Special Issue:

Emerging and Re-emerging Animal Health Challenges in Low and Middle-Income Countries

Boer Crossbred Goats Fed Jackfruit Leaves as a Soybean Meal Replacement: Feed Intake, Nutrient Digestibility And Nitrogen Retention

Nguyen Thi Hanh Chi1,2, Ho Xuan Nghiep1,2, Vu Ngoc Hoai1,2, Nguyen Binh Truong1,2*

1Department of Animal Sciences, Faculty of Agriculture and Natural Resources, An Giang University, Vietnam; 2Vietnam National University, Ho Chi Minh City, Vietnam.

Received | November 26, 2025; Accepted | October 28, 2025; Published | November 02, 2025

*Correspondence | Nguyen Binh Truong, Department of Animal Sciences, Faculty of Agriculture and Natural Resources, An Giang University, Vietnam; Email: [email protected]

Citation | Chi NTH, Nghiep HX, Hoai VN, Truong NB (2025). Boer crossbred goats fed jackfruit leaves as a soybean meal replacement: Feed intake, nutrient digestibility and nitrogen retention. J. Anim. Health Prod. 13(s1): 706-712.

DOI | https://dx.doi.org/10.17582/journal.jahp/2025/13.s1.706.712

ISSN (Online) | 2308-2801

Copyright: 2025 by the authors. Licensee ResearchersLinks Ltd, England, UK.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

INTRODUCTION

Goat production is developing in the Mekong Delta, Vietnam. Crossbred goats are better than local goats; the famous goat is the Boer (Nguyen et al., 2023). However, not only the good crossbreed goats, but also the importance of forage quality for farmers with the increased agricultural by-products to improve income and protect the environment from global warming.

A previous study showed that Jackfruit leaves, Operculina turpethum vines, and Wedelia trilobata L. gave better feed intake, nutrient digestibility, nitrogen retention, and weight gain than the cabbage waste. The protein solubility of Jackfruit leaves was lower than that of Operculina turpethum vines and Wedelia trilobata L. and cabbage waste (2.84, 3.59, 5.07, and 6.06%, respectively), as concluded by Truong and Trung (2023). According to Preston and Leng (2021), rumen escape protein is a protein source of low solubility, facilitating the partial escape of the protein from the rumen fermentation. Moreover, Thu et al. (2025) suggested that low protein solubility makes a valuable forage option for ruminants, as it can enhance nitrogen utilization efficiency and potentially reduce methane emissions. In another study, soybean meal was determined to be the source of rumen scape protein with a low protein solubility of about 2.22% (Truong and Preston, 2021; Truong and Tuan, 2024). Our previous study suggested that rumen escape protein of forage is essential, and agricultural by-products with low soluble protein content in livestock rations are crucial. The protein solubility of Jackfruit leaves is almost equal to that of soybean meal (2.84 and 2.22%, respectively). Therefore, the experimental hypothesis is that jackfruit leaves protein can replace soybean meal protein on nutrient digestibility and nitrogen retention of Boer crossbred goats.

MATERIALS AND METHODS

Location and time

The experiment was conducted at the experimental farm in An Giang University, An Giang Province, Vietnam. The feeds, refusals, feces and urine were analyzed at laboratory E205 of the Faculty of Animal Sciences, Can Tho University.

Experimental design

Five crossbred Boer goats, with an average initial body weight used in this experiment was 11.4±0.43 kg at about 4 months old. The Latin Square design was used in the experimental goats with five treatments and 5 periods. Five treatments were replacing soybean meal protein with jackfruit leaves at 0% (JL0), 25% (JL25), 50% (JL50), 75% (JL75), and 100% (JL100) (Table 1).

