Sorghum silage: Impacts on diet formulation according to NASEM (2021) model

Abstract

The use of sorghum silage (SS) in dairy herd feeding is a common practice during the dry season in Brazil. The objective of this study was to evaluate, through simulations with the NASEM-2021 model, the quality and efficiency of SS in meeting the nutritional requirements of high-production dairy herds. Four sorghum hybrids were planted and ensiled at the UFJ experimental farm. The SS of this study can be considered as having medium to low quality as compared to international data. DMI was estimated using NASEM-21 equation that considers both animal and dietary fiber. In addition to SS, the diet contained wilted alfalfa, soybean meal, bypass soybean meal, whole cottonseeds, soybean hulls, rehydrated corn, Flexypro®, urea, buffers, inert fat, sugar, mineral/vitamin supplement and Smartamine®. The same diet with corn silage is used to feed a group with 50 kg/d. Although the diets were identical and varied only in the sorghum hybrids, DMI and milk production were affected. Simulations indicated that no diet would reach a production of 50 kg/d. However, production close to or greater than 40 kg/d could be obtained. The test hybrid 1 (64.3% NDF and 15% starch) had the lowest DMI and predicted milk production (25.6 kg/d and 38.8 kg/d respectively), while the DMI and predicted production with a commercial hybrid were 26.3 and 41.1 kg/d, probably due to the lower NDF and higher starch content (56.9% and 24.1% of DM, respectively). Therefore, sorghum silage-based diets meet nutritional requirements of cows with up to 40 kg/d of milk yield. Although sorghum is a viable alternative in adverse conditions, the results indicate that, for high production systems, its use requires strict criteria in the selection of hybrids, and even so, it may not achieve the same milk production when compared to corn silage.