Selecting rumen-protected fats for dairy feed formulation
Beyond energy: Selecting rumen-protected fats for dairy feed formulation
Rumen-protected fats have long been used to increase energy density of dairy diets, but fatty acid profile, manufacturing method and physical characteristics can influence everything from milk production and composition, fertility, body condition, methane reduction and feed efficiency to pellet quality in feed mills.
For feed manufacturers, nutritionists and dairy farmers alike, the days of selecting a fat supplement without determining full characteristics of the ingredient are long gone. Fatty acid profile is the key determinant of the nutritional value of the ingredient to the animal, and along with the physical characteristics of the supplement, will have a strong bearing on pellet quality when used as part of the mix for manufactured compound pellets.
According to Dr Richard Kirkland, Global Technical Manager for Volac Wilmar Feed Ingredients (VWFI), understanding these differences allows for moving beyond simply supplying ‘fat’ and toward formulating feeds for specific production objectives, including performance when used in a compound feed mill.
“Fat is the most concentrated energy source available to dairy cows, with proven rumen-protected fats providing more than 2.5-times the energy density of cereals,” he explains. “But we now understand much more about how individual fatty acids affect cow performance. The question is no longer simply how much fat is in a feed, but which fatty acids are being supplied, how they are protected in the rumen, and how we want the cow to respond to supplementation.”
The science behind rumen protection
Standard vegetable oils added to rations, or as components of high-oil ingredients such as brewer’s grains, can interfere with fibre digestion in the rumen, physically coating fibre particles as an ‘oil slick’ effect and preventing fibre-digesting microorganisms from attaching to and degrading the fibre. Some of the individual fatty acids in liquid oils are also directly toxic to fibre-digesting bacteria, further exacerbating the negative effects on fibre digestibility. Furthermore, ruminal biohydrogenation is high, converting unsaturated fatty acids to saturated forms, and reducing delivery of metabolically-active forms of fatty acids to the small intestine for absorption. However, incomplete biohydrogenation of unsaturated fatty acids, in combination with an altered rumen environment such as lower pH conditions, leads to generation of specific trans fatty acids which cause milk fat depression.
Rumen-protected fats are manufactured to minimise these effects, enabling fat concentration of diets to be increased to required levels and facilitating delivery of fatty acids in their active form through the rumen for digestion and absorption in the small intestine.
The most common types of rumen-protected fat supplements are calcium salts of fatty acids and high-melting point fat supplements, manufactured according to the properties of the individual fatty acids or blends. With the calcium salt supplements, fatty acids are reacted with calcium to create a rumen-insoluble compound that remains relatively stable at normal rumen pH before breaking down under the acidic conditions of the abomasum – these supplements are primarily based on palmitic (C16:0) and oleic (C18:1) fatty acids. Volac were the pioneers of rumen-protected fat development, working with Prof. Palmquist at Ohio State University, USA, through the late 1970s and early 1980s to develop the Megalac brand using the latter’s evolving research into calcium salt technology.
High-melting-point fat supplements are based primarily on palmitic and/or stearic (C18:0) fatty acids with melting points typically in the range of 60-70°C, enabling them to remain solid at the lower (body) temperature in the rumen.
“Rumen-protection serves two primary purposes,” explains Dr Kirkland. “It protects the rumen from the fat to avoid negative effects on fibre digestion, and it protects the fatty acids from ruminal biohydrogenation, ensuring they reach the small intestine where they can be absorbed and utilised by the cow in their active form.”
However, physical characteristics of fat supplement products are also important.
Research by VWFI at the National University of Singapore has shown that particle size influences the stability of calcium salts in the rumen. Results demonstrate that smaller granules break down more readily as they pass through the rumen than larger granules, reducing the effectiveness of rumen protection.
“Due to the unique manufacturing process, the Megalac calcium salt brand contains a higher proportion of larger granules, improving rumen-protection efficiency as an effective way to optimise cow performance by minimising negative rumen effects and improving fatty acid supply,” says Dr Kirkland.
Matching fatty acids to farm production needs
Alongside rumen-protection technology, fatty acid profile is the key nutritional determinant of animal response and should be matched to a farm’s individual production goals. Two of the most important fatty acids in dairy feed formulation are palmitic acid (C16:0) and oleic acid (C18:1), which have very different effects and also influence how nutrients are partitioned within the cow.
