Citation of this paper

Coconut meat residue supplementation in Californian rabbit diets improves nutrient digestibility and growth performance

Nguyen Thi Kim Dong and Nguyen Van Thu

Tay Do University, 68 Tran Chien Street, Thanh My Area, Cai Rang Ward, Can Tho City, Vietnam
ntkdong@tdu.edu.vn

Abstract

A study was conducted to determine the optimal supplementation level of coconut meat residue (CMR) in the diets of growing Californian rabbits, with a focus on feed intake, nutrient digestibility and growth performance. A total of 60 Californian rabbits, with initial body weights of approximately 600, 850 and 1100 g, were assigned to a randomized complete block design consisting of five dietary treatments and three weight-based blocks. The dietary treatments included CMR supplementation at 0, 10, 20, 30 and 40 g/rabbit/day, designated as CMR0, CMR10, CMR20, CMR30 and CMR40, respectively. The trial lasted for 12 weeks. Results indicated that dry matter (DM), organic matter (OM), ether extract (EE) and metabolizable energy (ME) intakes increased (p<0.01) with higher levels of CMR supplementation, with the highest intakes observed in CMR30 and CMR40 groups. Rabbits fed the CMR30 diet achieved the greatest final live weight (2.663 kg) and daily weight gain (21.7 g/day), along with the highest economic return. Digestibility coefficients for DM, OM, EE and neutral detergent fiber (NDF) were also improved (p<0.01) with increasing CMR levels. In conclusion, supplementation of coconut meat residue at 30 g/rabbit/day optimizes growth performance and nutrient utilization in growing Californian rabbits and is therefore recommended for practical application in rabbit production.

Keywords: coconut meat waste, digestion, growth rate, nutrient utilization, rabbit

Introduction

Rapid industrialization in developing countries has increasingly encroached upon agricultural land, posing significant challenges to food production and security. In response, there is a growing need to adopt efficient and sustainable livestock systems. Among various options, rabbit farming emerges as a promising strategy due to rabbits' rapid growth rates, high feed conversion efficiency, adaptability to diverse environments and relatively low production costs. Moreover, rabbits can be raised using simple, locally available housing and can thrive on a variety of natural feed resources and agro-industrial by-products such as soybean meal, soya waste, sweet potato vines and natural grasses.

To optimize rabbit production, particularly in smallholder systems, identifying cost-effective and nutritionally adequate feed supplements is essential. The Mekong Delta of Vietnam, a key coconut-producing region, generates large quantities of coconut-based food products -including rice dishes, sweet soups, cakes and candies processed using coconut milk and meat to enhance flavor and texture. The extraction of coconut milk from coconut meat yields a substantial quantity of fresh coconut meat residue, which remains underutilized despite retaining a significant nutritional value, particularly in fat content (34- 41%) (Conatfood, 2013). Mohd Nor et al (2017) reported that coconut meat residue contains 55.4% moisture, 1.69% crude protein, 17.3% crude fat and 25.7% carbohydrates. Also, Harnentis et al (2022) showed that coconut meat waste contains low crude protein (5.81%), however high in ether extraction and carbohydrate contents. This by-product was supplemented in diets, improved feed intake and body weight gain for chicken. Previous studies have suggested the potential of this residue as a dietary supplement for ruminants, goats, pigs and fish (Tuong and Tuyen, 2024; Trung and Truong, 2024; Nhanthuy Food, 2025). Given its availability and nutrient profile, coconut meat residue may also be a viable feed supplement for rabbits when combined with other agricultural by-products. However, to date, no studies have evaluated its effects on the performance of growing Californian rabbits. This study aims to evaluate the effects of incorporating coconut meat residue into the diet of growing Californian rabbits, focusing on nutrient intake, digestibility, growth performance and economic efficiency. The findings are expected to contribute to the development of more sustainable and cost-effective feeding strategies for rabbit production in coconut-producing regions.

