Dietary fiber - A double-edged sword for balanced nutrition supply and environment sustainability in swine industry: A meta-analysis and systematic review

The raising cost and relative shortage of the conventional feedstuffs drive the livestock husbandry to seek alternative feed ingredients, most of which are rich in dietary fibers. A systematic review and meta-analysis were conducted in the current study to explore quantitative patterns of nitrogen emission and nutrient digestibility of pigs fed dietary fiber at different inclusion levels, and to investigate prospects of using biological enzymes to solve some problems brought by high-fiber consumption in swine industry. The results showed that the fecal nitrogen and urine nitrogen emission after dietary fiber ingestion by growing pigs could be predicted by the following models: Fecal N output, g/d = 0.28 × NDF, % + 2.65, and Urine N output, g/d = 11.24–0.25 × ADF, %, and the nitrogen excretion is shifted from urine as urea to feces as bacterial protein when fibrous feedstuffs are included in diets of growing pigs (Urine N output: Fecal N output = 2.87–0.10 × NDF, % + 0.0053 × NDF, % 2 ). However, increased dietary fiber supplementation in swine diets decreases energy and phosphorous digestibility, resulting in excess emission of minerals and soil and water pollution. In practice, biological enzymes supplementation can be an effective approach to compensate negative effects of high amounts of dietary fibers on energy digestibility and phosphorous emission in pig production. Both pros and cons of dietary fiber supplementation on balanced nutrition supply and farm environment sustainability in pig production are systematically summarized, and it is imperative to standardize the utilization of fibrous ingredients in swine industry. • Nitrogen excretion is shifted from urine to feces when dietary fiber is included in swine diets. • Dietary fiber supplementation decreases energy digestibility and increases phosphorous excretion. • Microbial fermentation of dietary fiber is beneficial to intestinal health of the host via producing volatile fatty acids. • Biological enzymes supplementation balances nutrition supply and environment sustainability.