A comparison of sugar cane juice and maize as energy sources in diets for growing pigs with equal supply of essential amino acids

A comparison of sugar cane juice and maize as energy sources in diets for growing pigs with equal supply of essential amino acids

Two experiments were performed with growing pigs, given diets based on maize or sugar cane juice, balanced for 8 essential amino acids, fibre, oil, calcium, phosphate and sodium. The experimental diets were formulated by Multiple Objective Programming (MOP) using conventional supplements. In the first experiment, live weight gains were 634 ± 12.7 g/day for maize and 732 ± 12.6 g/day for sugar cane juice; respective backfats (P2) were 13.5 ± 0.32 and 14.7 ± 0.36 mm. The gains in the second experiment (when the relative amounts of maize and sugar cane juice were adjusted) were 760 ± 16.1 and 616 ± 9.4 g/day respectively; corresponding backfats were 13.2 ± 0.51 and 11.1 ± 0.48 mm. There were only small differences in carcass weight, killing-out percentage and backfat thickness which can be explained by differences in live weight gains resulting from actual feed consumption. The results do not support previous conclusions that there are differences in lean and fat growth between sugar cane juice and maize diets. The importance of correct balance of nutrients and the value of the MOP technique in this experiment is stressed.

Sugar cane fractionation to provide feed for monogastric and ruminant animals has been advocated by Preston (1980, 1988) as an alternative to the use of cereal grains. Milling of fresh cane results in the separation of liquid juice (approx. 48%) and fibrous bagasse (52%). The use of the fresh juice as the energy source in pig diets was demonstrated in Mexico by Mena et al. (1981, 1982) and is now the basis of commercial pig production systems in Colombia and other tropical countries (Sarria et al. 1990).

Anecdotal evidence from South America suggested that pigs fed on sugar cane juice were leaner than conventionally fed pigs. There is also evidence that the efficiency of use of soluble sugars and the resulting body composition of pigs may be different compared with conventional diets where starch is the energy source (Ly 1988)

Schumacher et al. (1986) reported that pigs fed raw sugar diets had superior liveweight gains, dressing percentages and feed conversion efficiencies, while backfat thickness was significantly less, compared to those fed a conventional cereal-based diet. George et al. (1988), however, found that there was no evidence that a sugar based diet stimulated protein deposition more than a wheat-based diet of similar energy density (made isoenergetic by the addition of soyabean oil).

The main problem with such comparisons is that the protein component of maize grain is not insignificant (c. 100 g/kg) but has a poorly balanced amino acid profile, whereas sugar cane juice contains virtually no protein. Thus, when the diet is supplemented with equal amounts of protein from extracted soya bean meal, fishmeal or other sources, the sugar cane juice diet is likely to have a better amino acid composition. Even if the lysine component is correctly balanced, other amino acids may be in greater deficit on a maize-based diet.

Recent work in the UK by Wang and Fuller (1989) has used single amino acid displacement studies to produce accurate individual amino acid requirements for maintenance and growth (Fuller et al., 1989). These standards provide for formulation of diets with the same levels of all essential amino acids, not just lysine.

The work was carried out at a commercial pig unit on the Royal Swaziland Sugar Corporation estate at Simunye, Swaziland (26.3S, 31.3E), which is in the low veld.

Two experiments were carried out, starting in April and July 1990. The objective was to achieve similar growth rates on the two diets and to compare the resulting carcass fatness. The experiments were essentially similar, with adjustments made to the amount of the rations fed in the second experiment. The pigs in the first experiment were slaughtered at about 90 kg, whereas those in the second experiment were killed at 65 kg.

A total of 144 Large White (males) and Large White x Landrace (females) pigs were used in the two experiments.

6 litters of 12 pigs were used for each experiment, all between 58 and 68 days of age. Each litter was divided in two, approximately by size and sex. The analysis therefore allowed litters to be counted as blocks and the effects of sex to be removed by covariance. The design was therefore a randomised block with two treatments, 6 blocks and 6 replicates per block (total 72).

All pigs were ear-tagged and weighed every Monday morning. The average weight at the start was 23.2 ± 0.72 for the maize and 24.2 ± 0.71 kg for the sugar cane juice treatments in the first experiment; the corresponding starting weights in the second experiment were 25.7 ± 0.75 and 24.44 ± 0.63 kg respectively.

