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Published on: September 7, 2015
Energy intake and gross efficiency comparisons from calorimetric and field data on the same lactating cows
P M Saama1, I L Mao, J B Holter
1Department of Animal Science, Michigan State University, East Lansing 48824-1225, USA.
Abstract:
Field estimates on gross efficiency were obtained from intake and production data on 30 pluriparous Holsteins cows during wk 5, 7, 9, 11, 13, and 15 postpartum. Energy intake and efficiency from the energy chamber on the same cows were measured during wk 6, 10, and 14 postpartum. Measures of gross efficiency were expressed in terms of the utilization of metabolizable energy or net energy for lactation and maintenance. Within corresponding postpartum periods, chamber measures and field estimates were compared by canonical correlation analysis. All estimates from field data of energy and gross efficiencies closely approximated measures of the same traits from energy chamber data. Variation among cows in traits of energy partition and gross efficiency was similar for field estimates and energy chamber measures. Correlations were > .66 between field estimates and chamber measures on observations of maintenance energy and milk energy. Field estimates and chamber measurements of metabolizable energy and net energy had correlations of .76 and .70, respectively.
