Soybean Meal or Starea for Microbial Protein Synthesis or Milk Production with Rations Above Thirteen Percent Natural Protein

Open Access
Publisher Website
Google Scholar
Abstract
The hypothesis was tested that microbial protein cannot be synthesized from urea if it is added to rations that contain 13% crude protein. A 6-h in vitro fermentation and rations containing 13-30% crude protein were used. All rations contained brome hay, sorghum grain and soybean meal or Starea. With Starea, microbial protein increased steadily as the crude protein content of the substrates increased from 17 to 30%. Maximum microbial protein was produced when ammonia N of the rumen was 76 mg/100 ml. The sample of soybean meal was not fermented readily in vitro. Adding cooked grain to soybean meal equal to that in Starea improved protein synthesis in rations containing soybean meal. In 2 lactation studies with 50 Holstein cows, a cross-over experimental design was used to test 2 rations that contained 13% crude protein (all natural) or 16.5% crude protein (3.5 percentage points crude protein form Starea). In both trials, milk and milk protein production were higher by cows receiving the ration with high protein. Lactating cows can use urea in the form of Starea in rations that already contain 13% natural protein.