Changes of amino acid concentrations in Polish Merino sheep between 21 and 150 days of life

The aim of this study was to evaluate plasma amino acid profiles and their interrelationships in male Polish Merino sheep at two different stages of their systemic development - at the neonatal monogastric stage and as a fully grown ruminant. Male lambs (n = 12, singles) were kept indoors in pens under standard rearing conditions and weaned at the age of 10 weeks of life. Blood samples were collected on day 21 and 150 of life. Free amino acids were determined in plasma using ion-exchange chromatography. There was a significant reduction in plasma amino acid concentrations between neonatal and functioning ruminants for threonine, serine, glutamate, proline, citrulline, tyrosine, tryptophan, lysine, histidine and arginine. Significant increases in the plasma concentrations of alpha-amino-butyrate and isoleucine were observed in 150 day old lambs. Except for glutamine in 21 day old sheep which was significantly negatively correlated with serine, glutamate, proline and tyrosine concentrations in plasma, the obtained results in younger and older groups of lambs showed 47 and 22 significant positive correlations between the evaluated amino acids. This study shows that decreases in plasma amino acid concentrations in 150 day old sheep with physiologically developed forestomachs are dominant in comparison to 21 day-old animals receiving maternal milk as a basic diet. Our results address the possibility of utilising improved amino acid supply for growing lambs with developed forestomachs.