Supplementation with barley or spineless cactus (Opuntia ficus indica f. inermis) cladodes on digestion, growth and intramuscular fatty acid composition in sheep and goats receiving oaten hay

An 84-day experiment, comprising growth and digestibility trials, was conducted to evaluate the effect of replacing barley with spineless cactus (Opuntia ficus indica f. inermis) cladodes (cactus) on feed intake, digestion, blood metabolites, growth and meat quality of male lambs and kids consuming oaten hay. The replacement of barley by cactus decreased drinking water intake (P = 0.002) but had no effect on feed intake, diet digestibility and N balance (P > 0.05). Irrespective of animal species, the barley diet exhibited higher concentrations of allantoin in urine (P = 0.005) and therefore a higher microbial N supply (P = 0.063) than the cactus diet. Average daily gain was greater for the barley than for the cactus diet (P < 0.05), with a tendency for a greater difference for goats (46 g/day vs. 24 g/day) than for sheep (46 g/day vs. 39 g/day). The replacement of barley with cactus did not produce major differences in meat intramuscular fatty acid composition. Vaccenic acid concentration was significantly affected by treatment, being higher in meat of animals offered the cactus diet compared with the barley diet, while the accumulation of conjugated linoleic acid was not affected by the inclusion of cactus in the diet. Total saturated fatty acids, monounsaturated fatty acids (FA) and polyunsaturated FA were not influenced by supplementation with cactus. Despite the higher level of total n-6 FA in kids’ meat, the n-6/n-3 ratio had a very low value, which is favourable for human health. It is concluded that, in terms of equivalent energy, cactus cladodes could replace barley in the diet of lambs and kids without substantial detrimental effects on digestion, growth and meat quality. Therefore, cactus could be used as a cost-effective feed supplement for sheep and goats on low quality roughages raised in dry areas.