Effective Microorganisms as a Probiotic Strategy to Improve Performance and Reduce Ammonia Emissions in Guinea Pigs (Cavia porcellus)

In Andean production systems, guinea pigs (Cavia porcellus) are a key source of animal protein for food security; however, their productivity is limited by inefficient nutrient use, antimicrobial misuse, and gut microbiota imbalances. These factors reduce performance and increase nitrogen emissions (NH₃), affecting system sustainability. This study evaluated the effect of dietary supplementation with effective microorganisms (EM) on productive performance, intestinal morphometry, and ammonia emissions during the fattening phase. A total of 120 animals (60 males and 60 females) were assigned to a completely randomized bifactorial design with four EM levels (0, 100, 150, and 200 mL) and sex. Productive variables were analyzed using generalized linear models, intestinal morphometry by ANOVA, and ammonia descriptively. Significant effects (p < 0.05) were observed for all productive parameters. The 100 mL dose showed the best performance, with higher weight gain (607.1 g), final weight (1052.8 g), carcass yield (71.9%), and improved feed conversion (3.94). Males outperformed females. EM increased villus length and width without affecting crypt depth, suggesting improved absorption. Ammonia levels decreased and stabilized, with no association with weight gain. EM improves productivity and environmental conditions, with intermediate doses being optimal.