Citation of this paper

Effects of maize and molasses supplementation with different levels in diets on growth performance of New Zealand White crossbred rabbits

Pham Thi Cam Nhung, Nguyen Thiet¹ and Truong Thanh Trung

College of Agricuture, Can Tho University, Can Tho City, Vietnam
tttrung@ctu.edu.vn
¹ College of Rural Development, Can Tho University, Can Tho City, Vietnam

Abstract

The aims of this study was to evaluate the effects of maize and molasses supplementation with different levels in diets on growth performance of New Zealand White crossbred rabbits. The experiment was a completely randomized design with 5 treatments and 4 replications, and 4 rabbits with balanced sexually per trial unit. The treatments were the different dietary digestible energy levels and sources including 10 MJ/kgDM (control, DE10); either supplementation with maize: 11 MJ/kgDM (DE11M) and 12 MJ/kgDM (DE12M) or molasses: 11 MJ/kgDM (DE11Mo) and 12 MJ/kgDM (DE12Mo). The experiment was carried out 12 weeks. The results of experiment showed that DE12M group was higher daily weight gain and final live weight than other treatments (p<0,05). However, DE11Mo group was lowest FCR and best economic efficiency as compared to other groups. It concluded that supplementation of molasses in diet with 11 MJ/kg DM have improved growth performance in crossbred rabbit.

Key words: crossbred rabbit, maize, molasses, performance

Introduction

Mekong Delta has known as an area with diversity vegetation, cheap and available agro-industrial by-products. Rabbits are one of herbivorous, which not only utilizes agro-industrial by-products, but also converts 20% of their protein intake into meat compared to 16-18% in pigs and 8-12% in cattle (Thu and Dong 2011). O'Meara et al (1992) reported rabbit meat has great nutritional value, due to its high protein content (20 - 21%), low fat (4 - 5%) and low cholesterol (45 mg/kg), it is recommended for people patients with cardiovascular disease can use (Hu and Willett 2002). Therefore, it is possible to meet requirements for high quality protein in human food. Molasses is a by-product of the sugar processing industry. The main component of molasses is sugar, mainly sucrose with a little glucose and fructose (Trach 2003). Kpodékon et al (2008) showed that molasses supplementation in the diet of fattening rabbits did not affect the daily weight gain and weight of rabbits during rearing. Besides, maize is also known as a source of energy in the diet, rich in carotene that can be supplemented for cattle. Some studies have suggested that the optimal DE in the diet of growing rabbits is 2500 kcal/kg feed (NRC 1977; Lebas 1980) de Blas and Mateos 2020 recommended DE for breeding doe rabbits to be 10.7 MJ and fattening rabbits to be between 9.7 - 11.5 MJ without any adverse effects. Linga and Lukefahr (2000) showed that supplementation of Molasses in alfalfa diets improved the growth performance of New Zealand rabbits and Altex rabbits compared with alfalfa-based diets. Amici and Finzi (1995) recommended the use of molasses block as a feed source to increase the growth performance of rabbit meat in developing countries.

The use of maize and molasses in the diet as energy sources for growth rabbits both utilizes the agricultural by-products and lowers production costs, however, currently studies on these feeds are still very limited in terms of livestock production in Vietnam. The study of effects of digestible energy sources and levels in diets on growth performance of New Zealand White crossbred rabbits was carried out with the following objectives: to determine the optimal level of digestible energy in the diet for growth performances of crossbred rabbits. Besides that, identification of an appropriate energy source for growth rabbits. From there, the results are recommended to farmers to contribute to the development of rabbit farming and increase income, contributing to improving the lives of farmers.

Materials and methods

Location and time

The experiment was carried out at the farm in Thoi Hoa ward, O Mon district, Can Tho city, Vietnam. The chemical composition of experimental diets was analyzed at the laboratory E205 of the Faculty of Animal Sciences, College of Agriculture, Can Tho University. The implementation of this study was from Feb to October 2022.

Experimental design

The experiment consisted of 80 New Zealand White weaned crossbred rabbits (New Zealand White x local rabbits) at period 30 – 40 days old (560±11,64 g/head) were produced at the farm. Rabbits are vaccinated against parasitic diseases, polio and respiratory diseases. The experiment was a completely randomized design with 5 treatments and 4 replications with 2 males and 2 female rabbits per trial unit. The treatments were the different dietary digestible energy levels and sources including 10 MJ/kgDM (control, DE10); either supplementation with maize: 11 MJ/kgDM (DE11M) and 12 MJ/kgDM (DE12M) or molasses: 11 MJ/kgDM (DE11Mo) and 12 MJ/kgDM (DE12Mo). The experiment was carried out 12 weeks consisting a week for adaptation and 11 weeks for data collection. The rabbits were housed in individual cages and had free access to clean drinking water. The ingredients and chemical composition of experimental diets were shown in Table 1 and 2.