Materials and methods

Experimental Animals

The experiment was conducted on 60 purebred Californian rabbits, divided into three weight classes with average body weights of 600 g, 850 g and 1100 g per animal. All rabbits were vaccinated against parasitic and hemoggaric diseases prior to the experiment.

Experimental Design

The study consisted of two phases: a growth trial and a nutrient digestibility trial. A completely randomized block design was used with five dietary treatments and three blocks. The five treatments corresponded to diets supplemented different coconut meat residue levels of 0 g, 10 g, 20 g, 30 g and 40 g per rabbit per day. The three blocks were based on initial body weight groups (600 g, 850 g and 1100 g). Each experimental unit consisted of 4 rabbits (2 males and 2 females). The growth trial lasted for 12 weeks. The nutrient digestibility trial was conducted when the rabbits reached 12 weeks of age and lasted 7 days. Feed ingredient composition of diets in the experiment was showed in Table 1.

Table 1. Feed ingredient composition of diets in the experiment (g/rabbit/day)
Feed	Treatment
Feed	CMR 0	CMR 10	CMR 20	CMR 30	CMR 40

Coconut meat residue (CMR)	0	10	20	30	40
Soya waste	90	90	90	90	90
Extraction soybean meal	10	10	10	10	10
Operculina turpethum	80	80	80	80	80
Brachiaria mutica	Ad-libitum	Ad-libitum	Ad-libitum	Ad-libitum	Ad-libitum
CMR0, CMR10, CMR20, CMR30, CMR40 were diets supplemented Coconut meat residue at levels of 0, 10, 20, 30 and 40g/rabbit/day, respectively.

Housing, feeds and management

The experiment was conducted in 15 individual cages, each equipped with a feeder and drinker. Nylon mesh and plastic sheets were used to collect feces, urine and feed refusals.

Forages (Brachiaria mutica and Operculina turpethum) were harvested daily surrounding the experimental farm area. Soya waste and extraction soybean meal were sourced locally. Coconut meat residue was purchased from local factory, then sun-dried to increase dry matter content and improve its intake. All feed ingredients were analyzed for chemical composition before and during the trial. Feed given was weighed before feeding; refusals were collected and weighed in the next morning. Every two weeks, feed and refusal samples were analyzed. Rabbits were weighed weekly before feeding to calculate weight gain.

In the digestibility trial, feed intake was recorded daily. Feces and urine were collected two times per day (at 07:00 and 16:00 h), weighed and analyzed. Feeds, refusals and feces were dried, ground and analyzed for DM, OM, CP, EE, NDF, ADF and ash. Urine was analyzed for nitrogen on the day of collection.

Measurements

During the growth trial, the following parameters were recorded such as feed and nutrient intake, final live weight, weight gain, feed conversion ratio and economic efficiency.

In the digestibility experiment, data collected included nutrient intake, apparent digestibility coefficients of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF) and acid detergent fiber (ADF), as well as nitrogen retention (g/kgW^0.75).

Chemical Analyses

Feed samples were analyzed for dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE) and total ash following AOAC (1990) methods. NDF and ADF were determined according to Van Soest et al (1991). Apparent digestibility coefficients were calculated using the method described by McDonald et al (2010).

Statistical Analysis

Data were analyzed using the General Linear Model (GLM) procedure in Minitab Release 20.3 (2021). Differences among treatments and pairwise comparisons were assessed using Tukey’s test as implemented in Minitab 18.1.

Results and discussion

Growth experiment

Chemical composition of feeds

The chemical composition of feed ingredients in growth trial was presented in Table 2.

