Optimizing the use of spineless cactus in the diets of cattle: Total and partial digestibility, fiber dynamics and ruminal parameters

•Spineless cactus replacing Tifton hay could interfere the ruminal metabolism.•Higher energy intake occurred with inclusion of 418 g kg−1 spineless cactus.•Total and ruminal digestibility of DM increased with spineless cactus inclusion.•Spineless cactus inclusion did not significant effect on VFA concentration.

The effects of the inclusion of spineless cactus (0; 147; 294; 441 and 588 g kg−1) in replacement of Tifton hay on intake, total and partial (ruminal and intestinal) digestibility obtained from samples of digesta collected in reticulum and omasum, fiber dynamics, and rumen parameters were evaluated. Five rumen fistulated crossbred steers with an average body weight of 380 ± 5.3 kg were assigned to a 5 × 5 Latin square design. The nutrient intake showed a quadratic effect, with a maximum intake of dry matter (8.89 kg d−1; P = 0.012) and digestible organic matter (5.75 kg d−1; P = 0.013) estimated with 339 and 418 g kg−1 of inclusion, respectively. The total (P < 0.01) and ruminal (P < 0.05) digestibility of dry matter (DM), organic matter (OM), crude protein (CP), and degradation rate (Kd) of DM increased linearly. There was no effect on the total and ruminal digestibility, ingestion rate (Ki), passage rate (Kp) and Kd of neutral detergent fiber (NDF; P > 0.05). The maximum pool of NDF (2.46 kg; P < 0.05) was estimated with 201 g kg−1 of spineless cactus inclusion. Except for the proportion of volatile fatty acids that did not differ (P > 0.05) with the inclusion of spineless cactus, there was a linear decrease (P = 0.001) of rumen pH, and a quadratic effect (P < 0.001) of ammonia nitrogen. It is recommended to include 418 g kg−1 of spineless cactus on a DM basis as a replacement of Tifton hay in the diet of cattle to maximize energy intake.