 

Table 1: Ingredients used in this study

Ingredients (%CP)	JL0	JL25	JL50	JL75	JL100
Tofu waste	17.0	17.0	17.0	17.0	17.0
Soybean meal	39.4	29.5	19.7	9.84	0
Jackfruit leaves	0.00	9.84	19.7	29.5	39.4
Operculina turpethum vines	27.2	27.2	27.2	27.2	27.2
Elephant grass	16.4	16.4	16.4	16.4	16.4
Premix	0	0	0	0	0
Total	100	100	100	100	100

 

Measurements taken

Feeding procedure

All the feed was supplied separately and weighed before feeding to the experimental goats. In detail, the Jackfruit leaves and soybean meal were fed at a crude protein consumption depending on the treatments. However, the amount of protein was calculated on a dry matter basis and converted to the fresh state of the food. The tofu waste was mixed with the premix before feeding. Elephant grass was fed ad libitum, and drinking water was always available. Refused feeds were weighed each morning.

Feeds, nutrient and energy intakes

The nutrient composition of feeds, refuses, feces, and urine was examined in this study. Dry matter (DM) and organic matter (OM) were analyzed using the AOAC (1990) method. The nitrogen (N) in feed, refusals, feces, and urine was specified using the Kjeldahl procedures of AOAC (1990) . However, acid detergent fiber (ADF) and neutral detergent fiber (NDF) were analyzed using the method of Van Soest et al. (1991).

Apparent nutrient digestibility

The nutrient digestibility method was practiced in three weeks for each experimental period by McDonald et al. (2010), such as the first week for adaptation, the second for diet stabilization, and the third for feces and urine collection.

Metabolizable energy (ME)

The metabolisable energy (ME) in goat diets was calculated according to the suggestion of Bruinenberg et al. (2002).

ME (MJ/head/day) = 14.2 x DOM + 5.9 x DCP (with DOM/DCP < 7)

ME (MJ/head/day) = 15.1 x DOM (with DOM/DCP > 7)

In this instance, DOM was the digestible organic matter, while DCP was the digestible crude protein.

Nitrogene balance (N)

Daily N retention was calculated using formula:

N retention = N intake - (N feces + N urine)

Daily weight gains (DWG)

At the beginning and end of each experimental period, the goats were weighed on two consecutive days.

Daily weight gain (g/goats/day) = (body weight of period final - body weight period initial)/21 day

Statistical analysis

ANOVA Linear Model (GLM) of Minitab Reference Manual Release 20 was analyzed using the data (Minitab, 2021). Tukey’s pairwise comparisons (P≤0.05) were applied to determine differences between treatments. Data were analyzed using the model Yijk = µ + Ti + Gj + Pk + eijk; where Yijk: = the dependent variable, µ: the overall mean, Ti = the effect of jackfruit leaves as a soybean meal replacement ratio (i = 1 to 5), Gj: the effect of goats (j = 1 to 5), Pk = the effect of period (j = 1 to 5), eijk = the random error.

RESULTS AND DISCUSSION

Chemical composition of feeds using in this study

The nutrients of feed in Table 2 showed that soybean meal (Figure 1) has the highest CP than tofu waste, jackfruit leaves (Figure 2), Operculina turpethum vines (Figure 3), and elephant grass (44.8, 17.5, 14.9, 13.6, and 6.67%, respectively). However, the NDF was lowest in soybean meal compared to tofu waste, Operculina turpethum vines, jackfruit leaves, and elephant grass, corresponding to 8.09, 34.7, 36.3, 36.8, and 69.4%. The result analysis of the feed in this experiment was similar to that of another study. The CP of jackfruit leaves was 12.9% as reported by Thanh et al. (2021). However, the CP of jackfruit leaves in the study of Keir et at (1997) was 15.0% and Dahlanuddin (2001) was 14.6%. The CP of soybean meal was 46.4%, as Hang et al. (2023) reported. A previous Truong and Preston (2021) study concluded that the CP of soybean meal was 41.5%. The nutrients of feed change by time of year, harvest, and soil structure. The nutrient content of elephant grass in this study was similar to the results of Rusdy (2016), who reported that the CP and NDF of elephant grass were about 7.20-18.1% and 57.4-75.4%, respectively.

 

Table 2: Chemical composition of feeds (% DM basis) used in the experiment.

