Nutritive value and morphological characteristics of Mombaca grass managed with different rotational grazing strategies

Light competition increases and plants' growth pattern change to optimize light utilization when the leaf area index increases. It has been previously shown that using 95% canopy light interception (LI) as a grazing frequency criterion resulted in a greater proportion of leaves and a lower proportion of stem. The objective of the study was to characterize the forage production, morphological composition and nutritive value of Panicum maximum cv Mombaca. The experiment was carried out during summer, autumn-winter and spring. Treatments corresponded to combinations of two pre-grazing conditions (95% and maximum LI at pre-grazing; LI95% and LIMax, respectively) and two post-grazing heights (PGHs; 30 and 50 cm). The statistical design was a randomized complete block, with a 2 x 2 factorial arrangement. Swards managed with LI95% had greater proportions of leaves and lower proportions of stems compared to LIMax. Leaf proportion was lower during autumn-winter compared to summer and spring. The LI95% had greater crude protein (CP) and digestibility (IVOMD), and lower acid detergent fibre (ADF) concentrations than LIMax. The 50 cm PGH pastures had greater CP content and IVOMD, and lower ADF content than 30 cm PGH pastures. Lower IVOMD was observed during autumn-winter than summer and spring. The variability observed on morphological characteristics was primarily associated with seasonality, whilst the nutritive value was primarily affected by grazing management. The pre-grazing target of LI95% combined with 50 cm PGH was the combination that resulted in an increased proportion of leaves, decreased stems in basal stratum and the greatest nutritive value of the produced forage.