| Abstract: | Introduction Newborn development is characterized by high protein synthesis and nitrogen (N) turnover rates in many tissues, especially in the gastrointestinal (GI) tract (G oldspink and K elly 1984; Y oung et al. 1988; S immen et al. 1990; X u 1996). Colostrum provides particularly large amounts of nutrients (especially proteins) and immunoglobulins as well as non-nutrient growth-promoting factors; it therefore plays a major role in the development of the neonatal gut, especially protein synthesis, and other organs, as shown in several species including cattle (B erseth et al. 1983; P atureau M irand et al. 1990; C ampana and B aumrucker 1995; O dle et al. 1996; X u 1996; B urrin et al. 1997). Rates of body protein synthesis and N turnover were greater during enteral than during parenteral feeding, indicating considerable involvement of the GI tract in protein metabolism (D uffy and P encharz 1986). Protein components in colostrum provided about 35% of amino acids (AA) in newborn lambs, suggesting that amounts of ingested protein with colostrum greatly influence the AA status of the neonate (Y von et al. 1993). Glutamine and glutamate are the most abundant AA in bovine milk protein (M eijer et al. 1993) and glutamine is of special interest for postnatal gut development (S ouba 1991; K imura 1996; H eird 1998). The glutamine:glutamate ratio was markedly changed in neonatal calves (D emign & eacute ; and R& eacute ; m & eacute ; sy 1979) after colostrum intake. Recently, we have demonstrated that gut growth and absorptive capacity of the intestine, as well as metabolic and endocrine changes in newborn calves, are greatly dependent on amounts of ingested colostrum (H ammon and B lum 1997, 1998; B& uuml ; hler et al. 1998). Based on that AA absorption, metabolism and status may be influenced by amounts of fed colostrum. Therefore in this study we have tested the hypothesis that feeding colostrum for different durations, or feeding only milk replacer, affects plasma protein and free AA concentrations during the first week of life in calves. |
