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Protein extraction from pasture: Effect of crop species, regrowth age and season on the quality of the extracted protein
Author(s) -
Donnelly Paul E.,
McDonald Rod M.,
Rattray Peter V.
Publication year - 1983
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.2740340809
Subject(s) - trifolium repens , lolium perenne , pasture , biology , agronomy , medicago sativa , methionine , forage , poaceae , biochemistry , amino acid
Leaf protein concentrates (LPC) were prepared from ryegrass ( Lolium perenne ), white clover ( Trifolium repens ), lucerne ( Medicago sativa cv. Wairau), and from ryegrass/white clover dominant pasture, harvested after a range of regrowth intervals in spring, summer and autumn seasons. Protein quality was measured by rat growth (to give Relative Nutritive Value, RNV) and in‐vivo rat true digestibility. RNV for LPC prepared from all crops was about 50% of that for lactalbumin. Results were highest for lucerne and lowest for ryegrass and ryegrass/white clover. When LPC was supplemented with methionine, RNV improved to 80–90% of that for lactalbumin. Quality was highest and similar for white clover and lucerne and lowest and similar for ryegrass and ryegrass/white clover. The true digestibility of protein was highest for lucerne (82%) and lowest for ryegrass and ryegrass/white clover (70%). These variations may be related to the proportions of cytoplasmic and chloroplastic protein in the juice. There was no effect of season (autumn vs spring) or age of herbage at harvest (4, 6, or 8 weeks regrowth) on the quality of protein. Despite standardised procedures for harvesting, processing, and drying the LPC and for assessing protein quality, undefined factors caused variation in methionine‐supplemented protein quality.