Influence of Inclusion of Cactus Pear in <i>Senna obtusifolia</i> Haylage on Nutritional, Ruminal, and Metabolic Parameters of Sheep

This study evaluated the effects of increasing levels of cactus pear ( Opuntia spp.) included in haylage of Senna obtusifolia on intake, ingestive behavior, nutrient digestibility, nitrogen balance, ruminal and blood parameters, and performance of fattening sheep. Twenty‐four uncastrated Santa Ines × undefined breed male lambs (initial body weight: 31.16 ± 2.65 kg) were randomly assigned to diets containing 0%, 35%, or 70% cactus pear (DM basis), with eight replicates per group. Dry matter intake (DMI) was greater at 35% inclusion ( P = 0.022) than at 0% or 70%. Digestibility of most nutrients was not significantly altered, except for crude protein (CP), which increased at 35% and 70% inclusion. Neutral detergent fiber assayed with a heat‐stable amylase and expressed as residual ash ( a NDFom) intake decreased at 70% ( P = 0.032), while ether extract intake was unaffected ( P = 0.302). Sheep fed 35% cactus pear showed higher DMI, final weight, total and daily gains, and feed conversion efficiency compared to 0% and 70%, which were similar. Rumination time was lower, while ruminating DM and a NDFom efficiency rate were higher at 35% cactus inclusion compared to control (0%), while a NDFom eating rate and amount of chewing (g DM/bolus) were lower at 70% cactus inclusion ( P &lt; 0.05). Dietary treatments influenced ruminal fermentation parameters, with elevated ammonia nitrogen (NH 3 ‐N) concentrations and protozoal populations ( P = 0.045) observed in ruminal fluid of sheep fed 70% cactus inclusion in Senna obtusifolia haylage compared to those fed 0% and 35% ( P = 0.027). Combining cactus pear with Senna obtusifolia haylage at a 35:65 ratio resulted in higher dietary quality and superior fattening performance of sheep over a 40‐day finishing period.