Feed intake, milk production and feed conversion of dairy cows fed re-ensiled press cake from grass-clover silage compared to unprocessed grass-clover silage.

Abstract

Press cake silage (PCS) is a by-product of biorefining, which can substitute unprocessed grass or grass-clover silage (GCS) in ruminant feeding. The aim of this study was to examine the effect of including re-ensiled PCS from GCS in dairy cows' diet on feed intake, milk production and composition, feed conversion, apparent total tract digestibility (ATTD) as well as feed sorting and rumination behaviour compared to a control ration. Three total mixed rations (TMR) were tested in this experiment differing in PCS and GCS proportion in forage: 0% PCS and 50% GCS (CON), 25% PCS and 25% GCS (PCS25) and 50% PCS and 0% GCS (PCS50). The study was designed as a cross-over trial with six Holstein Friesian and nine Simmental cows (average 624 ± 68 kg body weight and 60 ± 20 days in milk at the start of the trial). The experiment consisted of three experimental runs, each lasting for 35 days with a 14 days adaptation phase and a 21 days measurement period. Diets were fed as TMR containing 37% grass silage, 26% concentrates and differing proportions of PCS or GCS depending on experimental group (37% GCS in CON, 18.5% PCS and 18.5% GCS in PCS25, 37% PCS in PCS50). Dry matter intake of dairy cows was higher in the PCS25 compared to the PCS50 group with both groups being not different from the CON treatment. Energy-corrected milk (ECM) production was lowest in the PCS50 group but did not differ significantly between treatments. Milk composition was also similar in all three treatments, except for milk urea content, which was lower in the PCS50 group. Moreover, ATTD of crude protein and ruminal nitrogen balance as well as phosphorus intake and the phosphorus effort for production of 1 kg ECM decreased with rising PCS inclusion in the diet. In contrast, no differences between treatments were found for dry matter, crude protein and energy effort for ECM production as well as for feed sorting and rumination behaviour. In conclusion, replacing GCS by re-ensiled PCS in TMR-diets did not affect ECM production and feed conversion of dairy cows while increasing the utilisation of crude protein and phosphorus. Therefore, re-ensiled PCS can substitute GCS in dairy cows' TMR-diets. However, the long-term effects of decreased phosphorus intake and ATTD of crude protein in cows fed PCS-rich diets should be examined in future studies.