Molasses, from sugar beets or cane, is a common enough food ingredient throughout most of the world, yet it is rarely used in piglet diets beyond a mere 2 percent to 5 percent. The reasons for using even such a low amount of molasses are far beyond nutritional, focusing mostly on the pellet-binding properties of molasses, and of course, on its taste-enhancing qualities in animal feed.
What is not readily recognized is the fact that typical molasses contains about 50 percent simple sugars in the form of sucrose, free glucose and free fructose (the free sugars are in balance with the sucrose). This aspect alone makes molasses an attractive alternative for replacing lactose in diets for young pigs, especially in countries where molasses is produced. This is even more the case in regions that produce cane molasses, where milk-based sugars (lactose) are traditionally very expensive.
Challenges of molasses
There are several reasons for the restricted use of molasses in piglet feeds. The most important has been the fact that few are aware of the small difference between lactose and other simple sugars; that is, from a nutritional point of view. Moreover, molasses is a rather viscous liquid material that requires special handling and storage, especially during the winter months when it thickens and requires heating. Molasses has been also blamed, contrary to scientific evidence, for increasing the incidence of diarrhea in weaned pigs due to its high concentration of potassium (more than 4 percent).
To add to the list of negative connotations, high dietary levels of molasses command special pelleting conditions. To be able to replace lactose with molasses, we must first realize that during the initial couple weeks post-weaning, piglets benefit mainly from the lactose part of milk products. This understanding will free us from formulation restrictions that erroneously call for minimal milk protein levels.
This fact is illustrated in Figure 1, where, based on results from The Ohio State University, it is clearly demonstrated that when given a source of highly digestible protein (which can be just crystalline amino acids or any source of high-quality protein), piglets require just lactose to thrive. From the same study, it is also evident that after the first two weeks post-weaning, piglets respond to lactalbumin (or any high-quality protein) supplementation and not to lactose, indicating a rapidly maturing digestive system and increased need for highly digestible protein.
The next question we must answer is whether piglets can really use molasses instead of lactose to fuel their energy requirements. In fact, sucrose is actually toxic to newborn pigs, but only during the very first few days of life. After the first week of age, piglets digest and metabolize sucrose normally and with high efficacy. Actually, as early as the 1950s, it was discovered that sucrose and its components – glucose and fructose – can be digested and absorbed as efficiently as lactose by young pigs after weaning. And, molasses is just that, a viscous liquid solution of sucrose, and free glucose and fructose. In fact, glucose in the form of dextrose is frequently added in high-quality piglet diets and milk replacers.
To answer the same question under more practical conditions, a series of trials at Kansas State University demonstrated that molasses can replace half or even all of lactose, in diets containing up to 20 percent lactose, without any negative effect on piglet growth and health (Figure 2). In fact, piglets fed diets based entirely on molasses had higher growth performance compared to pigs fed diets based on lactose; a fact that, if it is real (and it appears to be, based on commercial experience – see Figure 4), can only be attributed to the better taste of the molasses-based diets. It should be noted here that these experimental diets, which were pelleted, contained a source of immunoglobulins, antibiotics and zinc oxide – all of which ensure optimal gut health conditions.
Molasses-based nutrition programs
Finally, under commercial conditions, molasses-based nutrition programs for piglets have been developed by the author in the United States, Europe and Latin America. These programs contain either heavy levels of molasses replacing most of lactose, or even exclusively molasses without any added lactose. This concept has been applied in diets with and without antibiotics (or other growth/health promoting agents) with equal success. Results from two such commercial programs are presented in Figures 3 and 4. The best application of this molasses concept has been in low-cost simple diets that usually support very low feed intake during the first weeks post-weaning. The addition of high levels of molasses has a feed-intake enhancing effect that is comparable to that obtained by other more expensive means.
Feed manufacturing, of course, requires special attention because at temperatures where normal pellets with 0 percent molasses are produced (about 60-70 degrees Celsius or above), molassed pellets will come out burned. This is due to the formation of Maillard products that is normal to any product containing free sugars and amino acids. So, molasses-based diets should be pelleted at lower temperatures (around 50 degrees Celsius).
Nevertheless, molassed pellets will invariably turn out darker in color compared with normal pellets, due to the natural dark color of molasses. The same dark coloration will also affect the feces from piglets fed diets high in molasses; a similar effect can be seen in piglets fed diets with high levels of copper sulfate. Finally, pellets high in molasses tend to stick together and create a block in stacked paper bags, but this is easily broken down by means of simply handling the bags. Here it should be noted that molasses may dampen the paper bags containing the pellets, not unlike with high-fat diets.
Practical experience and research has demonstrated that although sucrose indeed has a laxative effect (soft feces will be produced in any high-sugar diet), it is never the cause of pathogenic diarrhea. In fact, sucrose is no more laxative than lactose, a fact that forces commercial diets to contain low levels of lactose in Europe, but not in the Americas, to avoid the appearance of soft feces (an undesirable, but totally harmless side effect – unless it is coupled with pathogenic diarrhea). If secretory scours occur, the treatment should focus not on antibiotics (and their replacements), but on realigning the electrolyte balance and then adjusting the fiber concentration of the diet – and perhaps adding an absorbant to reduce gut liquidity.
From a marketing standpoint, commercial diets based heavily on molasses should be introduced to the market following an educational campaign and after consultation with the customers. Based on local feedback, adjustments in formulation can be affected to reduce feed cost without sacrificing piglet growth and health. However, the strongest marketing point has always been the substantial cost savings that can be as lucrative as 20 percent to 30 percent less per unit of weight gain in pigs fed all-molasses diets.