The purpose of this study was to evaluate herbal extracts as alternatives to antimicrobial growth promoters for weanling pigs based on growth performance and organ weights. A 35-d randomized complete block design experiment was carried out to compare five treatments: control (C) - basal diet; antimicrobial (A) - basal diet supplemented with colistin + tiamulin (75 ppm of each); herbal extract - basal diet supplemented with 420 ppm of extracts of clove (Ec); oregano (Eo) and clove + oregano (Ec + Eo), respectively. Herbal extracts consisted of essential oils of clove + eugenol and oregano + carvacrol. Eighty pigs sorted in eight replications per treatment, and two animals per experimental unit were used for growth performance evaluation. At the end of experimental period, one animal per pen from the first four blocks was slaughtered for organ morphometry evaluation. Specific contrasts of practical importance were tested. For 1-14 d of experimental period (24 to 38 days of age), pigs fed the antimicrobial supplemented diet showed better feed conversion rate (CA) than the mean of those fed herbal extract treatments, while pigs fed Ec supplemented diet had better CA than those fed Eo. For the total period (24 to 59 days of age), pigs fed antimicrobial showed higher body weight at 59 days of age (P59) and average daily gain (GDP) than the mean of those fed herbal extracts. Pigs fed Ec + Eo had higher P59 and GDP than the mean of those fed other herbal extract treatments. For the organ morphometry data, the antimicrobials provided a higher relative weight of kidneys compared to the mean of treatments with herbal extracts. Overall, antimicrobial agents provided the best growth performance of weanling pigs. Concerning to herbal extracts, the combination of clove and oregano provided growth performance close to that of pigs fed antimicrobials, showing that this combination can be a potential alternative as growth promoter for weanling pigs.
additives; essential oil; growth performance; morphometry; nutrition; swine
