll b , zoology , chlorophyll a , chemistry , agronomy , biology , botany
Abstract This study examined (i) changes in the lipids of alfalfa ( Medicago sativa ) as a result of wilting and ensiling, and (ii) the breakdown of forage protein in direct cut and wilted forages following ensiling in relation to the remaining quantity of chlorophyll pigments a and b and forage pH. Lipid and malondialdehyde (MDA) were estimated in whole homogenates, chloroplast membranes and soluble fractions of freshly cut, wilted and ensiled alfalfa. Chlorophyll a and b , hot‐waterinsoluble nitrogen (HWIN) and pH were also determined during the ensiling of freshly cut and 24 h wilted alfalfa herbages. Highest levels ( P < 0·05) of lipid and MDA were observed in wilted alfalfa. The soluble fractions had the lowest levels of both lipids and MDA. Chlorophyll pigments showed an initial rapid decrease, followed by gradual decrease with time of ensiling. The rate of chlorophyll b disappearance in both direct ensiled and wilted ensiled forages was significantly ( P < 0·05) correlated ( r = 0·81 and 0·86, respectively) to the breakdown rate of forage protein. Forage pH was also significantly ( P < 0·05) correlated to the forage protein breakdown ( r = 0·59 and 0·61) for direct and wilted ensiled forages, respectively. Regression analyses of pH, chlorophyll pigments a and b versus forage HWIN showed that chlorophyll b was a better predictor of alfalfa HWIN quantity. These findings suggest that peroxidation of alfalfa chloroplast membrane lipids occurred during wilting and ensiling. Alfalfa chlorophyll pigments can potentially be employed to estimate alfalfa protein quantity during ensiling. Methods that arrest chloroplast disintegration such as forage blanching could increase ruminant utilization of alfalfa silages.