Skim Milk vs. Whey: Both Have Merits

In our quest to achieve high-quality dairy replacement and market animals, we want to raise them using the best ingredients to support their health and growth. Plus, we want to do that as affordably as possible.

As dairy markets fluctuate in ingredient price and availability, there is flexibility in terms of calf milk replacer (CMR) formulations that utilize co-products of dairy manufacturing. In seasons of high cheese demand, we have access to abundant quantities of whey. When butter is popular, its co-product, non-fat dry milk (NFDM), may be more readily available.

Both of these all-dairy ingredients play a useful role in CMR formulation, and nearly every product we manufacture at Strauss Feeds contains various combinations of both as important sources of dairy protein. Rather than attempting to decipher which ingredient is a “better” choice, it is far more productive to focus on the quality and consistency of these protein sources in milk replacer. In short, both NFDM and whey-based ingredients can be really good, or really bad.

“Whey and its more processed components have come a long way since the days when it was a waste product used as fertilizer and pig feed. It is now embraced for its excellent amino acid profile, ease of digestion, and protein-rich qualities.”

The Ingredients

NFDM is the dry component of the leftover fluid that remains when the fat is removed from milk in butter production. It is a non-standardized product with protein levels ranging from about 34-37% and fat content ranging from 1-4%. Skim milk powder (SMP) is made from further processing NFDM and is standardized at 34% protein and 1.5% or less fat. Milk Protein Concentrate (MPC), where some of the lactose is removed from NFDM, is also an available ingredient.

Whey is the liquid portion that remains after cheese is made. It typically contains about 12% protein and 72% lactose. When standardized into Whey Protein Concentrate (WPC), it, too, contains 34% protein and a lactose level identical to that of NFDM. WPC is slightly higher in fat than NFDM, at 2-3% versus 1.5%. Highly concentrated WPC also can be extracted from whey as High Protein WPC, which can range from 40% protein to as high as 92%.

What we want to avoid in either of these products is inferior quality in terms of bacteria levels (standard plate count or SPC) and/or solubility. There has been talk in the industry about some products are human grade and some others are not. The USDA specifies that human grade whey products have an SPC less than 25,000 CFU (Colony Forming Units) per gram and NFDM must have no more than 10,000 CFU/gram. We utilize that same standard in our Quality Assurance program for whey and NFDM based ingredients. Every ingredient brought into our plants is tested for SPC and those approaching or over 25,000/10,000 are rejected.

Heat is also a quality factor for both. Both NFDM and WPC need to be processed via low heat methods to maximize digestibility of their proteins and prevent denaturing of the proteins.

All dairy processing plants (cheese and butter/NFDM) have strict protocols regarding the product temperature and time at that temperature to limit bacterial growth in their products, which are closely monitored. Well over 50% of the whey produced in the United States is processed to meet USDA human-grade standards, which means it must be pasteurized after leaving the cheese vat. Even if it is not processed to these standards, it always is heat-treated to kill bacteria before moving further in the processing chain.

Whey and its more processed components have come a long way since the days when it was a waste product used as fertilizer and pig feed. It is now embraced for its excellent amino acid profile, ease of digestion, and protein-rich qualities. That’s why we now see it as a key ingredient in sports drinks and liquid supplements in human nutrition. If you know anyone who has required tube feedings, odds are they were fed a whey-based product.

Performance Comparisons

There was a time when we thought skim milk was a superior ingredient because it contains casein, the protein fraction of milk that ends up in cheese – which means whey contains no casein. While it is true that casein encourages curd formation in the abomasum, researchers have found that feeding NFDM does not improve calf health or performance compared to feeding whey-based protein sources.

A review of calf nutrition studies published 25 years ago showed that clotting did affect the rate of passage of nutrients, but not nutrient digestibility or calf performance. The authors of that study concluded that other factors aside from clotting were more important in determining the quality of a calf milk replacer protein source, and ultimately, calf health and growth outcomes.

Another study compared dry-matter intake (DMI), average daily gain (ADG), gain:feed ratio, and scour days for calves fed milk replacer at 10-12% of bodyweight with 100% NFDM; 33% WPC/67% NFDM; 67% WPC/33% NFDM; and 100% WPC as protein sources. One trial in the study fed exclusively milk replacer; the other included ad libitum calf starter. Both trials covered the first 6 weeks of life.

In the milk-replacer-only group, there was no significant difference in DMI or scours incidence among any of the feeding groups, and ADG and feed efficiency improved as WPC inclusion increased. In the trial in which starter grain was added, there was no significant difference in any of the factors regardless of protein source.

The Upshot

Both NFDM and WPC have their place in CMR formulations. We can net out with our comparison of the two with the following conclusions:

(1)   There is no significant calf performance difference between the two protein sources, assuming equal quality (bacteria load and solubility) of both ingredients. 

(2)   Most “all-milk” CMR products contain both ingredients. They may be included in different ratios, but you’ll likely find both NFDM and WPC listed on the tag of nearly every all-milk formulation. Very few products contain strictly one or the other.

(3)   Whey protein inclusion goes up in higher-protein formulations. As we have learned more about calf nutrition and lean tissue growth, many CMR formulations now are higher in protein than the old 20:20 standards. It is much easier and more efficient to utilize highly concentrated WPC to raise protein levels compared to NFDM and its derivatives.

Skim milk and whey both have common origins: whole milk. Especially in the first few weeks of life, calves’ digestive systems fare best on real dairy protein in their CMR formulations. Either protein source is workable, and most formulations include both.

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