Adaptation of Gut Microbiome to Transgenic Pigs Secreting β-Glucanase, Xylanase, and Phytase

Digestion and utilization of plant-based diets by transgenic pigs secreting β-glucanase, xylanase, and phytase in their salivary glands

Novel transgenic (TG) pigs co-expressing three microbial enzymes, β-glucanase, xylanase, and phytase, in their salivary glands were previously generated, which exhibited reduced phosphorus and nitrogen emissions and improved growth performances. In the present study, we attempted to explore the age-related change of the TG enzymic activity, the residual activity of the enzymes in the simulated gastrointestinal tract, and the effect of the transgenes on the digestion of nitrogen and phosphorus content in the fiber-rich, plant-based diets. Results showed that all the three enzymes were stably expressed over the growing and finishing periods in the F2 generation TG pigs. In simulated gastric juice, all the three enzymes exhibited excellent gastrointestinal environment adaptability. The apparent total tract digestibility of phosphorus was increased by 69.05% and 499.64%, while fecal phosphate outputs were decreased by 56.66% and 37.32%, in the TG pigs compared with the wild-type littermates fed with low non-starch polysaccharides diets and high fiber diets, respectively. Over half of available phosphorus and water-soluble phosphorus in fecal phosphorus were reduced. We also found the performance of phosphorus, calcium, and nitrogen retention rates were significantly improved, resulting in faster growth performance in TG pigs. The results indicate that TG pigs can effectively digest the high-fiber diets and exhibit good growth performance compared with wild type pigs.

Improvements in pig agriculture through gene editing

Genetic modification of animals via selective breeding is the basis for modern agriculture. The current breeding paradigm however has limitations, chief among them is the requirement for the beneficial trait to exist within the population. Desirable alleles in geographically isolated breeds, or breeds selected for a different conformation and commercial application, and more importantly animals from different genera or species cannot be introgressed into the population via selective breeding. Additionally, linkage disequilibrium results in low heritability and necessitates breeding over successive generations to fix a beneficial trait within a population. Given the need to sustainably improve animal production to feed an anticipated 9 billion global population by 2030 against a backdrop of infectious diseases and a looming threat from climate change, there is a pressing need for responsive, precise, and agile breeding strategies. The availability of genome editing tools that allow for the introduction of precise genetic modification at a single nucleotide resolution, while also facilitating large transgene integration in the target population, offers a solution. Concordant with the developments in genomic sequencing approaches, progress among germline editing efforts is expected to reach feverish pace. The current manuscript reviews past and current developments in germline engineering in pigs, and the many advantages they confer for advancing animal agriculture.