# Effects of Multi-Strain Probiotic Supplementation in Low–Crude Protein Diets on Growth Performance, Apparent Nutrient Digestibility, Fecal Microbial Indicators, and Nitrogen Utilization in Weaned Piglets

## TL;DR

Adding probiotics to low-protein diets helps piglets grow well and reduces nitrogen waste, making it an eco-friendly option.

## Contribution

This study demonstrates that multi-strain probiotics can mitigate the negative effects of low-protein diets in piglets.

## Key findings

- Probiotic supplementation improved growth performance and feed efficiency in low-protein diets.
- Nitrogen utilization increased, and fecal nitrogen excretion decreased with probiotic addition.
- Fecal Lactobacillus increased while Escherichia coli decreased in probiotic-treated piglets.

## Abstract

Lowering protein levels in piglet diets can reduce nitrogen pollution but may impair growth. This study shows that adding a mixture of beneficial bacteria to low-protein diets improves growth rate and feed efficiency in weaned piglets, achieving performance similar to that of pigs fed high-protein diets. Probiotic supplementation also enhanced nitrogen use, reduced nitrogen losses in manure, and modulated selected fecal bacterial indicators by increasing Lactobacillus counts and reducing Escherichia coli counts. Overall, adding probiotics to low-protein diets may represent a promising and environmentally sustainable nutritional strategy that supports piglet growth while lowering environmental nitrogen emissions.

This study evaluated the effects of supplementing a multi-strain probiotic (MSP) in low–crude protein (LP) diets on growth performance, apparent nutrient digestibility, selected fecal microbial populations, and nitrogen (N) utilization in weaned piglets. A 7-week feeding trial was conducted using 105 weaned crossbred piglets (Duroc × [Landrace × Yorkshire]) with an initial body weight of 6.55 ± 1.09 kg. Based on initial body weight and sex, piglets were randomly assigned to three dietary treatments using a randomized complete block design, with seven replicates per treatment and five pigs per pen (two gilts and three barrows). The dietary treatments included CON: normal crude protein (CP) diet; TRT1: LP diet; and TRT2: LP diet supplemented with 0.01% MSP. At week 7, the final body weight (BW) was higher in CON and TRT2 than in TRT1 (p < 0.05). During weeks 1–3, the feed conversion ratio (FCR) was lower in CON than in TRT1 (p < 0.05). In weeks 5–7, average daily gain (ADG) was higher in CON and TRT2 than in TRT1 (p < 0.05), while only CON showed a reduced FCR (p < 0.05). Over the entire trial, ADG was highest in TRT2 (p < 0.05), and FCR was lower in both CON and TRT2 compared with TRT1 (p < 0.01). At the end of the experiment, apparent nitrogen digestibility was significantly improved in CON and TRT2 relative to TRT1 (p < 0.05). Fecal Lactobacillus counts were elevated, and Escherichia coli abundance decreased in TRT2 (p < 0.05), indicating a more favorable profile of selected fecal bacterial indicators. In the N balance trial, six healthy piglets (three barrows and three gilts) per treatment were randomly selected and housed individually in metabolism cages. After a 3-day adaptation, total feces and urine were collected for four days to determine N intake, fecal and urinary N excretion, and N retention. At week 7, DM and N intake were unaffected by dietary treatment, whereas fecal N excretion was lower in TRT2 and CON relative to TRT1 (p < 0.05). Overall, supplementation of MSP in LP diets partially mitigated the adverse effects associated with reduced dietary protein by enhancing feed efficiency and nitrogen utilization, resulting in growth performance comparable to that of piglets fed a normal CP diet.