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Intake Energy, Energy Retention and Heat Production in Lambs from Birth to 24 Weeks of Age¹

University of Alberta^,4, Edmonton, Alberta, Canada T6G 2E3

Abstract

Intake energy (IE), metabolizable energy intake (MEI), energy retention (ER) and heat production (HP) were estimated in twelve male and six female suckling lambs from birth to 4 wk of age and in nine of these male lambs after weaning from 9 to 24 wk of age. Intake energy and MEI were estimated from the milk intake and combustible energy of the milk in the suckling lambs and from digestibility trials and energy content of feed and feces in the weaned lambs. Energy retention was estimated from body composition changes and HP was calculated from MEI - ER and from the rate of O₂ consumption. The 0₂ consumption of the ewes was also measured during late pregnancy and during lactation. In the suckling lambs, daily MEI was 277 kcal/kg.75 and ER was 112 kcal/kg^.75. Daily HP as calculated by MEI - ER was 165 kcal/kg^.75 and as calculated from O₂ consumption was 168 kcal/kg^.75 Daily maintenance HP was equal to 121 kcal/kg^.75 and the efficiency of utilization of energy for ER was 70.7%. In the weaned lambs, HP as measured from O₂ consumption was 10% lower than that estimated using MEI and ER. Comparison of 9- to 16-wk-old with 17- to 24-wk-old lambs, showed daily increases in MEI from 212 to 228 kcal/kg^.75, in ER from 54 to 95 kcal/kg^.75 and in HP from 158 to 194 kcal/kg^.75 , whereas there was a daily decrease in maintenance HP from 101 to 90 kcal/kg^.75. Efficiency of utilization of energy for production was similar in the two postweaning periods (48.8 and 46.5%, respectively). The O₂ consumption of the ewes (/kg^.75) was increased over that of nonpregnant, nonlactating controls by 30% in late pregnancy, by 62% in the first month of lactation and by 50% in the second month of lactation.

¹ Supported by grants from the Agricultural Research Council of Alberta and the Natural Sciences and Engineering Research Council, Canada. Appreciation is expressed to J. A. Francis, C. A. Breakey, A. L. Schaefer and G. A. Hills for technical assistance.

² Present address: The Jacob Blaustein Institute for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Israel 4990.

³ Present address: Animal Production and Health Section, International Atomic Energy Agency, P. O. Box 100, A-1400, Vienna, Austria.

⁴ Dept. of Anim. Sci.