Effect of diets containing cactus cladodes on physical and histomorphometric parameters, and bone mineral content of feedlot lambs and goats

Abstract

This study aimed to investigate the effects of the parcial substitution of Tifton hay by cactus cladodes on macrominerals intake, physical and histomorphometric characteristics, and bone mineral content of lambs and goats in feedlot. Two parallel studies, with the same dietary treatments, were performed: the first one (study 1) lasted 86 days, and thirty-six Santa Inês lambs, uncastrated males, with an average initial body weight (BW) of 22.0 ± 2.9 kg were used; in second study (study 2), lasting 100 days, thirty-six crossbred goats, castrated males, with an average initial BW of 19.0 ± 2.8 kg were used. In both studies, the animals were distributed in a completely randomized design, with three treatments and twelve replicates. Experimental diets consisted of in a diet containing Tifton hay as exclusive roughage (control) and two more diets in which the hay was partially (75%) replaced by Miúda or Orelha de Elefante Mexicana (O.E.M.) cactus cladodes. At the end of the feedlot periods, lambs and goats were slaughtered and the 13th rib of carcass of each animal (both antimeres) was collected for physical and histological analysis, and macromineral dosage. No significant differences (P < 0.05) were observed between physical properties of the ribs of lambs and goats fed with cactus cladodes varieties, compared to the control group. Cactus cladodes-based diets increased the intake of Ca (P = 0.001), and Mg (P = 0.001) by lambs and goats, and decreased the Na intake by lambs (P = 0.001). Lambs fed with cactus cladodes-based diets tended to deposit less Ca (g/kg ash; P = 0.061) in the bone tissue, and the Mg content was higher (P = 0.002). In addition, Miúda cactus cladodes promotes lower intake (P = 0.014) and lower bone concentration (P = 0.024) of P, compared to the control diet. In goats, the diet containing Miúda cactus cladodes decreased P, Na and K intakes (P < 0.05). Goats fed with cactus cladodes-based diets tended to deposit less Ca (g/kg DM; P = 0.063) in the bone tissue. Regardless of variety, cactus cladodes changed the number of osteocytes and Havers canals, and bone matrix thickness of small ruminants. In conclusion, the partial substitution (75%) of Tifton hay by cactus cladodes in lambs and goats diets is capable to increase the macrominerals intake and, consequently, improve bone Mg deposition in lambs, without altering the physical properties of the ribs of both species. However, cactus cladodes-based diets cause changes in bone histomorphological parameters.