COMPOSICIÓN BOTÁNICA Y EVALUACIÓN NUTRICIONAL IN VITRO DE PASTO KIKUYO COMPARADO CON GRAMÍNEAS DE CLIMA TEMPL

Abstract

<p><strong>Background: </strong>Intensive continuous grazing of temperate grass and legume pastures has been a feeding strategy adopted in small-scale dairy systems (SSDS) in the highlands of central Mexico that reduces costs and increases profitability of farms. However, temperate grasses have low persistency due to agroclimatic and management conditions, so that pastures are invaded by kikuyu grass (<em>Cenchrus clandestinus</em>), a sub-tropical grass that may be a valuable forage resource in these systems. There are not many studies in Mexico on kikuyu grass pastures and on the relationship between botanical composition, nutritional value and ruminal fermentation parameters, important aspects for their inclusion in feeding strategies for dairy cattle. <strong>Objective: </strong> The objective was to determine the botanical composition and to assess the <em>in vitro </em>digestibility of dry matter (DM), organic matter (OM), and neutral detergent fibre (NDF), and to characterize the kinetics of <em>in vitro </em>ruminal fermentation of a pasture based on with kikuyu grass (KY) in comparison to pastures based on festulolium cv. Spring Green (FL), tall fescue cv. TF-33 (TF), and perennial ryegrass cv. Pay Day (RG), all associated with white clover. <strong>Methodology: </strong> There were four sampling periods every 14 days. On the last day of each period, five random samples in each pasture were cut to ground level to determine botanical composition by manual separation, and 200g samples from each pasture taken by simulated grazing to determine digestibilities and the <em>in vitro </em>fermentation dynamics. Statistical analyses were following a split-plot model. <strong>Results: </strong>There was a higher proportion of grasses in KY and a better <em>in vitro </em>nutritional value for RG, related to a higher content of structural carbohydrates in KY, being a subptropical grass compared to temperate pastures with lower content of cell walls. <strong>Results: </strong>There was a higher proportion (P<0.05) of live grass in KY. There were no differences (P>0.05) among pastures for <em>in vitro </em>nutritional value. There were differences (P<0.05) among pastures and periods for the insoluble fraction fermentation rate (C<sub>B</sub>) and for the interaction between pastures and periods for gas production in 4.0 h of the soluble fraction (A) and the soluble carbohydrate fermentation rate (C<sub>A</sub>), but no differences between pastures, periods or the interaction (P>0.05) for other parameters of ruminal fermentation (lag time and total gas production). <strong>Implications: </strong> Pastures of kikuyu grass associated with white clover have a similar <em>in vitro </em>nutritional value as pastures of temperate grasses representing a valuable forage resource for SSDS. <strong>Conclusion: </strong>In spite of differences in some <em>in vitro </em>ruminal fermentation parameters, the <em>in vitro </em>nutritional value of kikuyu grass pastures associated with white clover is similar to pastures based on temperate grasses with white clover.</p>