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Journal of Animal Science Abstract - Forage Based Livestock Systems

Rumen-protected arginine alters blood flow parameters and luteinizing hormone concentration in cyclic beef cows consuming toxic endophyte-infected tall fescue seed

 

This article in JAS

  1. Vol. 95 No. 4, p. 1537-1544
     
    Received: Dec 13, 2016
    Accepted: Feb 22, 2017
    Published: April 13, 2017


    1 Corresponding author(s): jmulli@utk.edu
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doi:10.2527/jas2016.1309
  1. M. A. Green*,
  2. B. K. Whitlock,
  3. J. L. Edwards*,
  4. E. J. Scholljegerdes and
  5. J. T. Mulliniks 1*
  1. * Department of Animal Science, University of Tennessee, Knoxville 37996
     Department of Large Animal Clinical Sciences, University of Tennessee, Knoxville 37996; and
     Department of Animal and Range Sciences, New Mexico State University, Las Cruces 88003

Abstract

The objective of this study was to determine the effect of rumen-protected arginine on median caudal artery blood flow and LH dynamics in cows fed toxic endophyte-infected tall fescue seed. Four ruminally cannulated nonlactating beef cows (539 ± 30 kg) were used in a 2 × 2 factorial arrangement of treatments utilizing a 4 × 4 Latin square design with 4 periods of 31 d each. Each cow was assigned to individual pens and fed orchardgrass hay (10.3% CP and 85% NDF; OM basis) during a 10-d adaptation period, followed by a 21-d collection period in which each cow was assigned 1 of 4 treatments: 1) rumen-protected Arg (180 mg/kg of BW) and 1.0 kg/d of toxic endophyte-infected fescue seed (AE+), 2) rumen-protected Arg (180 mg/kg of BW) and 1.0 kg/d of endophyte-free fescue seed (AE−), 3) 1.0 kg/d of toxic endophyte-infected fescue seed (E+) alone, or 4) 1.0 kg/d of endophyte-free fescue seed (E−) alone. In each period, Doppler ultrasound measurements for blood flow parameters were quantified on d 1, 5, 10, 15, and 20. On d 20 of each period, blood samples were collected every 10 min for 6 h and then once every hour for 12 h for LH response following exogenous GnRH. There was an Arg × fescue seed type interaction (P = 0.05) for median caudal artery blood flow due to an increase in blood flow in cows fed rumen-protected Arg with endophyte-free fescue seed. In addition, mean blood flow velocity in the artery was greater (P = 0.01) with the inclusion of rumen-protected Arg in the diet. Median caudal artery area (P = 0.03) and diameter (P = 0.01) were decreased in cows consuming E+ compared to those consuming E− with no effect (P ≥ 0.38) by Arg inclusion. Circulating nitric oxide (NO) concentrations tended to be influenced (P = 0.09) by the interaction of Arg × fescue seed type with E+ alone decreasing NO concentrations. Circulating NO concentrations were unaffected by rumen-protected Arg (P = 0.48). Mean serum LH concentration exhibited (P = 0.02) an Arg × fescue seed type interaction. Cows consuming E+ had decreased (P < 0.05) LH concentrations compared to all other treatments. However, cows consuming AE+ had (P ≥ 0.67) LH concentrations similar to those of cows consuming AE− and E−. Thus, supplementing rumen-protected Arg to cows consuming toxic endophyte-infected fescue seed has the potential to increase reproductive performance and peripheral blood flow.

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