Table 1. Ingredients and chemical composition of experimental diets
Feed (%DM)	Treatments
Feed (%DM)	DE10	DE11M	DE12M	DE11Mo	DE12Mo

Ingredients
Operculina turpethum	65	43	26	52	37
Soybean extraction meal	11	17	23	18	25
Soya waste	24	19	10	16	9
Maize	0	21	41	0	0
Molasses	0	0	0	14	29
Total	100	100	100	100	100
Chemical composition
DM, %	15.9	21.1	31.2	19.7	26.1
OM, %	90.5	92.6	94.3	90.2	89.9
CP, %	19.0	19.0	18.9	19.0	18.9
EE, %	6.86	5.89	4.84	5.55	4.20
NDF, %	40.0	33.1	27.0	33.2	25.7
ADF, %	28.1	21.6	15.5	22.8	17.2
CF, %	20.0	14.7	10.0	16.1	11.9
Ash, %	9.51	7.40	5.71	9.84	10.10
DE, MJ/kgDM	10.0	11.0	12.0	11.0	12.0
DE 10: digestible energy containing in diet was 10 MJ/kgDM without using maize and mollases , DE 11.0M: digestible energy containing in diet was 11 MJ/kgDM with using maize, DE 12.0M: digestible energy containing in diet was 12 MJ/kgDM with using maize, DE 11.0Mo: digestible energy containing in diet was 11 MJ/kgDM with using mollases, DE 12.0M: digestible energy containing in diet was 12 MJ/kgDM with using mollases

Data collection and management

The rabbits were fed twice daily at 7:00h and 17:00h. All rabbits were weighed once a week throughout the experiment and before feeding in the morning.

Feed offered and refusals were recorded daily in the morning during the experiment. The samples were collected every 2 weeks. Samples were dried at 55⁰C for 48 hours until the weight unchanged, then finely ground for chemical composition analysis.

The experimental of nutrient digestible period was conducted at the 6 ^th week of the experiment and carried out during 6 days continuously. The feeds offered, refusals, feces and urine were collected for nutrient digestibility and nitrogen retention measurement. Samples of feed offered, refusals and feces were dried and finely ground. Then mix the samples of 3 days according to each experimental unit to analyze the nutrient components such as DM, OM, CP, EE, NDF and Ash.

Statistical analysis

All data were analyzed with the General Linear Model of Minitab 13.21 program (Minitab, 2016). The significance of pairwise comparisons was determined by Tukey posttest. Significance was declared at p <0.05.

Results and discussion

Table 2. Effects of maize and molasses supplementation on nutrient intake in crossbred rabbits
Feed	Treatments					SE	p
Feed	DE10	DE11M	DE12M	DE11Mo	DE12Mo	SE	p

Dry matter, g/per/day
Operculina turpethum	48.1^a	32.7^c	18.3^e	38.3^b	26.6^d	0.600	0.001
Soybean extraction meal	7.09^c	13.0^b	19.0^a	12.6^b	18.6^a	0.663	0.001
Soya waste	14.2^a	13.8^a	7.82^c	11.2^b	6.62^c	0.590	0.001
Maize	-	17.1^b	34.0^a	-	-	0.692	0.001
Molasses	-	-	-	10.8^b	19.7^a	0.481	0.001
Nutrient intake daily, g/per/day
DM	69.3^c	76.6^ab	79.1^a	73.0^bc	71.5^bc	1.932	0.018
OM	62.5^c	71.0^ab	74.8^a	65.8^bc	64.3^bc	1.821	0.001
CP	13.0^b	14.5^ab	15.1^a	13.7^ab	13.9^ab	0.405	0.025
EE	4.71^a	4.46^a	3.75^b	4.01^b	3.06^c	0.094	0.001
NDF	28.2^a	25.2^b	20.8^c	24.1^b	18.7^d	0.464	0.001
ADF	19.7^a	16.3^b	11.7^c	16.6^b	12.5^c	0.293	0.001
CF	14.2^a	11.1^b	7.42^d	11.8^b	8.62^c	0.183	0.001
Ash	6.82^a	5.63^b	4.32^c	7.26^a	7.15^a	0.122	0.001
DE, MJ	0.69^c	0.85^b	0.96^a	0.80^b	0.85^ab	0.024	0.001
^{a, b, c, d, e} Mean values with different superscripts within the same row are different at p<0.05 DE 10: digestible energy containing in diet was 10 MJ/kgDM without using maize and mollases , DE 11.0M: digestible energy containing in diet was 11 MJ/kgDM with using maize, DE 12.0M: digestible energy containing in diet was 12 MJ/kgDM with using maize, DE 11.0Mo: digestible energy containing in diet was 11 MJ/kgDM with using mollases, DE 12.0M: digestible energy containing in diet was 12 MJ/kgDM with using mollases

