Se evaluó la producción de materia seca (MS) y composición morfológica en función de la edad de rebrote (ER; cuatro, seis y ocho semanas) y altura de pradera (AP) en Pennisetum ciliare cv. H-17, durante época de lluvias (ELL) y seca (ES). Las variables fueron MS total (MSTT), hoja (MSh), tallo (MSt), material muerto (MSmm) y AP. Se utilizó un diseño completamente al azar con cuatro repeticiones y análisis de regresión lineal. Durante ELL, la MSTT fue similar (p > 0.05) entre ER (8342 kg ha-1) y disminuyó 90% en la ES. Durante ELL, se presentó mayor (p < 0.05) MSh a cuatro semanas, mientras que a ocho se presentó mayor MSt y MSmm. La MSt y MSmm se manifestaron cuando la AP fue de 34 cm y 47 cm, respectivamente. La ER y AP tuvieron efecto significativo en el rendimiento y comportamiento estructural de MS en Pennisetum ciliare cv. H-17.

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<p><strong>Background.</strong> An alternative in animal nutrition, to replace the use of synthetic additives, are essential oils, considered additives of vegetable origin. They are bioactive compounds, that have been shown to improve ruminal fermentation, nutrient digestibility, productivity and animal welfare. <strong>Objective.</strong> To review the current knowledge on the benefits of essential oils and their active compounds on ruminal fermentation, as well as the results obtained when using them in small ruminant production. <strong>Methodology</strong>. A search for bibliographic information was carried out using key terms in publications in scientific databases on the Web and electronic journals available on the Internet. <strong>Main findings.</strong> This paper presents the main essential oils used in animal production, their chemical structure and the results obtained from their use in small ruminants. Emphasis is made on the need to know the specific mode of action of each bioactive compound of essential oils, to optimize a dose without causing adverse effects. <strong>Implications.</strong> The limited information from <em>in vivo</em> studies on the biokinetics of essential oils in the rumen make it necessary to evaluate the specific mode of action of each bioactive compound, the biokinetics in the animal, as well as the optimal dose. This would provide scientific basis for the prudent and planned management of essential oils as additives commonly used in the feeding of small ruminants. <strong>Conclusions.</strong> Plant-derived essential oils can be useful in improving animal health and welfare, as well as meat and milk quality, and have potential environmental benefits such as mitigating enteric methane and ammonia nitrogen.</p>

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