Feeds	DM, %	In DM, %
		OM, %	CP, %	NDF, %
Tofu waste	15.7	97.0	17.5	34.7
Soybean meal	87.6	93.5	44.8	8.09
Jackfruit leaves	35.6	87.3	14.9	36.8
Operculina turpethum vines	15.1	88.9	13.6	36.3
Elephant grass	15.6	92.4	6.67	69.4

 

DM: dry matter, OM: organic matter, CP: crude protein, NDF: neutral detergent fiber.

 

Feed and nutrient intake of experimental goats

The DM intake was significantly different (P<0.05) in this study. It was 352, 415, 427, 470, and 503 g/head/day corresponding to JL0, JL25, JL50, JL75, and JL100 treatments (Table 3). In detail, the proportion of DM per BW (Figure 4) of JL100 treatment (3.73%) was not different (P>0.05) from JL75 treatment (3.34%), but it was higher than JL50, JL25, and JL0 treatments (3.09, 3.03, and 2.58%, respectively). The result in this study was similar to information from Thanh et al. (2021), who reported that DM intake as Jackfruit leaves replacing para grass on a DM basis (equivalent to: 0, 36.9, 52.7, and 70% of diet DM) was 2.83-4.45%. Another study of Truong and Trung (2023) for Jackfruit leaves on goat concluded that Jackfruit leaves was good feed for goats by extracting nitrogen in urine lower than feces.

 

 

 

Table 3: Feed and nutrient intake of experimental goats

Items	JL0	JL25	JL50	JL75	JL100	SEM	P
Feed intake, g DM/head/day
Tofu waste	59.1	59.8	65.7	67.3	64.4	6.470	0.860
Soybean meal	53.0a	47.6a	34.3b	17.6c	0.00d	1.570	0.001
Jackfruit leaves	0.00e	47.4d	97.5c	146b	208a	9.550	0.001
Operculina turpethum vines	105	124	140	128	135	11.60	0.308
Elephant grass	133a	135a	87.2b	109ab	92.7b	8.320	0.004
Premix	1.70c	2.04b	2.20b	2.26ab	2.54a	0.062	0.001
Nutrients intake, g DM/head/day
DM	352c	415bc	427bc	470ab	503a	16.70	0.001
DM/BW, %	2.58c	3.03bc	3.09b	3.34ab	3.73a	0.102	0.001
OM	324c	380bc	387abc	425ab	453a	14.80	0.001
CP	59.7b	67.2ab	70.0a	69.9a	72.1a	2.240	0.017
NDF	148c	173abc	161bc	191ab	199a	7.530	0.003
ME*, MJ/head/day	3.34b	3.94ab	3.73ab	3.83ab	4.36a	0.163	0.013

 

JL0, JL25, JL50, JL75 and JL100 treatment contained jackfruit leaves protein replacement soybean meal protein at 0, 25, 50, 75 and 100% based on crude protein. DM: dry matter, OM: organic matter, CP: crude protein, NDF: neutral detergent fiber, BW: body weight. *Bruinenberg et al (2002). a,b,c Means within a row with different letters differ significantly (p<0.05).

 

Crude protein consumption

The CP consumption (%) was increased (P<0.05) in the experiment (Table 4). It was 59.7, 67.2, 70.0, 69.9, and 72.1 g/head/day corresponding to JL0, JL25, JL50, JL75, and JL100 treatments. In this study, Boer crossbred goats fed jackfruit leaves as a soybean meal replacement, the total DM of the feed intake was increased (P<0.05). The protein value of jackfruit leaves is lower than that of soybean meal. A result as CP/DM (%) decrease from JL0 treatment to JL25, JL50, JL75, and JL100 treatments (16.9, 16.4, 16.5, 14.8, and 14.3%, respectively). However, the CP/DM of JL50 treatment (16.5%) was not different (P>0.06) from JL25 (16.4%) and JL0 treatments (16.9%), but it was higher than (P<0.05) JL75 (14.8%) and JL100 treatments (14.3%). The CP/DM in this study was higher than that of Chanjula et al. (2022) was 11.0-11.6%, and Gunun et al. (2023) was 13.7%.

