Effect of the stage of growth, wilting and inoculation in field pea (Pisum sativum L.) silages. II. Nitrogen fractions and amino acid compositions of herbage and silage
2006
Cavallarin, L. | Antoniazzi, S. | Tabacco, E. | Borreani, G.
The aim of the study was to investigate the effects of stage of maturity, wilting and inoculant application on proteolysis in field pea herbage and silage in northern Italy. Semi-leafless field peas were harvested at four progressive morphological stages (end of flowering, I; beginning of pod filling, II; advanced pod filling, III; beginning of ripening, IV). For each stage of growth, the herbage was field wilted to a dry matter (DM) content around 330 g kg⁻¹. The unwilted and wilted herbages were ensiled with (I) and without (C) a lactic acid bacteria (LAB) inoculant. The stage of growth significantly affected all the nitrogen fraction concentrations both in herbage and in silage. Extensive proteolysis took place in silages made at early morphological stages and characterised by a high crude protein content (around 240 g kg⁻¹ DM), as shown by the non-protein nitrogen (NPN) value (around 700 g kg⁻¹ total N or higher). Neither inoculum nor wilting helped to reduce the protein degradation in these silages. The level of proteolysis was reduced in silages made from the pod filling stage onwards where most of the protein was localised in the seed and a better fermentation pattern was observed. The amino acid (AA) composition of silages made at stage IV was close to that of fresh herbage, with minimal losses of nutritionally essential amino acids for ruminants.
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