Sorghum silages below 25 percent dry matter resulted in higher dry matter and feed value losses, as well as higher levels of ammonia, lactic acid, acetic acid and alcohol. The pH levels of sorghum pits were between 3.6 and 3.9. This was shown by research of 12 silage sorghum lots grown in 2019.
The silage research - funded by ZuivelNL, Dairy Fund and the Ministry of Agriculture, Nature and Food Quality - is part of the food and animal research of the Public Private Partnership Sorghum (2019-2022). Nine sorghum silages were ensiled in barrels of 10 liters and three in sealed bales of approximately 400 kg of product. Three silages in barrels contained a maximum of 24 percent dry matter at harvest and showed twice as high dry matter losses during the silage period as the other silages (10.6% versus 5.1%). Higher conversions of carbohydrates and proteins to lactic acid, volatile fatty acids and ammonia and also a higher chance of press juice formation were responsible for this.
The silage density in relation to the dry matter content provides an indication of the silage quality. Lower densities (less than 180 kg dry matter per cubic meter) in combination with low dry matter contents (less than 24 percent dry matter) resulted in not only higher losses but also a higher susceptibility to spoilage during silage. The pits with 27 to 29 percent dry matter in barrels had an average density of 200 kg dry matter per cubic meter. The density of the silages in bales - 26 to 29 percent dry matter - was 30 percent higher with 260 kg dry matter per cubic meter than that of the silages with comparable varieties in barrels. The bales were used at the beginning of 2020 in a digestion test with wethers at ILVO (Belgium).
In the coming six months, follow-up research will be carried out in two trials. The first trial focuses on the effect of sorghum silage on rumen characteristics, the second trial focuses on the effect on feed intake, milk yield, milk composition and enteric methane formation in dairy cows.