Effects of a commercial fermentation byproduct or urea on milk production, rumen metabolism, and omasal flow of nutrients in lactating dairy cattle

J Dairy Sci. 2019 Apr;102(4):3023-3035. doi: 10.3168/jds.2018-15447. Epub 2019 Feb 22.


The objective of this study was to evaluate the effects of a fermentation byproduct on rumen fermentation and microbial yield in high producing lactating dairy cattle. Eight ruminally cannulated multiparous Holstein cows averaging (mean ± standard deviation) 60 ± 10 d in milk and 637 ± 38 kg of body weight were assigned to 1 of 2 treatment sequences in a switchback design. Treatment diets contained (dry matter basis) 44% corn silage, 13% alfalfa silage, 12% ground corn, and 31% premix containing either a control mix of urea and wheat middlings (CON) or a commercial fermentation byproduct meal (Fermenten, Arm and Hammer Animal Nutrition, Princeton, NJ) at 3% diet inclusion rate (EXP). Diets were formulated to be isonitrogenous and isocaloric, with similar levels of neutral detergent fiber and starch. The trial consisted of three 28-d experimental periods, where each period consisted of 21 d of diet adaptation and 7 d of data and sample collection. Omasal nutrient flows were determined using a triple-marker technique and double-labeled 15N15N-urea. The EXP diet provided 18 g/d more nonammonia N versus the CON diet, representing 3.0% of total N intake. Energy-corrected milk yield (41.7 and 43.1 kg/d for CON and EXP, respectively), milk fat, and protein yield and content did not differ between treatments. Total dry matter intake was similar between treatments (25.5 and 26.4 kg/d for CON and EXP, respectively). Ammonia N concentration and pool size in the rumen was greater in cows fed the EXP diet. No differences were observed in rumen or total-tract dry matter, organic matter, or neutral detergent fiber digestibility. Ruminal degradation of feed N was 15% lower in cows fed EXP diets, resulting in differences in omasal N flows. Results demonstrated the fermentation byproduct meal had a sparing effect on degradable feed protein, but did not increase microbial N flow from the rumen.

Keywords: Cornell Net Carbohydrate and Protein System; Fermenten; microbial protein synthesis; omasal sampling; soluble protein.

MeSH terms

  • Ammonia / metabolism
  • Animal Feed
  • Animals
  • Body Weight
  • Cattle
  • Diet / veterinary*
  • Dietary Fiber / metabolism
  • Female
  • Fermentation
  • Lactation*
  • Medicago sativa
  • Milk*
  • Nutrients
  • Omasum / metabolism*
  • Rumen / metabolism*
  • Rumination, Digestive*
  • Silage
  • Starch / metabolism
  • Urea / pharmacology*
  • Zea mays


  • Dietary Fiber
  • Ammonia
  • Urea
  • Starch