Expert’s Corner: The nutrients in your calf starter

By Lucas Mitchell, Ph.D., dairy calf and heifer specialist
Carbohydrates, protein, fat, vitamins, minerals and water are all absolutely necessary to produce a high-quality calf starter. Let’s explore the functions of these nutrients – and their inclusion in calf starter – in more detail.

Carbohydrates
Carbohydrates are the most abundant nutrient in calf starters and come from three primary sources: starch, sugar and fiber.

• Starch and sugar are rapidly fermentable and serve as primary sources of energy. The fermentation products of starch and sugar are primarily responsible for the physiological development of rumen papillae.
• Depending on the fiber source and age of the calf, it is probably not digested nearly as quickly. Fiber in a calf starter can help buffer rumen pH, which will help stimulate intake up to a certain point, but, if too much undigestible fiber is in the starter, it also can limit intake due to gut fill. Some undigestible fiber is necessary as it will help stimulate rumination and rumen contractions, which will help to develop rumen musculature.

Starch is the predominant carbohydrate in most calf starters, especially texturized starters. It is common to see it at levels between 20% and 40% of dry matter (DM). The ideal level will vary depending on the farm and its individual goals. Corn is usually the primary source of starch in calf starters. Oats are another common starch source, though they are often thought of as a fiber source. Oats contain about 38% starch and 29% neutral detergent fiber (NDF) on a DM basis. Other less-common sources of starch include small grains like wheat or barley.

Sugar is usually a small portion of calf starters (4% to 9% on a DM basis). Some unique calf starters contain high levels of lactose, which may push the sugar level higher, but these tend to be cost-prohibitive. In most cases, much of the sugar comes from inclusion of molasses either within pellets or coated on the outside of texturized starters. Research has shown exceeding 10% molasses is detrimental to starter intake and, therefore, affects calf growth.

Fiber content varies between calf starters, especially between complete pellets and texturized starters. Fiber content is typically lower than starch in texturized starters, but may be higher in complete pellets, depending on the preferences of the farm and the formulator. Texturized starters may contain 10% to 20% fiber on a DM basis while complete pellets are more likely to contain 20% to 30% fiber on a DM basis.

Wheat midds are a critical ingredient in most pellets and a significant contributor of fiber in calf starters. Wheat midds contain about 40% NDF and 21% starch on a DM basis. Soyhulls and cottonseed hulls are other common fiber sources that don’t bring any starch to the diet. Soyhulls and cottonseed hulls may be included within complete pellets, but are also commonly included in pelleted form as part of a texturized starter. Comparing these fiber sources, the fiber in soyhulls and wheat midds are quite digestible, while cottonseed hulls contain a greater amount of undigestible fiber. This is beneficial for stimulating rumination, but care must be taken that the proper amount is included so intakes are maximized and not hindered.

Protein
Protein is the second-most-prevalent nutrient in calf starters. In most cases, protein content will be between 18% and 22% on an as-fed basis. Protein is necessary for health, adequate growth, and development of skeletal muscle. The level of protein needed will vary depending on feeding strategies and growth goals. Calves that consume large amounts of starter may not need a starter with as high of protein concentration because they consume enough starter to achieve adequate grams of protein.

The most common source of protein in calf starters is soybean meal. It is a highly palatable, highly digestible source of protein for calves that should be prioritized as a protein source for young calves. Whole or split roasted beans are another excellent source of protein that calves find quite palatable. Other common sources of protein are dried distiller’s grains and canola meal. Research has shown that distiller’s grains may be used in calf starters, but only up to about 20% of the diet DM. Exceeding that level will result in reduced performance. Canola meal, however, is best avoided for young calves as it is not regarded as very palatable and may hinder intake and growth performance.

Fat
Fat should be limited in calf starters to 5% or less on an as-fed basis as increased fat has been shown to impair calf starter intake and unsaturated fats are toxic to microbes. It would be counterproductive for rumen development if microbial populations are suppressed by too much fat inclusion.

Most of the fat in calf starters comes from fat inherently within the ingredients. For example, roasted beans are a high-fat ingredient that may be included in calf starters. Calves find them palatable, but care should be taken to keep fat at a reasonable level.

Calves will utilize fat in starter as an energy source, but that is not its sole purpose within calf starters. There is often some additional fat included in pellets to help with flow through pellet mills, and texturized starter will commonly have some extra fat applied at the end as a coating to help pick up fines and add a nice glossy look to the starter. Sources of additional fat in calf starters are typically liquid fats like corn or soy oil.

Vitamins and minerals
Vitamins and minerals are necessary in calf starters as they are essential for the health and development of young calves. Vitamins A, D, and E as well as choline, niacin, vitamin B12, riboflavin, and thiamine are commonly added vitamins to ensure sufficient supply. The minerals calcium and phosphorus are added as they are critical for proper bone development and growth. Trace minerals are also included to ensure adequate supply of these critical low-inclusion nutrients.

Water
Most calf starters will contain 10% to 15% moisture, all of which is inherent within the raw ingredients. Water is not critical per se for calf starters, but, if a calf starter is too dry, it could be be brittle, leading to increased fines that can hinder starter intake.