Níveis de torta de algodão em silagens de sorgo forrageiro.

Abstract

Sorghum is the second crop used in Brazil for ensiling. Despite its desirable characteristics for ensiling, sorghum have some negative issues as high moisture and surplus of water-soluble carbohydrates, leading to fermentative issues and increased losses. Thus, it the aim was to determine the optimal inclusion level of cottonseed cake (CSC) in sorghum silage evaluating fermentative profile, microbial profile, aerobic stability and ensiling losses. The cultivar used was the ‘BRS Ponta Negra’, which was sown at Barra de Santana town, Paraiba, Brazil. The harvest occurred 105 days after sowing. The material was chopped and the ensiling process was performed in experimental silos made of PVC tubes on March 30, 2019. Experiment was carried out in a completely randomized design. Treatments consisted of 5 inclusion leves of cottonseed cake: sorghum + 0% CSC; sorgo + 5% CSC; sorgo + 10% CSC; sorgo + 20% CSC e sorgo + 40% CSC, with 4 replicates, totalizing 20 silos with were opened 55 days after ensiling. Variables analyzed was pH; dry matter; water-soluble carbohydrates (at ensiling and opening); ammoniacal nitrogen; microbial population; gases and effluent losses and dry matter recovery and; aerobic stability of silages. Analysis of variance and regression were performed using the PROC GLM of SAS, with significant level of 5%. CSC inclusion provided pH and dry matter increases, with a decrease in water-soluble carbohydrates at ensiling. At opening, silages showed linear increase in dry matter content (P<0.0001) and pH (P=0.0006), whereas there was linear decrease in residual water-soluble carbohydrates after fermentation process (P<0.0001) and of ammoniacal nitrogen (P<0.0001). LAB counting showed a quadratic effect (P<0.0001) with maximum point in the level of 20% of CSC inclusion, whereas yeasts showed linear decrease (P<0.0001). Thus, there was a decrease in gases and effluent losses with significant increase of dry matter recovery in silages containing higher proportion of CSC (P<0.0001). Similarly, aerobic stability was higher in silages with more CSC level (20 and 40%), taking more than 80 hours to start aerobic deterioration. Thereby, CSC is a nutritional additive with potential utilization in acid silages, because it act as a moisture absorbent, medium buffer and yeast inhibitor, leading to greatest dry matter recovery.