Feeding Value of Singed Walkingstick Cholla

Walkingstick cholla cactus (Opuntia imbricata [Haw.] DC) has been used in New Mexico as an emergency feed during drought for more than 100 years. Most reports present only the chemical composition of walkingstick cholla, and limited data exist regarding its feeding value. Three wethers (avg wt 65 +/- 7 kg) were fed a basal diet of mature blue grama hay (Bouteloua gracilis [HBK] Lag. ex Steud., 9.0% crude protein [CP] and 69.0% neutral detergent fiber [NDF], organic matter [OM] basis) in a replicated 3 X 3 Latin square to determine digestibility of singed walkingstick cholla and to measure nitrogen balance. Treatments consisted of 0%, 15%, and 20% walkingstick cholla in the diet on a dry matter (DM) basis. Walkingstick cholla contained 20.3% DM, 79.6% OM, 36.4% NDF, and 9.0% CP (OM basis). Walkingstick cholla clippings, consisting of green, nonwoody cladodes, were harvested in September. Cactus was singed with a propane torch until no spines remained, chopped, and added to the diet each day. Walkingstick cholla and hay were sampled daily and compiled by period. Total fecal and urine collections were subsampled and frozen for later analysis. Feed and fecal samples were analyzed for DM, OM, NDF, and nitrogen (N); urine samples were analyzed for N. Nutrient digestibilities and N-retention values were calculated. Walkingstick cholla digestibilities were determined by difference. Mean walkingstick cholla DM, OM, NDF, and CP digestibilities averaged 32.6%, 44.3%, 27.9% and 67.6%, respectively. Diet OM and CP digestibilities were similar for all treatments. Diet DM digestibility tended (P = 0.08) to decrease linearly with increasing dietary walkingstick cholla. As walkingstick cholla increased in the diet, NDF digestibility decreased linearly (P = 0.04). Because of its poor feeding value and low DM content, use of walkingstick cholla as an emergency feed should be carefully considered.