Citation of this paper

Dietary kudzu (Pueraria thomsonii Benth.) leaf effect on growth performance of Local rabbits

Le Thi Lan Phuong, Nguyen Minh Hoan, Le Nu Anh Thu, Le Duc Thao, Duong Thanh Hai, Dinh Van Dung, Huynh Van Chuong¹ and Nguyen Hai Quan

Faculty of Animal Sciences and Veterinary Medicine, University of Agriculture and Forestry, Hue University; 102 Phung Hung, Hue City, Thua Thien Hue 530000, Vietnam
¹ Institute of Biotechnology, Hue University, Hue city, Vietnam
lethilanphuong@hueuni.edu.vn

Abstract

The study was performed to determine the effect of kudzu leaves (Pueraria thomsoni Benth.) in diets on feed intake, growth performance and feed conversion ratio of rabbits. Forty Local rabbits (2.5-3.0 months of age, body weight of 1118.5±75.6 g) were randomly assigned to 5 treatments with 4 replications. Five treatments correspond to 5 replacing levels of para grass (Brachiaria mutica) by kudzu leaves in diets (0%, 25%, 50%, 75% and 100%). The results showed that the increase in substitution rates of para grass with kudzu leaves were affected on feed intake, nutrient intake, daily weight gain, and FCR of rabbits (p<0.05). In conclusion, rabbits fed diets containing para grass replacement by kudzu leaves were optimized growth and FCR rates at 75% replacement level.

Keywords: feed conversion, Zeed, feed intake, Pueraria thomsonii Benth, rabbit, weight gain

Introduction

Rabbit farming in Vietnam is increasingly receiving attention and development from farmers and the Government. The government has approved strategy and orientation for rabbit farming development in Vietnam to reach about 2.5 million heads by 2025 and about 4.0 million heads by 2030 (Decision 703/QD-TTg, 2020). Rabbits are seen as a means to raise the incomes of the rural poor mainly because of its low investment capital, variety, availability and does not compete for feed with other livestock (Nguyen Van Thu 2019).

Rabbit farming in Thua Thien Hue is mostly household-based and spontaneous. Most households use natural grass as green feed for rabbits with an unstable supply (Le Thi Lan Phuong et al 2022). The harsh climate in Thua Thien Hue province is not conductive to growing and developing high-yield feed plants for rabbits (Le Thi Lan Phuong et al, 2012; Le Thi Lan Phuong et al, 2022). To solve the difficulties in feeding sources for livestock, it is necessary to research and utilize local plant sources as feed for livestock, diversify feed sources and help farmers proactively source feed sources to improve livestock efficiency (Preston et al, 2021).

Kudzu leaves (Pueraria thomsoni Benth.) have high yield and nutritional value for livestock. According to Nguyen Van Hiep and Ngo Van Man (2008), the yield of kudzu leaves ranges from 2-4 tons of dry matter/ha/year with crude protein content ranging from 18-22% in dry matter. Le Thi Lan Phuong et al (2023) reported that, rabbits accepted to consume kudzu leaves and have a good digestion of nutrients, with dry matter digestibility rate of 69.1% and protein digestibility rate of 75.3%. However, information on the effects of using kudzu leaves on growth performance of Local rabbits not much has been announced yet. This study were conducted to determine the effects of dietary kudzu leaves on feed intake and growth performance of rabbits.

Materials and methods

Location

We performed the experiment at the experimental farm of Faculty of Animal Sciences and Veterinary Medicine, University of Agriculture and Forestry, Hue University, Vietnam. Experiment implementation period was from August to October 2023.

Animals

Local rabbits of about 3 months of age were used in this study. Rabbits were injected Rabbit haemorrhagic disease vaccine, took medicine to prevent coccidiosis, and had parasites removed before conducting the experiment.

The cages of rabbits was constructed from wood and wire mesh. The dimensions (width, length, height) of the growth cages were 50, 40 cm and 40 cm. The cage is placed 50 cm above the ground. Rabbits were provided with water automatically by a specialized water supply valve in each cage. The forage trough is placed in the front of each cage, while the paddy rice trough is placed inside the cage.

