Effects of Increasing Levels of Total Tannins on Intake, Digestibility, and Balance of Nitrogen, Water, and Energy in Hair Lambs

SIMPLE SUMMARY: Sheep farming plays a prominent role in the agriculture and economy of tropical regions, including the Brazilian semi-arid region. Rural producers have adopted Mimosa tenuiflora hay as a feed option for sheep and goats due to its prevalence in these areas. However, it is important to point out that Mimosa tenuiflora hay contains tannins, compounds with antinutritional and astringent properties. Therefore, it is crucial to understand the interaction of natural tannins derived from legumes with a ruminal metabolism in terms of energy and water balance. The inclusion of Mimosa tenuiflora hay as a source of tannins in the diet of hair lambs can potentially have positive effects on animal consumption. ABSTRACT: This study aims to evaluate the effects of increasing tannin levels from Mimosa tenuiflora hay on the intake, digestibility, and balance of nitrogen (N), water, and energy in hair lambs. Thirty-two Santa Ines lambs, at an average age of 150 days and body weight of 26.75 ± 2.29 kg, were randomly assigned to four treatments in a completely randomized design. The treatments consisted of four diets: a control diet, tannin-free, and three diets with increasing levels of total tannin, 26.2, 52.4, and 78.6 g tannin/kg dry matter (DM). Including the total tannins in the lambs’ diet led to a quadratic increase in the intake of nutrients, N-retention (g/day), water intake, water absorption and retention, energy intake, and energy excretion in feces and gases. However, the digestibility of crude protein, neutral and acid detergent fibers, and total carbohydrates decreased. It was observed that there is a correlation between the variable nutrient digestibility and N-ingested and the N-absorbed, N-urinary, and N-retained. However, the N-excreted in feces did not correlate with any of the variables studied. It is recommended to include 33 g/kg DM of total natural tannins from Mimosa tenuiflora hay in the diet of hair lambs, as it improves intake, energy balance, dietary N, and body water composition while reducing the excretion of N-urinary and gas emissions to the environment.