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RELATIONSHIP OF BODY COMPOSITION AND FASTING HEAT PRODUCTION IN THREE BIOLOGICAL TYPES OF GROWING BEEF HEIFERS (MAINTENANCE, ENERGY, PREDICTION)
Abstract
Thirty-four heifers from each of three breeds (Hereford, Charolais and Simmental) were used to investigate the effects of age and body composition upon energy utilization. At birth and 3, 7, 10 and 14 months of age, fasting heat production (FHP) was measured on 6 heifers per breed in open-cirucit calorimeters. Each heifer was then slaughtered, and digesta-free empty body (EBW) was dissected into viscera and blood (VB), gastro-intestinal tract and internal fat (GI), head, hide and shanks (HHS) and carcass (CARC) and analyzed for chemical composition. Individual ad libitum feed intake was obtained for heifers from 7 to 14 mo of age. The CARC fraction contained between 57 and 67% of EBW, VB less than 10%, GI 7 to 13% and HHS 15 to 26%. Expressed as a percentage of EBW, fat increased with age, water decreased and protein remained stable. Herefords were lighter, fatter, but had a smaller proportion of fat located in the GI and more in the CARC than Simmentals or Charolais. Regressions of FHP/hr on activity reduced within-animal variation by nearly 50%. Activity adjusted FHP/kg('.75) was highest at birth. Hereford had lower FH/kg('.75) than Charolais and Simmental. Partial regressions of adjusted FHP/hr on EBW and on weights of chemical components indicated that FHP was most accurately predicted by weight of non-fat components and fat did not improve prediction. Partial regressions on weights of chemical components in the four fractions indicated positive and similar heat production per unit of non-fat contained in the VB, GI or CARC fractions, but nearly significant negative regression on non-fat tissue located in the HHS fraction. Non-fat CARC weight determined most variation in FHP/hr, because it constituted nearly two-thirds of the total non-fat weight. Partial regression estimates for energy costs of maintenance, and for protein and fat deposition indicated growing animals utilized metabolizable energy for maintenance with an efficiency of 70 to 80% and required an additional 9.5 to 11.5 kcal/g of fat deposited, similar to estimates from non-ruminants and from 17.4 to 31.0 kcal/g, of protein, higher than non-ruminants estimates.
Subject Area
Livestock
Recommended Citation
BUCKLEY, BRENT AUBREY, "RELATIONSHIP OF BODY COMPOSITION AND FASTING HEAT PRODUCTION IN THREE BIOLOGICAL TYPES OF GROWING BEEF HEIFERS (MAINTENANCE, ENERGY, PREDICTION)" (1985). ETD collection for University of Nebraska-Lincoln. AAI8526614.
https://digitalcommons.unl.edu/dissertations/AAI8526614