"A" molasses in diets for growing pigs

Faculty of Veterinary Medicine and Animal Husbandry, University of Agriculture and Forestry, Ho Chi Minh City, Vietnam

Two experiments were performed with growing pigs which were allocated to two dietary treatments based on rice bran or "A" molasses and a protein concentrate (soybean meal:fishmeal in ratio 3:1). In the first experiment, the same amount of protein supplement was supplied for both diets (200 g protein/day/pig), and rice bran and molasses were given free choice. The daily weight gains were 458"62 g for rice bran and 397"72 g/d for molasses. Total daily dry matter intake of pigs fed molasses was less than for those on the control diet, thus feed conversion ratio was better for the molasses diet. In the second experiment, pigs on the molasses treatment were fed a total amount of protein equal to that in the rice bran diet. The liveweight gains of the molasses and rice bran groups were: 520"53 and 548"81 g/d respectively.

Sugar cane is one of the main crops in South Vietnam and in numerous other tropical countries. By-products of the sugar cane industry in the form of molasses have been widely used as a cereal substitute in livestock feeds (FAO 1992). Final cane molasses ("C" molasses), despite its laxative effect, can be an effective energy substitute for cereals (Figueroa y Ly 1990; Figueroa 1990).

In Vietnam, two types of molasses are produced; "C" molasses from industrial sugar production and "A" molasses from the artisan method. Van and Men (1990) described the production of "A" molasses and showed that pig growth was similar to that on rice bran with a slight tendency for better feed conversion on the molasses.

The aim of these experiments was to obtain further information on the comparative value of "A" molasses and rice bran as an energy source in diets for growing-fattening pigs.

Two feeding trials were carried out with growing pigs. Experiment 1 was carried out from July to December 1990 at Dong A State farm, Ho Chi Minh City. Sixteen purebred Yorkshire pigs (8 females and 8 castrates) of 130 days of age and an initial weight of about 30 kg were randomly allocated to one of two dietary treatments with two replicates of 4 pigs per treatment.

550 g/d of a protein concentrate (Table 1) was supplied to both groups throughout the trial (soybean meal and fish meal in a ratio 3:1), supplying 200 g protein/day/pig.

Table 1: Composition and chemical analysis of concentrate supplement

	(%)

Soybean meal	71.15
Fishmeal	23.71
Bone powder	3.79
Salt	0.94
Premix	0.37

Chemical composition :
N x 6.25*	40-42
Lysine*	2.26
Methionine + cystine*	1.16

Experiment 2 was carried out from April to July 1991 at the University of Agriculture and Forestry, Ho Chi Minh City. Sixteen Yorkshire pigs (8 females and 8 castrates) of 115 days of age with initial weights of about 33 kg were randomly allocated to two dietary treatments, with 4 replicates of 2 pigs for each treatment.

Treatment RB: Rice bran ad libitum plus 200 g protein/day/pig from a concentrate (soybean meal: fish meal in a ratio 3:1).

Treatment AM: "A" molasses ad libitum and with extra amounts of the same protein concentrate to give the same amount of total protein to that of the rice bran group (adjusted according to the intake of rice bran in the control group). In both experiments, the pigs were fed four times daily and were weighed at intervals of two weeks. There was free access to water. The following information was also recorded: initial and final weights, number of days on experiment, daily weight gain, daily food consumption, and faeces moisture content. At the end of experiment 2, 4 pigs from each treatment were slaughtered to evaluate the carcass quality.

Feed intake and growth performance are shown in Tables 2 and 3. Daily weight gains (DWG) of pigs fed "A" molasses were lower than those of the rice bran fed group, especially in experiment 1. It has been shown that some of the non-sugar compounds in molasses are fermented rather than digested enzymatically and this would tend to reduce growth rates (Ly 1990). This was demonstrated in the higher moisture content of the faeces from the pigs fed the "A" molasses.

