# Efficacy of Three Doses of Halquinol on Growth Performance, Diarrhea Incidence, Nutrient Digestibility, and Fecal Microbiome of Weaned Pigs

## TL;DR

This study shows that halquinol, an antibiotic, improves feed efficiency and digestion in weaned pigs, potentially replacing colistin.

## Contribution

The study identifies 240 ppm halquinol as an effective alternative to colistin in improving piglet health and digestion.

## Key findings

- Pigs fed 240 ppm halquinol had the lowest feed conversion ratio and improved fat digestibility.
- Halquinol reduced harmful bacteria like E. coli and increased beneficial Enterococcus microbes.
- Halquinol improved propionate concentration and reduced the A/P ratio in feces.

## Abstract

This study of halquinol provides an informative dataset, including information on the nutrient digestibility, fecal volatile fatty acid fermentation, and microbiome structure in pigs. Halquinol can serve as an alternative antibiotic in nursery pigs by preserving digestive capacity, stimulating enzymatic digestion and improving subsequent nutrient utilization. Although no significant differences in growth performance were observed between experimental diets, a reduced bacterial diversity in the microbiomes of halquinol-treated pigs might have contributed to an improvement in energy utilization. Understanding the development of pig microbiota during weaning, and its modulation in response to colistin and halquinol, is essential to designing alternative formulations for rational drug use.

The weaning period is a critical phase for nursery pigs that is characterized by rapid growth and alterations in the intestinal microbiome associated with nutrient utilization. The present study aimed to investigate the efficacy of halquinol, when used as an antibiotic (ABO), on the growth performance, diarrhea incidence, coefficient of apparent total tract digestibility (CATTD), fecal volatile fatty acids (VFAs), and microbiota in pigs. A total of 210 healthy weaned pigs with an average initial weight of 6.9 kg and aged 28 ± 2 days were assigned to five treatments (six pens/treatment) in a complete randomized design, including a control group (T1, CON; feed with no ABO), a colistin group (T2, CLT; feed containing 120 ppm colistin), and three halquinol groups (T3 to T5, HAL; feed containing 180, 240, and 360 ppm halquinol, respectively). The experiment period lasted for 10 days. Field recordings, observation, and feces collection were performed on D1, D5, and D10. CATTD and VFA assessments were conducted on D10. The composition of the fecal microbiota was analyzed via 16S rRNA gene sequencing using the Illumina Miseq platform. The results demonstrated that the in-feed ABO groups exhibited a significantly lower ADFI (p < 0.01). Pigs fed the T3 and T4 diets had the lowest FCR (p < 0.01) on D5 and D10 and, thus, had reduced ADFI (p < 0.01). A quadratic contrast was found in ADFI and FCR on D5 and D10, indicating a negative correlation with HAL concentration (p < 0.01). Pigs fed CLT and HAL had significantly reduced levels of coliform (p < 0.01) and E. coli (p < 0.01). Moreover, pigs receiving ABO also had a lower fecal score compared to those on the CON diet (p < 0.01). Dietary in-feed ABO had no effect on all the parameters of the CATTD on D10 (p > 0.05), except for fat digestibility in pigs that received T4 (p < 0.01). Pigs fed the T4 and T5 diets had higher propionate concentrations and lower A/P ratios than pigs fed T1, T2, and T3 (p < 0.01). The microbial diversity shifted quickly through the early weaning period. The relative abundance of beneficial Enterococcus microbes increased in pigs fed in-feed ABO, whereas the relative prevalence of pathogenic bacteria, such as Escherichia and Klebsiella, decreased. Escherichia and Bacteroides were negatively correlated with carbohydrate digestibility and butyric and valeric acid production (p < 0.05). Overall, the appropriate HAL dosage was 240 ppm (T4), and this antimicrobial can potentially be characterized as an in-feed colistin replacer that improves feed efficiency and fat digestion, enhancing VFA production, alleviating post-weaning diarrhea, and protecting ABO-resistant piglets.