Nutritional modulation of the somatotropin/insulin-like growth factor system: response to feed deprivation in lactating XXXX .

@entity4208 @entity21904 @entity12304 @entity37644 @entity291 @entity413
Mid-lactation Holstein @entity291 (n = 4) were used to evaluate the effects of complete feed deprivation on circulating insulin-like growth factors (IGF) and their binding proteins (IGFBP). Comparisons were made between @entity291 in fed and unfed conditions and included response to a single injection of @entity291 somatotropin (bST). Two days of feed deprivation decreased milk yield 66%. Concentrations of bST nearly doubled during feed deprivation, whereas @entity413 and insulin steadily decreased. Circulating concentrations of @entity4208 decreased nearly 50%, @entity12304 decreased 28% and @entity21904 increased 49% during the 2 d of feed deprivation. In contrast, @entity37644 was not affected. Eighteen to 24 h after the bST challenge, circulating concentrations of @entity4208 rose 100% during the fed period, but there was no response during the unfed period. Blood concentrations of @entity12304 decreased 17% after bST challenge in the fed period but were unchanged in the unfed period. More moderate undernutrition (80% of requirements) did not affect circulating @entity21904 but did alter the response of @entity21904 to bST. A conceptual model was developed that illustrates that nutritional regulation of the ST/IGF system represents a key component signaling the appropriate use of nutrients. Overall, results demonstrate that nutritional modulation of the ST/IGF system plays a key role in animal performance and well-being over a wide range of physiological situations.
