Issue No. 3 ~1999

Molasses is a by-product of the sugar industry, defined as the end product of sugar manufacture or refining from which no more sugar may be economically crystallised by conventional means. About 75% of the world’s molasses comes from sugar cane (Saccharum officinarum) and the majority of the remainder comes from sugar beet (Beta vulgaris). Other sources of molasses include citrus, corn and sorghum. Sugar cane is grown in tropical climates (Asia, South America), whereas sugar beet has its origin in the temperate climates (Europe and North America). The most important constituent of molasses is sugar, being predominantly sucrose with some glucose and fructose.

Sugar is extracted by crushing sugar cane stems to extract juice. Lime (Calcium Hydroxide) is added to the juice, which is then heated and filtered in order to remove impurities. The juice is then evaporated, to concentrate the sugar and several crystallisation processes follow to extract as much sugars as possible. Centrifugal machines then separate the sugar and syrup. The residual syrup is often called blackstrap cane molasses.

Sugar Beets are washed and sliced before undergoing a diffusion process to extract the juice. Once the juice is extracted it is processed in the same way as cane sugar

In general, world molasses production is approximately one third that of the sugar production. For every 100 tonnes of sugar cane processed, 3 to 4 tonnes of molasses is produced and for every hundred tonnes of sugar beet 4 to 6 tonnes of molasses is produced. The quantity of molasses produced is influenced by the market price of sugar. The higher the sugar price the more sugar extraction’s the molasses is put through to get as much sugar out as possible.

WORLD MOLASSES PRODUCTION

Molasses production is a function of the sugar industry. During the last 35 years the world sugar demand has risen dramatically resulting in world molasses production increasing tremendously from no more than 15 million tonnes in the early 1960s to an estimated 46 million tonnes in 1998/99. The main world producers at the moment are summarised in (Table 1). The majority is cane molasses, produced in Asia and South-America, about 16 and 10 million tonnes respectively.

Table 1: Major world producers of molasses

Source: SvG Research

Almost all of the Brazilian and Indian molasses is consumed in the country of origin. Pakistan and Thailand are important exporters with almost all of Pakistan exports going to the EU. Export and import figures for the harvest year Oct97/Sep98 are presented in Table 2.

Table 2: Major world exporters and importers of molasses (Oct 97/Sep98)

Source: SvG Research

EU MOLASSES PRODUCTION

The EU (15) currently produces 4.27 million tons of beet molasses per year (Table 3). France and Germany are the most important contributors to this figure with 950 and 900 thousand tons respectively. The Irish molasses yield is only 50 thousand tons. Irish imports of molasses are summarised in Figure 1. 284 thousand tons had to be imported during the harvest year October’97/September’98 to fulfil demand. These imports came mostly from Pakistan, France and Poland.

Table 3: Total EU and member state molasses production 1990-1999 (000t)

Source: SvG Research

CONSUMPTION OF MOLASSES

Animal feed is the main market for molasses using approximately 51 percent of the molasses. The EU and the USA are the largest consumers of molasses worldwide, as they have highly developed livestock industries, however the feed industries in emerging economies are forecasted to grow strongly.

Table 4: Total EU and member state molasses consumption 1990-1998 (000t)

Source: SvG Research

It is likely that animal feeds will continue to be the dominant category of usage. Molasses is also used as a silage additive. Other markets include the fermentation industry producing such products as ethanol, yeast, amino acids and citric acids and the bricketing industry.

Source: CSO

MOLASSES COMPOSITION

It is difficult to predict the exact composition of cane molasses. Soil and climatic conditions, the variety and maturity of the cane and the processing conditions in the factory all influence molasses composition. Consequently, considerable variation may be found in nutrient content, flavour, colour and viscosity. The ranges with indicative averages of the composition of molasses can be found in Table 5.

Table 5: Typical nutrient analysis (%) of cane molasses

Source: Wolfrom & Binkley, 1953

The composition of standard cane and beet molasses is generally divided in three parts: Sugar, Non-sugar organic matter and mineral matter.

