Temporal variation in faecal n-alkane ratios and estimation of pasture intake in calves

BAKKER, M.; ALVARADO, P. I.; GONDA, H. L; HIDALGO, L. G.; INZA, M. C.; WADE, M. H.; DALLA VALLE, D. E:; OTERO, M. J.; YUÑO, M.

Revista de la Asociación Argentina de Producción Animal

Asociación Argentina de Producción Animal

Lugar: Buenos Aires; Año: 2017 vol. 17 p. 17 - 53

0326-0550

SUMMARY The temporal variation (between and within sampling days) in the faecal n-alkane ratios (C32/C31 and C32/C33), and the effectof AM or PM faecal sampling on the estimation of pasture intake, was studied in Holstein-Friesian calves in two independenttrials. In Study 1, calves strip-grazed at different pasture allowances: Low or High (2.5 or 7.5 kg DM/100 kg LW/day). In Study2, calves strip-grazed at different grazing time schedules but same total daily pasture allowance (4-h: one fresh grazingarea/day for 4 h (11:00 AM to 3:00 PM) at a pasture allowance of 4.2 kg DM/100 kg LW, or 2x2-h: two fresh grazingareas/day, each one for 2 h (11:00 AM to 1:00 PM and 3:00 PM to 5:00 PM) at a pasture allowance of 2.1 kg DM/100 kg LW).In both trials, calves (LW range: 117-173 kg) were dosed orally with C32 embedded in paper stoppers twice a day. Thevariation between days in the faecal n-alkane ratios, estimated from the coefficient of variation (CV, %) over days 7 to 12(Study 1) or 6 to 10 of dosing (Study 2), was not significantly different between pasture allowances (Low: 17%, High: 14%) orgrazing time schedules (4-h: 16%, 2x2-h: 12%). In both studies, AM had significantly lower faecal n-alkane ratios than PM(p