The pigs were slaughtered as they reached 85-90 kg live weight in the first experiment and 65-70 kg live weight in the second. They were weighed alive and dead, and carcass fat was determined using a manual probe (Meat and Livestock Commission, UK) in the first experiment and an electronic probe (MEDATA Ltd., UK) in the second. A standard measurement was taken at position P2 (backfat depth 65 mm from the mid-line at the last rib).

Diet formulation was carried out on the basis of the Multiple Objective Goal Planning technique (Romero and Rehman, 1989), using the computer program What's Best (Lindo Systems Inc.), in conjunction with Lotus 123 (Lotus Development Corporation). The principle is similar to least-cost ration formulation where cost is minimized, subject to nutrient constraints; in Multiple Objective Programming, the objective coefficient is the sum of the deviations from a set of targets (including cost, but also nutrients). Local feed analyses were used, supplied by Lurex Pty., Nelspruit, RSA.

It was found possible to formulate diets that were very similar in composition and conforming to the amino acid pattern proposed by Fuller et al. (1989), as well as the specifications for Ca, P and Na. Only threonine proved impossible to match to the target on the maize diet and the two diets were therefore made to achieve 90% of the threonine target. The diets were also made similar in ash, fat and fibre content, the last being achieved on the sugar cane juice diet by the inclusion of a high level of lucerne meal.

The first expressed juice was obtained from the sugar mill by means of a pipe installed for the purpose. Analysis of Brix (total solids) and Pol (sucrose content) were undertaken on site; 145 samples were analyzed. The average composition was 18.5 Brix and 16.1 Pol, an average purity of 87.2%, over the whole period. There was a steady increase from 18.3 Brix 15.9 Pol (87.0% purity) in April to 19.1 Brix 17.6 Pol (92.0% purity) in July.

Various methods of preservation were considered, including a proprietary bacteriostat AButan 881" (rejected on grounds of toxicity), sodium benzoate (rejected for difficulties in dissolving) and formalin (accepted as practical and available). 40% formaldehyde solution was added at the rate of 0.04 v/v, as recommended by Mena (1988). The juice was kept up to 6 days, with only slight deterioration towards the end of the period, although it was mainly used on the day of extraction.

Table 1: Experimental diets.

INGREDIENTS IN MIX	TREATMENT 1	TREATMENT 2
	Maize meal 60.0%	Sugar cane juice equivalent to 60% (DM basis)

Soya oilcake	4.1%	9.8%
Fishmeal	9.2%	13.5%
Lucerne meal	7.6%	10.7%
Wheat bran	16.0%	5.0%
Hominy feed	1.6%	0.0%
Limestone	0.75%	0.35%
Fine salt	0.16%	0.074%
L-lysine HCL	0.185%	0.0%
DL-Methionine	0.014%	0.111%
Min/vit premix	0.40%	0.40%

NUTRIENT COMPOSITION (targets shown in brackets)

CRUDE PROTEIN (%)	17.33	16.99
ASH (%)	4.8	5.1
CRUDE FIBRE (%)	5.7	4.3
FAT (%)	3.9	2.0
DE (MJ/kg)	13.0	*

	%		%

METHIONINE+CYSTINE (0.630)		0.630		0.630
AVAILABLE LYSINE (1.000)		1.000		1.036
TRYPTOPHAN (0.180)		0.180		0.214
THREONINE (0.690)		0.641		0.640
ISOLEUCINE (0.600)		0.600		0.600
LEUCINE (1.110)		1.493		1.120
VALINE (0.750)		0.804		0.820
PHENYLALANINE+TYROSINE(1.200)		1.360		1.280
Ca (0.800)		0.800		0.800
AVAILABLE P (0.400)		0.400		0.449
Na (0.160)		0.160		0.160

* The amount of sugar cane juice was adjusted in an attempt to equalize energy intake.

Maize was grown on the estate and grinding performed on site. All other ingredients were obtained from a feed company (Lurex Pty., Nelspruit, RSA).

The maize diet was mixed and fed as one feed; the sugar cane juice was fed separately, together with a supplement containing the other ingredients which was given at the rate of 40 per cent of the target (maize diet) feeding level. The composition of the supplement to the sugar cane diet was therefore soya oilcake 24.5%, fishmeal 33.8%, lucerne meal 26.7%, wheat bran 12.5%, limestone 0.875%, fine salt 0.175%, DL-methionine 0.275%, mineral/vitamin premix 1%.

