Cassava (Manihot esculenta Crantz) foliage as a soybean meal substitute in growing rabbit diets: Impacts on feed intake, digestibility and N retention

Bui Phan Thu Hang^1,2 and Vo Lam^1,2

¹ An Giang University, An Giang Province, Vietnam
volam.agu@gmail.com
² Vietnam National University, Ho Chi Minh City, Vietnam

Abstract

Thirty male crossbred rabbits (New Zealand White × local breed), aged 10 weeks with an initial body weight of 1,295 ± 98 g (mean ± SD), were randomly allocated in a completely randomized design (CRD) consisting of five dietary treatments with six replicates per treatment (one rabbit per experimental unit). The objective was to evaluate the effects of dietary treatments on feed intake, nutrient digestibility and nitrogen retention. In the experimental diets, the protein contribution of soybean meal in the control diet was progressively replaced by cassava foliage meal at levels of 25%, 50%, 75% and 100%.

There were no significant differences in DM, OM and CP intake among the various dietary treatments. However, partial replacement of soybean meal with cassava foliage meal, particularly at inclusion levels up to 50%, had a positive effect on nitrogen retention. These findings suggest that cassava foliage meal is a promising unconventional protein source that can be effectively used to partially substitute soybean meal in the diets of growing rabbits.

Key words: cassava foliage meal, crossbred rabbit, substitute, soybean meal

Introduction

The rising demand for animal protein in many developing countries has placed increased pressure on feed resources, particularly protein-rich ingredients such as soybean meal. While soybean meal remains one of the most commonly used protein sources in monogastric animal nutrition due to its high crude protein content and favorable amino acid profile, its escalating cost, reliance on imports and competition with human food and industrial uses pose significant challenges to sustainable livestock production systems (Lebas et al 1997; Teguia and Beynen 2005; Lopes et al 2017; Lu et al 2019; Alfonso-Avila et al 2022). Cassava (Manihot esculenta Crantz) foliage, a by-product of root harvest, is abundant in tropical regions and has attracted attention due to its relatively high protein content, good palatability and favorable digestibility when properly processed (Phiny et al 2003; Ngoan and Lindberg 2001; Promkot and Wanapat 2005; Régnier et al 2013; Ampapon et al 2016; Bui Phan Thu Hang et al 2022; Vo Lam et al 2022). Rabbits, as herbivorous monogastrics with efficient digestive systems for fiber-rich feeds, are well-suited for utilizing non-conventional forage-based ingredients. Previous studies have shown that cassava foliage can be incorporated into rabbit diets without negatively affecting growth performance, provided that anti-nutritional factors such as hydrocyanic acid are adequately controlled through drying or wilting (Kamatali et al 1992; Tran et al 2011; Wanapat and Kang 2013).

The present study was conducted to evaluate the effects of replacing soybean meal with cassava foliage meal at graded levels on feed intake, nutrient digestibility, nitrogen retention and nitrogen retention efficiency in growing rabbits. The findings aim to provide scientific evidence for the practical use of cassava foliage as a sustainable protein alternative in rabbit production systems.

Materials and Methods

Location and experimental design

The experiment was carried out in a private farm in Thoai Son district, An Giang province. Male crossbred rabbits (New Zealand White x local female) were fed diets composed of homemade concentrate pellet (CP=18%),in which soybean meal was substituted with ground cassava foliage at 0, 25, 50, 75, or 100% based as protein of soybean meal (Table 1). Water spinach (Ipomoea aquatica) provided ad libitum. The experiment was a complete randomized design with 6 replications.

Feeds, animals and management

Sweet cassava foliage (around 50 cm) with leaves, petioles and stems were collected in fields around Long Xuyen city, An Giang province. They were then cut with length 2-3 cm and dried in an oven at 55⁰C for 12 hours. All ingredients used in the diets were previously ground fine for making pellet. Homemade pellets were offered in feeders (amounts offered were based on live weight at the star of experiment) and water spinachforages were hung in bunches above the feed trough with 50% of the daily supply offered at 08.00h and the remainder at 14.00h. Fresh water was provided ad libitum.

