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Changes in glutamine metabolism indicate a mild catabolic state in the transition mare¹

H. C. Manso Filho^*,, K. H. McKeever^*, M. E. Gordon^*, H. E. C. Costa^,, W. S. Lagakos and M. Watford^,2

^* Department of Animal Sciences, Rutgers University, New Brunswick, NJ 08901; and Department of Animal Sciences, Federal Rural University of Pernambuco, Recife, Brazil; and Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ 08901

² Corresponding author: Watford{at}aesop.rutgers.edu

Glutamine is the most abundant free -AA in the mammalian body, and large amounts of glutamine are extracted by both the fetus during pregnancy and the mammary gland during lactation. The work presented here addressed the hypothesis that there would be major changes in glutamine metabolism in the mare during the transition period, the time between late gestation, parturition, and early lactation. Eight foals were born to Standardbred mares provided with energy and protein at 10% above NRC recommendations, and foals remained with mares for 6 mo. During lactation, lean body mass decreased by 1.5% (P < 0.05), whereas fat mass was unchanged throughout gestation and lactation. There was a sharp increase in the concentration of most plasma metabolites and hormones after birth, which was due in part to hemoconcentration because of fluid shifts at parturition. Plasma glutamine concentration, however, was maintained at greater concentrations for up to 2 wk postpartum but then began to decrease, reaching a nadir at approximately 6 wk of lactation. Skeletal muscle glutamine content did not change, but glutamine synthetase expression was decreased at the end of lactation (P < 0.05). Free glutamine was highly abundant in milk early in lactation, but the concentration decreased by more than 50% after 3 mo of lactation and paralleled the decrease in plasma glutamine concentration. Thus, lactation represents a mild catabolic state for the mare in which decreased glutamine concentrations may compromise the availability of glutamine to other tissues such as the intestines and the immune system.

Key Words: body composition • equine • glutamine • glutamine synthetase • lactation • pregnancy

This article has been cited by other articles:

				H. C. Manso Filho, K. H. McKeever, M. E. Gordon, H. E. Manso, W. S. Lagakos, G. Wu, and M. Watford Developmental changes in the concentrations of glutamine and other amino acids in plasma and skeletal muscle of the Standardbred foal J Anim Sci, August 1, 2009; 87(8): 2528 - 2535. [Abstract] [Full Text] [PDF]