Kiatti, Dieu donné (2024) Sustainability of Animal Nutrition and Environmental Protection Approach by Recycling Fruit By-Products. [Tesi di dottorato]

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Abstract

The crop production is continuously increasing to meet the world population demand which is also growing. Among the crops, fruit and vegetable production generates a huge amount of waste from the farm to the table during the harvesting time, transportation, and processing which is thrown due to their perishability and lack of knowledge to reuse them in other fields. The decomposition of these wastes contributes to environmental pollution and climate change. However, the breeders, particularly in tropical and subtropical areas, are facing the challenge of feeding their animals year-round due to the long dry season and the key role of natural pasture in the production system. In addition, the cost of conventional feedstuff, such as maize, and its competition between humans and animals, weakens the livestock production system in tropical and subtropical areas. The thesis's general goal was to propose sustainable animal nutrition strategies in West Africa to preserve the environment and the circular economy through cashew, pineapple, and mango by-product recycling in livestock nutrition. To achieve the aim, the AOAC methods and in vitro gas production technique (IVGPT) were applied to the by-products to determine chemical composition, polyphenol, sugar, and in vitro fermentation patterns. Sheep rumen liquor and pig caecum content, in ruminant and monogastric respectively, were used for the in vitro fermentation trials evaluating the digestibility, fermentation kinetics, gas, and end-product production. To study by-products in monogastric nutrition, gastrointestinal digestion was performed using enzymes (pepsin and pancreatin) before microbial digestion. Some by-products were also tested in vivo on West African Dwarf (WAD) lambs to evaluate intake, apparent digestibility, growth performance, and feeding behavior. In particular, the thesis opens (Chapter 1) with a general introduction dressing the literature on animal nutrition in West Africa including by-products, successively followed by the studies of each specific objective (Chapter 2 – 5) and finishes with some considerations and future possible investigations (Chapter 6) to reach the principal goal in the nearby future. The first experimental study (Chapter 2) focused on cashew apple by-products (CABP; whole, up, down, middle part, and pomace) from red and yellow varieties collected in the Sudanian Zone (SZ) and Sudano-Guinean Zone (SGZ) of the West Africa area. The study showed that the by-product characteristics depend more on the sampling area than on variety. The dry matter (DM) in the SZ and SGZ varied from 12.76 to 26.10 % and 7.41 to 22.9 %, respectively. The pomace showed the highest crude protein, lipids, and neutral detergent fiber (NDF) content (SZ: 9.48, 3.94, and 31.7 % DM; SGZ: 14.0, 4.94 and 34.1 % DM, respectively) but the lowest non-structural carbohydrate (NSC) and sugar for both zones. Regarding the in vitro fermentation, the organic matter degradability (OMD) was higher in the middle part (73.7 %) and whole apple (61.6 %) of SZ and SGZ, respectively. In contrast, the pomace from both zones showed the lowest in vitro fermentation parameters. The total polyphenols were more concentrated in the CABP from SZ (whole: 2736 μg/g DW; pomace: 3813 μg/g DW) compared to those from SGZ (whole: 1755 μg/g DW; pomace: 1374 μg/g DW). Results suggest that CABP should be collected in each - 11 - cultivation zone regardless of variety, separating pomace from other by-products and might be used as alternative feedstuff for small ruminants during the dry season in the West Africa region. The individual pineapple by-products (PBP; crown, bud end, peel, core, and pomace) from two West African varieties (Smooth Cayenne - SC and Sugarloaf - SL) were characterized in the second experiment (Chapter 3). The results showed a low DM superimposable between varieties, averaging 17.7 %. On a DM basis, pomace showed the highest protein content (SC 8.10 % and SL 8.81 %, p < 0.001), whereas the crown showed the highest (p < 0.001) NDF content (47.6 % and 39.0 % for SC and SL, respectively). Due to the high sugar content, the core and pomace showed high in vitro OMD (SC: 85.1 % and SL: 84.0 %), estimated metabolizable energy (ME; SC: 7.91 KJ/kg and SL: 7.66 KJ/kg), and volatile fatty acid production (SC: 96.9 mmol/g and SL: 90.6 mmol/g). Based on chemical composition and in vitro digestibility results, this study suggests that pineapple by-products have the potential to be used in ruminants’ nutrition, considering the crown, bud end, and peel as fiber sources and the core and pomace as substitutes or supplements to concentrate feedstuffs. In the third experimental study (Chapter 4), three diets containing different levels (CTR: 0 %, Test 1: 14 %, and Test 2: 28 %) of industrial pineapple by-products (IPBP) were tested either in vitro with IVGPT and in vivo on No. 24 WAD lambs in three groups completely randomized design. The in vitro results related to the inclusion of IPBP in lambs’ diet revealed the improvement of ME (8.32 and 9.13 vs. 7.68 MJ/kg, for Test 1, Test 2, and CTR, respectively), fermentation rate, and branched chain fatty acid production. The in vivo experiment showed that IPBP in the WAD lamb diet increased nutrient intake and apparent digestibility (except OM). The OM intake and apparent digestibility varied from 504 to 597 g/day and 81.6 - 84.3 %, respectively. The animals’ growth performances (daily weight gain, DWG) ranged between 61.3 to 75.5 g/day and were slightly higher in the Test 2 group without significant differences. The feeding time and number of ruminating chews per bolus increased while chewing time per ruminated bolus decreased when IPBP inclusion increased in the WAD lamb diet. These findings suggest that IPBP can be included in the WAD sheep diet up to 28 % without detrimental effects. The by-products evaluated for pig nutrition (e.g., cashew, pineapple, and mango) were tested in a two-step in vitro trial (Chapter 5). A low DM content specifically in the pomace, peel, and whole apple (13.0 – 27.2 %) was found while higher lipids were observed for cashew nut testa (26.4 % DM) and mango kernel (11.2 % DM). The by-products investigated fall within the interval of referenced feeds such as corn meal, Soybean meal, and beet pulp for structural carbohydrates (NDF: 7.6 – 47.1 % DM) and protein (7.65 – 51.2 % DM) except mango by-products due to its low protein (2.51 – 4.69 % DM) content. The total DM digestibility, short-chain fatty acid, and gas production were low for cashew by-products stopped after 48 h of incubation while the same parameters for other by-products stopped at 72 h were not so far to the referenced feeds. Specifically, the results suggest that pineapple pomace, cashew whole apple, pomace, and testa can be considered as feedstuff in fattening pigs, presenting characteristics partly - 12 - similar to beet pulp. Mango peel and kernel should be combined with a protein source, such as Soybean meal, to feed pigs. In conclusion, the studies conducted in the current thesis suggest the possibility of using West African fruit by-products derived from cashew, pineapple, and mango processing in livestock nutrition. However, the studies point out the low dry matter content of these by-products and encourage future investigations on preservation issues. The future research must include also in vivo experiments with animal product quality evaluation to produce more data related to cashew, pineapple, and mango by-products which will encourage their adoption in livestock feeding plans.

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