"A" molasses in diets for growing pigs

Faculty of Veterinary Medicine and Animal Husbandry, University of Cantho, Cantho, Hauglang, Vietnam

Sugar cane "A" molasses was included at a level of around 55% in the diet of growing pigs between 50 and 80 kg liveweight, replacing a mixture of broken rice and rice bran. The daily intake of molasses was restricted to a maximum of 1.22 kg to reduce the risk of diarrhoea. Average daily liveweight gains were slightly lower for the molasses fed pigs, but as total daily dry matter feed intakes were lower than for the control pigs, feed conversion efficiency was better for the molasses fed group.

Pigs are the most important source of animal protein in Vietnam, and although the majority are kept on a subsistence level as scavengers, consuming household wastes and agricultural by- products and surpluses, the larger commercial units use balanced diets based on cereals, thus competing with the human population for scarce food resources. It is important therefore to evaluate local alternatives, such as "A" molasses, which is readily available in the cane harvesting season from the numerous small artisan sugar factories (Bui Xuan Men and Vuong Van Su 1990).

This study was carried out between March and May, 1990, at the Thot-Not district state pig farm in the Mekong delta. A total of 30 three-way cross (Landrace x Large White x Duroc) castrate male pigs were used, with an initial liveweight of around 49 kg. The experiment was designed as a randomized block, with two dietary treatments, and three replicates of 5 pigs per treatment. "A" molasses replaced on a fresh weight basis a mixture of broken rice and fine and coarse rice bran. The composition and chemical analysis of the diets used are shown in Table 1.

The "A" molasses used in the trial was collected from a small local sugar refining factory, and is the residue after the heated syrup from sugar cane juice is centrifuged to separate the crystalline sugar. The sample used had the following analysis: °Brix 78.5; total sugars 64.1%; dry matter 66.4%; crude protein 1.71%; ash 3.8%; ME 9.43 MJ/kg (calculated); K 1.14%; Mg 0.17%.

The control pigs were group fed twice daily and given an allowance of 2 kg per day for the first 30 days of the trial, and then 2.3 kg per day up to slaughter. To avoid the risk of diarrhoea the molasses fed pigs were restricted to 1.15 kg per day of molasses for the first 30 days, rising to 1.22 kg per day up to slaughter. The molasses was mixed with water in a ratio of 1:3 molasses to water, and offered in a single trough to the pigs 4 - 5 times per day. The molasses fed groups were also given 720 g per day of a protein concentrate for the first 30 days, rising to 780 g per day up to slaughter, and 0.24 kg per day of broken rice and rice bran.

Table 1: Composition and chemical analysis of the diets.

	Control diet	Molasses diet

Ingredient (%)
"A" molasses	-	55.0
Broken rice	30.0	3.3
Fine rice bran	35.0	4.0
Coarse rice bran	16.0	3.0
Fish meal	8.0	12.5
Groundnut oil meal	6.0	12.0
Coconut oil meal	4.8	10.0
Vit/min premix	0.2	0.2
Analysed composition (%)
Crude protein	14.4	12.4
Ether extract	9.7	4.7
Crude fibre	7.6	3.7
ME (MJ/kg; calculated)	12.16	10.86

The analysed value for the dry matter content of the molasses of 66.4% was obtained by oven drying at 100 °C, and as this would entail the loss of volatile sugars and would therefore have tended to underestimate the true dry matter content, the °Brix value was used in the calculations, giving an assumed dry matter content of 78.5%.

The molasses was readily consumed from the start of the trial, although it was noted that the animals that consumed most tended to have flushed skins and slight diarrhoea for the first couple of weeks. However these symptoms soon disappeared, and did not affect performance. Feed intake and growth performance are shown in Table 2.

Although both daily feed dry matter and protein intakes were significantly lower for the molasses fed pigs, growth rates were only slightly lower than for the control group, due to more efficient utilization of feed, probably as a result of the high sugar content of the "A" molasses and the better amino acid balance of the protein supplement given to the molasses group.

Table 2: Effect of "A" molasses on the performance of growing pigs.

	Control	Molasses	SEmean (Prob)

Liveweight, kg
Start	49.7	49.5
Slaughter	79.4	78.5
Days on experiment	54	54
Daily gain, kg	0.551	0.538	0.031 (0.79)
Feed intake, kg/day
Molasses	-	1.18
Supplement	0.99
Total DM	2.06	1.84
Feed conversion,
kg DM/kg gain	3.74	3.42	0.20 (0.36)
Cost of feed, Dong/kg #	415	488
Cost of feed/kg gain	1651	1992

"C" (final) molasses has been reported to cause severe diarrhoea in growing pigs at levels higher than 20-30% of the diet (Velasquez et al 1969) due to its hypertonic nature (Ly and Castro 1984). However the mineral content of the "A" molasses used in this trial was considerably lower than the 7-9% reported for final molasses (Gohl 1981), and the level of molasses inclusion could probably have been increased in the final fattening phase without any negative effects.

At the time of the experiment the price of "A" molasses was rather high (around 400 Dong/kg), and that of rice bran relatively low (around 250 Dong/kg). By the end of August 1990, however, the price of rice bran had increased to 650 Dong/kg and that of molasses fallen to 380 Dong/kg, with a further decrease to less than 300 Dong/kg forecasted for the sugar harvesting season (November - January), which would make its inclusion very profitable. It can be concluded therefore that "A" molasses is a satisfactory substitute for rice by-products in growing pig diets in terms of performance, and its use is economically advantageous during the sugar harvesting season in southern Vietnam.

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

Gohl B 1981 Tropical Feeds. FAO Animal Production and Health Series No 12; p 432.

Ly J and Castro M 1984 Pig fattening with sugar cane molasses. Cuban Journal of Agricultural Science 18:35.

Velasquez M, Ly J and Preston TR 1969 Digestible and metabolizable energy values for pigs of diets based on high-test molasses or final molasses and sugar. Journal of Animal Science 29:578