Amino acid utilization from corn distillers grains-based diets for dairy cows

Ethanol production has increased remarkably in the last decade, resulting in large amounts of distillers dried grains with solubles (DDGS) as feedstuffs for livestock animals. In addition, new fractionation and fermentation technologies to maximize ethanol yield have resulted in the availability of a variety of products of different chemical compositions. Recent studies have demonstrated that milk yield and DMI are similar or greater when DDGS were fed between 20 to 30% of the diet compared with soybean based diets. Moreover, milk protein percentage was rarely affected when DDGS were fed up to 20% of the diet. Despite the availability of considerable data supporting that DDGS is a good source of protein, rates of its inclusion are still below potential partly because of concerns about a possible decrease in milk protein synthesis. "New generation" DDGS may be of higher protein quality than commonly thought. In fact, there are indications in the literature that both dietary lysine concentration and amount of AA available for absorption from DDGS are greater than values used in most feed formulation systems. The objectives of our research were to evaluate the quality and feeding of different types of DDGS (conventional and reduced-fat) to dairy cows in different stages of lactation. First, we utilized the arterio-venous technique to assess the utilization of AA in diets containing different concentrations and types of DDGS. Second, we estimated the in vitro intestinal digestibility of CP and AA for different types of distillers grains including conventional, reduced-fat, high protein, and modified wet distillers grains. The results allow us to conclude that DDGS are a highly digestible source of RUP, but a poor source of absorbable Lys. Different DDGS can be effectively fed up to 20% of the diet of early and mid lactation cows without affecting milk yield or components. Arterial Lys concentration decreased with the inclusion of DDGS however, this decrease was compensated by adaptation in mammary extraction of AA to maintain adequate milk protein synthesis when DDGS was fed up to 20%. This adaptation capacity appears to be inadequate when DDGS is included in the diet at 30% because milk protein percentage decreased. The AA profile and digestibility of RUP may be greater than values currently used in feed formulation and improvements in AA availability may allow for greater inclusion of DDGS in dairy cow diets.Keywords. Distillers dried grains with solubles, amino acid, milk protein synthesis, intestinal digestibility.