TITLE:
Intake, Energy Expenditure and Methane Emissions of Grazing Dairy Cows at Two Pre-Grazing Herbage Masses
AUTHORS:
Cecilia Loza, José Gere, María Soledad Orcasberro, Alberto Casal, Mariana Carriquiry, Paula Juliarena, Efren Ramírez-Bribiesca, Laura Astigarraga
KEYWORDS:
Dairy Cow, Herbage Mass, Intake, Grazing Behavior, Methane
JOURNAL NAME:
Open Journal of Animal Sciences,
Vol.11 No.3,
July
1,
2021
ABSTRACT: A grazing experiment was undertaken to assess the
effects of two levels of herbage mass (HM) on herbage DM intake (DMI), fat and
protein corrected milk yield (FPCM), grazing behaviour, energy expenditure
(HP), and methane emissions (CH4) of grazing dairy cows
in spring. Treatments were a low HM (1447 kg DM/ha; LHM) or a high HM (1859 kg
DM/ha; HHM). Pasture was composed mainly of cocksfoot (Dactylis glomerata) and lucerne (Medicago
sativa), offered
at a daily herbage allowance of 30 kg DM/cow, above 5 cm. Eight multiparous
Holstein cows were used in a 2 × 2 Latin Square design in
two 10-day periods. Despite the differences in pre-grazing HM between
treatments, OM digestibility was not different (P = 0.28). Herbage mass did not
affect DMI or FPCM. Grazing time was not different between treatments, but cows
had a greater bite rate when grazing on LHM swards. However, HP did not differ
between treatments. Daily methane emission (per cow), methane emission
intensity (per kg FPCM) and methane yield (as percentage of gross energy
intake) were not different. The lack of effect of the amount of pre-grazing HM
on energy intake, confirms that the difference between HM treatments was beyond the limits that impose
extra energy expenditure during grazing.