Effects of Litter Reuse on Performance, Welfare, and the Microbiome of the Litter and Gastrointestinal Tract of Commercial Broiler Chickens

In Australia, the majority of broilers are reared on single-batch litter. However, production costs and concerns regard bedding material availability are forcing additional Australian producers to attempt multi-batch litter production. The Australian broiler industry is forecasted to increase 3-4% annually through 2017, while more of Australia's producers are expected to adopt multi-batch litter production and, consequently, take on all challenges associated with it. Therefore, a study was conducted to investigate a novel litter reuse approach and its associated challenges on broiler performance and welfare, as well as to better understand both litter and intestinal microbiomes associated with this novel litter reuse approach.;The objective of the first study was to investigate the effects of reused litter on litter pH and moisture, air ammonia concentrations, and bird performance and welfare on three commercial broiler farms in New South Wales, Australia. On each farm, litter from the previous batch within six on-site sheds was assigned to one of three treatments: 1) a full cleanout replenished with new litter (NL); 2) litter reuse in the entire shed following heaping and turning (RL); and 3) RL plus the addition of an acidifying litter amendment (RL+A). Welfare measures provided no evidence of sustained reduction in welfare status of birds on reused litter, or any clear benefits or disadvantages of the litter amendment. Under proper management, results indicate bird performance and welfare can be maintained when incorporating reused litter.;The objective of the second study was to characterize and compare both the litter and intestinal microbiomes of commercial broiler chickens reared on different litter management treatments (new litter, NL; reused litter, RL; and, reused litter plus an acidifying amendment, RL+A) over the course of one grow-out period using Illumina sequencing of 16S rRNA gene amplicons. Baby chicks arrived on farm with intestinal microbiomes that exhibited considerable richness and diversity at the time of placement. Venn analysis showed that 56% of OTUs were shared across the core microbiomes of all three treatments; however, reused litter microbiomes were more similar to one another, as they shared 5 additional OTUs that were not present in the NL. These data suggest that although the microbiome may differ between new shavings and reused litter, its impact on the development of the intestinal microbiome and the performance of birds reared on those litters is not obvious. Instead, the temporal succession of the NL microbiome to become more similar to that of the reused litter microbiomes at d35 suggests that the bird may have a greater influence on the development of the litter microbiome.;The objective of the third and final study was to test the effects of in-house litter "composting" with and without the addition of an acidifying litter amendment on the abundance of enteric pathogens associated with commercial broiler production, as a means to validate alternative litter reuse management strategies for Australian producers. Specific quantitative PCR (qPCR) assays were used to quantify Campylobacter, Salmonella , generic C. perfringens, and virulent C. perfringens that carried the gene encoding NetB-toxin (netB) from samples of litter and digesta (ileal and cecal). The effects of "composting" and litter amendment on the presence/abundance of pathogens within litter were not obvious. There were no treatment (litter) effects (P > 0.05) on the presence/abundance of pathogens in digesta samples, indicating that horizontal transmission of pathogens from the litter to intestines of birds did not occur in this study. One advantage to reused litter is that its diverse microbiome may exude competitive inhibition-like properties toward the colonization of pathogens.;Collectively, these studies present an alternative to single-batch litter production that some Australian producers may want to adopt. Despite the inherent challenges associated with litter reuse, bird performance and welfare on reused litter were comparable to if not better than that observed on single-batch litter in this study. In addition, high-throughput sequencing has revealed the microbiomes unique to both the litter and broiler gastrointestinal tract with a level of depth and clarity that have only been seen a few times before. (Abstract shortened by UMI.).