Valor nutricional e produtivo da silagem de Panicum maximum cv. miyagui com diferentes idades de colheita

Abstract

The objective of this study was to evaluate the production capacity and nutritional values of Panicum maximum cv. Miyagui silage under the influence of grass cutting age. The experiment was carried out at the Agrostological Field of the Experimental Station of the Federal Technological University of Paraná, Dois Vizinhos campus. The treatments evaluated were PO, PO+7d, PO+14d and PO+21d, where PO = optimum cutting point and d = days after the optimum point. The first cut was made with the grass at its optimum cutting point, approximately 80 cm high. Then, three more cuts were made, with intervals of 7 days. All treatments had the addition of food and biological additives, the food additive being soybean hulls, used to correct the DM content of the silage, and the commercial product Silomax Centurium was applied as a biological additive, with the objective of improving the fermentation parameters and the quality of the silage. The forage was processed according to the recommended particle size (5 cm) in PVC micro silos with a density of 600 kg/m3 and stored for 60 days. After opening the silos, gas and effluent losses, pH, buffering capacity, and bromatological analyses were evaluated. The data obtained were subjected to statistical analysis to evaluate the effects of cutting age on the quality of Miyagui grass silage. The mean values were then compared using the SNK test, considering a significance level of P>0.05, and a randomized block experimental design was used. There was a linear increase in grass height with advancing cutting age; similarly, cutting age influenced MV production, but had no effect on DM production of the grass. Cutting age did not influence (P>0.05) the DM, MM, and OM contents of the grass. A loss of nutritional value was observed due to the reduction in CP contents and an increase in the percentages of the components of the fibrous fraction of the grass. The chemical composition of the silage varied with the cutting age, showing a reduction in crude protein and an increase in the fibrous fraction content with the aging of the plant, while the pH and buffering capacity of the silage decreased with the advancement of maturation. It is concluded that, for the ensilage of Miyagui grass, it is essential to consider a set of factors related to the cutting age. It was observed that the greatest nutritional losses of the silage occur in the first 7 days of delay in relation to the ideal cutting point. On the other hand, the most significant increase in mass production occurs from 14 days of delay, remaining high until 21 days. Thus, it is necessary to balance the gain in productivity with the preservation of the nutritional value of the forage at the time of ensilage.