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What’s in a milk replacer and why?

Drew A. Vermeire for Progressive Dairy Published on 06 November 2019

Milk secretion is a defining characteristic of mammals. Milk composition varies by species, by stage of lactation, age and there are dietary influences, as well.

In developing a product to replace milk to feed neonatal animals, that is to say we’re going to make a “milk replacer,” step one will be to try to match the composition of the milk the target animal would consume from its dam. For example, an average composition for sheep would be 26% protein and 40% fat and for goats it would be 24% protein and 34% fat.

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On a solids basis, the composition of cows’ milk is typically 25%-29% protein, but fat content is much higher in dairy milk than beef milk. This is likely a reflection of genetic selection of dairy cows over hundreds or thousands of years for milk with high butterfat. Interestingly enough, the milk composition that research shows is best for both dairy and beef calf performance is most similar to beef milk. This milk is higher protein (26%-28%) and lower fat (14%-17%), which is different than today’s typical milk replacers.

Milk replacer ingredients

Milk replacers require unique ingredients because neonatal animals cannot digest typical feed ingredients like soybean meal, corn or typical byproduct ingredients. Milk replacers are produced using ingredients that are highly digestible to neonatal animals, nutrient dense and cost-effective for producers to use.

Traditionally, ingredients used in milk replacers are byproducts of milk manufacturing to produce butter or cheese. When butter is made, milk fat and water combine to produce butter and the co-product, called “skim milk” or “non-fat dried milk,” which contains both casein and whey proteins, lactose and minerals. When cheese is produced, the co-product is whey.

Cheese contains casein, butterfat, calcium and phosphorus while whey proteins and lactose are contained in whey, along with varying amounts of sodium, potassium and chloride, which may be added in the cheese-making process. Non-fat dried milk contains about 35% protein, and whey protein is concentrated to “whey protein concentrate” or “WPC,” which contains 34% protein through removal of lactose by crystallization or ultrafiltration.

Fats used in producing milk replacers include tallow and lard plus some vegetable fats such as coconut oil and limited amounts of vegetable oils. A simple milk replacer formulation could be made with whey; WPC; a blend of tallow, lard and coconut oil; and a premix containing vitamins and minerals. Increasing or decreasing the relative amounts of WPC, whey and fat can adjust the amount of protein and fat in the formula.

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Modern formulations and modern ingredients

For many years, the industry standard milk replacer contained 20% protein and 20% fat (20/20) and was fed at the rate of 1 pound per day, which barely meets the energy requirements for a 100-pound calf. The 20/20 milk replacer was originally a finishing milk replacer for veal calves and was never intended to feed to baby calves because 20% protein is too low for normal growth, and 20% fat is too high to maximize starter feed intake, which is the primary driver for rumen development.

Composition of all-milk or wheat protein milk replacers

Since the 1970’s there have been continuous improvements in ingredients for milk replacers, particularly non-milk protein sources, because the cost of protein is the highest cost in producing milk replacer. Today, we have high-quality ingredients derived from soy, wheat, corn and animal byproducts to replace protein and carbohydrates in milk replacer formulations. While none of these ingredients are perfect replacements for milk ingredients, both research and experience have shown that replacing a portion of milk ingredients with non-milk ingredients can substantially lower the cost of milk replacer with equal or better calf performance than an all-milk formulation.

Non-milk protein ingredients include soy protein concentrate, soy isolate, blood plasma, pea protein and hydrolyzed wheat protein. As an example of replacing milk ingredients with non-milk protein, an experiment was conducted at the University of Illinois in which hydrolyzed wheat gluten protein replaced some of the whey protein in heifer milk replacer containing 28% protein and 15% fat. Calves were fed 1.33 pounds per day milk replacer during weeks one two and eight; 1.76 pounds per day during weeks three and seven, and 2.65 pounds per day during weeks four five and six. Calves were fed milk replacer without starter during weeks one through four.

