Maintenance requirements in metabolizable energy of adult, nonpregnant, nonlactating Charolais cows.
Ortigues I. | Petit M. | Agabriel J. | Vermorel M.
The objective of this study was to determine the maintenance requirements in metabolizable energy (MEm) of adult, nonlactating, nonpregnant Charolais cows. A feeding trial was conducted using 12 cows fed at one of two feeding levels (75 [L] and 113 [H] kcal of ME.kg BW(-.75).d(-1)) for 116 d. Body composition was estimated from subcutaneous adipocyte diameter. Body weight changes averaged -468 and +46 g/d, respectively. Diet DM digestibility averaged 0.496. The L cows spent less time eating and ruminating but had other behavioral characteristics similar to those of H cows. Estimates of MEm were calculated from BW or body composition changes and amounted to 109 and 124 kcal of ME.kg BW(-.75).d(-l), respectively. Heat production (HP) was then measured over 67 d in a second trial on two L and two H cows from the feeding trial and planes of feeding were switched after 14 d. Estimates of MEm varied from 112 to 105 kcal.kg BW(-.75).d(-1). Within animal, day-to-day variations in heat production were high (4.6% on average) and prevented the detection or any precise changes of HP with time on treatment. None of the trials showed any significant effect of level of feeding on MEm.
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