Experimental feed and diet

Experimental feeds were fresh kudzu leaves (Pueraria thomsonii Benth.), para grass (Brachiaria mutica) and paddy rice. Kudzu leaves and para grass used during the study period were collected in Hue city, in the afternoon of the day before feed offering. The kudzu leaves was cut included leaf blades and petioles. The para grass was cut with 20-25 cm in length. We only harvested kudzu leaves and para grass when they are still green. Leaves that are yellow or withered were removed before providing them to the experimental rabbits.

There were 5 diets corresponding to 5 replacing levels of fresh para grass with fresh kudzu leaves in diets and paddy rice, as follows:

Diet contains kudzu leaf 0% (KL0): rabbits were fed 100% para grass + paddy rice at 3% of body weight.

Diet contains kudzu leaf 25% (KL25): rabbits were fed 25% kudzu leaves + 75% para grass + paddy rice at 3% of body weight.

Diet contains kudzu leaf 50% (KL50): rabbits were fed 50% kudzu leaves + 50% para grass + paddy rice at 3% of body weight.

Diet contains kudzu leaf 75% (KL75): rabbits were fed 75% kudzu leaves + 25% para grass + paddy rice at 3% of body weight.

Diet contains kudzu leaf 100% (KL100): rabbits were fed 100% kudzu leaves + paddy rice at 3% of body weight.

Animals and design

Growth experiments on rabbits were carried out according to the recommendations of the European Rabbit Nutrition Research Association (EGRAN) described by Fernández-Carmona et al (2005). Forty Local rabbits (2.5-3.0 months of age, body weight of 1118.5±75.6 g) were randomly assigned to 5 treatments with 4 replications. Five treatments corresponding to 5 replacing levels of para grass by kudzu leaf in diets (0%, 25%, 50%, 75% and 100%). Each treatment had 4 replications and rabbits were kept in same-sex pairs in 1 cage. The experiment lasted for 56 days. The rabbits were fed 3 times a day at 7:00; 14:00 and 22:00. The feed and refused feed of experiment were collected and recorded daily. The body weight rabbits were measured and recorded weekly.

Chemical analysis

The feeds and refusals were taken for analyses of dry matter (DM), organic matter (OM), crude protein (CP), Ether extract (EE), crude fiber (CF) and Ash following the procedures of AOAC (2000). Acid detergent fiber (ADF) and neutral detergent fiber (NDF) was determined according to Van Soest et al (1991).

Nitrogen-free extract (NFE) and gross energy (GE) value were calculated according to the formula of FAO (2003) as follows:

NFE (g/100 g feed) = 100 − Water − Ash − Crude proteins − Ether extract, Crude fiber

GE (kcal/100 g feed) = g Crude proteins × 4.27 kcal + g Ether extract × 9.02 kcal + g NFE × 3.87 kcal

Statistical analysis

The experimental data were analyzed by ANOVA using the General Linear Model (GLM) procedure (Minitab Version 16.1, 2010). The pairwise comparison between means was performed using Tukey’s HSD test. A significant difference was declared p<0.05. Results will be presented as Least Squares Means with their pooled standard errors.

The following statistical model was used for the study: Yij = μ + Ti + eij;

Where: Yij = represents the j observation in the i treatment level (response variables were feed intake, live weight gain and feed conversion ratio); μ = overall mean, Ti = i treatment effect (feeds) (i= 1, 2, 3); eij = random error.

Results and discussion

Feed characteristics

The nutrient content of experimental feeds is shown in Table 1. There were major differences in chemical composition of experimental feeds (Table 1). Dry matter, crude protein and ADF were higher in kudzu leaves than para grass. On the contrary, EE, CF, NDF were higher in para grass than kudzu leaves. According to Gidenne (2015), the high ADF in rabbit diets will affect feed intake, leading to reduced rabbit growth, so the nutritional advantages for rabbits is higher in kudzu leaves than para grass. Joseph P. Gulizia and Kevin M. Downs (2019); Le Thi Lan Phuong et al (2023) reported that, DM, CP, ADF, NDF in kudzu leaves were range of 19-33.65%, 17.5-25.8%DM, 38.2-44.9%DM and 48.1-51.54 %DM, respectively. Thus, the DM, CP, ADF, and NDF of kudzu leaves in this study have accordance with the authors' previous publications.

