calves, two 16-week-old calves, three Holsteins and three Jerseys in late lactation and
two groups of cows each having a Holstein and a Jersey in early lactation). Each group
was fed a different diet so as to effect wide variations in body composition. Body
water volume and kinetics were estimated by deuterium oxide (D2O) dilution in trials
lasting 10-12 days for each animal. The experimental animals were slaughtered at the
end of the trials for direct chemical analyses of body components. The following pre
diction equations were derived from DjO measurements and direct chemical analyses
(slaughter studies) in kilograms except energy, which is in megacalories: TBW
= 1.501D0898 (sy.x = 0.285); P = 1.501 (D0898 - 2.682T0605); protein = 0.147P1095
(sy.x = 0.895); ash = 0.0381P1057 («„.*= 0.298); fat = 0.00122P'2 '""LW4 m (sy.x
= 0.342); energy = fat x 9.226 + protein x 5.926 where TBW = total body
water, D = DZO space in kilograms, T = water turnover (L/day), P = predicted
empty body water and LW = liveweight (kilograms). It was concluded that further
studies are required, with more animals, to improve and/or verify the utility of the
above equations. J. Nutr. 114: 2127-2137, 1984.
INDEXING KEY WORDS deuterium oxide •body composition •live
dairy cattle.
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