EFFECT OF DRAFT WORK ON PERFORMANCE AND METABOLISM OF CROSSBRED COWS .2. EFFECT OF WORK ON ROUGHAGE INTAKE, DIGESTION, DIGESTA KINETICS ANDPLASMA METABOLITES
E. Zerbini et al., EFFECT OF DRAFT WORK ON PERFORMANCE AND METABOLISM OF CROSSBRED COWS .2. EFFECT OF WORK ON ROUGHAGE INTAKE, DIGESTION, DIGESTA KINETICS ANDPLASMA METABOLITES, Animal Science, 60, 1995, pp. 369-378
Forty F-1 crossbred dairy cows (20 Friesian X Boran and 20 Simmental X
Boran) in a 2 X 2 factorial arrangement (not working-not supplemented
, NWNS; not working-supplemented, NWS; working-not supplemented, WNS a
nd working-supplemented, WS) were used to study the effect of work and
diet supplementation on roughage intake, apparent digestibility of nu
trients, digesta kinetics and plasma metabolites. Dry matter (DM) and
organic matter (OM) intakes were greater for working than for non-work
ing cotes. Work and supplementation increased DM and OM in vivo appare
nt digestibility. This effect was particularly significant when compar
ing working cotes at vest and at work. Passage rate and rumen mean ret
ention of Cr-mordanted hay were sin milar for working and for non-work
ing cows. Liquid turn-over rate of Co-ethylene diamine tetra acetic ac
id (EDTA) was lower and rumen mean retention time of Co-EDTA was great
er in working than in non-working cows whether supplemented or not. Wo
rking cows had lower plasma glucose during and immediately after worki
ng than non-working cows. Plasma non-esterified fatty acid (NEFA) was
higher in working cows at the end of the working period and after vest
between working hours. This effect was greater in non-supplemented th
an in supplemented cotes. In working cows, beta-hydroxybutyrate was lo
wer at the end of working hours than in non-working cows. Lactate was
greater in working than in non-working cows after the 3rd and 4th hour
s of work. Digesta kinetics could explain only partially the possible
mechanisms responsible for greater roughage intake and apparent digest
ibility in working cows. The decrease of plasma glucose and the increa
se in NEFA during work indicates an increasing utilization of NEFA by
muscle during consecutive working hours.