Levels of Immunoreactive Insulin, Neurotensin, and Bombesin in Porcine Colostrum and Milk

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Abstract
High concentrations of insulin (411 ± 214 μU/ml), neurotensin-like (265 ± 72 pg/ml), and bombesin-like immunoreactivities (1995 ± 288 pg/ml) were detected in porcine colostrum using radioimmunoassay, as compared to the levels found in sow blood serum at farrowing (5 μU/ml, <12 pg/ml, and 17 pg/ml, respectively). After 72 h of lactation, the levels of insulin and neurotensin-like immunoreactivities had decreased to 28 ± 17 μU/ml and 89 ± 23 pg/ml, respectively, while the bombesin-like activity remained constant. Characterization with reversed-phase high performance liquid chromatography showed that the insulin immunoreactivity eluted at the same position as the insulin standard, while the elution patterns of the neurotensin-like and bombesin-like immunoreactivities (eluted in three separate peaks) did not correspond to that of their respective standards. The biological function of the peptide hormones in colostrum/milk may be as triggers of the developmental changes taking place in the nursing neonate, especially in the gastrointestinal tract.