Soluble carbohydrates (disaccharide and monosaccharide hexose sugars) account for the major proportion of the feeding value of molasses, sucrose being the major sugar present (Table 6). A characteristic of cane molasses is the relatively high proportion of reducing sugars. During the crystallisation cycles the reducing sugars increase to such an extent that no more sucrose can be crystallised, because reducing sugars decrease the solubility of sucrose. Mineral matter tends to hold sucrose in solution, so it is the balance of reducing sugar and mineral matter that determines the theoretical yield of sucrose from sugar cane. The residual syrup is very often referred to as blackstrap molasses. The total sugars of beet molasses are on average lower than those of cane, but consist almost entirely of sucrose with a small quantity of the trisaccharide raffinose. Molasses and molasses based liquid feeds are the only products that supply significant levels of sucrose.

Table 6: Organic matter composition of beet and cane molasses

Source: Steg and Van der Meer, 1985

Non-sugar organic matter

The non-sugar organic matter of molasses accounts for many of its physical properties, in particular viscosity. It consists mainly of carbohydrates, such as starch, nitrogen compounds (which gives beet molasses its earthy flavour and smell) and organic acids. Generally the total non-sugar organic matter in beet molasses is higher than in cane.

The proportion of crude protein in standard cane molasses is very low averaging about 3-5% (CVB Animal Feed Table, 1997). In beet molasses, about half the total content of the non-sugar organic matter is in the form of nitrogen compounds, particularly betaine and glutamic acid. There is also a significant quantity of organic acids in cane molasses, the major one being aconitic acid. Molasses also contains volatile fatty acids averaging about 1.3%.

Table 7: Chemical composition and energy value of beet and cane molasses

Source: R &H Hall, Feed Tables 1996

Mineral matter

Molasses is a rich source of minerals. In comparison to other commonly used sources of dietary energy, e.g. cereal grains, the calcium content of cane molasses is high (up to 1%), whereas the phosphorus content is low. Cane molasses is also high in sodium, potassium (which are present as chlorides), magnesium and sulphur. Beet molasses tends to be higher in both potassium and sodium but lower in calcium content. Molasses also contains significant quantities of trace minerals, copper for example (7ppm), zinc (10ppm), iron (200ppm), manganese (200ppm).

DIETARY USE OF MOLASSES

The use of molasses in livestock and poultry feeds dates back to the nineteenth century. At that time, the properties of molasses as a source of dietary energy and as a dust eliminator were already known. This dust prevention is extremely important, since animals, are prone to bronchial diseases caused by dust. Dust is also a problem for the people feeding livestock and legislation has attempted to minimise personal exposure to dust. Dust may also result in feed wastage. Literature reports have shown that 10% molasses practically eliminated all dust and 30% eliminated fine particles.

Molasses may be fed to livestock in several ways such as molassed meal, molasses blocks, and liquid form to provide energy directly or be used as a carrier for non-protein nitrogen, vitamins and minerals as well as medicinal compounds.

According to Harland (1995), the main advantages of including molasses in feed are:

• Increased energy density
• Improved palatability
• Reduced dustiness
• Improved throughput, with consequent cost reductions
• Improved physical quality of the product
• Masking of less palatable ingredients
• Cost effectiveness

The viscosity of molasses varies widely. It depends on several factors; dry matter, the area of production and temperature. Table 8 shows a typical viscosity range of cane molasses for animal feeding purposes.

Table 8: Viscosity of cane molasses for animal feeding purposes

Technology

Blending improves the nutritional value and physical characteristics of molasses. However extensive research work has lead to the development of more complex processes. An example of this is a process in which urea is bonded to the sugars in molasses to form a urea-sugar complex with a feed value comparable to natural protein. This technology is termed "Regulated Release".

In general, the pelleting properties of molasses are good for pellet quality, press capacity and die wear (Thomas et al., 1998). Use of sugar increases pellet hardness and durability. In the presence of water, preferably steam, solubilisation of sugars occurs and upon cooling/drying, recrystallisation of sugars or a glass transition may take place, creating fixed binding points "solid-solid" interactions between particles. It is suggested that the binding properties of molasses may occur via these mechanisms (Thomas et al., 1998).

Microbial protein supply to the duodenum should be maximised for efficient use of feed protein and energy (Firkins, 1996). Matching the rates at which energy and nitrogen from the basal forage and concentrate become available to the microbial population – synchrony, is seen as a method of enhancing rumen microbial protein synthesis (Dewhurst, 1999).