Table 1. Chemical composition of experimental feeds (% DM)
	DM (%)	% in DM						NFE	GE (kcal/kg)
	DM (%)	OM	CP	EE	CF	ADF	NDF	NFE	GE (kcal/kg)

Kudzu leaves	23.6	89.4	18.1	2.1	21.3	44.9	51.5	16.33	3640
Para grass	15.5	87.3	16.8	5.4	28.9	34.4	59.7	10.06	3722
Paddy rice	83.5	95.8	6.5	1.8	11.3	16.8	27.6	73.06	3826
DM: dry matter, OM: organic matter, CP: crude protein, E E: ether extract, CF: crude fiber, ADF: acid detergent fiber, NDF: neutral detergent fiber, NFE: nitrogen free extract, GE: gross energy

Feed intake, growth rate and FCR

Data on the feed intake in DM of rabbits were presented in Table 2. Results of Table 2 and Figure 1 showed that the increase in substitution of para grass by kudzu leaf in diets affect on kudzu leaf, para grass and total DM intake (p<0.05). Total DM intake of rabbit were higher in KL100 treatments than KL0, KL25 and KL50 (p<0.05).

The increase in substitution rates of para grass with kudzu leaf were not affected on total DM intake as % body weight of rabbits (p>0.05). The total DM intake as % body weight of rabbits ranging from 6.1-6.5% body weight, consistent with the results of previous studies that rabbits had DM intake as 5-10% of body weight (Lebas F 2013; Nguyen Thi Duong Huyen et al 2013; Al-Amin 2019).

Table 2. Mean values for DM intake of rabbits
Item	Treatments					SEM	p
Item	KL0	KL 25	KL 50	K L75	K L100	SEM	p

Para grass intake, g/d	56.5^a	35.7^b	20.8^c	10.3^d	0^e	1.691	<0.001
Kudzu leaf intake, g/d	0^a	18.6^b	31.7^c	47.4^d	59.5^e	0.180	<0.001
Paddy rice intake, g/d	45.2	44.4	44.3	46.0	46.5	0.797	0.307
Total DM intake, g/d	101.7^bc	98.7^cd	96.8^d	103.7^ab	106.0^a	0.963	<0.001
DM intake, as % body weight	6.4	6.3	6.1	6.3	6.5	0.110	0.166
DM: dry matter; OM: organic matter; KL0, KL25, KL50, KL75, KL100 corresponding to replacing levels of para grass by kudzu leaf in diets at 0%, 25%, 50%, 75% and 100%; ^a,b,c,d,e values with different superscript letters within one row are significantly different at the level of 5%.

Figure 1. Effect of replacing levels of para grass leaf by kudzu leaf in diets levels on DM feed intake of rabbits

Effect of replacing levels of para grass leaf by kudzu leaf in diets levels on nutrient intake of rabbits were presented in Table 3. Results showed that the increase in substitution rates of para grass with kudzu leaf were affected on nutrient intake of rabbits (p<0.05). The amount of DM, OM, CP, NDF and GE intake of rabbits were highest in treatment KL100 and lowest in treatment KL50 (P<0.05). The nutrient intake of rabbits tends to gradually decrease when increasing the replacement level of para grass with kudzu leaves from 0-50%, but then increases correspondingly with the increase in replacing para grass with kudzu leaves from 50-100%, except for EE intake (Table 3).

