Effects of extruded tannin-enriched protein concentrates on intake and digestibility in sheep fed a corn silage-based diet

Abstract

Tannins are plant-derived polyphenolic compounds with the potential to improve nitrogen utilization and reduce methane emissions in ruminants when included in diets. However, their dietary inclusion can negatively affect feed intake and digestibility, particularly in forage-based diets, due to the formation of complexes between tannins and fiber. Therefore, incorporating tannins in the concentrate during the extrusion process could be a strategy to mitigate their negative impact on fiber digestion. This study aimed to evaluate the impact of including tannin-treated protein concentrates during the extrusion process on intake and digestibility in sheep fed maize silage-based diets. A digestibility trial was conducted in metabolic cages using eight castrated male Santa Inês lambs. The experimental design was a 4×4 double Latin square, with four periods of 17 days each, including 10 days of adaptation and 7 days of sample collection. Four experimental diets were offered, consisting of 60% corn silage and 40% concentrate (dry matter (DM) basis) composed of corn grain and one of the following protein sources: soybean meal (SM), soybean expeller (SE), SE plus tannins diluted in water (TA) or in sodium hydroxide solution (TH). Tannins were added to 1% of the SE. During the sample collection period, individual intake and fecal output were recorded. Samples of feeds, refusals, and feces were collected and analyzed for DM, organic matter (OM), and neutral detergent fiber (NDF), and their digestibility were subsequently calculated. Statistical analysis was carried out using the MIXED procedure of SAS. The inclusion of SE, TA or TH, did not affect intake or digestibility of DM, OM, or NDF (P > 0.05). The intake of digestible OM was also similar between treatments (P > 0.05). Including tannin-treated protein concentrates in maize silage-based diets did not affect intake or digestibility of DM and NDF in sheep.