Amino Acids

, Volume 43, Issue 5, pp 2165–2177

Effects of rumen-protected methionine on plasma amino acid concentrations during a period of weight loss for late gestating beef heifers

Authors

    • Fort Keogh Livestock and Range Research LaboratoryUnited States Department of Agriculture, Agricultural Research Service
  • Valerie L. Ujazdowski
    • School of Veterinary MedicineUniversity of Wisconsin
  • Mark K. Petersen
    • Fort Keogh Livestock and Range Research LaboratoryUnited States Department of Agriculture, Agricultural Research Service
Original Article

DOI: 10.1007/s00726-012-1301-3

Cite this article as:
Waterman, R.C., Ujazdowski, V.L. & Petersen, M.K. Amino Acids (2012) 43: 2165. doi:10.1007/s00726-012-1301-3
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Abstract

This study determined changes in plasma amino acid concentration in late-gestating (beginning 58 ± 1.02 days prior to calving), primiparous, winter-grazing range heifers receiving wheat middling-based supplement without (CON) or with rumen-protected methionine (MET) to provide 15 g dl-MET each day. Plasma was collected on days −2 and 0 (start of MET supplementation just prior to individually receiving supplement at 0700 hours). Plasma was sampled again on days 40, 42 and 44 prior to supplementation at 0700 and 1100 hours (4 h after receiving daily supplement). Data were analyzed with cow as the experimental unit. Continuous variables were analyzed by the main effects of treatment, date, or time and their interaction when appropriate. Comparable BW (P = 0.32) and BCS (P = 0.83) over the 44-day metabolism trial were found between both CON- and MET-fed heifers. MET-supplemented heifers had greater (P < 0.01) plasma concentrations of methionine indicating that the rumen-protection technology successfully delivered methionine to the small intestine. Supplementation with rumen-protected dl-MET caused a significant supplement × date interaction for glutamine (P = 0.03), glycine (P = 0.02), methionine (P < 0.01), and serine (P = 0.05). In addition, trends for supplement × date interactions were detected for leucine (P = 0.07), threonine (P = 0.09), valine (P = 0.08), total amino acids (TAA; P = 0.08), non essential amino acids (NEAA; P = 0.08), branched chain amino acids (BCAA; P = 0.08), and glucogenic amino acids (GLUCO; P = 0.08). These results suggest that the BCAA (leucine and valine) were utilized more efficiently with MET supplemented heifers compared to CON supplemented heifers. Plasma AA concentrations for glutamic acid (P < 0.01), histidine (P = 0.01), tyrosine (P < 0.01), and EAA (P < 0.01), all decreased throughout the study. These results further confirm methionine is a limiting amino acid in forage fed late-gestating heifers and further suggests the limitation when grazing dormant range forages as shown by improved utilization of other plasma amino acids when supplemental methionine was provided.

Keywords

Amino acidsPrimiparous heifersRumen-protected methionine

Abbreviations

AA

Amino acids

BCAA

Branch-chain amino acids

BCS

Body condition score

BW

Body weight

CP

Crude protein

DM

Dry matter

dl-MET

dl-Methionine

EAA

Essential amino acids

GLUCO

Glucogenic amino acids

ISNDFD

In situ neutral detergent fiber disappearance

KETO

Ketogenic amino acids

LARRL

Livestock and range research laboratory

M85

Mepron® M85

NDF

Neutral detergent fiber

NEAA

Non essential amino acids

OM

Organic matter

TAA

Total amino acids

Copyright information

© Springer-Verlag (outside the USA) 2012