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

[摘要] English: The effects of incremental inclusion levels (0, 24, and 36%) of sun-dried and coarsely groundOpuntia cladodes in balanced sheep diets on certain aspects of the digestive processes wereinvestigated in sheep. The treatment diets (TO, T24 and T36) comprised respectively (air drybasis) 0, 240 and 360 g/kg sun-dried, coarsely ground Opuntia; 660, 410 and 285 g/kgcoarsely 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 randomlydivided and allocated according to body weight into three groups of six animals each. Thethree groups were each fed one of the three treatment diets (TO, 1'24, or 1'36). Theexperimental animals were housed indoors in individual metabolism crates and fed ad libitumduring the 7-day or 14-day trial periods. The feed and water intake, urine and faecesexcretion, as well as the apparent digestibility of the diets and specific nutrients wereevaluated and compared. At the end of the 7-day trial period a random selection of nineanimals, three wethers from each treatment diet, were slaughtered. The other nine animalswere slaughtered at the end of the 14-day trial period. The GIT (gastrointestinal tract) of eachwether was carefully removed and dissected. Samples of digesta contents and also intestinaltissue 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 forDorper wethers resulted in small decreases of OM, CP and GE of the diets and a considerabledrop 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 thelipid content. The results obtained in this present study concur with the generalrecommendation to add protein (including NPN) and energy sources to sheep diets with highinclusion levels of sun-dried and coarsely ground Opuntia cladodes.The inclusion of sun-dried and coarsely ground Opuntia cladodes at 24 and 36% levels aspartial substitution of lucerne hay in diets of Dorper wethers had no adverse effects on feedintake during the 14-day period of the feeding trial. The feed intake of the Dorper wetherstended 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-driedand coarsely ground Opuntia cladodes up to a level of 36% did not affect the acceptability ofthe 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 theincremental inclusion of sun-dried and coarsely ground Opuntia cladodes up to a level of36% 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 adiet with 36% sun-dried and coarsely ground Opuntia cladodes drank on average about 1 100ml/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 waterintake was secreted via another route, namely through the faeces. The faeces excreted byDorper wethers fed on diets containing Opuntia cladodes were softer in consistency andcontained visibly more water than those produced by animals feel on the control diet withoutOpuntia cladodes.The daily nutrient intake of DM, CP, GE, and OM was not affected by the inclusion ofOpuntia cladodes in the diet, but the intake of ADF and NDF tended to decrease withincremental levels of Opuntia cladodes and the concomitant reduction of lucerne hay in thediet. It is important to note the increases in apparent digestibility of the DM, CP, and lipids ofthe 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 Dorperwethers fed on the three experimental diets appears not have been changed by the inclusionof sun-dried and coarsely ground Opuntia cladodes up to a level of 36% of the diet. Mostchanges that were observed at the end of the first 7-day trial period of the study occurred inthe reticule-rumen, omasum and in the lower GIT (colon and rectum). The inclusion ofOpuntia cladodes to a level of 36% in the diet had a positive increasing effect on CP whilethe ADF content of the digesta was reduced. Very little changes were noted in the digestacontents of the small intestine.The histological results showed no visible pathologic alterations in the mucosa of the GIT ofDorper wethers when ingesting sun-dried and coarsely ground Opuntia cladodes to a level of36% in diets for a period of 14 days. Therefore, the reasons and mechanism whereby wetfaeces are produced when sheep is fed diets containing considerable amounts of sun-driedand coarsely ground Opuntia cladodes were not histological demonstrable.Based on the results of this study, it is concluded that inclusion of sun-dried and coarselyground Opuntia cladodes as partial substitution of lucerne in balanced sheep diets has nodetrimental effects at a 36% inclusion level. No detrimental effects were observed in feedintake, apparent digestibility, and histological characteristics of the GIT mucosa of youngDorper wethers.Further research is needed to establish the optimum inclusion level of sun-dried and coarselyground Opuntia cladodes in the diet of different ruminant species. It is also important tofurther investigate the effects of Opuntia cladodes in ruminant diets on the digestiveprocesses and especially also on the renal functions. The physiological and/or biochemicalmechanisms (enteric secretion and/or absorptive alterations) responsible for the production ofwet faeces in ruminants ingesting considerable amounts of Opuntia cladodes require furtherinvestigation.

[发布机构] University of the Free State