Formic acid treated whole crop barley and wheat silages in dairy cow diets: effects of crop maturity, proportion in the diet, and level and type of concentrate supplementation

Abstract

Three trials in dairy cows were carried out to study the effects of replacing grass silage (GS) with wholecrop silage (WCS) made of barley (BS) or wheat (WS) harvested at dough stage with a dry matter (DM) concentration of 300-450 g kg-1. All silages were ensiled using a formic acid based additive 5 l t-1. Milk production responses to energy and protein supplementation of diets were studied. In Exp. 1, BS replaced GS at the rates of 0, 200, 400 or 600 g kg-1 forage DM. Also 10 kg of concentrate containing 0 or 2 kg of rape seed meal was fed. In Exp. 2, barley was harvested at three times (BS1, BS2, BS3) at one week intervals. Barley silages were fed as a mixture with GS (40:60) and in addition BS2 and GS alone. Silages were supplemented with a cereal based farm-made concentrate (FC) or a commercial compound having a lower concentration of starch than FC. In Exp. 3, barley and wheat were harvested at two week intervals, fed as a mixture with GS (40:60) and supplemented with low or high amount of concentrate. The fermentation quality of whole crop silages was good. Weather conditions and maturity affected the proportion of ear in the crop and subsequently the ratio of non-structural carbohydrates to NDF in the silage. The inclusion of WCS depressed diet OM digestibility depending on the digestibility of GS and the proportion of WCS in the diet. However, mixing GS and WCS did not depress intake. Subsequently the use of mixtures maintained or even increased milk yield as compared with GS diet in Exp. 2 and 3. In Exp. 1, higher proportions (400, 600 g kg-1) of BS decreased milk yield. Minor effects of growth stage on milk production were observed with barley whereas delaying wheat harvest increased milk yield. Different types and levels of concentrate induced mainly similar intake and milk yield responses with diets based on GS alone or on mixtures of GS and WCS. The synergistic effect of mixing GS and WCS was more positive in experiments where the protein concentration of concentrate was high (200 g kg-1 DM).;