Utilization of catfish oil in diets based on dried cassava root waste for crossbred fattening pigs in the Mekong delta of Vietnam

Le Thi Men, Huynh Huu Chi, Ngo Vi Nghia, Nguyen Thi Kim Khang and Brian Ogle

Department of Animal Science, College of Agriculture,
Cantho University, Vietnam

* Song Hau State Farm, Cantho Province, Vietnam

** Tapioca Enterprise ,Tri Ton - Angiang Province, Vietnam

*** Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Sweden

Abstract

An experiment was carried out at Song Hau State farm from April to June in 2002 with 48 crossbred growing pigs (Landrace * Large White) with an average initial live weight of 57 kg and final live weight of 90 kg. The trial included 4 diets: Cassava root meal, catfish oil 0 (Control, CRM-OIL0); Cassava root waste, catfish oil 0 (CRW-OIL0); Cassava root waste, catfish oil 5% (CRW-OIL5) and Cassava root waste, catfish oil 10% (CRW-OIL10) and 4 blocks, corresponding to the initial live weights of the groups, randomly allocated to 16 pens. The mean dietary crude protein (CP) content was 15.3 % in dry matter and the daily DM feed intake equal to 3 % of the mean pen live weight.

Mean daily gains were significantly different (P<0.05) among treatments, and were 685 g, 598 g, 715 g and 634 g for CRM-OIL0, CRW-OIL0, CRW-OIL5 and CRW-OIL10 diets, respectively. The FCRs were 2.9, 3.1, 2.9 and 3.0 for these diets, respectively. The carcass quality parameters of back fat thickness (2.2, 2.2, 1.9 and 2.4 cm, respectively) and loin eye area (46.7, 45.2, 47.5 and 45.6 cm², respectively) were not significantly different between diets. Similarly the content of crude protein in loin muscle was not affected by treatment (P>0.05). The Iodine No of back fat was higher (P<0.01) in the 10 % catfish oil diet.

The highest economic benefit was for the CRW-OIL5 diet.

Key words: Carcass quality, cassava root waste, catfish oil, fattening pigs, feed conversion, growth, iodine number

Introduction

The mountain and acid sulphate soil regions of Angiang province in the Mekong Delta include large areas suitable for growing cassava. Cassava is the main source for starch production and there is abundant cassava root waste produced. This material is normally dried and used as a carbohydrate source for animal feeding.

A large water surface area on the Tien and Hau rivers is suitable for aquaculture, especially for Mekong catfish cultivation in floating houses. Large factories produce frozen white cobbler filet for export. Of the abundant residues, the belly is pressed to give raw fish oil, which mainly consists of the fatty acids C16:0 (30.1%), C18:1 (38.3%) and C18:2 (13.2%) and has an energy content of 37.6 MJ/kg.

The main objectives of the study were to determine whether cassava root waste meal and catfish oil can be used in diets of fattening pigs without affecting performance and carcass quality.

Materials and methods

Experimental design and pigs

The experimental design included 4 dietary treatments and 4 blocks (according to initial live weight), within which pigs were randomly allocated to the treatments. There were 3 pigs in each pen, and they were given the experimental diets two times daily. The daily allowance was restricted to 3% of body weight. Samples of feed stuffs and mixed feed were taken for analysis of chemical composition. All animals were given free access to drinking water, and were weighed at the start and end of the trial and monthly.

Parameters measured

The pigs were slaughtered after 12 hours of starvation at a mean live weight of 100 kg. The empty body weight and carcass percentage of 12 pigs (3 pigs on each of the 4 treatments) were calculated. Carcass measurements were made on the hot carcasses. The back fat thickness and loin eye area were measured at the 10^th rib and samples taken for the analysis of chemical composition (DM, CP and pH). Back fat at the 10^th rib was also extracted and the Iodine Index determined. Feed costs per kg live weight gain were calculated using current market prices in VND.

Statistical analyses

Data were analyzed by ANOVA using the General Linear Model of Minitab Statistical Software version 13. Sources of variation were treatments and blocks. The Tukey Test for paired comparisons was used to separate means when the differences were significant at the 5% level.