“C16:0 directs nutrients toward milk and milk fat production, making higher-C16 products particularly useful where milk solids are a priority,” explains Dr Kirkland. “C18:1 improves total diet fat digestibility and supports body condition, as well as egg and embryo development, making it particularly valuable during early lactation.”
This allows nutritionists to align fatty acid selection with both stage of lactation and the market for the milk being produced. Where milk fat and solids carry a premium, higher-C16 formulations can be used to support milk fat production. In early lactation, or where milk volume, body condition and reproductive performance are greater priorities, higher-C18:1 calcium salts can be more appropriate. A balanced C16:0 and C18:1 profile provides a multipurpose option for feeds intended for cows across different stages of lactation.
“There isn't one fat supplement that is right for every formulation,” concludes Dr Kirkland. “Fatty acid profile needs to be considered alongside stage of lactation, milk market, fertility issues, rumen-protection and how the ingredient performs during feed manufacture.”
Efficient and sustainable output
Improving feed efficiency is increasingly important as dairy producers look to increase output while making better use of feed resources. Rumen-protected fats can contribute by supplying a highly concentrated energy source without increasing acid production in the rumen.
Recent research from Cornell University, USA, highlights the efficiency benefits of this approach. Supplementation with Megalac increased milk yield by 3.2 kg per day while improving feed efficiency, meaning cows produced more milk and milk solids from each kilogram of feed consumed, while also reducing methane production. Furthermore, increasing inclusion of rumen-protected fats reduced methane intensity up to 15.5%, highlighting a new area of interest going forward for natural nutritional mitigation of greenhouse gases at farm level.
“Feed efficiency and sustainability are closely connected,” explains Dr Kirkland. “If a cow can convert more of the nutrients she consumes into milk and milk solids, we are improving the efficiency of the whole production system while reducing the environmental impact per unit of output.”
This adds another consideration when assessing the value of a rumen-protected fat. Alongside supporting energy supply and targeted production responses, improving the efficiency with which feed is converted into saleable milk and milk solids can deliver both economic and environmental benefits. Together, these factors reinforce the importance of looking beyond energy value alone when selecting a fat supplement.
Pellet quality brings another dimension to fat selection
For compound feed manufacturers, type of rumen-protected fat used in the mix has implications beyond what happens inside the cow. The physical characteristics of different rumen-protected fats can also have a significant effect on manufacturing ability and efficiency, and the quality and durability of finished compound pellets.
Recent data from an independent test site in the Netherlands compared pellet durability (Holmen test) of conventional ruminant compound with increasing concentrations (0, 2.5, 5.0 and 10.0%) of either a high-palmitic acid (88%) prill (Mega-Fat 88) or a calcium salt of palmitic (58%) and oleic (28%) fatty acids (Mega-Max). Durability of the control pellets was 96% and maintained at 92% for pellets with 2.5% inclusion of the calcium salt, and remained relatively high at 76% even at 10% inclusion rate. In contrast, addition of 2.5% of the high-palmitic acid prill reduced durability to 84%, but declined linearly to only 3.9% at the 10% inclusion level.
“The physical properties of fat become very important in compound feed manufacture,” explains Dr Kirkland. “Typical industry high-C16 supplements have a melting point around 60°C meaning they will act as a lubricant when passing through a die in the feed mill, but equally higher levels result in much softer pellets that are particularly vulnerable in hot weather, especially after being subject to many physical movements before they arrive in front of the cow at farm level.”
In contrast, calcium salts have quite different physical properties, chiefly as they do not melt at temperatures encountered through the feed chain. Hence, they generate greater friction during pelleting to aid pellet compaction and maintain pellet structure even at high environmental temperatures.
“This creates opportunities for feed formulators,” adds Dr Kirkland. “Where higher levels of supplemental fat are required in a compound pellet, calcium salt technology can offer a considerable advantage in maintaining physical pellet quality.”
“For modern feed formulation, the value of a rumen-protected fat extends well beyond its headline energy content,” concludes Dr Kirkland. “Type of supplement influences pellet quality, while fatty acid profile is the primary determinant of response achieved, including how nutrients are partitioned within the cow. Bringing these factors together allows formulators to select the right fat for feed manufacture, animal performance and efficient milk production.”
Dr Richard Kirkland, Global Technical Manager for Volac Wilmar Feed Ingredients.