Chitin analysis of hay as a means of determining fungal invasion during storage

Abstract

An ion-exchange chromatography method was tested for quantification of fungal invasion in alfalfa forage. The concentration of chitin, an N-acetyl- D-glucosamine polymer found in spore and mycelium cell walls, was measured to quantitate the degree of forage fungal invasion. Chitin concentrations ranged from 1.583 to 7.530 g kg −1 DM in the alfalfa forage. Stored hay chitin concentration can be influenced by standing crop and harvesting conditions as well as hay moisture content at the time of stacking. Chitin concentrations at the time of stacking and after 60 days storage were: 6.26 ± 0.12 and 6.85 ± 0.12; 2.69 ± 0.16 and 3.57 ± 0.12; 2.50 ± 0.12 and 3.95 ± 0.12 g kg −1DM for hay baled at 14.8, 21.5 and 29.1% moisture, respectively. High chitin concentrations for hay baled at the lowest moisture level reflected post-cutting fungal and bacterial invasion of forage exposed to precipitation while lying in a swath. Pre-storage fungal invasion for hay baled at the lowest moisture level resulted in a negative correlation between post-storage chitin concentration and visual mold assessment. Alfalfa hay containing 14.8, 21.5 and 29.1% moisture at the time of stacking had 9.6 ± 5.9, 33.7 ± 7.3 and 60.9 ± 5.9% increases in chitin concentration during a 60-day storage period. Change in chitin concentration during storage was positively correlated ( P < 0.01) with visual mold scores of hay removed from storage and negatively correlated ( P < 0.05) with dry matter retention during storage.