Corn Silages: development of novel inoculant and particle size on rehydrated grain

Abstract

Paper1. Fifty - three strains of lactic acid bacteria (LAB) isolated from corn silages were evaluated for use as inoculants in corn silages harvested at late maturity . LAB strains were characterized for growth and pH reduction in corn extract, growth at different temperatures and the ability to inhibit silage- spoilage microorganism growth. Strains CCMA1362, 1363 and 1364 (Lactobacillus farraginis); CCMA1365 (L. plantarum); CCMA1366 (L. buchneri) and CCMA1367 (Pediococcus acidilactici) isolated from corn silage; and CCMA170 strain (L. hilgardii) isolated from sugarcane were evaluated in corn silages with 45.4% of dry matter (DM). The experimental silos were opened after 10, 32 and 100 days of storage. CP, ash and starch contents were not affected by the inoculation or storage time. Control and inocula ted silages with homofermentative BAL showed higher DM loss and lower aerobic stability. Silages with obligate heterofermentative strains, especially with CCMA1362 (L. farraginis) and CCMA170 (L. hilgardii), showed the smallest yeast population (<2.00 log cfu g -1 ) after 10 days of storage. Silage inoculated with strain CCMA1362 showed lower DM loss, showed a smal ler population of undesirable microorganisms and was among the silages with higher lactic acid and acetic acid production and greater aerobic stability. The species Lactobacillus farraginis is reported for the first time in studies with silage, and strain CCMA1362 isolated from corn silage is shown to be promising for use as an inoculant in corn silages harvested at late maturity. Paper 2. The objective of this study was to evaluate the effect of particle size and storage time on fermentative profile, aerobic stability, and ruminal degradability of rehydrated corn grain silage. Corn grains were ground to pass either a 3 mm (fine) or 9 mm (co arse) screen, rehydrated to achieve around 40% of moisture and ensiled in 200 L polyethylene silos. Samples were taken before and after ensiling at 10, 30, 90 and 200 days of storage to assess microbial counts, fermentation end products, and ruminal DM degradability. The DM degradation was evaluated with samples without ground to accessing the effect of original particle size, with incubatio n times of 0 (bag wash), 3, 6, and 48 h in 3 rumen cannulated cows. The effective rumina l degradation (ERD) was calculated based on soluble fraction (A), degradable fraction (B), and passage rate (kp) defined as 7.0% h- 1: A + B [kd / (kd + kp)]. Aerobic stability was evaluated in silages with 200 days of storage. At 90 and 200 d of storage, fine rehydrated corn grai n silage resulted in lower crude protein and greater NH3 - N concentration than coarse grain. Coarsely ground rehydrated corn silage had lower temperature at the beginning of storage times and greater aerobic stability than finely ground corn (206 vs. 115 hour). Ruminal DM degradability increased over the storage times. Particle size of rehydrated corn grain silage did not affect kd values after 90 d of storage, while for the ERD was necessary a long time of fermentation (200 days). In summary, coarsely grou nd rehydrated corn silage storage by 200 days reaches the ruminal degradability of finely ground, with greater aerobic stability than finely ground corn .