Prediction of the nutritional values by INRA (2018) feed evaluation system of Megathyrsus maximus subjected to different grazing strategies

Abstract

Grazing management is a key element to optimize growth cycle of forages, which are enhanced in their chemical composition leading to the reception of greater nutritive values for feeding ruminants. Several studies have showed that the accuracy and precision of the feeding values are critical to achieve this goal, unfortunately, in Ecuador there are not referential data, despite of Megathyrsus maximus is the most forage used by livestock farmers. The predominant aim of the current study was to approach and estimate the feeding values by INRA feed evaluation system of Tanzania grass (Megathyrsus maximus) subjected at different grazing strategies. The statistical design was a randomized complete block, with a 3 × 2 factorial arrangement. Where the treatments were combinations of three grazing frequencies (GF) (30 d; termed GF30, 45 d, GF45 and 60 d, GF60) and two cutting heights (CHs; 30 and 45 cm). The agronomic data did not vary by season effect (P = 0.24 to 0.82), but GF60 had higher plant heigh and dry matter (DM) contents (P < 0.001) than other GF, although with less tiller populations (241 vs. 304 tiller/m2). By CHs effect, Tanzania grass at 30 cm had a greater DM content than 45 cm of CHs (5565 vs. 4221 ± 603 kg/ha-1; P = 0.073). All chemical determinations were affected by GF, CHs and their interaction (P < 0.001 to 0.004) with the exception on ADF between CHs (P = 0.50). Whereas only the CP and ADF values were conditioned by season effect (P = 0.001 to 0.011). Subsequently, Tanzania grass subjected at moderate rest periods and low defoliation intensities showed greater energy and proteins values than traditionally used GF60. Based in these findings, the defoliation frequency had influence on agronomic and chemical characteristics, whilst the feeding values was mainly affected by grazing intensities and weather conditions. So, the best combination regarding nutritive values should be at GF30 and GF45 combined with 45 cm of CHs.