CHANGES IN LIPIDS, CHLOROPHYLL PIGMENTS, HOT-WATER INSOLUBLE-N AND PHOF ALFALFA DURING ENSILING

This study examined (i) changes in the lipids of alfalfa (Medicago sat iva) as a result of wilting and ensiling, and (ii) the breakdown of fo rage protein in direct cut and wilted forages following ensiling in re lation to the remaining quantity of chlorophyll pigments a and b and f orage pH. Lipid and malondialdehyde (MDA) were estimated in whole homo genates, chloroplast membranes and soluble fractions of freshly cut, w ilted and ensiled alfalfa. Chlorophyll a and b, hot-water-insoluble ni trogen (HWIN) and pH were also determined during the ensiling of fresh ly cut and 24 h wilted alfalfa herbages. Highest levels (P < 0.05) of lipid and MDA were observed in wilted alfalfa. The soluble fractions h ad the lowest levels of both lipids and MDA. Chlorophyll pigments show ed an initial rapid decrease, followed by gradual decrease with time o f ensiling. The rate of chlorophyll b disappearance in both direct ens iled and wilted ensiled forages was significantly (P < 0.05) correlate d (r = 0.81 and 0.86, respectively) to the breakdown rate of forage pr otein. Forage pH was also significantly (P < 0.05) correlated to the f orage protein breakdown (r = 0.59 and 0.61) for direct and wilted ensi led forages, respectively. Regression analyses of pH, chlorophyll pigm ents a and b versus forage HWIN showed that chlorophyll b was a better predictor of alfalfa HWIN quantity. These findings suggest that perox idation of alfalfa chloroplast membrane lipids occurred during wilting and ensiling. Alfalfa chlorophyll pigments can potentially be employe d to estimate alfalfa protein quantity during ensiling. Methods that a rrest chloroplast disintegration such as forage blanching could increa se ruminant utilization of alfalfa silages.