Effect of maize variety harvested at different maturity stages on feeding value and performance of dairy cows

Maize silage was produced from two different varieties (SG: "stay-green" and DD: "dry down") at two different stages of maturity (target: 30-32 and 38-42% DM). Dry matter and nutrients of plant fractions and silages, fermentation parameters of silages and digestibility in sheep were determined. Furthermore a feeding trial was conducted in which the effect to the maize silage on feed intake and performance of dairy cows was studied. This trial series (TS 1) was replicated in the following year (TS 2). In both years, variety SG had higher ear (dehusked) dry matter content and lower residual plant dry matter content (58.9% and 23.7%) than variety DD (54.9% and 26.7%) and a slightly lower ear (dehusked) proportion. The constituents of the ear (dehusked) and residual plants were affected by maturity stage but not by variety. The maize silages of variety DD had slightly lower crude ash, crude fat and crude fibre contents and a higher starch content than SG. In TS 1, the digestibility of the organic matter averaged about 77% for variety SG and 80% for variety DD; in TS 2 this value was uniform at about 77%. While the maize variety had little effect on the average daily feed intake over both feeding trials (SG 17.2 kg DM per cow and DD 16.9 kg DM per cow), the stage of maturity had a significant effect. Maturity stage 2 increased the total daily feed intake from 16.4 to 17.8 kg DM per cow relative to maturity stage 1. The daily milk yield, which averaged 24.9 kg (TS 1) and 25.2 kg per cow (TS 2) was not significantly affected either by the variety or the maturity status, although there was a slight quantitative advantage of 1.1 kg (TS 1) and 0.7 kg (TS 2) milk per cow and day in favour of variety SG over variety DD.