Table 2. Chemical composition of feed ingredients in growth trial
Feed	DM	OM	CP	EE	NDF	ADF	Ash	ME, MJ/kgDM

Brachiaria mutica	17.4	89.6	12.3	3.56	64.3	42.2	10.4	7.60
Operculina turpethum	16.0	88.4	16.4	4.85	40.2	30.3	11.6	9.69
Coconut meat residue	41.5	97.3	4.06	36.1	58.3	32.6	2.70	13.2
Soya waste	12.3	95.4	21.2	23.1	32.3	27.1	4.60	12.3
Extraction soybean meal	92.5	95.0	42.0	10.5	18.7	12.3	5.00	12.9
DM: dry matter, OM: organic matter, CP: crude protein, EE: extracted ether, NDF: neutral detergent fiber , ADF: acid detergent fiber, ME: metabolizable energy (Maertens, 2002)

The feed ingredients used in this study demonstrate a diverse nutrient profile, supporting balanced rabbit nutrition. Brachiaria mutica with moderate dry matter (17.4%), crude protein (12.3%) and neutral detergent fiber (64.3%) are consistent in DM and NDF results, while higher CP value than that of a previous study on Brachiaria mutica reported (Thanh et al 2025). Although lower in protein than legumes, it provides essential fiber for gut motility in rabbits. Operculina turpethum with higher CP (16.4%) and lower NDF (40.2%) than Brachiaria mutica contributes significantly to dietary protein while maintaining acceptable fiber levels for digestion. Coconut meat residue (CMR), though low in CP (4.1%), had a high ether extract content (36.1%), confirming its value as an energy-dense ingredient. The DM, CP and NDF contents of CMR are in a range of those (42.2, 3.7, 57.5%, respectively) reported by Trung and Truong (2024). These complementary nutritional profiles-forages like Brachiaria mutica supplying essential fiber for gut motility (Gidenne, 2015). Operculina turpethum boosting protein intake and coconut residue delivering dense energy-support efficient digestion and performance in growing rabbits, as evidenced by improved ME and EE intakes in this study. Soya waste, a by-product of soymilk processing, provided moderate protein (21.2%) and was consistent with values reported by Trung et al (2025), who highlighted its potential as a sustainable protein source in rabbit diets. Similarly, extraction soybean meal had the highest protein content (42.0%), aligning with global standards for commercial protein supplements used in rabbit nutrition.

These feed ingredients, especially when locally sourced, support cost-effective and nutritionally adequate rabbit diets. The integration of agro-industrial by-products like coconut meat residue and soya waste is in line with sustainable feeding strategies promoted by recent research (FAO 2023), reducing feed costs while maintaining growth performance.

Feed and nutrient intakes of rabbits in the growth experiment

Feed and nutrient intakes of rabbits in the growth experiment was presented in Table 3.

Table 3. Daily feed and nutrient intakes of rabbits in the growth experiment
Item	Treatment					SEM	p
Item	CMR0	CMR10	CMR20	CMR30	CMR40	SEM	p

Feed intake, DM g/ani.
Brachiaria mutica	114	110	108	109	116	6.44	0.857
Operculina turpethum	128	122	119	111	127	7.67	0.551
Coconut meat residue	_	12.7^d	21.3^c	32.3^b	42.7^a	0.38	0.001
Soya waste	135	135	135	135	135	0.89	0.461
Extraction soybean meal	19.7	18.0	17.7	19.7	19.0	0.95	0.477
Nutrient intake, g DM/ani.
DM	74.9^b	77.1^b	79.2^b	84.7^ab	92.3^a	2.03	0.002
OM	68.9^c	71.1^bc	73.3^ab	78.6^ab	85.7^a	1.85	0.001
CP	16.9	16.3	16.1	16.9	17.4	0.51	0.473
EE	7.40^e	9.07^d	10.2^c	12.0^b	13.7^a	0.19	0.001
NDF	27.9^c	29.8^c	31.3^bc	34.0^b	38.3^a	0.82	0.001
ADF	20.8^c	21.9^bc	22.8^bc	24.2^ab	27.2^a	0.61	0.001
Ash	6.10	6.00	5.97	6.06	6.58	0.18	0.201
ME, MJ/ani.	0.79^c	0.82^c	0.85^bc	0.93^ab	1.01^a	0.02	0.001
^{a,.b,c,d, e .} mean values with different superscripts within the same row are different at p<0 05.