Table 2: 2. Effect of "A" molasses on the performance of pigs in experiment 1 (8 per treatment)

	Control	"A" Molasses	Prob

Liveweight (kg)
Initial	30.3±2.27	30.6±3.4
Final	88.4±8.30	80.5±9.0
Daily weight gain (g)	457.6±61.8	396.5±72.6	0.091
Feed intake (kg/d):
Rice bran@	1.44
"A" molasses**		2.38
Concentrate	0.52	0.52
Total DM	1.96	1.65
Feed conversion ratio
(kg DM/kg LWG)	4.28±0.12	4.11±0.16	0.54
Faeces moisture (%)	62.30±4.5	84.70±1.25	0.025

* Composition of rice bran: N x 6.25 10.3%, crude fibre 11.20%
** Composition of "A" molasses: DM 50% (dried at 105EC), ash 3.8%.

Table 3: 3. Effects of "A" molasses on the performance of pigs (experiment 2) (8 pigs per treatment; 106 days on trial)

	Control	Molasses	Prob

Liveweight (kg)
Initial	33.4±4.5	33.0±2.47
Final	91.7±7.61	88.5±5.43
Daily weight gain (g)	549±71.2	524±45.1	0.41
Feed intake (kg/d)
Rice bran*	1.31
±A± molasses**		2.08
Supplement	0.45	0.75
Total DM	1.76	2.20
Feed conversion ratio
(kg DM/kg LWG)	3.25±0.10	4.14±0.17	0.001
Faeces moisture (%)	70.20±3.06	75.60±2.56	0.034

* Composition of rice bran; protein 12.9%; crude fibre 5.54%
* Composition of molasses; DM 70% (dried at 105EC) ash 5.6%.

The growth rate of the "A" molasses-fed pigs was improved in experiment 2. In this experiment they were fed an amount of protein equal to that of pigs fed rice bran. However, the quality of the "A" molasses in this experiment was better (a lower content of fermentable compounds) than in the first. This was shown by the much smaller difference in the moisture content of the faeces (only 7% higher in experiment 2 compared with 34% higher in experiment 1).

Slaughter results for the pigs in experiment 2 are in Table 4. The backfat thickness of pigs fed molasses was slightly lower than those of pigs fed rice bran, and the molasses fed pigs had a higher lean meat content. This could be due to the better amino acid balance of the complete diet of the molasses fed group, which received more of the protein concentrate.

The lung and heart weights of the molasses-fed group were higher than those of the rice bran fed group. Indications of heat stress were noted in this treatment with a higher frequency of panting being observed.

Table 4. Effects of molasses on carcass and organ weights (experiment 2; 4 pigs in each sample)

	Control	Molasses	Prob

Live weight (kg)	93.0±6.3	90.4±5.1	0.55
Carcass yield (%)	74.7±1.2	74.7±1.8	0.98
Carcass length (pubis
bone-1st rib) (cm)	73.0±1.6	72.8±1.2	0.82
Backfat (cm)	3.59±0.37	3.06±0.70	0.24
Iodine index	80.0	58.7
Heart weight (g)	300±40.8	337±47.9	0.28
Lung weight (g)	975±50	1212±217	0.077
Pancreas weight (g)	237±25	212±25	ns
Liver weight (g)	1562±48	1583±193	0.84
Stomach weight (g)	638±25	562±95.6	0.18
Small intestine (g)	2325±132	2138±229	0.21
Large intestine (g)	1663±475	1438±301	0.45
Large intestine (cm)	560±53	413±18	0.002

The stomach, small intestine, and large intestine of the "A" molasses pigs tended to decrease in weight, possibly due to the lower fibre content in the diet they were fed. Pancreas and kidney weights of the molasses group also tended to be lower.

The iodine index was lower for pigs fed "A" molasses (80.0 and 58.7 for the control and molasses pigs, respectively). This indicates a higher degree of unsaturation of the body fat in the rice bran fed animals, probably a result of the high concentration of unsaturated fatty acids in the oil in the rice bran.

In both experiments, the replacement of rice bran with molasses did not give any financial advantage because, in the molasses diets, all the protein must be added; this is the most expensive element and in recent years, "A" molasses has been used in alcohol manufacture or export, so that its price has increased. Under these economic conditions, the use of "A" molasses will only be profitable if its price is about 50% lower than that of rice bran. Van and Men (1990) arrived at similar conclusions.

"A" molasses can be used as the sole energy source in growing pig diets, replacing rice bran, without any negative effects on performance. The economics of feeding molasses will depend on its price relative to rice bran.

Grateful acknowledgement is made to SAREC (S/E VIE 22) and FAO (TCP/VIE/8954) for technical and financial support for this work.

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