Results and discussion

The health of the pigs was good and the growth rates normal for each experimental group.

Diet composition

Crude protein and essential amino acid concentrations were similar for the four dietary treatments (Tables 1 and 2), but the ME content of the CRW-OIL0 diet (12.6 MJ/kg) was lower than of the CRM-OIL0, CRW-OIL5 and CRW-OIL10 diets (13.0, 13.2 and 13.3 MJ/kg, respectively).

Table 1. Mean values with SEM for the chemical composition of the feed stuffs used in the experiment
	DM, %	% of dry matter
Feed stuff	DM, %	CP	EE	CF	Ash
Broken rice	87.3±0.19	8.6±2.80	1.8±0.12	1.8±0.12	1.5±0.10
Rice bran	90.1±0.04	13.5±0.19	10.6±0.24	8.6±0.32	6.5±0.02
Cassava root meal	89.1±0.32	4.5±0.51	0.04±0.02	3.1±0.05	2.3±0.09
Cassava waste	90.2±0.23	4.2±0.58	0.7±0.23	10.3±0.27	1.4±0.10
Soybean, extracted	89.0±0.03	50.6±1.23	1.7±0.39	6.6±0.06	7.9±1.30
Soybean, dehulled	90.5±0.42	41.9±0.89	9.2±1.57	7.4±1.02	7.4±1.02

Table 2. Ingredient and chemical composition of the experimental diets (%)
	CRM-	CRW-	CRW-	CRW-
	OIL0	OIL0	OIL5	OIL10
Broken rice	35.2	38.8	26.9	19.8
Rice bran	10	10	20	25
Cassava root meal	30	0	0	0
Cassava waste	0	25	25	25
Catfish oil	0	0	5	10
Soybean, extracted	13.1	13.9	20.6	17.7
Soybean, dehulled	9.3	10	0	0
Minerals	1.2	1.2	1.7	1.7
Premix	1.2	1.1	0.8	0.8
Total	100	100	100	100
Feed cost/kg (VND)	2334	1988	1938	2093
ME (MJ/kg)	13.0	12.6	13.2	13.3
CP, %	15.2	15.3	15.3	15.2
Lys., %	0.71	0.72	0.70	0.70
Met. + Cys., %	0.46	0.47	0.45	0.45
Thr., %	0.50	0.51	0.50	0.50
Trp., %	0.17	0.17	0.16	0.17

Feed intake

The daily feed allowance generally was consumed (Table 3), although intake for each dietary treatment was somewhat lower than the allowance of 3 % of live weight when the mean temperature was highest (34^oC in April). However, dietary nutrient concentrations in all treatments were sufficiently high, and so the protein and energy intakes met recommended daily intakes of 350 g CP and 30 MJ ME for the finishing period (man 1987).

Table 3. Feed and nutrient intakes of the experimental diets
Item	CRM-OIL0	CRW-OIL0	CRW-OIL5	CRW-OIL10
Basal feed, kg/d	2.3	2.1	2.3	2.5
ME, MJ/d	29.8	26.4	30.7	32.8
CP, g/d	350	321	352	380
Lysine, g/d	16.3	15.1	16.1	17.5

Daily weight gain

Mean daily weight gains (Table 4) were significantly different (P<0.05) among treatments. The lowest daily gains were on the CRW-OIL0 diet, probably because of the low ME concentration, as other nutrient concentrations, such as CP and essential amino acids were similar among diets. Harmon (2000) recommended adding lipids at 3 to 7 % of the diet in areas with high environmental temperatures.

Table 4. Effect of dietary treatment on fattening pig performance
	CRM- OIL0	CRW-	CRW-	CRW-	Prob.	SEM
Item	CRM- OIL0	OIL0	OIL5	OIL10	Prob.	SEM
Live weight, kg
Initial	57.8	57.3	57.6	57.3	0.986	1.102
Final	92.4	85.5	94	89.3	0.128	2.672
Daily gain, g	685^ab	598^a	715^b	634^ab	0.032	29.448
FCR (DM basis)	2.9	3.1	2.85	3.04	0.24	0.087
ab Means in the same row without letter in common differ at P<0.05

Feed conversion

Feed conversion ratios (Table 4) did not differ among diets. The polyunsaturated fatty acids in catfish oil were clearly effectively utilized as an energy source by the pigs, as reported by Harmon (2000).