Post-ensiling, sugars in grass are fermented to much lower energy yielding sources and consequently animal performance is lower on grass silage than fresh grass. This is attributed to a limited energy supply to the rumen microbes resulting in a much lower level of microbial protein synthesis.

Asynchronous release of energy and nitrogenous components is often proposed as the reason for the low efficiency of microbial protein synthesis on grass silage diets (Van Vuuren et al., 1995) due to the rapid release of ammonia from the large amount of non-protein nitrogen compounds present (Chamberlain and Choung, 1995). While there is no convincing evidence of a need for close synchronisation, as microbes appear to withstand transient periods of asynchronous nutrient supply in many cases, severe mismatching of energy and nitrogen release may be detrimental (Chamberlain and Choung, 1995; Firkins, 1996). In the literature, confounding results are often a problem because of the difficulty in separating the effects of synchrony from different dietary ingredients.

Chamberlain et al. (1993) concluded that sugars, particularly sucrose are clearly superior to starch as an energy source for the microbial fixation of nitrogen in the rumen. Sucrose gives a greater microbial protein synthesis than starch (Table 9). Supplementing grass silage with molasses or sucrose significantly reduces ruminal ammonia N concentrations compared to other carbohydrate sources such as starch (Chamberlain et al., 1985; Moloney et al., 1994; Keady and Murphy, 1997; Moloney, 1997; Y-G Oh et al., 1999).

High rumen ammonia levels are associated with poor reproductive performance in dairy cows (Butler, 1998).

Table 9: The effect of sucrose supplementation on rumen ammonia levels and microbial protein synthesis

Source: Chamberlain et al. 1993; Chamberlain and Choung, 1995

Grass, especially when well fertilised with nitrogen, contains a high level of crude protein and relatively low levels of water-soluble carbohydrates particularly in the spring and autumn. Because of a shortage of fermentable organic matter, large quantities of grass nitrogen are not converted into microbial protein but rapidly degraded into NH₃ (De Visser et al., 1997). Thus, there is a potential benefit to supplementing grass with a rapidly degradable energy source.

Supplementation of a grass diet with an energy source (O’Mara et al., 1997) or synchronisation of the ruminal release of supplemental carbohydrate with pasture nitrogen (Kolver et al., 1998) appears to improve the capture of ruminal N and increase the efficiency of microbial synthesis.

Molasses supplies the rumen with rapidly fermentable energy in the form of sugars.

Dairy

Inclusion of molasses (complete diet form) in grass silage/concentrate diets at up to 23% (Casssidy et al., 1997), 31% (Yan and Roberts, 1997) or 26% (Murphy and Younge, 1996; Murphy, 1999) (i.e. ~ >4.0kgDM) of the total DM significantly increased milk yield, milk protein concentration and yield, casein concentration and total DMI. In the studies of Yan et al. (1997) increasing the molasses concentration up to 47% of the total DMI did not significantly increase milk yield and resulted in some scouring in a proportion of the cows.

The increase in milk protein concentration with molasses or sucrose inclusion in silage diets (Keady and Murphy, 1998; Murphy, 1999; Phipps et al., 1999) is attributed to an increased microbial protein synthesis, thus amino acid production. Murphy (1999) reported a significant linear decline in milk fat concentration and milk non-protein nitrogen with increasing molasses inclusion.

McKendrick et al. (1996) found that the partial replacement of concentrate with cane molasses (1.8kg DM) significantly increased total DMI, milk yield (by 1 kg/day) and milk protein content and reduced milk fat content of cows on a grass silage based diet. Cassidy et al. (1997) concluded that cow DMI and performance was similar between diets containing 4kg DM of molasses, barley or unmolassed beet pulp when fed as part of an isonitrogenous supplement to a grass silage diet. Similarly, Phipps et al. (1999) showed that 7% molasses could replace a selection of energy and protein ingredients without affecting DMI or milk yield of cows on a maize silage based diet.

Evidence also suggests that there is a greater response to an increase in dietary UDP when lactating cows are fed high levels of molasses.

Beef

In a series of experiments carried out at Grange, Drennan (1985) feeding isoenergetic and isonitrogenous supplements (barley v. cane molasses/soyabean) to finishing steers or bulls on grass silage obtained similar animal performance between diets when molasses was included at 21% of the DMI (2.3-2.9 kg fresh weight/day). However unlike barley, increasing the level of molasses to 33% or 37% of DMI (3.6-5.7kg fresh weight/day) did not significantly increase animal performance. In other words, cane molasses is used more efficiently at the lower ration inclusion rates where its feeding value is similar with that of barley dry matter.