Thirty male New Zealand crossbred rabbits, at 10 weeks of age and with initial live weight of 1,295 ± 98 g (Mean ± SD) were housed in individual cages. The rabbits were vaccinated against Hemorrhagic disease and de-wormed with Ivermectin and introduced to the study feeds during a 2 weeks adaptation. The experiment lasted 21 days consisting of 14 days of adaptation and 7 days of collection of faeces and urine.

Chemical analysis

Samples of feeds offered and refused were analysed for DM, CP, CF and ash according to AOAC (2005). The CP content of feedstuffs, refusals, fresh faeces and urine were analysed using the Kjeldahl method.

Statistical analysis

The data from the experiment were subjected to analysis of variance using the General Linear Model (GLM) procedure of Minitab Software Release version 17 (2013). Sources of variation were treatments and error. Polynomial equations were fitted to the changes for N retention using the Excel option in Microsoft software.

Results and discussion

Soybean meal and cassava foliage meal composition

Soybean meal was higher crude protein content than cassava foliage meal (CFM). However, soybean meal was lower crude fiber content than in cassava foliage meal (Table 2).

Feed intake, live weight gain and feed conversion

Dry matter, OM and CP intake were slightly affected replacing soybean meal with CFM (p>0.05; Table 3). This finding indicates that the inclusion of cassava foliage meal did not compromise feed palatability in growing rabbits. However, the replacement with CFM had impact CF intake (p<0.01). The results showed that the CF intake increased with the higher inclusion of CFM. De Blas and Gidenne (2010) emphasized the pivotal role of dietary fiber in modulating the activity of gastrointestinal microbiota, supporting intestinal motility and consequently maintaining gut health in rabbits. However, they also noted that excessively high fiber levels can accelerate digesta passage rate, which may reduce nutrient absorption and overall nutrient intake. Similar conclusions were reported by Nguyen Thi Kim Dong and Nguyen Truong Giang (2008) as well as Gidenne et al (2013).

Apparent nutrient (DM, OM and CP) digestibility was higher for control diet (without cassava foliage meal) than on cassava foliage meal replacement (p<0.01; Table 4). However, the rabbits were offered 50% substitution level of soybean meal with CFM, there are no effect on nutrient digestibility as compared to the control group.

Replacing soybean meal protein with CFM did not affect nitrogen intake among the dietary treatments (p=0.07). However, there was a 13% increase in N retention as substituting soybean meal with CFM up to 50% (Table 5; Figure 1).

Figure 1. Curvilinear trend in N retention/%N intake as replacing soybean meal with cassava foliage meal in the diet of growing rabbits

Conclusions

There was no effect on nutrients consumption as soybean meal substitution by cassava foliage meal in the study diets.

Replacing up to 50% of soybean meal with cassava foliage meal in the diets of growing rabbits improved about 13% in N retention and 17% in N retention efficiency.

Cassava foliage meal represents a potential alternative, non-conventional protein source for partially replacing soybean meal in the diets of growing rabbits.

Acknowledgements

The authors are grateful acknowledge for the infrastructure support for this research from a smallholder rabbit farm in Thoai Son district, An Giang province. We also acknowledge group of students in Animal Science and Veterinary Medicine Department for their technical assistance.

References

Alfonso-Avila A R, Cirot O, Lambert W and Létourneau-Montminy M P 2022 Effect of low-protein corn and soybean meal-based diets on nitrogen utilization. litter quality. and water consumption in broiler chicken production: Insight from meta-analysis. Animal. 16(3). p.100458.

Ampapon T, Wanapat M and Kang S 2016 Rumen metabolism of swamp buffaloes fed rice straw supplemented with cassava hay and urea. Tropical Animal Health and Production. 48. pp.779-784.

AOAC 2005 Official methods of analysis of AOAC international - 18^th edition. Horwitz. W. (Ed.). Association of Official Analytical Chemists. Washington DC. USA.