Cost of these milk replacers at today’s ingredient prices are $61.64 per bag for the all-milk control milk replacer and $59.41 per bag for all-milk supplemented with wheat protein. Average daily gain through 8 weeks of age was 1.43 pounds per day for calves fed the control milk replacer and 1.46 pounds per day for calves fed milk replacer supplemented with wheat protein. Total cost of milk replacer would be $133.17 per calf and $128.35 per calf, respectively, for control and wheat-supplemented milk replacers. This gives the wheat protein-supplemented milk replacer a cost-of-gain advantage of $0.09 per pound of gain. A very similar example could be found with soy protein, blood plasma, or combinations of soy protein, blood plasma, pea protein and wheat protein.

Lactose is the primary carbohydrate in milk and is also called “milk sugar.” Many modern milk replacers replace some lactose with dextrose, pre-gelatinized starch, and/or extruded wheat flour. Unlike milk ingredients that are subject to wide price variation with the ingredient market, one advantage of non-milk ingredients is a more consistent price within years and from one year to the next.

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Performance of calves fed all-milk  or wheat protein milk replacers

Other ingredients shown on milk replacer ingredient labels include vitamins; minerals; emulsifiers such as lecithin and polyethylene glycol 400, which help mix fats into water-based milk replacer; additives such as sorbitol, which improves fat digestion; and additives to improve calf health and performance. Among popular additives are probiotics, which are live cultures to improve microbial population of the intestine.

Prebiotics are additives, usually carbohydrates, which are not digested by the calf but are utilized by “friendly bacteria” that proliferate and crowd out pathogenic bacteria. Prebiotics include fructooligosaccharides (FOS), mannanoligosaccharides (MOS), galactooligosaccharides (GOS), and citric acid press cake (Citristim). Acidification, usually with citric acid, is another strategy to improve calf health because pathogenic bacteria are sensitive to pH and adjusting pH of milk replacer can reduce pathogens. Many milk replacers contain proteinates, glycinates, polysaccharide complexes or other organic trace mineral sources because they have higher bioavailability than sulfates or oxides.

Antibiotics

Years ago, many milk replacers were made with a combination of oxytetracycline and neomycin. Today, most milk replacers are non-medicated, but many may have additives to improve calf health and performance. There is an option today to feed a milk replacer with oxytetracycline and neomycin at a much higher level than used in the past, but for only 14 days. This is not a strategy I personally advocate because calves suffer from diarrhea during the first 14 days and respiratory problems develop around 21 days of age.

If the medicated milk replacer were fed for the first 14 days, neomycin has some benefit for bacterial scours, but oxytetracycline is beneficial for respiratory, but it would be fed prior to respiratory problems. Secondly, most scours are caused by viruses (Rotavirus and Coronavirus), which are not affected by antibiotics.

Formulation of 28/15 milk replacer

My recommendation is to feed non-medicated milk replacers and work with your veterinarian to develop a more targeted antibiotic program to address bacterial scours, which occur within the first week of life, and respiratory problems, which develop around 3 weeks of age. Milk replacers containing lasalocid (Bovatec) or deccoquinate (Deccox) are fairly common because these additives prevent coccidiosis, may have some effect on cryptosporidia and give opportunity to include fly control into the milk replacer to control flies.

In the U.S., we are world leaders in many technologies, so we generally assume we hold a leadership position in all technologies. While we have approximately 9.5 million dairy cows in the U.S., by comparison, Europe has approximately 23 million dairy cows and has been the technological leader in milk replacers. There is no such thing as an “all-milk” milk replacer in Europe. As milk ingredients such as whey are used in an increasing number of human food products, non-milk ingredients will become more common in American milk replacers to lower cost of milk replacer and maintain or enhance calf performance.  end mark

References ommited but are available upon request. Click here to email an editor.

Drew A. Vermeire
  • Drew A. Vermeire

  • Nutritionist
  • Nouriche Nutrition Ltd.
  • Email Drew A. Vermeire

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