Growth and development
Boletín Médico del Hospital Infantil de México
Crecimiento y desarrollo
Early postnatal morbidity and mortality of mammalian neonates represent significant challenges to the agricultural and medical sciences. While many stressors come to bear on the neonate soon after birth, it is convincingly clear that gastrointestinal maladies are among the most prominent. This is not surprising given the relatively quiescent state of the intestine in utero and the rapid ontogeny required following birth. Furthermore, the intestinal mucosa, initially sterile, must be protected
... must be protected from viral and bacterial pathogens that are ubiquitous in the postnatal environment. Because the intestine is a "supply organ", the overall systemic health and vitality of the neonate hinges on its development and function. Therefore, understanding the role of various nutritional, hormonal and pharmacologic agents in ushering the growth, development and function of the intestine is seminal. Our studies have specifically examined rotaviral gastroenteritis, a leading cause of neonatal intestinal injury and diarrhea, with the ultimate goal of improving the rate and extent of recovery. Using rotaviral infection within a neonatal piglet model, we have shown that the level of enteral nutrition delivered postinfection can starkly affect the clinical, biochemical and immunological response during recovery. While a brief period of "gut rest" may be beneficial, if prolonged, it can significantly delay recovery. We also have documented a modest mitogenic response of damaged intestine to supplemental epidermal growth factor, and have shown attenuation of rotaviral damage to the intestine of pigs fed milk replacer formulated with plasma proteins compared with soy-protein-based formulas. However, we have been unable to measure beneficial effects of enteral glutamine or alanyl-glutamine. Our collective findings suggest several positive (but modest) effects of various enteral-treatment regimens/agents on intestinal recovery. Further research is needed to understand better the complex interplay between nutrients, growth factors, immunological, and bacterial determinants which impact intestinal health and ultimately neonatal vitality. Nutrient requirements of preruminant dairy calves are not well described. Current practices, often favoring a least cost approach, may compromise growth performance and health. The present study evaluated and compared immune function in neonatal calves on a higher nutritional plane with that of calves fed a diet meeting current industry standards. Colostrum-fed, Holstein bull calves (n=19) were assigned randomly at ∼4 d of age to one of two treatment groups. Treatment (TRT) 1 calves were fed a 20% crude protein (CP): 20% fat milk replacer (MP) at a rate of 1.4% BW of dry matter (DM)/d for 8 wk. Calves assigned to TRT 2 were fed a 30% CP: 20% fat MR at a rate of 2.4% BW of DM/d. The functional capacity of mononuclear (MNL) populations from peripheral blood collected at 0, 4, 6, and 8 wk during the study period was estimated using a battery of in vitro tests. Nitric oxide (NO) and interferon-γ production by mitogen-stimulated MNL were influenced (P≤.05) by nutritional plane, whereas mitogen-induced DNA-synthesis and secretion of tumor necrosis factor-α and polyclonal immunoglobulin were unaffected (P≥.05). The total number of peripheral blood leukocytes was also unaffected by nutritional plane. These results suggest that increased dietary energy and protein can modulate specific aspects of the neonatal immune system. Additional research is necessary to determine if these changes reflect increased immunocompetency (i.e. infectious disease resistance). Leukocytes from all calves demonstrated age-related changes in their capacity to produce IgM, both cytokines, and NO and to synthesize DNA, possibly reflecting the maturation of the calf's immune system. . gest that LPS challenge may affect peripheral metabolism of thyroid hormones outside the liver and(or) by other types of deiodinases. Accompanying the acute phase response (APR) to infection, blood shunting and regional tissue hypoxia contribute to free radical accumulation and disruption of tissue function. Tissue expression and circulating plasma concentrations of adrenomedullin (AM), a potent vasodilating peptide, increase with hypoxia and after in vivo challenge with bacterial toxins like LPS. The objective of the present study was to correlate the relative magnitude of AM response to LPS challenge with the capacity for steers to maintain normal plasma concentrations of IGF-I. Twentytwo Angus Hereford steers (mean BW 318 kg) fed to gain 1.25 kg/d were challenged with a single bolus of LPS (E. coli 055B5, iv; 0.2 µg/kg BW). Blood samples for plasma were collected at 0, 1, 2, 3, 6, 8, 12, 24, and 48 h relative to LPS; liver and kidney biopsy samples were collected at 8 h into Bouin's fixative for immuno-histochemical determination of nitrated proteins (a measure of aberrant nitric oxide-superoxide anion reactions), AM, and inducible nitric oxide synthase. Plasma IGF-I and AM were measured by RIA; plasma NO2 and NO3 (NOx) were measured by the Griess reaction. Animals were grouped by AM response, group 1 (G1) having responses < 100 pg/mL over baseline (22 pg/mL) and group 2 (G2) having AM responses > 150 pg/mL over baseline (P < .002). Decreases in plasma IGF-I in G1 were 11 and 27% lower at 8 and 48 h, respectively, after LPS than those in G2 (P < .02). Increases in plasma NOx (area under the curve) were 63% greater in G1 than G2 (P < .05). Cells with nitrated proteins were more frequent in G1 steers than G2 steers. IGF-I concentrations at 8 and 48 h were positively (P < .05) and NOx responses negatively (P < .05) correlated with AM response. In conclusion, steers with greater AM responses experienced fewer effects of the APR as reflected in lesser decline in circulating IGF-I concentrations.