Effect of replacing sugar cane juice with African palm oil (Elaeis guineensis) on performance and carcass characteristics of pigs

Le Duc Ngoan*, R B Ogle**, Patricia Sarria*** and T R Preston****

Instituto Mayor Campesino, Buga, Valle, Colombia,
*College of Agriculture and Forestry, Hue University, Vietnam
**Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Uppsala, Sweden (brian.ogle@huv.slu.se)
***Universidad Nacional Agropecuaria, Medellin, Colombia
**** Finca Ecologica, College of Agriculture and Forestry, National University of Ho Chi Minh City, Vietnam (tpreston@hcm.vnn.vn)

Abstract

At the Instituto Mayor Campesino (IMCA), Buga, Valle, Colombia, 15 Large White * Hampshire (LW*HS) growing- fattening pigs in individual pens were allocated to one of five dietary treatments, with one castrate and two females per treatment. The treatments were mixtures of SCJ and PO on an isocaloric basis of 100:0, 75:25, 50:50, 25:75 and 0:100. Feeding was ad libitum. The trial period was from 24 to 90 kg mean live weight, after which the pigs were slaughtered for carcass evaluation. Daily liveweight gains were in the range of 690 to 850 g/day and were not affected by dietary treatment (P>0.05). Dry matter intake was reduced and feed dry matter conversion ratio improved by increasing the proportion of PO in the diet (P<0.05). Loin eye area was increased and back fat thickness reduced as the proportion of energy derived from PO was increased.

Key words: palm oil, sugar cane juice, pigs, digestibility, growth, carcass traits

Introduction

The use of African palm (Elaeis guineensis) oil and its by products as a cereal grain replacement in pig production is a recent development of importance for tropical countries (Ocampo et al 1990a,b; Ocampo 1994a,b). In earlier experiments with palm oil (Balogun et al 1983; Abu et al 1984) the level in the diet was relatively low (less than 10%) and it was mixed with traditional ingredients. By contrast, recent research has shown that the oil-rich fibrous by-product (Ocampo et al 1990a,b), the oil itself (Ocampo 1994a) or even the whole fruit (Ocampo 1994b), can be the basic component of the diet with oil levels reaching as high as 50% of the dry diet matter, and that growth and carcass traits are of the same order as in pigs fed diets based on cereal grain.

The use of sugar cane juice as the major energy source in the diets of pigs was demonstrated in Mexico (Mena et al 1982) and further developed in Colombia (Sarria et al 1990). It is now the basis of commercial pig production in situations where alternative systems of use of sugar cane are economically less favourable (Preston and Murgueitio 1992).

Sugar cane juice and palm oil are two radically different energy sources, the former being composed essentially of soluble sugars, while the latter contains glycerol and fatty acids. It was therefore of interest to study the effect of different ratios of these contrasting energy substrates on growth and carcass characteristics of growing-finishing pigs.

Materials and methods

The experiment was carried out at the Instituto Mayor Campesino, located in Buga, Valle, Colombia from February to August 1993. The area is 1000m above sea level with 23.2 ºC daily mean temperature, 75.5 % mean humidity and 980 mm annual rainfall.

Treatments, design and animals

The treatments were five diets in which crude palm oil (PO) replaced sugar cane juice (SCJ) on an isocaloric basis in proportions (PO:SCJ) of 0:100 (PO0), 25:75 (PO25), 50:50(PO50), 75:25(PO75) and 100:0 (PO100). Soya bean meal was the sole protein supplement in the diets. Fifteen Large White-Hampshire crossbred pigs with an average initial live weight of 24.3 kg were grouped by sex and randomly allocated within sex groups to the five treatments with an outcome of 2 females and one castrate male per treatment. The pigs were housed individually.

Experimental diets

The sugar cane was cut either daily or every other day and was crushed in the morning and the extracted juice fed the same day . The average Brix (% soluble solids) determined by refractometer was 17.4. The dry matter content was 17.6% and the gross energy in the dry matter 15.8 MJ/kg. Two batches of crude palm oil were purchased. The mean chemical composition was 91.5 % DM with 0.02% N and 40.5 MJ/kg gross energy in the dry matter. The other dietary component was fortified soya bean meal (FSBM) consisting of soya bean meal (91.3 %), salt (1.3 %) minerals (6.4 %) and a vitamin complex (1%). The amounts of PO and SCJ were adjusted weekly according to the increase in the individual liveweight of the animals.

Housing management and feeding

The pigs were individually housed in covered pens (1.7*2.5m) constructed from bricks and with a concrete floor. They were adapted to the experimental diets for two weeks before the start of the feeding trial. The protein level of approximately 200 g/day was achieved by giving a fixed amount of 500g/day of the FSBM. This was maintained constant throughout the feeding trial on the basis of previous experiences with diets based on sugar cane juice (Sarria et al 1990) and palm oil by-products (Ocampo et al 1990b). The level of 200 g protein/day is less than recommended by ARC (1981) and NRC (1988) for growing pigs but is in accordance with the opportunity to reduce total protein levels when the protein source is well balanced in amino acids (Speer 1990).

