Uso de levaduras o aceites esenciales en sustitución de monensina sódica como aditivo nutricional en dietas concentradas ofrecidas a terneras Hereford alimentadas a corral

The aim of this study was to evaluate the potential use of essential oils and yeasts as nutritional additives as a replacement of monensin in calves’ diets under feedlot conditions. It arose in response to the European Union's ban on the use of antibiotics to stimulate animal growth. It was carried out at the “Estación Experimental Mario A. Cassinoni”, Paysandú, Uruguay, precisely in the confinement pens of the “Unidad de Producción Intensiva de Carne”, from August 12 to November 13, 2021.

Thirty Hereford heifers from the EEMAC experimental herd, born in the spring of 2020 and with an average weight of 204 ± 24.3 kg, were used. They were randomly assigned to 3 treatments determined by the additive incorporated to the diet: 1) Control: ad libitum feeding of TMR diet + 0.5 g 20% monensin sodium source; 2) Essential oils: ad libitum feeding of TMR diet + 0.7 g essential oil source; 3) Celmanax: ad libitum feeding of TMR diet + 1 g hydrolysed yeast source. Calves were fed in individual pens, therefore the experimental unit represents each animal and the treatments consisted of 10 individual replicates.

There were no significant differences between the control and alternative treatments for dry matter intake, conversion efficiency and growth, even though a trend was shown towards higher growth by the use of yeast. This suggests that alternative products, such as essential oils or yeast extracts, could be used to replace monensin in the diets of calves as part of a feedlot feeding strategy.