The rations were designed to achieve near to the maximum intake based on the liveweight.

At the start of the first experiment, the content of the juice was unknown and assumptions were based on published data. Göhl (1981) gives a value of 14.1% sugars in cane juice. Digestible energy values were taken as 14.5 for maize and 18.4 for raw sugar (MJ/kg DM). DM values were taken as 0.90 and 0.14 respectively. Thus 5 litres of juice were considered equivalent to 1 kg maize.

A weekly feeding scale was designed, based on F = 0.12W(0.75) (Whittemore, 1983) where F=amount offered (kg DM/d), W=live weight, adjusted weekly. The pigs started at 1.25 kg DM/day at 23 kg increasing to 3.5 kg DM/day at 90 kg.

The pigs were fed twice daily at 8 am and 4 pm. During the pre- treatment week, a mixture of 50% treatment and 50% previous diet was fed.

The actual results of the juice analysis were available for the second experiment and the sugar content was higher than the assumed value in the first experiment (see above). The rations were recalculated on the basis of the known composition. Four litres of juice were assumed to be equivalent to 1 kg maize. In addition, the level of feeding was increased to F = 0.14W(0.75). Hence the scale started at 1.5 kg/day at 23 kg, increasing to 3.2 kg/day at 65 kg. A similar changeover regime was applied at the start.

In the second experiment, problems were encountered with fibrous residues in the juice in the 5th week. This reduced the intake and weight gain for a short time. Thereafter the juice was filtered before feeding.

Statistical analysis was performed using MINITAB v. 7.2. The balanced design of the first experiment permitted the use of ANCOVAR for blocks and treatments, with sex as a covariate. One animal died in the second experiment and the data were therefore analyzed using GLM (General Linear Model) with the same factors and covariate. Similar analyses were carried out on the carcass data.

The results of the first experiment are shown in Table 2 and those of the second in Table 3.

Table 2: Live weight gain and carcass details of pigs fed diets containing either maize or sugar cane juice to 90 kg live weight (Experiment 1).

Treatment	Live weight gain (g/d)	Slaughter weight (kg)	Carcass weight (kg)	Backfat (mm) (P2)	Killing-out per cent.

Maize	634	87.1	67.4	13.5	77.5
	±12.7	±0.70	±0.48	±0.32	±0.50

Sugar cane juice	732	89.5	68.6	14.7	76.7
	±12.6	±0.61	±0.46	±0.36	±0.38

Table3: Live weight gain and carcass details of pigs fed diets containing either maize or sugar cane juice to 65 kg live weight (Experiment 2).

Treatment	Live weight gain (g/d)	Slaughter weight (kg)	Carcass weight (kg)	Backfat (mm) (P2)	Killing-out per cent.

Maize	760	74.6	57.0	13.2	76.4
	±16.1	±1.28	±1.08	±0.51	±0.29

Sugar cane juice	616	67.9	49.9	11.1	73.4
	±9.4	±0.92	±0.75	±0.48	±0.31

In Experiment 1, the pigs grew significantly faster (P<0.001) on sugar cane juice than on maize, were heavier at slaughter (P<0.05), had heavier carcasses (NS) and thicker backfat (P<0.01) but did not differ in killing out percentage.

In Experiment 2, the results were the opposite of Experiment 1. Pigs fed maize had higher live weight gains (P<0.001), were heavier at slaughter (P<0.001), had heavier carcasses ( P<0.001) and thicker backfat (P<0.01) and had higher killing out percentages (P<0.001).

Many experiments, even those which have attempted to provide iso- energetic and iso-nitrogenous diets (e.g. Schumacher et al., loc. cit.), have failed to achieve comparability of all essential amino- acids supplied, except by the use of expensive synthetic amino- acids (e.g. Wang and Fuller, loc. cit.) which is inappropriate in developing countries.

The use of Multiple Objective Programming (MOP) enabled diets to be formulated under Southern African conditions which were equal in eight essential amino-acids, fibre, fat, calcium and phosphorus, as well as achieving minimum costs. Furthermore, this was achieved using standard ingredients such as soyabean meal, fishmeal, lucerne meal, wheat bran, hominy feed, etc., plus minerals and vitamins, with small amounts of the normally available synthetic lysine and methionine supplements. It is interesting to observe that, given the availability of synthetic lysine and methionine, it appears that threonine is the next limiting amino-acid which is difficult to supply.

