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Effect of cashew nutshell extract on nutrient digestibility and rumen pH when simulating close-up or fresh-cow conditions under in vitro conditions.

C. Compton

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06-23-2020

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Abstract:

T148
Effect of cashew nutshell extract on nutrient digestibility and rumen pH when simulating close-up or fresh-cow conditions under in vitro conditions.
C. Compton*1, C. Hikita2, T. Watanabe2, T. C. Jenkins1, G. J. Lascano1, M. J. Aguerre1. 1Clemson University Clemson, SC, 2Agri-Bio Business Department, Idemitsu Koscan Co Tokyo, Japan.

The objective of this study was to determine the effects of cashew nutshell extract (CNSE, 59% anacardic acid and 18% cardol) on dry matter, neutral detergent fiber, total nitrogen digestibility (IVTDMD, IVNDFD, and TNd, respectively), and rumen fluid pH under in vitro conditions. The study was conducted as a randomized complete block design with 4 replicates per treatment incubated for 24-h during 4 incubation runs. Each incubation was inoculated with rumen contents collected from 3 ruminally fistulated cows fed either a close-up (CU; 15.1% CP, 38.1% NDF, and 20.8% starch) or a fresh-cow diet (FC; 16.4% CP, 31.8% NDF, and 28.0% starch) with substrate representing the respective diet. Treatments consisted of 4 levels of granulated CNSE formulated to contain 50% CNSE and added to the cultures in stepwise increments equivalent to 0, 2.5, 5, and 10 g of CNSE. Data were analyzed with the mixed procedure of SAS and pre-planned orthogonal contrasts to test for linear and quadratic effects. Overall, dietary treatments incubated to mimic FC condition had a higher IVTDMD (75.7 vs. 67.9% DM), IVNDFD (23.6 vs. 15.8% NDF) and TN (41.1 vs. 53.0% DM) compared with CU. Rumen pH after 24 h of incubation was similar for both dietary conditions (6.79 vs. 6.85, respectively). When mimicking CU conditions, increasing the level of CNSE tended (P = 0.10) to increase IVTDMD (67.8 to 69.7% of DM), but incremental levels of CNSE tended to decrease IVTDMD from 76.6 to 74.9% of DM, when mimicking FC conditions. A similar, but significant (P < 0.03), pattern was observed for IVNDFD. Adding CNSE to the diet had no impact on TNd (% DM) but we observed a quadratic response on pH when mimicking both CU and FC conditions. The highest pH (6.85) was observed at 2.5 g/cow/d level for CU conditions and the highest pH (6.99) for FC was observed at 5 g/cow/d level. Under the conditions of this study, adding CNSE to the diet had positive effects on DM and NDF digestibility in CU diets and pH of FC, but negatively impacts digestibility in FC. Further research is warranted to identify the optimal dosage of CNSE.

Keywords: digestibility, dairy, fermentation.