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Title:Avocado meal: A novel dietary fiber source in feline and canine diets
Author(s):Dainton, Amanda Nicole
Advisor(s):de Godoy, Maria R. C.
Contributor(s):Swanson, Kelly S.; Fahey, George C.
Department / Program:Nutritional Sciences
Discipline:Nutritional Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
dietary fiber
avocado meal
Abstract:With the increasing competition between the human food and the pet food industries for ingredient procurement and availability, the pet food industry is looking for new ingredients that do not compete directly with the human food supply chain. Many by-products from the human food processing industry are under-utilized or destroyed and may be suitable ingredients for the pet food industry. Avocado meal, the ground and dried defatted pulp, seed, and skin after avocado oil processing, has not been used in feline and canine diets, but limited research in rats, sheep, and broiler chickens has shown that avocado meal may be an adequate fiber source. The overall objective of this research was to assess the use of avocado meal as a novel dietary fiber source for feline and canine extruded diets in terms of processing, extrusion characteristics, and nutritional adequacy. Three diets containing either avocado meal (AMD), beet pulp (BPD), or cellulose (CD) as the dietary fiber source were formulated to meet the AAFCO (2016) nutrient requirements for adult cats and dogs and processed using a single screw extruder. Samples of each diet were taken at each processing stage (raw avocado meal, raw dry ingredient mixes, preconditioner, extruder, dryer, first coating, and second coating). Diets were fed to 8 neutered male cats for 21 days (d) and 9 intact female Beagles for 14 d. Periods consisted of 17 d or 10 d of diet adaptation, respectively, with 4 d of total fecal and urine collection. One fresh fecal sample was collected per animal per treatment within 15 minutes of defecation. The avocado meal ingredient, diets (including processing stages), feces, and urine were analyzed for macronutrient concentrations and apparent total tract digestibility (ATTD). Fresh fecal samples were analyzed for phenols, indoles, ammonia, short-chain fatty acids [SCFA (acetate, propionate, and butyrate)], and branched-chain fatty acids [BCFA (isobutyrate, isovalerate, and valerate)]. Extrudate samples for all three diets from the extruder (E), dryer (D), and first coater (CO) were analyzed for expansion and texture changes. Our first goal was to characterize the chemical composition of avocado meal and compare the processing of AMD to BPD and CD. The avocado meal ingredient contained moderately low levels of acid-hydrolyzed fat (AHF) (9.1%) and crude protein (CP) (11.5%) with higher levels of total dietary fiber (TDF) (37.4%) [values expressed on a dry matter basis (DM basis)]. Soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) were 27.0% and 10.4%, respectively. We expected chemical composition of the diets to be unaffected by processing, which was observed except for DM, AHF, and fiber fractions. Dry matter decreased with the addition of water and steam at the preconditioner and extruder and increased at the dryer when moisture was removed. Acid-hydrolyzed fat increased at the preconditioner for BPD and CD and at the coater for all three diets due to the addition of choice white grease. In general, TDF and IDF concentrations decreased after extrusion and were diluted with the addition of fat at the coater. Extrudates of AMD and BPD tended to have greater expansion and lower hardness compared to CD. Our second goal was to assess avocado meal as a novel dietary fiber for feline diets. In most cases, AMD performed similarly to BPD in terms of macronutrient apparent total tract digestibility and fecal fermentative end-product concentrations. While total and daily fecal output, daily DM intake, and ATTD of DM, organic matter (OM), and gross energy (GE) were not affected, CD had lower (P < 0.05) crude protein (CP) ATTD than did BPD and AMD, higher (P < 0.05) acid-hydrolyzed fat (AHF) ATTD than did AMD, with BPD not different (P > 0.05) from either, and lower (P < 0.05) TDF ATTD than either AMD or BPD. Beet pulp diet resulted in higher (P < 0.05) fecal scores compared to CD, and AMD was intermediate (P > 0.05). Fecal SCFA, acetate, and isobutyrate concentrations were greater (P < 0.05) for AMD and BPD than CD. The same relationship (P < 0.05) was noted with propionate and BCFA with AMD and CD, but BPD did not differ (P > 0.05) from either. Cats remained healthy on all treatments except for creatinine concentration, which are historically above reference ranges in this colony. A monadic acceptability test for AMD with only one coating (14.2% AHF, DM basis) resulted in poor and variable food intake, supporting our findings that an additional coating (16.7% AHF, DM basis) was needed to increase palatability. Our third goal was to determine if avocado meal could be a dietary fiber source for canines. More often than not, AMD performed similarly to CD. As-is daily fecal output and fecal scores were greater (P < 0.05) for BPD than for AMD and CD. Cellulose diet had the greatest (P < 0.05) fecal DM, followed by AMD (P < 0.05), then BPD (P < 0.05). Fecal pH was lower (P < 0.05) for BPD and AMD than for CD. As with the feline study, only CP, AHF, and TDF ATTD were affected by the treatments. Avocado meal diet and CD had greater (P < 0.05) CP ATTD than did the BPD. In contrast, cats fed CD had greater (P < 0.05) AHF ATTD and lower (P < 0.05) TDF ATTD than cats fed AMD or BPD. In terms of fecal fermentative end-products, BPD resulted in greater (P < 0.05) concentrations of total SCFA, acetate, and propionate than did AMD and CD. Beet pulp diet also had lower (P < 0.05) levels of isovalerate, ammonia, and total phenols and indoles than AMD and CD. Fecal butyrate concentration was lower (P < 0.05) for CD than for AMD and BPD, but BPD had a greater (P < 0.05) concentration of valerate than did CD and AMD. Dogs remained healthy during the study and serum metabolites were within reference ranges for adult dogs among all dietary treatments, even though statistical differences were detected for a few serum metabolites. As with the feline study, monadic food acceptability tests resulted in low consumption, indicating that additional fat and palatant were needed to increase acceptability of AMD (14.2% AHF, DM basis vs. 17.8% AHF, DM basis). Based on the research in this study, avocado meal appears to be an acceptable dietary fiber source for canines and felines. It processes well within standard extrusion conditions of commercial pet foods and resulted in physiological effects similar to standard fiber sources for the pet food industry. Although acceptability of AMD was low prior to the second coating, a commercial pet food would likely not contain as much avocado meal as the diets tested herein (18.67%, as-is basis), possibly minimizing the less favorable food acceptability outcomes observed in our studies. More importantly, no detrimental effects on health status of the cats and dogs fed the AMD were observed, which does not support current safety concerns related to the consumption of avocado by domestic dogs and cats due to acute persin toxicity, at least not during a feeding period of 14-21 d evaluated herein.
Issue Date:2018-04-26
Rights Information:Copyright 2018 Amanda Dainton
Date Available in IDEALS:2018-09-04
Date Deposited:2018-05

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