Struvite Precipitation as a Means of Recovering Nutrients and Mitigating Ammonia Toxicity in a Two-Stage Anaerobic Digester Treating Protein-Rich Feedstocks.

Accumulation of ammonia, measured as total ammonia nitrogen (TAN), a product of protein decomposition in slaughterhouse wastes, inhibits the anaerobic digestion process, reducing digester productivity and leading to failure. Struvite precipitation (SP) is an effective means to remove TAN and enhance the buffering of substrates. Different Mg and P sources were evaluated as reactants in SP in acidogenic digester effluents to reduce its TAN levels. In order to measure impact of TAN removal, a standard biochemical methane potential (BMP) test was conducted to measure methane yield from treatments that had the highest TAN reductions. SP results showed 6 of 9 reagent combinations resulted in greater than 70% TAN removal. The BMP results indicated that SP treatment by adding Mg(OH)2 and H3PO4 resulted in 57.6% nitrogen recovery and 41.7% increase in methane yield relative to the substrate without SP. SP is an effective technology to improve nutrient recovery and methane production from the anaerobic digestion of protein-rich feedstocks.

Successional changes in the chicken cecal microbiome during 42 days of growth are independent of organic acid feed additives.

BACKGROUND: Poultry remains a major source of foodborne bacterial infections. A variety of additives with presumed anti-microbial and/or growth-promoting effects are commonly added to poultry feed during commercial grow-out, yet the effects of these additives on the gastrointestinal microbial community (the GI microbiome) as the bird matures remain largely unknown. Here we compared temporal changes in the cecal microbiome to the effects of formic acid, propionic acid, and medium-chain fatty acids (MCFA) added to feed and/or drinking water. RESULTS: Cecal bacterial communities at day of hatch (n = 5 birds), 7d (n = 32), 21d (n = 27), and 42d (n = 36) post-hatch were surveyed using direct 454 sequencing of 16S rRNA gene amplicons from each bird in combination with cultivation-based recovery of a Salmonella Typhimurium marker strain and quantitative-PCR targeting Clostridium perfringens. Treatment effects on specific pathogens were generally non-significant. S. Typhimurium introduced by oral gavage at day of hatch was recovered by cultivation from nearly all birds sampled across treatments at 7d and 21d, but by 42d, S. Typhimurium was only recovered from ca. 25% of birds, regardless of treatment. Sequencing data also revealed non-significant treatment effects on genera containing known pathogens and on the cecal microbiome as a whole. In contrast, temporal changes in the cecal microbiome were dramatic, highly significant, and consistent across treatments. At 7d, the cecal community was dominated by three genera (Flavonifractor, Pseudoflavonifractor, and a Lachnospiracea sequence type) that accounted for more than half of sequences. By 21d post-hatch, a single genus (Faecalibacterium) accounted for 23-55% of sequences, and the number of Clostridium 16S rRNA gene copies detected by quantitative-PCR reached a maximum. CONCLUSIONS: Over the 42 d experiment, the cecal bacterial community changed significantly as measured by a variety of ecological metrics and increases in the complexity of co-occurrence networks. Management of poultry to improve animal health, nutrition, or food safety may need to consider the interactive effects of any treatments with the dramatic temporal shifts in the taxonomic composition of the cecal microbiome as described here.

Effects of broiler carcass scalding and chilling methods on quality of early-deboned breast fillets.

The impact of scalding and chilling methods on quality of broiler breast fillets (pectoralis major) was evaluated. In 4 replications, 6- to 7-wk-old male and female broilers were slaughtered and scalded either at 60°C for 1.5 min (hard scalding) or 52.8°C for 3 min (soft scalding). Following evisceration, the carcasses were either air-chilled (0.5°C, 120 min) or immersion-chilled in water and ice (79 L/carcass, 0.5°C, 40 min, air agitated). Breast fillets were removed from the carcass within 4 h postmortem. Quality attributes including fillet color (both dorsal-bone and ventral-skin sides), pH, total moisture content, water-holding capacity (drip loss and cook loss), and Warner-Bratzler shear force were determined. Significant interactions between replication and scalding were found for pH, ventral side redness (a*) value, and cook loss and between replication and chilling for pH and ventral side a* and yellowness (b*) values. There were no interactions (P > 0.05) between chilling and scalding methods for any of the measurements. Immersion chilling resulted in higher (P < 0.05) ventral side lightness (L*) values, dorsal side b* values, drip loss, cook loss, and shear force compared with air chilling. No significant differences (P > 0.05) between the 2 scalding methods were observed for any of the quality attributes. These results indicate that broiler carcass chilling method has a much greater impact on quality of breast meat than scalding method and that the influence of chilling on breast meat quality is independent of scalding treatment.