The use of deuterium oxide for the prediction of body composition in live dairy cattle.

Body composition was studied in five animal groups (two 8-week-old 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 prediction equations were derived from D2O measurements and direct chemical analyses (slaughter studies) in kilograms except energy, which is in megacalories: TBW = 1.501D0.898 (Sy.x = 0.285); P = 1.501 (D0.898 - 2.682T0.605); protein = 0.147P1.095 (Sy.x = 0.895); ash = 0.0381P1.057 (Sy.x = 0.298); fat = 0.00122P-2.769 LW4.275 (Sy.x = 0.342); energy = fat X 9.226 + protein X 5.926 where TBW = total body water, D = D2O 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.