Tropentag, September 19 - 21, 2012 in Göttingen "Resilience of agricultural systems against crises"

Silage of Sweet Sorghum Residues for Animal Production

¹National University of Colombia, Dept. of Animal Science, Colombia
²International Center for Tropical Agriculture (CIAT), Tropical Forages, Colombia

Abstract

A special sweet sorghum (Sorghum bicolor) cultivar has a high potential as primary material for paper production, due to its agronomic and compositional characteristics. The remaining forage parts such as leaves and panicle are by-products in Colombia, useful for animal nutrition. However, what first seemed to be the principal new business opportunity for farmers with the paper industry has meanwhile changed to a secondary income, the main benefit resulting from the animal feed. The objective of this study was to evaluate ensiling as a conservation option for sorghum residues, both under controlled and simulated field conditions. Sorghum bicolor ICRISAT 615 was harvested at milk-ripe stage (90 d), leaves and panicles were mixed. Two treatments (molasses alone at 33 g/kg fresh matter (FM), T1; molasses+homofermentative Lactobacillus inoculum, T2) × two types of packaging (vacuum sealed bags “Rostock Model Silages”, Co; standard plastic bag wrapped in black garbage bag, Fi) were applied. Silages were stored for 30 d at 25ºC and evaluated for their fermentation quality and aerobic stability afterwards. Silage dry matter (DM) ranged between 320 and 350 g/kg FM. The pH was significantly lower in the Co silages independent of the treatment (pH 3.7 vs. 4.2), the same applied for acetic acid contents (6.9 vs. 11.8 g/kg DM on average), explained by oxygen availability in Fi. Proteolysis expressed as ammonia-N from total N ranged from 89 to 106 g/kg without statistical differences, with an original crude protein content of 103 g/kg DM. Butyric acid content was slightly higher in FiT1 (47 g/kg DM) while lactic acid was lowest in this treatment (31 g/kg DM). Highest lactic acid content was achieved in CoT2 (57 g/kg DM), which is low compared to other forages and is explained by the low buffering capacity of sorghum (2.2 g lactic acid/100 g DM). All silages were of good quality according to DLG (German Society for Agriculture) criteria, but showed to be prone to aerobic deterioration indicated by pH increase after 7 d and yeast infestation, except for FiT2, which was least affected. Thus, ensiling offers a good option to preserve sorghum residues provided an adequate silo size.

Keywords: Additives, leave, panicle, silage quality, Sorghum bicolor

Contact Address: Siriwan Martens, International Center for Tropical Agriculture (CIAT), Tropical Forages, Cali, Colombia, e-mail: s.martenscgiar.org