title: Use of principal factor analysis to generate a corn silage fermentative quality index to rank well- or poorly preserved forages.
abstract: BACKGROUND
  To investigate corn silage fermentative quality, a principal factor analysis was carried out on a database consisting of 196 corn silages sampled from the core, lateral and apical parts of silo feed-out face and characterised by 36 variables. Eleven principal factor components (PCs) were retained and interpreted. Two PCs were related to chemical and digestibility variables; four PCs were characterised by end-products associated with clostridia, heterolactic, homolactic or aerobic fermentations; two PCs were associated with mycotoxins produced by Penicillium roqueforti or by Aspergillus fumigatus and Fusarium spp., while three PCs explained ensiling procedures adopted to store corn silages.
  
  
  RESULTS
  Lower (P < 0.05) yeast or mould counts and greater (P < 0.05) aerobic stability were measured in core than in peripheral samples. Excluding PCs related to ensiling procedures, other PCs were able to predict microbiological counts, aerobic stability or biogenic amine content as verified by multiple linear regression analysis. Based on these results, several corn silage quality index calculations were computed by using a summative equation approach in which different PCs as well as diverse relative weights multiplying each PCs were combined. To compute definitive index calculation, only PCs explaining clostridia, heterolactic and homolactic fermentations were used with relative weights of 30%, 50% and 20%.
  
  
  CONCLUSIONS
  The new proposed fermentative quality index was highly correlated to parameters related to corn silage fermentative quality, such as microbiological counts, aerobic stability or biogenic amines and it properly discriminated well- and poorly preserved forages.
authors.affiliation: Feed and Food Science and Nutrition Institute, Faculty of Agricultural, Food and Environmental Sciences, Università Cattolica del Sacro Cuore, 29122, Piacenza, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Gallo
authors.affiliation: Feed and Food Science and Nutrition Institute, Faculty of Agricultural, Food and Environmental Sciences, Università Cattolica del Sacro Cuore, 29122, Piacenza, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Giuberti
authors.affiliation: Feed and Food Science and Nutrition Institute, Faculty of Agricultural, Food and Environmental Sciences, Università Cattolica del Sacro Cuore, 29122, Piacenza, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Bruschi
authors.affiliation: Feed and Food Science and Nutrition Institute, Faculty of Agricultural, Food and Environmental Sciences, Università Cattolica del Sacro Cuore, 29122, Piacenza, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Fortunati
authors.affiliation: Feed and Food Science and Nutrition Institute, Faculty of Agricultural, Food and Environmental Sciences, Università Cattolica del Sacro Cuore, 29122, Piacenza, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Masoero
mesh_terms: D000332:Aerobiosis; D001419:Bacteria / Q000145:classification / Q000302:isolation & purification; D005285:Fermentation; D005519:Food Preservation; D063427:Food Quality; D005658:Fungi / Q000378:metabolism; D009183:Mycotoxins; D025341:Principal Component Analysis / Q000379:methods; D012820:Silage / Q000032:analysis*; D003313:Zea mays / Q000737:chemistry*
chemical_list: D009183:Mycotoxins
keywords: aerobic stability; corn silage; fermentative quality index; microbial counts; principal factor analysis