Abstract :
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 microbialNsupply (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.