Moloney et al. (1993a) found no difference in the intake or performance of steers offered isoenergetic and isonitrogenous barley based or molasses based (17% of dietary DM–2.2kg fresh weight/day) supplements with grass silage. Chapple et al. (1996) concluded that the replacement of barley with molasses did not affect liveweight gain of finishing bulls.

However, Drennan et al. (1994) working with bulls on grass silage based diets indicated that performance from cane molasses supplementation (40% of concentrate – 18% of total DM) was better at high concentrate protein intakes than low concentrate protein intakes partly due to the low protein digestibility of molasses.

The relative poorer utilisation of molasses at higher dietary inclusion levels is attributed to alterations in the end products of rumen fermentation (i.e. lower ammonia and L lactate concentrations, proportionately lower acetate and higher butyrate concentrations) resulting in a possible reduction in fibre digestibility and possible differences in the site of digestion (Moloney et al., 1993b; Moloney et al., 1994).

Butler (1974) reported that at dietary feeding levels of 15-40%, a substitution rate of 1.4kg sugarcane molasses for 1.0kg of barley was valid. Similarly Drennan et al. (1994) concluded that at dietary inclusion levels of greater than 0.1 to 0.2, cane molasses DM has ME and NE values relative to barley of approximately 0.8 and 0.7 respectively.

Sheep

Yan et al. (1996) reported that sheep can be given up to 25% molasses with grass silage/barley straw based diets without any health problems.

Fitzgerald (1987) found that the performance of finishing lambs on a grass silage-based diet offered a molasses/soyabean meal (6:1) supplement (34-47% of the total DMI) was similar to that of lambs fed on a barley supplement. It was calculated that in terms of carcass gain that the response was 4% better for molasses/soyabean DM then barley DM (or the replacement value of barley DM was 0.96 that of molasses/soyabean DM) when fed as supplements with grass silage fed ad libitum.

O’Doherty and Crosby (1992) concluded that stepped supplementation of a hay or silage diet offered to twin and triplet bearing ewes, with fortified (i.e. including 10% high UDP) molasses over the last 47 days of pregnancy and an additional 150g soyabean in the last 10 days, was successful in terms of both ewe and lamb performance. Molasses formed 35-40% of the dietary DMI in the last week of pregnancy.

Thus, molasses is an effective supplement at up to 40% inclusion in total sheep diets.

NON RUMINANTS

With both pigs and poultry the level of molasses inclusion in the diet is usually limited because of the risk of soft faeces or diarrhoea thought to be due to the risk of high levels of potassium and sodium rather than simply the level of sugar (Harland, 1995). Sugar cane molasses reduces faecal dry matter in pigs due to potassium, magnesium and impurities (Diaz and Ly, 1991).

There is an abundance of literature on feeding sugar cane molasses to pigs in countries such as Cuba and Mexico where there is surplus molasses but reported production/feeding systems and pig performance are different to here. Very high dietary levels of molasses are fed e.g. up to 60% in the diet of gilts and sows, and up to 25-30% for growing pigs/finishing pigs. The energy value of molasses decreases with increased inclusion level. With increasing molasses inclusion the performance of finishing pigs is associated with increased intakes and growth rates but reduced feed efficiency associated with a higher rate of passage. Unlike fattening pigs, growing pigs are unable to adapt as well to high inclusions of molasses. These data also suggest that when sugarcane molasses is fed at levels above 25% it has a laxative effect.

Other studies have concluded that sugar beet molasses may be included up to 20 and 40% in the diets of growing and fattening pigs respectively (Karamitros, 1987).

Mavromichalis et al. (1998) concluded that lactose can be replaced by cane molasses in the diets of nursery pigs.

Walker (1985) concluded that fatteners can tolerate about 15% and pregnant sows about 37% molasses in the diet. Harland (1995) reported studies suggesting that a safe level of inclusion is 5% in growing pigs and 10% in finishing pig diets.

Evidence in the literature suggests that the addition of molasses to sow lactation diets subsequently resulted in a larger litter size and a more rapid return to service after weaning.

