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

Abstract

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.