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Boer goats (7/8 and 1/8 Spanish breed) were used to characterize effects of gender and age on the ME requirement for maintenance (MEm). There were eight animals of each gender, doelings, intact males, and wethers castrated at 2 mo of age. Kids were weaned at 3.7 mo and thereafter consumed a 50% concentrate pelleted diet ad libitum while in group pens at most times. Measurement periods consisted of three segments of 12, 10, and 4 days with consumption ad libitum and near MEm and while fasting, respectively. Maintenance segment measures began at 4.9, 7.8, 11.7, and 14.8 mo of age in periods 1, 2, 3, and 4, respectively. Feed intake data, feces and urine collections, and a calorimetry system were used to determine ME intake and heat energy (HE). The MEm estimate was based on fasting HE and the slope (km) of the regression of recovered energy (RE) against ME intake with intake near MEm and while fasting, and kg was RE with ad libitum intake relative to ME intake above MEm. BW (kg) during the maintenance segment was 20.6, 30.8, 46.5, and 57.1 for doelings, 25.9, 40.1, 67.3, and 76.9 for males, and 23.1, 35.1, 53.9, and 65.0 for wethers in periods 1, 2, 3, and 4, respectively (SE=1.85). km was similar among genders and periods (P>0.05%; 70.2%, 69.5%, and 69.7% for doelings, males, and wethers, respectively; SE=1.25). Fasting HE and MEm were affected by gender×period interactions (P |
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