 

Table 4: Crude protein consumption of experimental goats.

Item	JL0	JL25	JL50	JL75	JL100	SEM	P
CP intake, g/head/day
Tofu waste	10.3	10.5	11.5	11.8	11.3	1.130	0.860
Soybean meal	23.7a	21.3a	15.3b	7.88c	0.00d	0.705	0.001
Jackfruit leaves	0.00e	7.05d	14.5c	22.0b	31.5a	1.370	0.001
Operculina turpethum vines	14.7	17.4	19.5	18.2	19.8	1.400	0.141
Elephant grass	11.0	11.0	9.13	10.0	9.55	0.596	0.156
Total	59.7b	67.2ab	70.0a	69.9a	72.1a	2.240	0.017
CP/DM, %	16.9a	16.4a	16.5a	14.8b	14.3b	0.240	0.001

 

JL0, JL25, JL50, JL75 and JL100 treatment contained jackfruit leaves protein replacement soybean meal protein at 0, 25, 50, 75 and 100% based on crude protein. DM: dry matter, OM: organic matter, CP: crude protein, NDF: neutral detergent fiber, BW: body weight. a,b,c Means within a row with different letters differ significantly (p<0.05).

 

Apparent digestibility

Both DM and CP digestibility were significantly different (P<0.05) in the experiment (Table 5). The DM digestibility was 65.1, 66.4, 61.5, 58.5 and 61.3% corresponding to JL0, JL25, JL50, JL75, and JL100 treatments. The CP digestibility of JL0 did not differ (P>0.05) from JL25 and JL50 treatments (73.0, 72.8, 64.4%, respectively), but it was higher than JL75 and JL100 treatments (57.0 and 60.5%, respectively). The trend of DM and CP digestibility was similar to the result of Thanh et al. (2021). The CP digestibility showed a reduced non-linear trend as increased JL in the diets (y = 0.001x2 - 0.2592x + 74.9; R² = 0.8246; Figure 5). This study’s CP digestibility was higher than that of Truong and Trung (2023), who reported that the CP digestibility of fed jackfruit leaves was 54.2%.

 

Table 5: Nutrient digestibility, and digestible nutrients of experimental goats.

Item	JL0	JL25	JL50	JL75	JL100	SEM	P
Feces, gDM//head/day	122c	141bc	167ab	201a	194a	9,710	0,001
Nutrient digestibility, %
DM	65.1ab	66.4a	61.5ab	58.5b	61.3ab	1.610	0.030
OM	66.6	68.1	63.8	60.9	63.7	1.600	0.056
CP	73.0a	72.8a	64.4ab	57.0b	60.5b	2.320	0.001
NDF	54.2	53.9	44.4	46.4	49.4	4.270	0.416
Digestible nutrient, g/head/day
DM	230b	274ab	259ab	269ab	309a	12.20	0.010
OM	217b	257ab	244ab	253ab	289a	11.10	0.010
CP	44.4ab	48.8a	44.8ab	39.4b	44.2ab	1.510	0.014
NDF	82.7	95.4	75.6	87.6	99.4	8.850	0.373

 

JL0, JL25, JL50, JL75 and JL100 treatment contained jackfruit leaves protein replacement soybean meal protein at 0, 25, 50, 75 and 100% based on crude protein. DM: dry matter, OM: organic matter, CP: crude protein, NDF: neutral detergent fiber, BW: body weight. a,b Means within a row with different letters differ significantly (p<0.05).

 

 

Nitrogen balances

Nitrogen retention (Table 6) showed the greater values (P>0.05) in goats fed jackfruit leaf diets (4.11-4.68 g/head/day) compared with goats fed only soybean meal (3.48 g/head/day). In this study, we could also detect a greater N in feces (P<0.05) of goats fed jackfruit leaves diets, and N in urine decreased (P>0.05) of goats fed jackfruit leaf diets compared with goats fed only soybean meal (Figure 6). The result of jackfruit leaves in this study was similar to that reported by Thanh et al. (2021). This characteristic makes it a valuable forage option for ruminants, as it can enhance nitrogen utilization efficiency, as Thu et al. (2025) concluded.

