Autumn-cut grass silage as roughage component in dairy cow rations. 1. Feed intake, digestibility and milk performance.

Abstract

A feeding trial was carried out with 56 dairy cows in >=2nd lactation. The duration of the experiment was 13 wk and started immediately after parturition. Basal diets consisted of maize silage, pressed beet pulp, moist ensiled maize gluten feed, ensiled brewers' grains and concentrates, which provided 70% of total DM. The remaining 30% of the DM consisted of grass silages, which were given as supplement to the basal diet. Treatments were wilted grass silage (WGS), moist grass silage ensiled with molasses (MGS), moist grass silage ensiled with formic acid (FGS) and wilted grass silage with added water (WW). The rations were given as a total mixed ration (TMR) to avoid selection. All grass silages were harvested between 30 Aug. and 1 Sept. from the same pastures. The moist grass silage differed in chemical composition from the wilted grass silage in ash (higher), crude fibre (lower) and NDF (lower). The in vitro and in vivo digestibility did not differ between silages. Total DM intake was lowest for both moist silages (MGS and FGS) and, as a consequence, net energy intake was also lowest with MGS and FGS. Milk yield was highest on WGS and WW, resulting from the higher energy intake. Milk fat yield and content did not differ between treatments. Milk protein yield was significantly lower for groups given MGS and FGS. Milk protein content tended to be lower for groups given FGS and MGS. During the experiment energy balance was negative on all treatments. Calculation of the duodenal digestible protein value (DVE), using the recommended equation for grass silage, gave WGS silage a better fit with the DVE balance measured in the feeding trial than found with high moisture silages (MGS, FGS), which appeared to be underestimated. Body weight changes correspond favourably with net energy balances, after correction of energy values for volatiles in grass silages, using individual net energy values for volatiles instead of an av. for grass silage OM. (Abstract retrieved from CAB Abstracts by CABI’s permission)