Table 3 indicates that the intake of Brachia mutica and Operculina turpethum did not differ significantly among treatments (p>0.05). Coconut meat residue intake increased (p<0.05) with dietary inclusion, from 12.7 g in CMR10 to 42.7 g/animal/day in CMR40. This contributed to a linear rise in total dry matter (DM) and organic matter (OM) intake (p< 0.05). Neutral detergent fiber (NDF) and acid detergent fiber (ADF) intakes increased with higher CMR inclusion levels (p<0.05), reflecting the fibrous nature of coconut meat residue (58% NDF).

Metabolizable energy (ME) intake rose from 0.79 MJ in the CMR0 to 1.01 MJ/animal/day in the CMR40 (p<0.05), consistent with findings by Diem (2022), who reported that coconut oil supplementation enhanced energy intake and nutrient digestibility in rabbits.

Overall, the inclusion of coconut meat residue improved total nutrient and energy intake without negatively affecting protein intake, suggesting its suitability as a fibrous energy source in rabbit diets.

The total dry matter intake increased progressively across the treatments, from 76.6 g/animal/day in the CMR0 treatment to 90.8 g/animal/day in the CMR40 treatment (p<0.05). The EE intake also increased (p<0.05), from 29.7 g/animal/day in CMR0 to 37.7 g/animal/day in CMR40. Also, metabolizable energy (ME) intake increased gradually from CMR0 to CMR40, ranging from 0.79 to 1.01MJ/animal/day (p<0.05). This increase may be attributed to the progressive inclusion of coconut meat residue. The effect of CMR intake on DM intake of Californian rabbit was presented in Regression equation, y = 0.402x + 72.9, with R² = 0.92 (Figure 1).

Figure 1. Effect of CMR intake (g/d) on DM intake of Californian rabbit

Growth performance and feed conversion ratio of experimental rabbits

Daily weight gain, final live weight, feed conversion ratio and economic efficiency of Californian rabbits are presented in Table 4.

Table 4. Daily weight gain (DWG), final live weight and feed conversion ratio (FCR) of rabbits
Item	Treatment					SEM	p
Item	CMR0	CMR10	CMR20	CMR30	CMR40	SEM	p

Initial live weight, g	861	863	855	841	867	21.7	0.92
Final live weight, g	2313^b	2399^ab	2483^ab	2663^a	2640^ab	71.9	0.04
DWG, g/rabbit	17.3^c	18.3^bc	19.4^bc	21.7^a	21.1^ab	0.66	0.007
FCR	4.33	4.22	4.08	3.91	4.39	0.18	0.37
^{a .b. c.}mean values with different superscripts within the same row are different at p<0.05.

Table 4 indicates that daily weight gain (DWG) differed among treatments (p< 0.05), with the lowest in CMR0 (17.3 g/day) and the highest in CMR30 (21.7 g/day). This increase corresponds with improved energy intake from coconut meat residue inclusion in the CMR30 treatment. Daily weight gains in the current trial are in a range of 18.3 - 21.8 g of a previous study on rabbits supplemented sweet potato tuber residue associated with copra cake in diets cited by Dong and Thu (2016). Also, comparable growth rates (16.9-20.9 g) in a study on rabbits fed natural plants and grasses with supplemented coconut oil, cited by Diem (2022). Results of final live weight (FLW) corresponded to the DWG, also increased (p< 0.05) for the treatments supplemented CMR, with the CMR30 achieving the highest (2,663 g) and CMR0 the lowest (2,313 g). The effect of ME intake on DWG was presented in the regression equations, y= -151x² + 290x – 118, with R² = 0.98 (Figure 2).

Figure 2. Effect of ME intake (MJ/d) on DWG (g) of Californian rabbit

Digestibility experiment

Feed and nutrient intakes of rabbits in the digestibility experiment

Feed and nutrient intakes of rabbits in the digestibility experiment were shown in Table 5.

