Because of the recent expansion of the ethanol industry, either dry distillers grains with solubles (DDGS) or wet distillers grains with solubles (DWGS) have become widely available to the dairy industry. Often, distillers grains can be purchased at highly competitive prices, making it a highly attractive feed to include in dairy replacement heifer diets. Typically, nutrients in distillers grains make it a desirable feedstuff, but positioning distillers grains in heifer diets can be challenging.
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Feeding Distillers Grains to Dairy Heifers
The primary advantage in feeding distillers grains to dairy heifers is cost. There are no known biological or nutritional advantages or disadvantages associated with feeding distillers grains to dairy heifers. Research trials in which distillers grains were fed to heifers observed normal growth rates, normal reproduction, and normal subsequent milk production.
Challenges with Feeding Distillers Grains to Dairy Heifers
The challenges associated with feeding distillers grains to dairy heifers are:
- Distillers grains are high in energy, and excessive supplementation may result in over-conditioned heifers.
- Distillers grains are rich in free, largely unsaturated oil of which the effects to feeding heifers is largely unknown.
- Distillers grains are high in phosphorus, and the phosphorus requirement of dairy heifers is low.
- Distillers grains are low in lysine, and the dynamics of lysine supply have not been extensively studied in dairy heifers.
The nutrient and fatty acid contents of distillers grains with solubles are presented in Table 1. In a moderate number of research trials, distillers grains were successfully fed to dairy heifers. But most of those trials were not designed to specifically evaluate distillers grains as a protein supplement per se.
In most of the trials, researchers limited distillers grains to <20% of the dietary dry matter (DM). Researchers at South Dakota State University have fed up to 40% of the diet as distillers grains, which resulted in excessive heifer growth rates (>2.4 lbs/d).
High supplementation rates of distillers grains result in diets high in dietary fat (7 to 9%), and the effects of high supplementation rates of unsaturated fat to dairy heifers have not been investigated. The fatty acid composition of distillers is primarily C18:2, which is biohydrogenated in the rumen to C18:0 (Table 1).
Under certain dietary conditions (high intake, fast passage rate, low ruminal ph, etc.), not all C18:2 will be biohydrogenated, resulting in some C18:2 being absorbed. Research with lactating cows and steers has demonstrated that some isomers of C18:2 (conjugated linoleic acid : CLA) can be absorbed, and these C18:2 isomers may have highly active metabolic effects.
Research data with growing steers fed high concentrate diets have observed an increase in pelvic fat deposition and increases in C18:2 composition of adipose tissue. Because heifers are fed high-forage, low-energy diets with moderate
ruminal passage rates, biohydrogenation of moderate amounts of C18:2 to C18:0 should readily occur.
Because very little information is available on the possible negative or positive aspects of feeding unsaturated fats to dairy heifers, it is prudent to take a conservative approach and limit unsaturated fat content in heifer diets to approximately 5.0% of dietary DM (Table 2). This guideline results in suggested guidelines of feeding heifers up to 20.0% of the dietary DM as distillers grains (Table 2).
An irreconcilable nutritional issue with feeding distillers grains to dairy heifers up to 20% of dietary DM is that excessive levels of phosphorus will be fed (Table 2). Feeding phosphorus at 100 to 200% of requirements has not been demonstrated to affect animal health, but nutrient management programs may be compromised because excess phosphorus will be excreted in the feces.
Distillers grains with solubles may also be high in sulfur (0.35 to 0.55% DM), and high dietary sulfur levels may be linked to polioencephalomalacia in rapidly growing heifers. There is no direct evidence that feeding distillers grains results in an increased incidence of polioencephalomalacia, but dietary sulfur levels should be carefully monitored as a prudent nutritional management practice.
Forages and Distillers Grains?
Because distillers grains are high in energy, fat, and phosphorus, forages that are low in these nutrients better facilitate the feeding of distillers grains. Good complements to distillers grains include corn stalks, corn stalk silage, mature oatlage, wheat straw, oat straw, sorghum-sudan grass, low-energy grasses, soybean stubble, and other low-energy forages. Heifer feeding programs based on high-energy corn silage and high-quality alfalfa hay or silage do not facilitate feeding high amounts of distillers grains in heifer diets.
|CP1||% of DM||26.7||23.0||29.0|
|NDF2||% of DM||30.2||24.7||39.7|
|NDF Digestibility||% of NDF||59.0||39.5||74.9|
|Nonfiber Carbohydrate||% of DM||35.8||24.2||45.9|
|Fat||% of DM||16.4||13.7||19.0|
|Fatty Acids||% of DM||13.2||11.4||15.5|
|C20-C24||% of Fatty Acids||0.8||0.4||1.1|
|C18:3||% of Fatty Acids||1.5||1.3||1.9|
|C18:2||% of Fatty Acids||53.9||51.8||58.0|
|C18:1||% of Fatty Acids||25.0||21.8||26.1|
|C18:0||% of Fatty Acids||2.1||1.9||2.2|
|C16||% of Fatty Acids||14.2||13.5||14.8|
|C8-C15||% of Fatty Acids||0.2||0.1||0.9|
|Ca||% of DM||0.1||0.0||0.5|
|P||% of DM||0.9||0.5||1.2|
|K||% of DM||1.2||1.0||1.5|
|Mg||% of DM||0.3||0.3||0.4|
|Ash||% of DM||5.7||2.9||8.8|
2Neutral Detergent Fiber
|Heifer Body Weight, lbs|
|Dry Matter Intake, lb DM/d||8.4||15.1||20.3||23.1|
|Distillers Grains, % of DM||20||20||20||20|
|Distillers Grains, lb DM/d||1.68||3.02||4.06||4.62|
|Dietary Fat, % of DM||5.0||5.0||5.0||5.0|
|Dietary Phosphorus, % of DM||0.37||0.37||0.37||0.37|
|Dietary Phosphorus Requirement, % of DM||0.25||0.25||0.20||0.18|
Patrick C. Hoffman