Development of a Mathematical Model for Predicting Digestible Energy Intake to Meet Desiered Body Condition Parameters in Exercising Horses
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Information regarding dietary requirements to maintain or alter body condition in the horse is scarce; however, a recently developed nutritional model was acceptably accurate in prediction of the energy required to alter BCS in sedentary mares. The objective of this study was to expand the scope of this model to include exercising horses. Previously published estimates of energy expenditure in the exercising horse were incorporated into the model. Stock type horses (n=24) were assigned to treatments of light exercise, heavy exercise or control and fed according to the model to gain or lose 2 BCS within 60 d. The energy expenditure for exercise was quantified for each horse via indirect calorimetry using the K4b2 (Cosmed) adapted for use in horses. Body parameters were also measured including, BCS, %BF estimated from RFT, BW, body length, heart girth circumference and neck circumference at 2 wk intervals throughout the study. Model evaluation revealed acceptable precision when predicting BCS and BW in control horses (r^2 = 0.91 and r^2 = 0.98 respectively) but was less precise when predicting %BF (r^2 = 0.51). Model precision for BCS, BW and %BF in lightly (r^2 = 0.29, 0.85, 0.57) and heavily (r^2 = 0.04, 0.84, 0.13) exercised horses was low. Statistical analysis of indirect calorimetry data revealed that the observed and model predicted DE (Mcal/d) expenditure for lightly exercised horses were similar (0.71 vs 0.81, P = 0.46); however, the observed energy expenditure in heavily exercised horses was lower than the model predicted value (3.63 vs 6.79, P = 0.04). Also, observed energy expenditures were lower than the NRC recommendations for both light and heavy exercise groups (P < 0.05). Regression analysis revealed that rider BW, environmental humidity and horse age are significant contributors to VO2. Further investigation into the relationship between these factors, VO2 and body composition could yield a more precise predictive equation which would increase the precision of both the model and NRC recommendations for exercising horses.
Zoller, Jennifer Leigh (2016). Development of a Mathematical Model for Predicting Digestible Energy Intake to Meet Desiered Body Condition Parameters in Exercising Horses. Doctoral dissertation, Texas A&M University. Available electronically from