Table 3 showed the amount of feed and nutrients daily intake of experimental rabbits in the growth period. In general, all the indicators in the table have statistically significant differences among treatments ( p<0.05). The DM intake of Operculina turpethum was the highest at DE10 (48.1 g/per/day) and the lowest at DE12M (18.3 g/per/day). In contrast, the DM intake of soybean extraction meal reached the highest value at DE12Mo (18.6 g/per/day) and the lowest at DE10 (7.09 g/per/day). The highest and lowest DM intake of soya waste was in DE10 and DE12Mo groups (14.2 g/per/day and 6.62 g/per/day respectively).

Total DM intake was statistically significant (p<0.05) among treatments, reaching the highest value at DE12M (79.1 g/per/day) and the lowest at DE10 (69.3 g/per/day). These results were higher than the study result of Dong and Thu (2021) when adding molasses to the diet of growing rabbits, the amount of DM increased gradually with the level of molasses addition in the diet from 0 to 24% molasses. The value of DM intake ranged from 69.3 to 79.1 g/per/day and was similar to the results of Trung et al (2016) when gradually increasing the level of ME10.0 to ME12.0, the DE intake gradually increased from ME10.0 – ME11.0 then decreased from ME11.5 and ME12.0 with DM intake ranging from 69.4 - 74.5 g/per/day.

The amount of OM and CP intakes had statistically significant differences (p<0.05) among treatments and reached the highest value at DE12M and the lowest at DE10 with values of 74.8 and 15.1 g/per/day compared with 62.5 and 13.0 g/per/day.

The amount of EE and NDF intakes was significantly different (p <0.05) among treatments and reached the highest value at DE10 (4.71 and 28.2 g/per/day) and lowest at DE12Mo (3.06 and 18.7 g/per/day). From these results, it showed that the NDF intake is lower than the optimal NDF intake for rabbits as recommended by De Blas and Mateos (2010).

The differences in ADF, CF and Ash intakes was statistically significant ( p<0.05) and reached the highest value at DE10 of 19.7; 14.2 and 6.82 g/per/day and the lowest at DE12M was 11.7; 7.42 and 4.32 g/per/day. The amount of ADF intake was lower than the optimal level which recommended by De Blas and Mateos (2010) from 18-20% of ADF. The amount of DE intake was significantly different (p<0.05) and reached the highest value at DE12M (0.96 MJ) and the lowest at DE10 (0.69 MJ). In summary, the DE12M and DE12Mo had the same energy levels, but nutrient intakes from DE12M were higher than in DE12Mo.

Table 3. Daily weight gain of the growth rabbit
Items	Treatments					SE	p
Items	DE10	DE11M	DE12M	DE11Mo	DE12Mo	SE	p

Initial live weight, g	560	562	563	568	565	11.64	0.986
Final live weight, g	2290^c	2482^ab	2535^a	2472^ab	2355^bc	30.87	0.001
Daily weight gain, g/day	20.6^c	22.9^a	23.5^a	22.7^ab	21.3^bc	0.312	0.001
FCR	3.37	3.35	3.37	3.22	3.36	0.090	0.743
^{a, b, c} Mean values with different superscripts within the same row are different at p<0.05 DE 10: digestible energy containing in diet was 10 MJ/kgDM without using maize and mollases , DE 11.0M: digestible energy containing in diet was 11 MJ/kgDM with using maize, DE 12.0M: digestible energy containing in diet was 12 MJ/kgDM with using maize, DE 11.0Mo: digestible energy containing in diet was 11 MJ/kgDM with using mollases, DE 12.0M: digestible energy containing in diet was 12 MJ/kgDM with using mollases

Table 4 showed the growth performance of experimental rabbits. Initial weight ranged from 560 – 568 g/per, and this difference was not statistically significant (p>0.05). Final weight gradually increased as maize supplementation increased, whereas final weight decreased as molasses supplementation (Table 4, p<0.05). DE12M had the best weight gain of 23.5 g/per/day, the final weight results were higher than that of the other treatments. This result is higher than the research result of Linh and Thu (2017) with the final weight ranging from 1908 to 2205 g.

