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Especially in times of very tight margins, the first step in balancing dairy cattle diets is to maximize rumen microbial protein yield and rumen energy absorption by optimizing carbohydrate and protein digestion and focusing on rumen health. It is a true balancing act to provide proper nutrition to high-producing dairy cattle while also keeping their digestive systems healthy. Attention must be paid to total dietary starch and sugars, the speed of starch digestion, dietary fiber, as well as the amount of chewable fiber in the diet. It is generally recommended that high production dairy rations contain 21-27% starch. However, at the same level of total dietary starch, one ration containing fast fermenting starches may result in acidosis, whereas a ration containing a more slowly degradable starch may not. A high extent of starch availability is desired but a combination of rapidly and slowly available starches can help with acidosis control and improve milk fat production.
For efficient growth of the rumen microbes to occur, the availability of carbohydrate and protein to the microbes must be synchronized. Sugars are digested and used by the rumen microbes very rapidly and may help to provide the energy needed at the right time in relation to the fermentation of other carbohydrates in the ration. Studies show that adding sugars to the diets almost always reduces the amount of ammonia in the rumen. This suggests that sugars help the rumen microbes capture and use more of the nitrogen in the diet, especially nitrogen coming from rapidly digestible sources such as the soluble protein in ensiled forages. Typical rations without supplemental sugars contain about 1.5 to 3% sugar but it is recommended that rations contain 5-7% sugar. Fiber digestion, microbial protein synthesis, and energy absorption from the rumen can increase with additional dietary sugars and positively impact dairy cow performance. Added dietary sugar has increased dry matter intake as well as percentage and yield of milk fat.