Original ResearchRelationships Among Digestible Energy Intake, Body Weight, and Body Condition in Mature Idle Horses

- Horses were offered 1.75-2.00 kg of dry matter/100 kg body weight (BW) in mixed grass hay and 0.2 kg/100 kg BW in whole oats during three, 42 days feeding trials.
- The combined digestible energy intake was 51.73 ± 3.33 Kcal·kg BW−1 day−1 (23.83 ± 0.36 Mcal/d).
- Horses required 24 Mcal/kg of BW gain.
- It is possible that variation in BW gain arose from differences in basal metabolism and energy expenditure.

The objective of this study was to evaluate the relationships among digestible energy (DE) intake, body weight (BW), and body condition score (BCS) in lean/moderate condition horses. The feed intake of 35 Quarter Horses (age 5.3 ± 1.2 years; BW 462 ± 39 kg; BCS 4.5 ± 0.5) was recorded daily over three, 42-day feeding trials. Horses were offered 1.75-2.00 kg DM/100 kg BW in Orchard grass hay and 0.2 kg/100 kg BW in whole oats. Body weight and BCS were recorded biweekly. Daily DE intake was calculated according to Pagan and recorded as the amount fed minus any refusal. The daily kilogram intake was multiplied by the DE (Mcal/kg) content of the feed to equal the total calories per day. The mean within-horse ΔBW and ΔBCS from 0 to 42 days of each trial were evaluated using paired t tests. Trial 1 horses consumed 24.5 Mcal/d and BW increased (P < .001) by 24 ± 3 kg; however, there was no significant change in BCS (0.0 ± 0.5). Trial 2 horses consumed 22.8 Mcal/d and BW increased (P = .009) by 8 ± 3 kg and BCS tended to increase (P = .06) by 0.5 ± 0.5. Trial 3 horses consumed 25.7 Mcal/d and BW and BCS increased (P < .001) by 22 ± 2 kg and 1.0 ± 0.5, respectively. According to trial, horses required approximately 19, 34, and 18 Mcal/kg of weight gain, respectively. Additional factors affecting weight gain are related to the individual.