The results of daily weight gain had a statistically significant difference (p< 0.05), the highest at DE12M and the lowest at DE10 was 23.5 and 20.6 g/per/day, respectively. Thus, the supplementation of maize and molasses in diet improved daily weight gain. Daily weight gain tended to increase gradually from DE10 to DE11M and DE12M, and gradually decreased at DE11Mo and DE12Mo. The weight gain of rabbits was from 20.6 to 23.5 g/per/day, this result was higher than the research results of Chau (2015) from 17.5 to 19.7 g/per/day with adding different levels of crude protein and essential amino acids and higher than the results of Dong and Thu (2021) with adding molasses to the diet of growing rabbits, the weight gain was from 15.2 – 20.0 g/per/day. This was suitable with the results of Trung et al (2016) with daily weight gain from 20.5 to 24.5 g/per/day.

FCR was not statistically significant differences among treatments (p>0.05). This result was lower than the results of Linh and Thu (2017), whose FCR of crossbred rabbits was 3.48 to 3.73 and lower than the results of Kpodékon et al (2008) had a FCR of rabbits in the fattening stage with molasses supplying in diets was 3.59. Economic returns of treatment DE12M had a profit of 57.531 VND/head, lower than 80.244 VND/head of DE11Mo.

Table 4. Digestibility nutrients of rabbits during the nutrient digestible period
Items	Treatments					SE	p
Items	DE10	DE11M	DE12M	DE11Mo	DE12Mo	SE	p

Digestibility nutrients
DMD	75.0^c	79.7^ab	80.9^a	77.7^bc	78.2^ab	0.709	0.001
OMD	74.8^c	79.9^ab	81.4^a	77.6^bc	78.3^ab	0.713	0.001
CPD	79.0^b	82.9^ab	83.4^a	81.4^ab	81.7^ab	0.912	0.031
EED	88.1^a	87.8^ab	85.5^b	86.4^ab	83.0^c	0.539	0.001
NDFD	57.4^b	63.2^a	61.1^ab	60.9^ab	58.8^b	0.918	0.004
ADFD	49.2	56.2	49.9	55.0	51.6	1.701	0.060
Nitrogen balance
N intake, g	2.37^b	2.56^ab	2.59^a	2.45^ab	2.48^ab	0.045	0.024
N feces, g	0.50	0.44	0.43	0.44	0.45	0.025	0.376
N urine, g	0.60	0.55	0.48	0.45	0.56	0.040	0.111
N retention, g	1.26^b	1.58^a	1.68^a	1.54^a	1.47^ab	0.057	0.002
%NR/NI	53.7^b	61.6^a	65.0^a	62.8^a	59.0^ab	1.654	0.003
NI/W^0.75	1.83	1.88	1.87	1.80	1.88	0.066	0.874
NR/W^0.75	0.98^b	1.16^ab	1.22^a	1.13^ab	1.10^ab	0.045	0.025
^{a, b, c} Mean values with different superscripts within the same row are different at p<0.05 DE 10: digestible energy containing in diet was 10 MJ/kgDM without using maize and mollases, DE 11.0M: digestible energy containing in diet was 11 MJ/kgDM with using maize, DE 12.0M: digestible energy containing in diet was 12 MJ/kgDM with using maize, DE 11.0Mo: digestible energy containing in diet was 11 MJ/kgDM with using mollases, DE 12.0M: digestible energy containing in diet was 12 MJ/kgDM with using mollases

The nutrient digestibility of DM, OM, CP, EE and NDF were all statistically significant (Table 4, p<0.05) among treatments, excepting for ADF (p>0.05). The digestibility of nutrients was highest at DE12M with DM, OM, and CP at 80.9; 81.4 and 83.4%. This result was almost same to the research result of Dong and Thu (2016) with the highest nutrient digestibility of DM, OM, CP at 75.9; 76.6 and 84 % and higher than results of Giang (2010) were 66.6; 68.3; 75.2%.

Nitrogen intake, N retention, NR/W^0.75and %NR/NI were significantly different (p<0.05) between treatments and reached the highest value at DE12M and lowest at DE10, the values were 2.59 g, 1.68 g, 1.22 and 65.0%, respectively, compared with 2.37 g, 1.26 g, 0.98 and 53.7%. This result was higher than that of Dong et al (2008) when water spinach leaves were added to the diet of Para grass on hybrid rabbits growing in the Mekong Delta, the nitrogen intake and nitrogen retention ranged from 1.21 to 1.6 and 0.76 to 1.07. This result was lower than that of Trung et al (2016) has the highest %NR/NI of 68.7% at ME12.0.

Conclusion

The results from current study indicated that crossbred rabbits supplemented molasses as energy sources with 11 MJ/kg DM is the best choice to improve economic return.

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