Table 5. Feed and nutrient intake of rabbits in the digestibility experiment
Item	Treatment					SEM/p
Item	CMR0	CMR10	CMR20	CMR30	CMR40	SEM/p

DM	76.6^b	82.3^ab	85.2^ab	88.2^ab	90.8^ab	1.97/0.007
OM	70.4^b	75.8^ab	78.8^ab	81.9^b	84.4^ab	1.76/0.004
CP	17.2	17.4	17.5	17.7	17.4	0.27/0.687
EE	7.97^e	9.67^d	11.1^c	12.5^b	13.8^a	0.10/0.001
NDF	29.7^b	33.0^ab	34.7^ab	35.9^ab	37.7^a	1.33/0.023
ADF	6.18	6.42	6.41	6.36	6.36	0.21/0.933
Ash	0.8^ac	0.86^bc	0.89^b	0.94^ab	0.96^a	0.01/0.001
ME, MJ/ani./day	0.80^c	0.86^bc	0.89^b	0.94^a	0.96^a	0.01/0.001
^{a .b. c, d, e.} mean values with different superscripts within the same row are different at p<0.05.

Dry matter intake (DMI) increased (p<0.05) across the treatments, ranging from 76.6 g/animal/day in the CMR0 to 90.8 g/animal/day in the CMR40 treatment. Metabolizable energy (ME) intake also increased (p<0.05), from 0.80 to 0.96 MJ/animal/day, likely due to the incremental inclusion of coconut meat residue, which contributed additional fermentable fiber and energy.

Nutrient digestibility and nitrogen retention of rabbits in digestibility trial

Nutrient digestibility and Nitrogen retention of rabbits in digestibility trial were shown in Table 6

Table 6. Apparent nutrient digestibility (%) and Nitrogen retention (g/kg W^0,75) of rabbits in digestibility trial
Item	Treatment					SEM /p
Item	CMR0	CMR10	CMR20	CMR30	CMR40

Digestibility, %
DMD	66.1^b	72.5^ab	75.6^a	79.0^a	76.0^a	1.67/0.005
OMD	66.5^b	73.0^ab	75.9^a	79.3^a	76.6^a	1.65/0.005
CPD	78.0	83.7	85.3	87.1	85.1	2.09/0.103
EED	70.2^c	76.7^b	81.2^ab	85.1^a	84.3^a	1.23/0.001
NDFD	46.4^b	58.8^ab	64.4^a	65.8^a	65.4^a	2.13/0.001
ADFD	45.7	45.9	46.8	49.7	48.0	2.06/0.212
N balance (g/kg W^0.75)
N intake	1.67	1.72	1.74	1.71	1.64	0.07/0.878
N retention	1.07	1.04	1.18	1.26	1.22	0.07/0.182
^{a .b. c} mean values with different superscripts within the same row are different at P<0 05.

Dry matter digestibility (DMD) improved (p<0.05) with increasing coconut meat residue inclusion, peaking at 79.0% in the CMR30 treatment before a slight decline in the CMR40 treatment. These values exceed the range (62-70%) commonly reported for high-fiber rabbit diets (Gidenne, 2015), indicating enhanced fermentability of the supplemented fiber. Crude protein digestibility (78.0-87.1%) showed a non-significant upward trend (p>0.05), likely due to improved microbial activity and better nitrogen synchronization. NDF digestibility was positively influenced by coconut meat residue inclusion, the significantly higher values for the diets supplemented coconut meat residue (p<0.05).

Nitrogen intake and retention did not differ significantly (p>0.05), though N retention improved slightly across treatments. This indicates stable nitrogen utilization, in agreement with findings by Gidenne et al (2012), who noted marginal effects of moderate fiber supplementation on nitrogen balance. The effect of NDF intake on NDF digestibility was showed in regression equation, y = - 0.355x² + 26.4x - 424, with R² = 0.99 (Fig. 3).

Figure 3. Effect of NDF intake (g/d) on NDF digestibility (%)

Conclusion

Rabbits fed a basal diet of Brachiaria mutica and Operculina turpethum supplemented with graded levels of coconut meat residue showed improved daily weight gain and final live weight. Nutrient digestibility coefficients, including DM, OM, EE and NDF were improved in diets supplemented with coconut meat residue.
The supplementation level of 30 g/rabbit/day resulted in the highest growth performance.

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