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Effects of rumen undegradable protein and amino acid sources and replacing forage or non-forage fiber in postpartum cows on production.

A. W. Tebbe

Abstract:

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Effects of rumen undegradable protein and amino acid sources and replacing forage or non-forage fiber in postpartum cows on production.
A. W. Tebbe*, W. P. Weiss. Ohio Agricultural Research and Development Center, The Ohio State University Wooster, OH.

Greater metabolizable protein (MP) supply from rumen undegradable protein (RUP) improves production in fresh cows. However, using one RUP source instead of blends may worsen AA imbalances as RUP (% of MP) increases. Replacing forage instead of non-forage fiber with RUP may also increase MP supply by increasing intake. Our objective was to determine whether high MP diets using one or a blend of RUP and AA sources and whether substituting forage NDF (fNDF) rather than non-forage NDF with RUP improves production in fresh cows. In a randomized block design, 40 primigravid and 40 multigravid Holsteins were blocked by calving date and fed a common diet (11.5% CP). After calving to 25 DIM, cows were fed 1 of 4 diets: 1) deficient MP (DMP, 17% CP, 24% fNDF), 2) adequate MP met with high inclusion of treated soybean meal (AMP, 20% CP, 24% fNDF), 3) adequate MP met with a blend of RUP and rumen protected AA (Blend, 20% CP, 24% fNDF), or 4) Blend but replacing fNDF rather than non-forage NDF with RUP (Blend-fNDF, 20% CP, 19% fNDF). Cows were fed a common diet (17% CP) from 26 to 92 DIM. Data were averaged by week and analyzed with models with fixed effects of diet, week (repeated), parity, their interactions and random effects of block nested within parity. During treatment, Blend vs. AMP tended to increase DMI (17.4 vs. 16.4 kg/d; P = 0.098) but not for Blend-fNDF (17.2 kg/d; P = 0.79). Blend and AMP had similar DMI from 26 to 50 DIM (19.2 vs. 20.1 kg/d; P = 0.16). For milk, fat and protein, AMP and Blend increased yields 2.1, 0.05 and 0.14 kg/d, respectively, vs. DMP (P ≤ 0.06) but AA profile and fNDF interacted with parity. Blend vs. AMP had similar yields during treatment, but energy-corrected milk and fat yields increased (P < 0.01) 5.6 and 0.33 kg/d from 26 — 92 DIM in multiparous cows only. Blend-fNDF vs. Blend decreased (P ≤ 0.01) milk and milk fat yields 2.8 and 0.32 kg/d in multiparous cows only. Lower milk fat yield (P = 0.01) carried over until 92 DIM (1.85 vs 1.65 kg/d). Blends of RUP and AA are better for fresh cows fed high MP, especially multiparous cows. Multiparous cows may also require more fNDF than primiparous cows.

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Biography: Alex Tebbe�is a graduate research associate and is in The Ohio State University Ph.D. Program in Nutrition, and his major advisor is Dr. Bill Weiss. Previously, Alex earned his B.S. at the University of Illinois Urbana-Champaign and M.S. at The Ohio State University both in Animal Sciences. The main focus of his M.S. thesis project was on magnesium metabolism in dairy cows also under Dr. Weiss. The major research focus of his Ph.D.�Dissertation involves investigating factors affecting protein and amino acid utilization and storage in dairy cattle. His anticipated graduation date is summer of 2020.