Bui Phan Thu Hang, Nguyen Van Cop, Dao Thi My Tien and Vo Lam 2022 Effect of fresh foliage leaves on biomass growth of crickets fed rice bran as the basal diet. Livestock Research for Rural Development. Volume 34. Article #36.From http://www.lrrd.org/lrrd34/5/bpthan3436.html

de Blas E and Gidenne T 2010 Digestion of sugars and starch. In: C, de Blas & J, Wiseman (Editors), Nutrition of the rabbit, 2nd edition. CABI. Wallingford, UK: 19-38.

Gidenne T, Kerdiles V, Jehl N, Arveux P, Eckenfelder B, Briens C, Stephan S, Fortune H, Montessuy S and Muraz G 2013 Protein replacement by digestible fibre in the diet of growing rabbits: 2-Impact on performances, digestive health and nitrogen output. Animal Feed Science and Technology, 183: 142-150.

Kamatali A, Moussavou M B and Lebas F 1992 Utilization of cassava leaves in rabbit feeding: Effect of drying methods on cyanide content and nutritive valu . World Rabbit Science, 2(1), 23–27.

Lebas F 2004 Reflections on rabbit nutrition with a special emphasis on feed ingredients utilization . Proceedings of the 8th World Rabbit Congress, Puebla, Mexico, 693–710.

Lopes J C, Harper M T, Giallongo F, Oh J, Smith L, Ortega-Perez A M, Harper S A, Melgar A, Kniffen D M, Fabin R A and Hristov A N 2017 Effect of high-oleic-acid soybeans on production performance. milk fatty acid composition. and enteric methane emission in dairy cows. J. Dairy Sci. 100:1122–1135. https: / / doi .org/ 10 .3168/ jds .2016 -11911.

Lu J, Zhang X, Liu Y, Cao H, Han Q, Xie B, Fan L, Li X, Hu J, Yang G and Shi X E 2019 Effect of fermented corn-soybean meal on serum immunity. the expression of genes related to gut immunity. gut microbiota. and bacterial metabolites in grower-finisher pigs. Frontiers in Microbiology. 10. p.2620.

Ngoan L D and Lindberg J E 2001 Ileal and total tract digestibility in growing pigs fed cassava root meal and rice bran diets with inclusion of fish meal and fresh or ensiled shrimp by-products . Asian-Australasian Journal of Animal Sciences, 14(2), 216–223.

Nguyen Thi Kim Dong and Nguyen Truong Giang 2008 Effect of different levels of neutral detergent fiber in the diets on feed utilization, growth rate and nutrient digestibility of growing crossbred rabbits, MEKARN Workshop 2008: Organic rabbit production from forages, Cantho University. http://mekarn.org/prorab/dong.htm

Phiny C, Preston T R and Ly J 2003 Cassava foliage as protein source for growing rabbits . Livestock Research for Rural Development, 15(8).

Promkot C and Wanapat M 2005 Effect of level of crude protein and use of cottonseed meal in diets containing cassava chips and rice straw for lactating dairy cows. Asian-Australasian Journal of Animal Science.18. 502–511.

Régnier C, Bocage B, Archimède H, Noblet J and Renaudeau D 2013 Digestive utilization of tropical foliages of cassava. sweet potatoes. wild cocoyam and erythrina in Creole growing pigs. Anim. Feed Sci. Technol. 180:44–54.

Teguia A and Beynen A C 2005 Alternative feedstuffs for rabbits. World Rabbit Science, 13(1), 15–26.

Tran G, Heuzé V and Bastianelli D 2011 Cassava leaves. Feedipedia, a programme by INRAE, CIRAD, AFZ and FAO. Retrieved from https://www.feedipedia.org/node/527

Vo Lam, Nguyen Thi Bich Hanh and Bui Phan Thu Hang 2022 Effect of replacing dietary protein with casava leaf meal on performance and nutritional composition of two-spotted crickets (Gryllus bimaculatus). Livestock Research for Rural Development. Volume 34. Number 6. Article #48. http://www.lrrd.org/lrrd34/6/3448vo.html

Wanapat M and Kang S 2013 Enriching the Nutritive Value of Cassava as Feed to Increase Ruminant Productivity, Journal of Nutrirional Ecology and Food Research 1(4).