Biorefined perennial ryegrass press cake as an alternative feed for dairy cows in late lactation and during the dry period: a demonstration

To investigate the potential application of replacing a proportion of a perennial ryegrass (PRG) silage diet with press cake on productivity and enteric methane (CH 4 ) emissions in late lactation and non-lactating spring-calving dairy cows, a study was undertaken in which control cows ( n = 21) were offered PRG silage, while treatment cows ( n = 21) were offered a diet consisting of 60% PRG press cake and 40% of the same PRG silage. Although treatment cows had higher group average dry matter intakes (DMI) and produced more enteric CH 4 , carbon dioxide (CO 2 ), milk solids, protein, fat- and protein-corrected milk yield (FPCM) in late lactation, the magnitude of the difference between treatment and control cows varied from week to week ( P < 0.050). When enteric CH 4 per kg of milk yield, milk solids and FPCM were considered, there was no significant difference between treatment and control. Absolute enteric CH 4 was higher for cows fed press cake during the non-lactating period but this tended to vary from week to week. Similarly, CO 2 ( P < 0.001) and hydrogen (H 2 ; P = 0.023) differed from week to week for cows offered press cake, and cows offered PRG silage in the non-lactating period. Although there was no significant effect of diet on body weight (BW) and body condition score (BCS), when enteric CH 4 was expressed on a per kg BW basis, cows offered press cake tended to produce more enteric CH 4 in both late lactation and during the dry period.