Energy expenditure and methane emissions of grazing dairy cows at two pregrazing herbage biomass

LOZA C.; GERE J. I.; ORCASBERRO M. S; CASAL A.; CARRIQUIRY M.

Cork

Congreso; 27 th European grassland federation general meeting.; 2018

European Grassland Federation EGF NEWS

We quantified the effect of biomass on energy expenditure (EE), methane emissions (CH4) and FPCM of grazing dairy cows. The experiment was carried out in November 2015.Treatments were two contrasting levels of pre-grazing biomass (LOW vs HIGH) at a daily herbage allowance (DHA) of 30 kg DM (above 5 cm). Eight multiparous Holstein cows, were used in a 2×2 latin square design. DMI was estimated using Cr2O3 and digestibility by faecal index (N and ADF). Grazing time was determined by observation between milking (9 hours).EE was estimated from heart rate and O2 pulse, CH4 was determined using the SF6 tracer technique. Pre-grazing herbage height and biomass above 5 cm differed significantly (48 vs 37 cm, P = 0.0374; 1859 vs. 1447 kg DM ha-1, P = 0.05). However, DMI (18.3 kg d-1 ; P = 0.5101), grazing time (324 min; P = 0.6522), and EE (725.8 kJ kg MW-1, P = 0.7986) did not differ among treatments. Therefore, FPCM and CH4 yield were similar (20.6 kg d-1, P = 0.7527; 21 g kg DM-1, P = 0.7115, respectively). In the current study, biomass in LOW was higher than intended, which would explain the lack of difference in daily intake and EE atgrazing.