The method is simple and effective with the small number of ingredients involved and can be applied on a microcomputer, even a small laptop, as was the case in this project. It is an improvement on the standard linear programming method that is commonly used.

In the two experiments, it was difficult to balance the energy supplied by sugar cane juice and maize. However, given the known differences in the amount of energy supplied, it is clear that growth rates can be similar and there are no real differences in carcass composition between pigs fed on these two basal feeds.

In the first experiment, pigs grew faster on sugar cane juice than on the maize based diet and in the second the position was reversed. Killing-out percentage and backfat thickness (P2) were ranked accordingly and the differences, although statistically significant, were small and in the normal range for this genotype of pig.

The problem of fibrous residues in the cane juice in the second experiment was probably responsible for failure to achieve similar gains on the cane juice. Taking this into account, it appeared that growth rates would have been very similar between the two treatments.

The overall performance of the pigs was good. It should be noted that the unit is situated in the low veld area which is very hot in summer (December - March) and warm and dry in winter. Despite the conditions, the herd has achieved excellent production figures for both reproduction and growth.

The results further support the concept that sugar cane juice is a very appropriate basal feed for monogastric animals in tropical and sub-tropical conditions.

Thanks are due to Greg Geldard, Agricultural Director, Royal Swaziland Sugar Corporation, Simuye for providing the facilities for the work and supporting AWS during his visit; Dr G. Norman of Booker Tate Ltd., Thame, Oxon., UK for arranging the visit of AWS; Dr H. Lung Kit, Process Manager, RSSC, Simunye for sugar analysis; and to Dr T.R. Preston, CIPAV, AA 7482, Cali, Colombia for helpful advice and discussion.

Fuller, M.F., McWilliam R., Wang, T.C. and Giles, L.R., 1989. The optimum dietary amino acid pattern for growing pigs. 2. Requirements for maintenance and for tissue protein accretion. Brit. J. Nutr. 62: 255-267.

George, S.A., Elliott, R. and Batterham, E.S., 1988. Utilization of raw sugar by growing pigs. Proc. Aust. Soc. Anim. Prod. 17: 401.

Ly, J., 1989. The physiological and biochemical basis for feeding pigs and poultry in the tropics. Paper presented at a Training Course. Royal Veterinary College, Copenhagen. 3-7 April, 1989.

Mena, A., Elliott R and Preston T R 1981 Sugar cane juice as an energy source for fattening pigs. Tropical Animal Production 6:338-344

Mena, A., Elliott R and Preston T R 1982 The substitution of grain sorghum by sugar cane juice in diets for growing pigs Tropical Animal Production 7:226-231

Mena, A., 1988. Sugarcane juice as animal feed: an overview. In: Sugarcane as feed. Ed. R. Sansoucy, G. Aarts and T.R. Preston. FAO Animal Production and Health Paper 72. pp.153-163. FAO, Rome.

Preston, T R 1980 A model for converting biomass (sugar cane) into animal feed and fuel In: Animal Production Systems for the Tropics International foundation for Science: Stockholm

Preston, T.R., 1988. Food, fuel and jobs from sugar cane and legume trees. In: New Crops for Food and Industry (Editors: G. Wickens, N. Haq and P. Day) Croom Helm: Beckenham, UK

Romero, C. and Rehman, T., 1989. Multiple Criteria Analysis for Agricultural Decisions. Elsevier. 257pp.

Sarria, P., Solano, A. and Preston, T.R. 1990. Utilización de jugo de caña y cachaza panelera en la alimentación de cerdos. Livestock Research for Rural Development. 2(2): 92-102.

Schumacher, E., Elliott, R., McMeniman, N.P. and Griffiths, I., 1986. Evaluation of raw sugar as an energy source for growing/fattening pigs. Proc. Aust. Soc. Anim. Prod. 16: 359-362.

Wang, T.C. and Fuller, M.F., 1989. The optimum dietary amino acid pattern for growing pigs. 1. Experiments by amino acid dilution. Brit. J. Nutr. 62: 77-89.

Whittemore, C.T., 1983. Development of Recommended Energy and Protein Allowances for Growing Pigs. Agric. Syst. 11: 159-186