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This Article Full Text (PDF) All Versions of this Article: jas.2008-1108v1 87/2/748    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Brown, K. R. Articles by Matthews, J. C. Search for Related Content PubMed PubMed Citation Articles by Brown, K. R. Articles by Matthews, J. C.

Growing steers grazing high versus low endophyte (Neotyphodium coenophialum)-infected tall fescue have reduced serum enzymes, increased hepatic glucogenic enzymes, and reduced liver and carcass mass

K. R. Brown^*, G. A. Anderson^*, K. Son^*, G. Rentfrow^*, L. P. Bush, J. L. Klotz, J. R. Strickland, J. A. Boling^* and J. C. Matthews^*

^* Department of Animal and Food Sciences, University of Kentucky, Lexington, 40546-0215 , Department of Plant and Soil Sciences, University of Kentucky, Lexington, 40546-0312 Forage-Animal Production Research Unit, USDA-ARS, Lexington, 40546-0091

jmatthew{at}uky.edu

Abstract

It is well established that grazing Neotyphodium coenophialum-infected forages results in reduced weight gain and serum prolactin levels of cattle. The objective of this study was to determine the potential effects of toxic endophyte-infected tall fescue consumption on blood metabolites, carcass characteristics, and content of proteins critical for AA metabolism in the liver, kidney, and LM tissue of growing steers. Steers grazed either a low toxic endophyte (LE; 0.023 µg/g ergot alkaloids) tall fescue-mixed grass pasture (n = 9; BW = 266 ± 10.9 kg; 5.7 ha) or a high toxic endophyte (HE; 0.746 µg/g ergot alkaloids) tall fescue pasture (n = 10; BW = 267 ± 14.5 kg; 5.7 ha) from June 14 through at least September 11 ( 89 d). No difference was observed for BW (P < 0.10) for the overall 85 d growth period. Also, no differences were observed for ribeye area/100 kg HCW (P > 0.91), backfat (P > 0.95), or backfat/100 kg HCW (P > 0.67). However, ADG (P < 0.01), final live BW (P < 0.05), HCW (P < 0.01), dressing percentage (P < 0.01), ribeye area (P < 0.01), whole liver wet weight (P < 0.01), and whole liver wet weight/100 kg of end live weight (P < 0.01) were greater for LE steers than HE steers. After 85 d of grazing, serum levels of alkaline phosphatase (P < 0.05), alanine aminotransferase (P < 0.01), aspartate aminotransferase (P < 0.03), cholesterol (P < 0.01), lactate dehydrogenase (P < 0.01), and prolactin (P < 0.01) were lower for HE than LE steers. At slaughter, hepatic content of cytosolic phosphoenolpyruvate carboxykinase (P < 0.01) was higher in HE steers than LE steers. Hepatic content of aspartate aminotransferase (P < 0.01) also was higher, whereas renal and LM content were not (P 0.42). No differences (P 0.15) were observed for hepatic, renal, and LM content of alanine aminotransferase, glutamate dehydrogenase, glutamine synthetase and three glutamate transport proteins. These data indicate that the HE steers displayed classic endophyte toxicity symptoms for growth and blood parameters, classic symptoms that were concomitant with novelly-identified altered glucogenic capacity of the liver and decreases in carcass characteristics.

Key Words: Alkaloid • Aspartate aminotransferase • Bovine • Liver • Phosphoenolpyruvate carboxykinase