The impact of dietary protein levels on nutrient digestibility and water and nitrogen balances in eventing horses.

This research examines how different levels of protein in the diet affect nutrient absorption and water and nitrogen balance in competition horses. The study found that a moderate protein level of 11.6% in the diet was optimal for these athletes, resulting in the best absorption of nutrients and balance of water and nitrogen.

Methodology and Research Design

• The researchers employed a randomized design involving 24 Brazilian Sport Horses, ranging in age from 8 to 15 years and in weight from 488 to 32 kg.
• The horses were subjected to four different levels of dietary protein: 7.5%, 9.0%, 11.0%, and 13.0%.
• A digestion analysis was performed using a partial collection of feces over 4 days, followed by a complete collection of urine on the 5th day.
• The collected data were subjected to regression analysis and fitted to linear and quadratic models.

Findings of the Study

• The horses’ intake of dry matter (DM), organic matter (OM), ether extract (EE), acid detergent fiber (ADF), and neutral detergent fiber (NDF) did not change across the varied dietary protein levels.
• Crude protein (CP) and Nitrogen (N) intake increased linearly as the protein level in the diet increased.
• There was a quadratic response observed in the digestibility of CP and NDF, with the maximum efficiency realized at a dietary protein level of 11.6% and 11.4%, respectively.
• ADF digestibility, digestible DM and protein intake, and CP/Digestible Energy (DE) ratio showed a linear improvement as dietary protein levels increased.
• Dietary protein levels didn’t affect the daily water intake, total water intake, or the amount of water excreted in the feces.
• As dietary protein levels increased, urinary excretion of minerals increased. However, overall water balance remained unaffected.
• Nitrogen intake, Nitrogen absorption, and urinary Nitrogen increased as dietary protein levels increased. But Nitrogen retention maintained an average of 7.5 g N/d regardless of dietary protein level.
• The digestion efficiency of CP, NDF, ADF, and digestible protein intake were impacted by the dietary protein levels.

Recommendations

• The study recommends a dietary protein level of 11.6% for intensively exercising horses. This provides an intake of 2.25 g CP/kg of body weight and 0.37 g N/kg of body weight.
• The NDF and ADF responses indicate enhanced digestion of dietary fiber with a higher presence of Nitrogen in the digestive tract. This suggests the need for an optimal balance in the diet for maximum nutrient absorption.