 

Table 6: Nitrogen retention and weight gain of goats in different treatments

Item	JL0	JL25	JL50	JL75	JL100	SEM	P
Urine, g/head/day	964	952	898	849	884	100,0	0,917
Nitrogen balance, g/head/day
N intake	9.56b	10.8ab	11.2a	11.2a	11.5a	0.358	0.017
N in feces	2.45c	2.94bc	4.02ab	4.88a	4.47ab	0.339	0.001
N in urine	3.63	3.32	2.87	2.19	2.40	0.454	0.198
N retention, g/head/day	3.48	4.49	4.30	4.11	4.68	0.553	0.612
N retention g/W0.75/day	0.483	0.638	0.603	0.565	0.654	0.073	0.508
Body weight, kg
Initial	13.2	13.1	12.8	13.1	12.9	0.365	0.950
Final	13.9	13.8	14.2	14.6	14.2	0.338	0.544
Average daily gain, g/head/day	34.2	36.1	66.2	73.1	61.4	13.70	0.213

 

JL0, JL25, JL50, JL75 and JL100 treatment contained jackfruit leaves protein replacement soybean meal protein at 0, 25, 50, 75 and 100% based on crude protein. DM: dry matter, OM: organic matter, CP: crude protein, NDF: neutral detergent fiber, BW: body weight. a,b Means within a row with different letters differ significantly (p<0.05).

 

 

The study’s results on the protein substitution of jackfruit leaves for soybean extract showed increased dry matter intake and protein intake. However, soybean extract’s protein value is higher than that of jackfruit leaves, so a large amount of jackfruit leaf dry matter is needed to meet the protein balance between soybean extract and jackfruit leaves. As a result, the CP/DM ratio (%) decreased, and DMD and CPD decreased significantly. However, converting N excretion (decrease in urine and increase in feces) when replacing jackfruit leaves with soybean extract is a positive transformation from inorganic nitrogen to organic nitrogen that helps protect the environment. According to Quang (2023), urinary nitrogen is mainly in urea, which is more rapidly hydrolyzed to ammonia and nitrified to nitrate, whereas fecal nitrogen is primarily in the organic form, which is less volatile. Therefore, decreased nitrogen excretion via urine could reduce ammonia and nitrous oxide emissions into the atmosphere. Because the conversion of ammonia in urine produces N2O, which is a gas that is toxic to the environment. Therefore, high N content in feces compared to urine is a method to help protect the environment. Increasing protein replacement from soybean meal to jackfruit leaves in the diet of Boer crossbred goats increased DMI, nitrogen retention but decreased digestibility of CP.

CONCLUSION

It was concluded that increasing substitution of jackfruit leaves for soybean meal at 50% in the diet CP of goats effectively reduces urinary N excretion while allowing improvement in DM intake. A level of 50% jackfruit leaves protein as a soybean meal protein replacement in the diet would be recommended to implement performance studies in the goat for better local by-product source utilization for farmers.

ACKNOWLEDGEMENTS

This research is funded by Vietnam National University Ho Chi Minh City (VNU-HCM) under grant number C2025-16-04. Author thanks the experimental farm, An Giang University (AGU), Vietnam National University Ho Chi Minh City (VNU-HCM).

NOVELTY STATEMENT

Effect of Jackfruit leaves on feed consumption, digestibility, and nitrogen retention of Boer crossbred goats studied in present work for new practical findings.

AUTHOR’s CONTRIBUTION

NBTand VNHconceived and designed the field trial. NBT, NTHC, HXN and VNHwrote the paper.

Generative AI and AI-assisted technology statement

This article used Grammarly for Windows software.

Conflict of interest

The authors have declared no conflict of interest.

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