Global milk production and processing industries have grown in recent decades, and changes in consumer preferences for milk products have resulted in a growing surplus of milk processing byproducts alongside it. The production of popular dairy products, such as cheese and butter, results in large volumes of cheese whey, skim milk and buttermilk – byproducts classified as solids-non-fat (SNF).
Cheese production creates nine times more whey than actual cheese, and with hundreds of thousands of tonnes of cheese produced annually in Canada in recent years, milk processing byproducts present a massive opportunity for revalorization. Unfortunately, the revalorization of milk processing byproducts is complicated by its low dry matter content, making handling, transportation and storage more difficult. Finding efficient methods of revalorization is crucial to maximize profit from milk production and lower the environmental impact of milk processing.
A multidisciplinary committee of engineers, food scientists and animal nutritionists at the University of Guelph have been developing strategies to make SNF dewatering simpler and more affordable by first removing the proteins with sodium bentonite clay. Traditionally, dewatering SNF byproducts through nanofiltration has required several steps, including ultrafiltration pre-filtration to remove proteins from the liquid and prevent fouling of the nanofiltration membrane. Current methods of SNF fractionation require significant time, energy and specialized equipment, making SNF revalorization cost prohibitive and thereby inaccessible to small and rural producers – until now.
Researchers conducted several preliminary experiments to assess if bentonite-separated whey byproducts were suitable for inclusion as a feed ingredient in ruminant diets. Sodium bentonite clay was mixed into cheese whey at 30 grams per litre to bind whey proteins through adsorption, creating a slurry which settles to the bottom of the container and separates naturally from the lactose supernatant. This whey protein bentonite slurry was concentrated to a dry matter of nearly 30% without the need for specialized equipment or facilities. From here, the lactose supernatant, with an initial dry matter of about 6%, can be concentrated to a dry matter of 15% to 20% through traditional nanofiltration dewatering, which may greatly extend membrane life. The lactose supernatant and whey protein bentonite slurry were found to have similar total digestible nutrients (TDN) to high-moisture corn, which suggests the lactose supernatant could serve as a substitution for corn grain in the ration. With this liquid ingredient, a liquid seepage experiment was done to determine the maximum inclusion of a liquid lactose solution mixed to 15% dry matter, and found that lactose could be included up to 15% in a dairy cow total mixed ration (TMR) without any seepage of the liquid ingredients. This prompted the research team to then evaluate this feed in a dairy cow trial.
Recently, the research team conducted a feeding trial at the Ontario Dairy Research Centre examining the inclusion of bentonite-separated ingredients in dairy cow TMR diets. In this small experiment, zero percent, 4%, 8% and 12% of the high-moisture corn in the diet was replaced with lactose on a dry matter basis (DMB), and another diet replaced 8% of the corn with lactose and replaced an additional 2% with bentonite-separated whey byproducts. Liquid lactose was mixed to a concentration of 15% for all diets to simulate the dry matter of the lactose supernatant post-nanofiltration dewatering.
Dry matter intake (DMI) was greatest at 8% lactose inclusion versus the zero percent control, where 12% DMI was similar to zero percent, showing a quadratic effect with increasing inclusion of dietary lactose. Over the course of the experiment, milk yield and milkfat production were similar across all inclusion rates of lactose in the diet. However, as dietary lactose increased, grams per kilogram of milk protein also increased linearly. Previous research has shown this could potentially indicate improved nitrogen utilization or microbial protein production from synchronized rates of carbohydrate and protein degradation in the rumen. Further analysis is ongoing to determine if these early results translate into improved nitrogen use efficiency.
In addition to daily yield of milk production and milk components, bodyweight and condition scoring were not affected by lactose content in the diet. When evaluating the inclusion of the whey protein bentonite slurry, current results suggest that there was no impact on any milk production or animal performance metrics measured in the experiment. These early results suggest that the lactose solution and whey protein from milk processing byproducts have potential to partially replace corn as a feed ingredient in lactating dairy cow diets. The research team plans to continue to investigate this and other strategies to include milk processing byproducts in ruminant rations.
The ease, affordability and energy efficiency of bentonite clay separation is key to facilitating the widespread use and large-scale application of these revalorization methods. When dairy waste is produced and recycled locally, small and rural producers can minimize transportation costs, potentially reduce feed costs and promote a circular economy.
The research team would like to thank Dairy Farmers of Ontario, Ontario Ministry of Agriculture, Food and Agribusiness, and the Natural Sciences and Engineering Research Council of Canada for funding this research.
Tatum Schooley is a master's candidate at the University of Guelph.
References omitted but are available upon request by sending an email to the editor.
