Is sugarcane molasses a sweetener, an energy feed, or a lactose substitute?
How is molasses from sugarcane added to feed?
With the continuous increase in the varieties and quantities of by-products and edible wastes, as an unconventional feed raw material, sugarcane molasses can reduce the dietary cost, but there are many limiting factors. 
In tropical regions, sugarcane is a crop with a relatively high energy yield. Due to its characteristic of high metabolic energy, it can be used as a rich source of feed energy. Molasses, the main by-product after sugarcane processing, as a cost-effective feed raw material, can directly provide energy and is cheaper than other traditional energy feeds. It can enhance appetite and improve the palatability of feed. It can remove feed dust and be used as a binder for pellet feed. It can also supplement trace elements. However, due to the fact that sugarcane molasses is prone to adhesion during the mixing and feeding processes, the usage limit in commercial feed is relatively low.
1. The definition of sugarcane molasses
Molasses from sugarcane is the main by-product after sugarcane sugar production. It is commonly known as molasses and orange water. In the past, the sugar industry called it waste honey. It is a brown viscous liquid obtained by pressing sugarcane as raw material, clarifying, purifying and filtering the sugarcane juice, then evaporating, concentrating, crystallizing and separating it. Its output is 2% to 4% of that of the raw sugarcane. According to its form, the current sugarcane molasses can be classified into liquid and solid types. Liquid sugarcane molasses is a dark brown, viscous liquid. Solid sugarcane molasses is made from liquid sugarcane molasses as raw material by adding auxiliary materials or carriers such as soybean meal, corn cob flour, wheat bran, and bagasse. Currently, sugarcane molasses is mainly in liquid form. China is a major producer of sugarcane sugar. Every year, there are abundant resources of sugarcane molasses, which are concentrated in the four southern provinces of Guangdong, Guangxi, Yunnan and Hainan. The main production is in Guangxi, where the raw materials are abundant.
2. Nutritional characteristics of sugarcane molasses
According to industry standards, sugarcane molasses is a dark brown, viscous liquid with a slightly sweet taste and a sugar-like aroma. The composition of sugarcane molasses varies significantly due to differences in sugarcane varieties, maturity levels, planting climates, soil conditions, field management, and sugar-making techniques. Sugarcane molasses is slightly acidic and mainly contains water, sugar and non-sugar. It contains about 25% moisture. The sugar content is approximately 48%, including 24%-36% sucrose and 12%-24% other sugars (free glucose, fructose, non-fermentable sugars, etc.). Non-sugar substances include organic matter, soluble gums and other carbohydrates, proteins, amino acids, mineral elements and plasma [3]. The nutritional group stereotypes of corn and sugarcane molasses are shown in Table 1 below.
The energy density of sugarcane molasses is lower than that of corn, and its metabolic energy and net energy are 65% and 56% respectively relative to corn. However, compared with corn, it has a better taste, is digested and absorbed quickly, and has a price advantage. The crude protein content in sugarcane molasses is relatively low, generally around 3%, mostly belonging to non-protein nitrogen types such as ammonia, amide and nitrate, while amino acid nitrogen only accounts for 38-50%, and the content of non-essential amino acids such as aspartic acid and glutamic acid is relatively high. Therefore, the biological value of protein is relatively low . The content of minerals such as calcium, potassium, chlorine, sodium and magnesium in sugarcane molasses is relatively high, about 8% to 10%. Especially, the potassium content is relatively high. Excessive addition can cause loose stools. Therefore, sugarcane molasses has a certain laxative property .
The quality of sugarcane molasses is closely related to its water content, sugar content, ash content and the amount of gelatinous substances. When the dry matter content in sugarcane molasses is between 72% and 78%, if the content of several substances decreases by 2 percentage points, its viscosity will be halved. To reduce the dry matter content, other liquids such as water or oil are generally used for dilution. The lower the viscosity of molasses, the easier it is to add it during feed production . The lower the ash and colloidal substances in molasses, the better. However, with the improvement of sugar-making technology, the extraction rate of crude sugar has increased, resulting in a decrease in the sugar content of molasses and an increase in the colloidal and ash contents, and the quality of molasses has become increasingly poor. Molasses used for feed production should be free of impurities, odors and signs of fermentation.
The application of Sugarcane molasses in Pig nutrition
3.1 Application in the diet of Weaned Piglets
Traditionally, molasses from sugarcane has rarely been used in the formulation of feed for weaned piglets. Even if it is used, it is usually to enhance the sweetness of the feed or facilitate the production of pellet feed, and the dosage typically does not exceed 5% to 8%. This is because although sugarcane molasses contains more than 50% sucrose, free glucose and fructose, it also contains as much as over 4% of the mineral element potassium, which is often believed to cause diarrhea in weaned piglets. However, no relevant reports have been found in the existing literature yet. On the contrary, sugarcane molasses is most likely to become a substitute for the expensive lactose in the diet of piglets.
Old research information indicates that sucrose is toxic to piglets. However, this only applies to piglets under 14 days of age, as piglets before this age are unable to utilize sucrose due to a lack of sucrase, while piglets after this age can normally digest and utilize sucrose. Scholars from Kansas State University in the United States studied in 2000 the effect of adding sugarcane molasses to the diet of 210 early weaned piglets at 19 days of age (with an average weight of 4.6 kg) to replace lactose. The results (Table 2) show that weaned piglets can utilize sugarcane molasses as effectively as lactose. Even the growth performance of the test pigs fed with a diet containing 20% sugarcane molasses did not decline. Contrary to the commonly believed results, the test pigs in the high-concentration sugarcane molasses group were in good health and did not have diarrhea. Only the feces of the test pigs in the molasses group were darker in color [7].
Piglets have a preference for sweet foods. Therefore, it can be expected that the feed intake of piglets will increase after being fed molasses from sugarcane. However, it can be known from the above results that the feed intake only increased to a certain extent in the first 10 days, and the effect time was relatively short. Therefore, it is necessary to further study the application effect of sugarcane molasses in the diet of piglets.
3.2 Application in Sow Diets
Some stages in the reproductive cycle of sows benefit from the intake of sugar. Feeding primiparous sows showing a complete estrus period with a diet containing 51% sugarcane molasses can increase their ovulation rate. The luteal number increased from 12.1 to 14.5 (sorghum - soybean diet), or from 11.9 to 14.5 (sorghum - soybean + raw soybean oil diet); The insulin concentration is relatively high and lasts for a long time, which indicates that glucose is involved in metabolism. More importantly, feeding sows molasses resulted in more piglets than feeding them fortified diets with oil, but similar to feeding them sorghum - soybean diets (10.5 heads), the interval from weaning to estrus was not affected [6].
Feeding lactating sows with a diet containing 36% sugarcane molasses during the 21-day lactation period can effectively compensate for energy deficiency by increasing feed intake. Moreover, the weaning litter weight (9 heads, 54.4 kg) is higher than that fed with a grain-fed diet (9.2 heads, 49.4 kg), and the peak period of progesterone also occurs earlier. During the remating period, feeding primiparous sows with a diet containing 36% sugarcane molasses compared to feeding them with a grain diet could detect more small and medium-sized follicles growing at a faster rate [8].
When molasses is used in the diet of sows in the breeding pig herd, the utilization period can be improved (the average littering of sows fed molasses, sorghum - soybean + soybean oil type diet, and sorghum - soybean type diet is 3.8, 3.2, and 2.6 respectively).