The use of effluent from grass silage in the diet of finishing pigs. I. Variation in composition of effluents

Effluent was collected in the fresh state from 3 batches of silage made from ryegrass, the dry matter content of the silages ranging from 203 to 265 g/kg. Samples of effluent were collected daily, stored at ?20°C and later bulked to form weekly composite samples. The pH ranged from 3.24 to 3.82, dry matter (DM) from 61.5 to 109.7 g/kg, crude protein from 190 to 337 g/kg DM and ash from 149 to 217 g/kg DM. These values were not related to source of effluent except for dry matter; the higher the dry matter in the silage the higher the dry matter in the corresponding effluent.On average, effluent contained 266 g crude protein/kg DM, of which 176 g was contributed by amino acids excluding tryptophan. The mean content of the more important acids per kg DM was lysine 11.2 g, methionine plus cystine 5.9 g and threonine 10.6 g. Lysine varied with source of effluent and also tended to decrease with increasing time from commencement of flow. The overall mean levels of mineral elements were: calcium, 18.6 g/kg DM; phosphorus, 10.6 g/kg DM; magnesium, 4.4g/kg DM; sodium, 7.4 g/kg DM; potassium, 23.4 g/kg DM; managanese, 378 mg/kg DM; iron, 1965 mg/kg DM; copper, 17 mg/kg DM; zinc 670 mg/kg DM. Lactic acid always exceeded the total volatile fatty acid content of the effluents and of the volatile fatty acids, acetic acid always predominated. The mean total acid content was 118 g/kg DM, which subtracted from a calculated nitrogen-free extract value of 538 g/kg DM indicated a total carbohydrate content of effluent of 420 g/kg DM.