The protein supplement and half of the PO were given as a mixture at 09.30 hours, half of the SCJ was given at 11.30 hours when the animals had finished their first meal, and then the rest of the PO and SJC allowances were given at 14.30 hours. The amounts of the mixtures of SCJ and PO were adjusted so that there were always refusals in the feed trough the following morning. The refusals of juice and oil were collected every day at 09.00 before feeding the morning meal, and then separated and weighed.

Measurements and analyses

The pigs were weighed at 14 day intervals and the trial was terminated when the animals reached a mean live weight of 92 kg. Individual weight gains were calculated from the linear regression of weight against time.

Feed intake was measured as fresh material offered minus refusals, and samples were taken of the dietary components for determination of dry matter, nitrogen, gross energy, ash, calcium, phosphorus and sodium using standard methods (AOAC 1985). Fatty acids were determined by the method of Sukhija and Palmquist (1988).

At the end of the experiment, all the pigs were slaughtered and the carcasses evaluated. Carcass weight was determined directly after slaughter to calculate hot carcass dressing percentage. The length of the carcass was measured between the first rib point and the symphysis pubic bone. The average back fat depth and loin eye area were determined at the tenth rib.

Statistical analysis

Statistical analysis was performed using the General Linear Model (GLM) procedure of Minitab statistical soft ware (Minitab Version 8). Growth and feed conversion traits were analysed with initial live weight as a covariant. The error term included the interaction "sex x animals". It was not possible to test for sex differences because on each treatment (diet) there were two females but only one castrate male. However, it was assumed that the interaction between sex and diet was negligible. For carcass traits the slaughter live weight was used as covariant.

Table 1: Chemical composition of palm oil, sugar cane juice and fortified soya bean meal mixture
		DM	GE	% of dry matter
		( %)	MJ/kg DM	N*6.25	EE	Ash	Ca	P	Na	K
Palm oil		88.1	40.3	0.1	82.6	0.33	0.03	0.02	0.02	0.03
Sugar cane juice		17.6	15.8	0.45	-	1.15	0.06	0.11	0.01	0.34
Soya bean meal*		89.4	18.3	48.9	1	12.3	2.06	1.4	0.28	2.29
*Includes mineral and vitamin supplement

Results and discussion

Chemical composition of the dietary ingredients

The chemical analysis of the dietary ingredients is shown in Table 1. The low ash content of the crude palm oil is noteworthy. By contrast, the sugar cane juice contained enough phosphorus to cover at least a third of the requirements for pig growth (ARC 1981), but the supply of calcium and sodium was negligible.

Table1: Chemical composition of palm oil, sugar cane juice and fortified soya bean meal mixture
	TDM	GE	% of dry matter
	%	MJ/kg	N*6.25	EE	Ash	Ca	P	Na	K
Palm Oil	88.1	40.3	0.1	82.6	0.33	0.03	0.02	0.02	0.03
Sugar cane juice	17.6	15.8	0.45	-	1.15	0.06	0.11	0.01	0.34
Soya bean meal*	89.4	18.3	48.9	1.0	12.3	2.06	1.4	0.28	2.29
*Includes mineral and vitamin supplement

The fatty acid composition of the crude palm oil is shown in Table 2. Palmitic and oleic were the principal fatty acids; however, the level of linoleic - one of the essential fatty acids - was relatively high. Lauric and myristic acids, which are implicated in raising serum cholesterol, were low. The unsaturated fatty acids accounted for half of the total.

Table 2: Composition of the palm oil (% of total fatty acids)
	Sample
Fatty acid	A	B	Mean
Lauric	0.3	1.6	0.95
Myristic	1.3	2.2	1.75
Palmitic	39.3	36.4	38.0
Stearic	5.9	8.0	6.95
Oleic	36.8	34.2	35.5
Linoleic	14.5	14.1	14.3
Saturated	46.4	49.3	48.4
Unsaturated	52.5	50.7	51.6

Feed intake

The mean intakes of the dietary ingredients are shown in Table 3. The proportions of SCJ and PO that were offered in treatments PO25, PO50 and PO75 were arranged so that the mixture was isocaloric. However, the pigs on all treatments were offered more of the energy ingredients than they could consume. Dry matter intake decreased significantly as the PO replaced the SCJ but there were no differences in intake of gross energy among treatments. This indicates that the pigs adjusted their intake on an isocaloric basis, irrespective of the source of the energy.

