Oxygen consumption and the energy costs of Na+, K+ -transport in
the rumen of Holstein-Friesian steers
J.M. Kelly, B.W. McBridge, L.P. Milligan, D.R. Waldo
Department of Animal and Poultry Science, University of Guelph,
Guelph, Ontario, Canada
Proceedings of the New Zealand Society of Animal Production.
1991, 51: 123-128
Forty-eight yearling Holstein-Friesian steers were assigned to
three diets (Panicum virgatum (P) var. Cave-in-rock, Dactylis
glomerata (D) var. Hallmark and Medicago sativa (M) var. Waterman
Loomis 316) fed at two levels of intake (low (L) 65g DM kg-1 liveweight
-0.75 day -1 or high (H) 90 g DM kg -1 liveweight -0.75 day -1) during a
6 month growth study. At the conclusion of the study animals were
stunned, exsanguinated and promptly eviscerated and the rumen quickly
emptied of its contents and subsequently weighed. Upon slaughter, rumen
tissue samples were acquired from the ventral sac and placed in
oxygenated M199 media. Mucosa and muscularis weights were determined
along with their total 02 consumption, ouabain-senitive- (OSO2) and
ouabain-insensitive-(OIO2) respiration. Tissue oxygen consumption was
determined in vitro using a YSI Clark style electrode. Total,
Mucosa and muscularis weights were greater (16.9-43.5%) with H and
tended to be affected by diet (P<0.10). On a tissue basis, rumen muscle
O2 consumption was not affected by treatment but mucosal OSO2 and
percent inhibition of O2 consumption by ouabain were higher (6.9-94%)
with Medicago. Total rumen O2, OSO2 and OIO2 consumption were higher
(8.6-80.5%) in H (P<0.05) and diet affected OSO2. Rumen muscle total O2
consumption was greatest (3.51 ul 02/mg/hr) for D and altered by level
of intake (P<0.03). Mucosal OSO2 and OIO2 were greater with H (P<0.04
and P<0.07, respectively). Total rumen O2 consumption is dominated by
organ size rather than changes in weight specific O2 consumption.
Therefore, at high forage intakes part of the decrease in the efficiency
of ME utilisation is a consequence of increased heat production from the
larger rumen.
Keywords: NZSAPAB;
Steers; rumen; oxygen consumption; Na+, K+-ATPase
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Last Updated 25-01-1997
