Silagem mista de palma forrageira e sorgo biomassa na alimentação de vacas mestiças em lactação

Abstract

Forage cactus stands out as a feeding strategy for ruminants in semiarid regions due to its high water content, adaptability to arid environments, and favorable nutritional composition. However, its exclusive use is limited by its low effective fiber and crude protein content. Ensiling with fibrous forages, such as biomass sorghum, emerges as a viable alternative to maximize its use in diets for dairy cow. The study aimed to identify the best proportion of forage cactus in silage with biomass sorghum BRS 716 for crossbred cows, evaluating the silage's nutritional quality, nutrient intake and digestibility, ingestive behavior, nitrogen balance, microbial synthesis, ruminal fermentation, and milk production and composition. The experiment was carried out at Experimental Farm of the Unimontes (Janaúba/MG), using 10 lactating cows (471.5 ± 52.8 kg) in a 5 × 5 simultaneous Latin square design, over 90 days. Five diets with increasing levels of inclusion of cactus (0%, 15%, 30%, 45%, and 60%) in silage with biomass sorghum (based on natural matter) were tested. The roughage:concentrate ratio of the diets was approximately 75:25. Data were subjected to analysis of variance and regression at 5% significance level. Increasing levels of cactus in the silage decreased intake (P = 0.01) and digestibility (P < 0.05) of NDFap, respectively, by 12.03 g/day and 2.14% for each additional 1% of inclusion of cactus in the silage. In contrast, there was increase in the intake (P < 0.05) and digestibility (P = 0.01) of non-fibrous carbohydrates (14.87 g/day and 0.0008% for each 1% of inclusion, respectively), besides reducing the intake of ether extract (0.67 g/day per percentage point). The lactic acid content increased (P = 0.05) by 0.8 g/L for each 1% increase in cactus, while the other ruminal parameters and microbial production remained similar between the inclusion levels. The increase in cactus extended the feeding time per kg of NDFap (P = 0.01) by 0.298 min/kg NDFap and reduced water intake (P < 0.01), decreasing approximately 0.26 L/day for each additional 1% of cactus. The difference in body weight showed a quadratic effect (P = 0.05) with maximum weight point at 31.4% of cactus, while milk production and composition remained similar between treatments, with the exception of UNM, which decreased with cactus inclusion. It is concluded that cactus can be included in silage at levels of up to 60% of the natural matter of silage with biomass sorghum, without compromising ruminal fermentation parameters and the productive performance of crossbred lactating cows.