Table 3. Mean value of nutrient intake of rabbits
Item	Treatments					SEM	p
Item	KL0	KL25	KL50	KL75	KL100	SEM	p

DM intake, g/d	101.7^bc	98.7^cd	96.8^d	103.7^ab	106.0^a	0.96	<0.001
OM intake, g/d	92.6^bc	90.3^c	88.9^c	95.4^ab	97.5^a	0.88	<0.001
CP intake, g/d	12.4^a	12.2^a	12.18^a	13.3^b	13.8^c	0.09	<0.001
EE intake, g/d	3.9^a	3.1^b	2.6^c	2.4^d	2.1^e	0.03	<0.001
CF intake, g/d	21.4^a	19.3^b	17.8^c	18.3^c	17.9^c	0.16	<0.001
ADF intake, g/d	41.3^a	37.1^b	34.1^c	35.1^c	34.5^c	0.30	<0.001
NDF intake, g/d	31.9^a	34.1^b	35.7^c	40.7^d	43.4^e	0.30	<0.001
GE, calo/d	383.3^a^b	370.4^bc	362.3^c	386.8^a	393.7^a	3.59	<0.001
DM: dry matter; OM: organic matter; CP: crude protein; EE: ether extract; ADF: acid detergent fiber; NDF: neutral detergent fiber; GE: gross energy; KL0, KL25, KL50, KL75, KL100 corresponding to replacing levels of para grass by kudzu leaf in diets at 0%, 25%, 50%, 75% and 100%. ^{a,b, c, d, e} values with different superscript letters within one row are significantly different at the level of 5%.

The increase in substitution of para grass with kudzu leaf were affected on daily weight gain, feed intake and FCR of rabbits (p<0.05), except for live weight (Table 4). Daily weight gain, total DM intake and FCR of rabbits tended to curve (Figures 2, 3 and 4). Daily weight gain and FCR showed positive trends when replacing 75% para grass by kudzu leaf in the diets (Table 4. Figures 3 and 4). According to Le Thi Lan Phuong et al (2022), daily weight gain of rabbits fed diets containing fish meal protein replacement by mulberry leaves were range of 15,4-18,5 g/d. Compared to this result, the daily weight gain of rabbits only eating kudzu leaf, para grass and supplemented paddy rice in the current study reached 15.9-19.5 g/day, which are equivalent and quite good.

Table 4. Mean values for live weight, daily weight gain, feed intake and FCR
Item	Treatments					SEM	p
Item	KL0	KL25	KL50	KL75	KL100	SEM	p

Live weight, g
Initial	1156	1111	1099	1110	1128	35.440	0.757
Final	2046	2039	2079	2193	2128	44.220	0.131
Daily gain, g/d	15.9^a	16.6^a	17.5^ab	19.5^b	17.9^ab	0.636	0.010
Total DM intake, g/d	101.7^bc	98.7^cd	96.8^d	103.7^ab	106.0^a	0.963	<0.001
FCR	6.4^a	6.0^a^b	5.6^ab	5.3^b	5.9^ab	0.198	0.014
DM: dry matter; FCR: Feed conversion ratio; KL0, KL25, KL50, KL75, KL100 corresponding to replacing levels of para grass by kudzu leaf in diets at 0%, 25%, 50%, 75% and 100%. ^{a,b, c} values with different superscript letters within one row are significantly different at the level of 5%.


Figure 2. Effect of replacing levels of para grass leaf by kudzu leaf in diets levels on total dry matter intake of rabbits	Figure 3. Effect of replacing levels of para grass leaf by kudzu leaf in diets levels on live weight gain of rabbits

Figure 4. Effect of replacing levels of para grass leaf by kudzu leaf in diets levels on FCR of rabbits

Conclusions

The substitution of para grass by kudzu leaf affected on feed intake and nutrient intake, daily weight gain and FCR.
Rabbits fed diets containing para grass replacement by kudzu leaf were optimized growth and FCR rates at 75% replacement level.

Acknowledgments

We thank Faculty of Animal Sciences and Veterinary Medicine, University of Agriculture and Forestry, Hue University for sponsoring this research through the science and technology project. Code: DHL2023-CNTY-04 and DHL2023-CNTY-SV-03.

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