Article

Energy expenditure of grazing cows and cows fed grass indoors as determined by the 13C bicarbonate dilution technique using an automatic blood sampling system

Agroscope Liebefeld-Posieux Research Station ALP, 1725 Posieux, Switzerland.
Journal of Dairy Science (Impact Factor: 2.57). 01/2011; 94:1989-2005. DOI: 10.3168/jds.2010-3658
Source: PubMed

ABSTRACT The objectives of the study were to assess the 13C bicarbonate
dilution technique using an automatic blood
sampling system and to use this technique to estimate
energy expenditure (EE) based on the CO2 production
of 14 lactating Holstein cows on pasture or in a freestall
barn. The effects of physical activity and eating
behavior on EE were also assessed. Cows were exposed
to each feeding system in a crossover design with two
14-d experimental periods, each consisting of an adaptation
period and a 7-d data collection period. Cows
either grazed on pasture or had ad libitum access, in
the freestall barn, to grass cut daily from the same paddock.
All cows were supplemented with a cereal-based
concentrate. The EE of each cow was determined from
0700 to 1300 h on 1 d of each collection period. Blood
samples for the 13C bicarbonate dilution technique were
taken either manually in the barn or using an automatic
blood sampling system on pasture. Eating pattern and
physical activity were recorded from 0700 to 1300 h
using a behavior recorder and an activity meter, respectively.
Milk yield was recorded daily. Individual feed
intake was estimated using the alkane double-indicator
technique. Two preceding experiments confirmed that
the sampling technique (manual or automatic) and the
following storage of the blood samples (frozen directly
after withdrawal or first cooled on ice and then frozen
6 h later) had no effect on 13CO2 enrichment in the extracted
blood CO2 or on the subsequent calculation of
CO2 production. During the 6-h measurement period,
the EE of cows on pasture was higher than that of
cows in the freestall barn. Daily feed intake and milk
production were not affected by the feeding treatment.
Grazing cows spent more time walking and less time
standing and lying than did cows fed indoors. Time
spent eating was greater and time spent ruminating
was lower for cows on pasture compared with grass-fed cows in the barn. In conclusion, the 13C bicarbonate
dilution technique, combined with an automatic blood
sampling system, is a suitable method to determine the
EE of lactating dairy cows on pasture. Positive correlations
between EE and walking and eating time indicate
that the higher energy requirements of dairy cows on
pasture may be at least partly caused by a higher level
of physical activity. However, before specific recommendations
about additional energy supply can be given,
it must be determined whether EE measured over 6 h
can be extrapolated to 24 h. Furthermore, the apparent
inconsistency between EE, feed intake, and milk
production needs to be resolved.

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