Use of barley fibre and wet distillers’ solubles as feedstuffs for Ayrshire dairy cows

The experiment was conducted to study use of barley fibre and wet distillers’ solubles (WDS), by-products from integrated starch–ethanol production, as feed in dairy cows’ diet. Barley fibre is a fibrous by-product with high content of neutral detergent fibre and low content of starch. Wet distillers’ solubles is the non-fermentable residue after distillation of ethanol. It has a high crude protein content with a high rumen degradability. Ayrshire cows, 12 multiparous and 12 primiparous, were divided into 6 blocks of 4 cows according to parity and calving date. Cows in each block were fed four different total mixed rations (TMR) according to a balanced 4 × 4 Latin Square design within a 2 × 2 factorial arrangement of the treatments. Treatments were two different energy sources (barley (B) or barley + barley fibre (BF, 1:1)) with two protein sources (rapeseed meal (RSM) or RSM + WDS). Thus, the treatments were B, B + WDS, BF and BF + WDS. Grass silage was the forage (400 g/kg diet dry matter). On the B + WDS and BF + WDS diets, the amount of WDS in TMR was 120 g/kg dry matter (DM). The crude protein content of the diets was 180 g/kg DM. Replacing half of the barley grain with barley fibre increased (P<0.01) milk yield (32.2 kg/day versus 33.0 kg/day) but had no effect on DM intake (DMI) (21.5 kg/day versus 21.7 kg/day). Replacement caused a small, but significant (P<0.001) decrease in milk protein content (35.3 g/kg versus 34.2 g/kg) with no change in protein yield. Inclusion of barley fibre in the diet had no effect on milk fat content but changed (P<0.001) its fatty acid profile by increasing the proportion of unsaturated fatty acids and conjugated linoleic acid. Replacing part of the RSM with WDS decreased performance of cows by reducing (P<0.001) DMI (21.0 kg/day versus 22.1 kg/day), milk yield (31.7 kg/day versus 33.6 kg/day) and yields of milk components. Inclusion of WDS in the diet decreased efficiency of N utilization. Barley fibre was a good fibrous component in concentrates for dairy cows’ TMR, but WDS was an inferior protein feed to RSM as a feed for lactating Ayrshire dairy cows.