Carcass evaluation

Carcass quality parameters were not significantly influenced by treatment (Table 5). Takada and Saito (1998) demonstrated that dietary g-Linolenic acid enriched oil reduced back fat thickness because of increased activities of liver fatty acids degrading enzymes, but this was not the case in the experiment reported here. The content of crude protein in loin muscle was not influenced by diet. However, the Iodine No of the back fat was higher (P<0.01) for the CRW-OIL10 diet. According to Vu Duy Giang (1997) this value for pigs is normally between 44 and 66, and obviously the higher level of unsaturated fatty acids in the 10 % catfish diet resulted in softer fat deposits (McDonald et al 1995).

Table 5. Effect of dietary treatment on carcass parameters and the composition of the loin muscle
	CRM-	CRW-	CRW-	CRW-	Prob.	SEM
	OIL0	OIL0	OIL5	OIL10	Prob.	SEM
No of pigs	3	3	3	3
Slaughter live weight, kg	101	99	99	104
Carcass yield , %	77.7	77.7	77.3	77.4	0.98	0.88
Loin eye area, cm²	46.7	45.2	47.5	45.6	0.99	4.88
Back fat depth, cm	2.2	2.17	1.93	2.37	0.09	0.18
Composition of loin muscle
Loin and ham, %	50.2	48	50.2	50.2	0.81	1.91
DM, %	26.8^b	27.8^a	27.2^a	27.2^a	0.001	0.21
CP, %	20.3	20.2	20.1	19.8	0.76	0.34
Iodine No. of back fat	55.6^a	52.4^b	60.7^c	69.8^d	0.001	0.33
abcd Means in the same row without letter in common differ at P<0.05

The feed cost per kg weight gain was lowest and net economic benefit highest (Table 6) when CRW replaced CRM and 5 % catfish oil was added (CRW-OIL5).

Table 6. Effect of dietary treatment on feed cost and economic benefit (1 USD = VND 15,000)
	CRM- OIL0	CRW-OIL0	CRW-OIL5	CRW-OIL10
Total weight gain, kg	34.6	28.2	36.4	32
Total income, VND	570,900	465,300	600,600	528,000
Feed cost/kg gain (VND)	6,769	6,163	5,523	6,363
Total feed cost (VND)	234,207	173,797	201,037	203,616
Income - feed costs (VND)	336,693	291,503	399,563	324,384
Relative to control	100	86.6	118.7	96.3

Conclusions

Cassava root waste can completely replace cassava root meal provided that the diet includes 5% catfish oil. This diet significantly improved growth performance without affecting carcass quality, and resulted in the highest economic benefit, and can thus be recommended for producers.

References

AOAC 2000 Official Methods of Analysis. American Association of Analytical Chemists.

Chhay Ty, T R Preston and J Ly 2003 The effect of graded levels of palm oil on N digestibility and N balance in growing pigs. Mekarn MSc thesis, 2003. http://www.mekarn.org/MSc/theses03/chhaexp1.htm

Göhl B 1981 Tropical Feeds. FAO Animal Production and Health Series. No. 12, pp: 320 – 322, 441-444.

Harmon B G 2000 Swine nutrition and management. Purdue University. USA .

Linh Quang Nguyen 2002 Fatty acid supply of growing pigs in Central Vietnam. Doctoral thesis. Utrecht University. The Netherlands.

McDonald P. Edwards R A Morgan C A 1995 Animal Nutrition. Longman Scientic & Technical. New York. pp: 28 - 48

Ryozo Takada and Mamoru Saito 1998 Effect of Dietary g-Linolenic Acid- Enriched Oil on Backfat thickness and Fatty Acid Degrading Enzyme Activities in Growing Pigs. Animal Science and Technology Vol. 69, No.5

Wiseman J 1987 Feeding of Non-Ruminant Livestock. Butterworths, pp: 39-53.

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