Poultry

Harland (1995) concluded that 10% molasses could be included in growing rations and 20% in laying hen diets. However, a problem with molasses is its high potassium content, which has a laxative effect on birds. While most birds perform well on balanced diets containing up to 20% molasses, inclusion levels much above 4% will likely result in increased water intake and manure wetness (Leeson and Summers, 1997). According to Leeson and Summers (1997) maximum dietary inclusion level for young birds 0-4 weeks is 1% and other categories is 5%.

CONCLUSIONS

• World molasses (a by-product of the sugar industry) production has increased tremendously from no more than 15 million tonnes in the early 1960s to an estimated 46 million tonnes in 1998/99.
• About 75% of the world’s molasses comes from sugar cane (Saccharum officinarum) grown in tropical climates (Asia, South America), and the majority of the remainder comes from sugar beet (Beta vulgaris) grown in the temperate climates (Europe and North America).
• Animal feed is the main market worldwide for molasses, using approximately 51 percent of the total.
• Molasses may be fed to livestock in several ways such as molassed meal, molasses blocks, and liquid form to provide energy directly or be used as a carrier for non-protein nitrogen, vitamins and minerals as well as medicinal compounds.

• Molasses supplies the rumen with rapidly fermentable energy in the form of sugars, primarily sucrose.
• Sugars, particularly sucrose are superior to starch as an energy source for the microbial fixation of nitrogen in the rumen. Sucrose gives a greater microbial protein synthesis than starch.
• Supplementing grass silage with molasses or sucrose significantly reduces ruminal ammonia N concentrations compared to other carbohydrate sources such as starch.
• Up to 25-31% molasses inclusion in the total diet of dairy cows increases total DMI, milk yield and protein yield without any adverse effects on cow performance. In addition, molasses can effectively replace moderate levels of common energy sources.
• A relatively high energy value is attained for molasses (with adequate protein supplementation) at up to 20% dietary inclusion in beef cattle diets.
• Molasses is an effective supplement at up to 40% inclusion in total sheep diets.
• With both pigs and poultry the level of molasses inclusion in the diet is usually limited because of the risk of soft faeces or diarrhoea.

• Maximum dietary inclusion is 5% for growing pigs, 10-15% for finishing pigs and 35% for pregnant sows.

• Maximum dietary inclusion level for young birds 0-4 weeks is 1% and other categories is 5%.

MAIN REFERENCES

Chamberlain D.G., Robertson, S. and Choung, J.J., 1993. Sugars versus starch as supplements to grass silage: Effects on ruminal fermentation and the supply of microbial protein to the small intestine, estimated from the urinary excretion of purine derivatives, in sheep. J. Sci Food Agric, 63:189-194

Chamberlain, D.G. and Choung, J.J., 1995. The importance of rate of ruminal fermentation of energy sources in diets for dairy cows. In: Recent Advances in Animal Nutrition 1995, Nottingham University Press. Chapter 1: 3-27

Drennan, M.J., 1985. Evaluation of molasses and ensiled pressed beet pulp for beef production. In: Feeding value of by-products and their use by beef cattle. Commission of the European Communities seminar. (Ed) Ch. V. Boucque: 171-183

Harland, J.J., 1995. By products. In: The Sugar Beet Crop. (Eds.) D.A. Cooke and R.K. Scott., Chapter 16: 619-647

Moloney, A.P., Almiladi, A.A., Drennan, M.J. and Caffrey, P.J., 1994. Rumen and blood variables in steers fed grass silage and rolled barley or sugarcane molasses-based supplements. Animal Feed Science and Technology 50: 37-54

Murphy, J.J., 1999. The effects of increasing the proportion of molasses in the diet of milking dairy cows on milk production and composition. Animal Feed Science and Technology 78: 189-198

Yan, T., Roberts, D.J. and Higginbotham, J., 1997. The effects of feeding high concentrations of molasses and supplementing with nitrogen and unprotected tallow on intake and performance of dairy cows. Animal Science 64: 17-24

ABOUT THE AUTHORS

Dr. Mark McGee is a Technical Executive with IAWS Group plc.

Lianne Zoeteweij (MBA) is a Market Researcher with Schuurmans & Van Ginneken.

Dr. Phil Holder is Sales Director and Farm Marketing Manager with SvG Intermol.