Abstract

INSUA, J.R; AGNUSDEI, M.G  and  DI MARCO, O.N. Calidad nutritiva de láminas de dos cultivares de festuca alta (Festuca arundinacea Schreb). RIA. Rev. investig. agropecu. [online]. 2012, vol.38, n.2, pp.190-195. ISSN 1669-2314.

Leaf nutritive qualitywas evaluated in two tall fescue (Festuca arundinaceaSchreb) cultivars, during a summer regrowth (average daily temperature: 21±2.8°C), in relation to morphogenesis parameters. Cultivars were El Palenque PlusINTA (traditional) and Grasslands AdvanceGentos (soft leaf type). The experiment was conducted in pots (250/cultivar) arranged in a completely randomised design (n=3) under natural climate conditions, with out limitation of water, N and P. Swards were sampled 8 times (~300 tillers/harvest) over a period of 14 weeks, to obtain leaves in 6 ontogenics stages of similar age (from growing to complete senescence) corresponding to the 3 first sequentially appearing leaf generations (G1, G2, G3). Morphogenesis traits were measured in 15 marked tillers/cultivar. Leaf age, leaf lifespan (LLS) and leaf appearance interval (LAI) were expressed in growing degree days (GDD:Σaverage temperature - 4.0 ºC). Leaf blades and sheaths were measured and leaf blade NDF and the in vitro digestibility (NDFD and DMD, incubation at 24 h DaisyII digestor) were determined. The morphogenesis traits were evaluated using repeated measures data analysis. Quality traits were analyzed by lineal function and dummy variables.The mean values of cultivars in each ontogenetic state were compared by ANOVA (Tukey, p <0.05). Cultivar did not differ in morphogenesis traits, with the exception of LLS and number of leaving leaves (NLL), which were lower in Advance. The NDFD declined with leaf age and length in both cultivars, with higher rate in Advance due to its shorter LLS. However, cultivars did not differ in NDF content, which remained stable throughout the leaf lifespan (54.5±3%) and increased during senescence (64.9±0.8%). Cultivars did not differ in NDFD at similar ontogenic stages, which indicates that Advance require more frequent defoliations than El Palenque to control changes of quality over time.

Keywords : Tall fescue; Cultivars; Leaf quality; NDF; DNDF; Morphogenesis; Defoliation.

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