Table 3: Mean values for intake of the dietary ingredients during the trial
	PO0	PO25	PO50	PO75	PO100	SE/Prob
Daily intake
FSBM (g)*	500	500	500	500	500
SCJ(litres)	9.1	7.2	5	3.6	0
PO (g)*	0	218	321	408	728
Protein (g)	226	225	223	222	220
DM,kg	2.29	2.12	1.78	1.6	1.19	0.17/0.001
GE,MJ	32.9	35.3	32.6	32.1	33.5	30/0.95
*Daily intake (fresh basis)

Growth performance

There were no differences among the treatments in growth rate nor in feed conversion when the latter was expressed on a gross energy basis (Table 4). Thus the pigs appeared to use with equal efficiency the dietary energy, irrespective of whether this was derived from soluble sugars (sucrose, glucose and fructose) or lipids. On a dry matter basis, feed conversion improved as the content of PO in the diet increased but this has no nutritional significance. These findings are similar to those of Campbell and Taverner (1986) who reported that adding fat to diets of growing pigs led to a decline in voluntary feed intake and improved feed dry matter conversion, while energy intake and growth rate remained relatively constant.

Table 4: Mean values for growth, intake and feed of pigs fed different ratios of sugar cane juice and palm oil
	PO0	PO25	PO50	PO75	PO100	SE/Prob
Live weight, kg
Inital	24.5	24.4	24.2	24.3	24.2
Final	91.1	98.9	89.8	88.7	91.7
Daily grain,g	673	746	658	653	684	30.0/0.29
Feed convesion ratio(-/kg gain)
DM, kg	3.34	2.78	2.76	2.43	1.75	0.11/0.001
GE,MJ	48	46.2	48.8	48.8	49.3

It was observed that the pigs fed the diets with high PO content voided liquid faeces and had lower rates of growth during the first four weeks of the trial. As the pigs became accustomed to the high PO diets the problem disappeared. The liquid faeces were probably due to undigested lipids reaching the large intestine where they would be fermented giving rise to a "physiological" diarrhoea.

Carcass measurements

For administrative reasons there was a delay of twenty days between slaughter and termination of the experiment. Thus the slaughter liveweights were higher than normal, but it was not considered that this would have influenced effects of treatments (Table 5). Surprisingly, the main criteria of carcass quality - back fat thickness and loin area - were both improved by substitution of SCJ by PO. The equations relating loin eye area (X = cm²) and back fat thickness (Z = cm) to the observed contribution of PO to the diet ( % of GE as PO derived from the mixture of PO and SCJ) were:

Y1 =29.6 + 0.0746 X (r²= 0.89, P=0.010) .... for loin eye area

Y2 = 0.0458 Z - 0.00514 X -1.67X² (r² = 0.71, P=0.001).... for back fat thickness

Table 5: Mean values for carcass traits of pigs fed different ratios of sugar cane juice and palm oil
	PO0	PO25	PO50	PO75	PO100	SE/Prob
Slaughter LWt, kg	102	106	104	102	102	2.08/0.95
Carcass Wt, kg	76.8	77.7	76.1	76.1	76.4	1.49/0.5
Dressing %	74.2	75.2	73.5	73.6	73.7	1.54/0.51
Length, cm	78.9	78.1	79.5	79.5	79.8	1.21/0.4
Back fat, cm	3.14	3.12	2.5	2.64	2.71	0.06/0.03
Loin eye area, cm²	29.4	31.6	34.1	33	37.2	2.92/0.004

Abu et al (1984) also reported that the loin eye area was higher when oil palm slurry was added to pigs diets. A similar result was observed by Balogun et al (1983) who found that increasing PO in diets based on cassava root flour and soya bean meal improved the development of the muscles. A possible explanation for the significantly higher loin eye area on the high PO diets could be that long chain fatty acids can provide ATP for muscle metabolism at faster rates than acetate or glucose, so the more ATP is made available for protein synthesis (Leng R A 1994, personal, communication).

Conclusions

Replacing sugar cane juice with crude palm oil decreased dry matter intake and improved feed dry matter of growing finishing pigs, but did not affect either daily gain or GE intake. Back fat thickness was reduced and loin eye area increased as the level of palm oil in the diet was increased.

Acknowledgments

The authors wish to thank Dr R A Leng and Mr Alvaro Ocampo for their advice and Mr B Ericson for the fatty acid analysis of the palm oil. The research was done in partial fulfillment of the MSc degree in Sustainable Use of Natural Resources in Livestock-based Farming Systems of the Swedish University of Agricultural Sciences, with financial support from the Swedish International Development Agency (SIDA). The experimental facilities were made available by the Instituto Mayor Campesino ( IMCA ), Buga and "La Fundacion Centro para la Investigation en Sistemas Sostenibles de Production Agropecuaria (CIPAV),Colombia.

References

Received 25 January 1998

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