Substitution of silage by soybean hulls in tropical forage-based dairy cow production system during the dry season.

Supplementary roughage during the dry season in forage-based systems mitigates the adverse effects of lower pasture availability and nutritional quality in forage-based milk production. This study evaluated the effects of soybean hulls as supplementary roughage on milk production, composition, and nitrogen utilization in lactating dairy cows in tropical forage-based systems during the dry season and verify the possibility of fully replacing silage with soybean hulls. Twelve multiparous Holstein-Zebu crossbred cows (453 ± 4.97 kg) in mid-lactation were used in a 4 × 4 Latin Square design. The cows grazed Urochloa brizantha cv. Marandu pasture with a continuous stocking rate and were subjected to four supplementation strategies: supplementation only with concentrate (Control); concentrate plus soybean hulls replacing 35% of forage intake (Soybean Hulls); concentrate plus corn silage replacing 50% of forage intake (Corn Silage); and concentrate plus sorghum silage replacing 50% of forage intake (Sorghum Silage). Soybean hulls and corn silage were the most consumed supplementary roughages (P = 0.012). Soybean hulls enhanced daily intakes of ether extract (EE) and neutral detergent fiber (NDF) (P < 0.05). Milk production increased with soybean hull supplementation (P < 0.001), however, did not differ to corn silage when corrected for 3.5% fat content. Milk fat and protein did not differ among treatments (P > 0.05), but lactose and total solids were higher in the soybean hull and control groups (P < 0.05). Soybean hull supplementation reduced milk urea nitrogen (MUN) compared to corn silage (P = 0.022). Overall, soybean hulls improved feed intake, milk production, and nitrogen utilization in dairy cows, supporting their use as a viable alternative to silage in forage-based tropical systems.