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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Cell Wall Biology and Utilization Research » Research » Publications at this Location » Publication #402361

Research Project: Developing Strategies to Improve Dairy Cow Performance and Nutrient Use Efficiency with Nutrition, Genetics, and Microbiology

Location: Cell Wall Biology and Utilization Research

Title: Effects of level and oscillation of dietary crude protein on ruminal conditions

item ERICKSON, MARYGRACE - University Of Wisconsin
item Zanton, Geoffrey
item WATTIAUX, MICHEL - University Of Wisconsin

Submitted to: American Dairy Science Association Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/13/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Our trial examined dietary crude protein (CP) feeding pattern (O = oscillating, S = static) at two levels of CP (LP, 13.9%; HP, 15.4%) to test for a hypothesized interaction on ruminal conditions. Using a 2x2 factorial arrangement, we assigned 8 mid- to late-lactation, cannulated Holsteins (mean = 142, SD = 23 days in milk) to treatment sequences in a Latin Rectangle with four 28-d periods. Treatment O alternated 2 diets (O-LP 12.2-15.5%, O-HP 13.9-16.9% CP) every 48 hr so average dietary CP equaled that of the corresponding S treatments (S-LP, S-HP). On d 25-28 of each period, we collected fluid from the ventral rumen at -2, 0, 2, 4, and 11 hr relative to 1x daily feeding. We measured pH with a portable meter and used colorimetric methods to quantify NH3-N and total free amino acids (TAA) on a flow injection analyzer. Data were analyzed using a linear mixed model with fixed effects for period, CP level, CP feeding pattern, day, hour, and all treatment by time interactions, and a nested random effects structure. During d 16-27 of the fourth period, we monitored ruminal pH and redox potential (Eh) at 1-min intervals with indwelling loggers and tested for differences in the daily minimum, mean, maximum, and range associated with diet changes in the oscillating condition (n = 4 cows). Ruminal pH (6.37 ± 0.03) and concentration of TAA (2.64 ± 0.11 mM) were unaffected by treatments but NH3-N was greater for HP than LP (2.32 vs. 1.84 ± 0.12 mg/dL, P<0.001). For all variables, non-significant feeding pattern by day interactions indicated that rumen conditions were unaffected by dietary changes in the O treatment (P = 0.326 to 0.726). This finding was consistent with indwelling logger measurements, which showed similar daily pH and redox potential across higher- and lower-CP phases within the oscillating CP feeding pattern (P = 0.166 to 0.978). In conclusion, large variations in the pattern of N entry in the rumen had little effect on within-day variation of ruminal NH3-N and TAA concentration.