Effects of sun-dried Opuntia ficus-indica cladodes on digestive processes in sheep

English: The effects of incremental inclusion levels (0, 24, and 36%) of sun-dried and coarsely ground Opuntia cladodes in balanced sheep diets on certain aspects of the digestive processes were investigated in sheep. The treatment diets (TO, T24 and T36) comprised respectively (air dry basis) 0, 240 and 360 g/kg sun-dried, coarsely ground Opuntia; 660, 410 and 285 g/kg coarsely ground lucerne hay; 300 g/kg yellow maize meal; 0, 10 and 15 g/kg feed grade urea; and 40 g/kg molasses meal. Eighteen seven month old Dorper wethers were randomly divided and allocated according to body weight into three groups of six animals each. The three groups were each fed one of the three treatment diets (TO, 1'24, or 1'36). The experimental animals were housed indoors in individual metabolism crates and fed ad libitum during the 7-day or 14-day trial periods. The feed and water intake, urine and faeces excretion, as well as the apparent digestibility of the diets and specific nutrients were evaluated and compared. At the end of the 7-day trial period a random selection of nine animals, three wethers from each treatment diet, were slaughtered. The other nine animals were slaughtered at the end of the 14-day trial period. The GIT (gastrointestinal tract) of each wether was carefully removed and dissected. Samples of digesta contents and also intestinal tissue from different sections of the GIT were collected and analyzed. In general, incremental inclusion of Opuntia cladodes to a level of 36% in the diets for Dorper wethers resulted in small decreases of OM, CP and GE of the diets and a considerable drop in the ADF and NDF fractions of the feed. Although the EE content of diets was small, inclusion of sun-dried and coarsely ground Opuntia cladodes at these levels increased the lipid content. The results obtained in this present study concur with the general recommendation to add protein (including NPN) and energy sources to sheep diets with high inclusion levels of sun-dried and coarsely ground Opuntia cladodes. The inclusion of sun-dried and coarsely ground Opuntia cladodes at 24 and 36% levels as partial substitution of lucerne hay in diets of Dorper wethers had no adverse effects on feed intake during the 14-day period of the feeding trial. The feed intake of the Dorper wethers tended to increase with incremental inclusion levels of Opuntia cladodes in the diets, especially during the 14-day trial period. This suggested that incremental levels of sun-dried and coarsely ground Opuntia cladodes up to a level of 36% did not affect the acceptability of the diets for Dorper wethers negatively and may even improve the acceptability of the diets. The voluntary daily water intake and urine excretion of the Dorper wethers increased with the incremental inclusion of sun-dried and coarsely ground Opuntia cladodes up to a level of 36% in the diet. Although these differences were negligible during the :first 7-day trial period, the differences were more evident during the 14-day trial period. The Dorper wethers fed on a diet with 36% sun-dried and coarsely ground Opuntia cladodes drank on average about 1 100 ml/day more water and produced 237 ml urine/day, than those fed the control diet (TO) without Opuntia cladodes. This suggested that a substantial part of the induced higher water intake was secreted via another route, namely through the faeces. The faeces excreted by Dorper wethers fed on diets containing Opuntia cladodes were softer in consistency and contained visibly more water than those produced by animals feel on the control diet without Opuntia cladodes. The daily nutrient intake of DM, CP, GE, and OM was not affected by the inclusion of Opuntia cladodes in the diet, but the intake of ADF and NDF tended to decrease with incremental levels of Opuntia cladodes and the concomitant reduction of lucerne hay in the diet. It is important to note the increases in apparent digestibility of the DM, CP, and lipids of the diet as the inclusion levels of Opuntia cladodes increase to a 36% inclusion level. The chemical composition of the digesta collected from different parts of the GIT of Dorper wethers fed on the three experimental diets appears not have been changed by the inclusion of sun-dried and coarsely ground Opuntia cladodes up to a level of 36% of the diet. Most changes that were observed at the end of the first 7-day trial period of the study occurred in the reticule-rumen, omasum and in the lower GIT (colon and rectum). The inclusion of Opuntia cladodes to a level of 36% in the diet had a positive increasing effect on CP while the ADF content of the digesta was reduced. Very little changes were noted in the digesta contents of the small intestine. The histological results showed no visible pathologic alterations in the mucosa of the GIT of Dorper wethers when ingesting sun-dried and coarsely ground Opuntia cladodes to a level of 36% in diets for a period of 14 days. Therefore, the reasons and mechanism whereby wet faeces are produced when sheep is fed diets containing considerable amounts of sun-dried and coarsely ground Opuntia cladodes were not histological demonstrable. Based on the results of this study, it is concluded that inclusion of sun-dried and coarsely ground Opuntia cladodes as partial substitution of lucerne in balanced sheep diets has no detrimental effects at a 36% inclusion level. No detrimental effects were observed in feed intake, apparent digestibility, and histological characteristics of the GIT mucosa of young Dorper wethers. Further research is needed to establish the optimum inclusion level of sun-dried and coarsely ground Opuntia cladodes in the diet of different ruminant species. It is also important to further investigate the effects of Opuntia cladodes in ruminant diets on the digestive processes and especially also on the renal functions. The physiological and/or biochemical mechanisms (enteric secretion and/or absorptive alterations) responsible for the production of wet faeces in ruminants ingesting considerable amounts of Opuntia cladodes require further investigation.