Objective.

The objective was to evaluate the effect of rainfall variability on the chemical composition, in vitro degradability and gas production of cacti in Semiarid region.

Materials and methods.

A completely randomized experimental design in a factorial arrangement of 2 rainfall periods (high and low rainfall) x 5 cactus species, with 5 replications was adopted. Cacti evaluated were Pilosocereus gounellei (Weber ex K. Schum). Bly ex Rowl, Cereus jamacaru DC., Opuntia ficus indica Mill, Nopalea cochenillifera Salm. Dyckand Opuntia stricta (Haw.) Haw, all fresh.

Results.

There was an interaction between rainfall variation and cactus species for dry matter, crude protein, neutral detergent fiber and acid detergent fiber (p<0.05), in vitro gas production (p<0.05) and for in vitro dry matter degradability (p<0.05). Among cacti, Pilosocereus gounellei presented a lower proportion of organic matter and an increase in the content of mineral matter in relation to the other cacti (p<0.05).

Conclusions.

The chemical composition, the gas production coefficients and the in vitro degradability were influenced by the cacti species and by the rainfall variation. Cacti species increase the dry matter, crude protein and neutral detergent fiber contents during the low rainfall. Varieties of cactus pear (Opuntia and Nopalea) stood out among the cacti tested in relation to gas production and in vitro degradability.

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