Particle size and storage length affect fermentation and ruminal degradation of rehydrated corn grain silage.

Particle size and storage time are factors that can affect the fermentation quality and digestibility of rehydrated corn grain silage (RCS). The objective of this study was to evaluate the effect of particle size and storage time on chemical and microbiological characteristics, aerobic stability, and ruminal degradability of RCS. Corn grains were ground to pass through either a 3 mm (fine) or 9 mm (coarse) screen, rehydrated to 44.3% moisture and ensiled in 200 L polyethylene buckets. Samples were taken before and after ensiling at 10, 30, 90 and 200 days of storage to assess microbial counts, fermentation end products, and DM ruminal degradability. DM degradation was evaluated with incubation times of 0 (bag wash), 3, 6 and 48 h in 3 rumen-cannulated cows. The effective ruminal degradation (ERD) was calculated based on soluble fraction (A), degradable fraction (B) and passage rate (kp) defined as 7.0%/h: A + B [kd/(kd + kp)]. Aerobic stability was evaluated in silages after 200 days of storage, and pH and temperature were analysed up to 240 h of aerobic exposure. At 90 and 200 d of storage, fine RCS resulted in lower crude protein and greater NH3-N concentrations than coarse RCS. Coarsely ground RCS had a lower temperature at the beginning of storage than finely ground corn. Finely ground RCS had greater yeast counts and ethanol concentrations than coarsely ground RCS during storage time. Fine RCS was more susceptible to aerobic deterioration, reaching maximum temperature and pH values faster than coarse RCS. DM ruminal degradability increased over the storage time. The particle size of the rehydrated corn grain silage did not affect the kd values after 90 d of storage, while for the ERD, a long fermentation time was necessary (200 d). Considering the fermentation characteristics and the kinetics of ruminal DM degradation, fine grinding is recommended for short storage periods and coarse grinding may be a strategy to increase the rate of grinding when the storage period is greater than 200 d.

Heat stress influence the microbiota and organic acids concentration in beef cattle rumen.

The objective of this study was to evaluate the effect of heat stress on meta-taxonomic and metabolic profiles of prokaryotes in beef cattle rumen. Six pure-breed Nellore heifers with ruminal cannulas were used in the study. Six treatments were tested in a 6 × 6 Latin Square with six periods of 21days. The treatments were evaluated in a 2 × 2 + 2 factorial arrangement, consisting of 4 combinations: two temperatures conditions (thermoneutral, TN: 24 °C; and heat stress, HS: 34 °C) and two dietary energy concentration [low-energy (37% non-fibrous carbohydrates - NFC, 12 Mcal of metabolizable energy per kg of dry matter) or high-energy concentration (50.5% NFC, 18.49 Mcal of metabolizable energy per kg of dry matter)] plus two additional treatments with animals maintained in TN conditions but with your intake restricted (TN-RI) to the same of the heifers in HS with the two dietary energy concentration. The meta-genome was sequenced by MiSeq Sequencing System platform, and the DNA sequences were analysed using Geneious 10.2.3 software. The metabolic profile was evaluated by liquid and gas chromatography. Animals under HS presented lower (P = 0.04) prokaryote richness than animals under TN conditions. The genera Flavonifractor (1.4%), Treponema (0.6%) and Ruminococcus (0.9%) showed the lowest (P < 0.04) and Carnobacterium (7.7%) the highest (P = 0.02) relative abundance when the animals were submitted to HS, in relation to animals in TN. A total of 49 different metabolites were identified in the ruminal samples. The concentration of isobutyric acid (4.32 mM) was highest in bovine rumen under HS conditions. Heat stress influenced the microbiota and concentration of some organic acids in beef cattle rumen. There was a reduction in the richness of rumen in cattle under heat stress, but the diversity of prokaryotes was not affected.

Production of γ-Decalactone by Yeast Strains under Different Conditions.

γ-Decalactone is a flavour compound that when obtained by biotechnological production using microorganisms is classified as natural. The aim of this study is to evaluate various conditions for γ-decalactone production by tropical yeast strains Yarrowia lipolytica CCMA 0242 and Lindnera saturnus CCMA 0243. The growth of and γ-decalactone production by Y. lipolytica CCMA 0242 were higher in castor oil than in glycerol. γ-Decalactone production in single batch or fed-batch fermentation did not differ significantly. The γ-decalactone production by L. saturnus CCMA 0243 was better at initial pH=5, while the production by Y. lipolytica CCMA 0242 was better at initial pH=6. The yeast L. saturnus CCMA 0243 produced more γ-decalactone than Y. lipolytica CCMA 0242 under the same fermentation conditions. The crude glycerol was not an alternative substrate for γ-decalactone production by Y. lipolytica CCMA 0242. Castor oil at volume fraction of 30% showed better results as a substrate. The strain L. saturnus CCMA 0243 showed better results of γ-decalactone production. This yeast species can be considered an alternative producer of γ-decalactone in biotechnological processes.