Hormonal response of pregnant gilts fed a high-fiber or a concentrate diet once or twice daily

The effects of fiber intake and feeding frequency on endocrine status were studied. Gilts were fed 2.2 kg d-1 of a concentrate diet (n = 6; 5.3% crude fiber) or 3.1 kg d(-1) of a high-fiber diet (n = 7; 18.2% crude fiber) as of day 23 of gestation. For a 1-mo, period, starting on day 60 of gestation, three or four animals within each dietary treatment received one daily ration at 0800 h while the others received two meals at 0800 and 1430 h. Feeding frequency was then reversed for the following 1-mo period. Jugular catheters were inserted on day 23 of each I -mo period and serial blood samples were obtained from 0730 to 1630 h on day 25, to measure cortisol, insulin, glucose and free fatty acids (FFA). The mean of three samples obtained before the morning or afternoon mealtime was used to establish a preprandial baseline and samples thereafter were used to measure area under the curve (AUC) and maximal values. Fiber intake had no effect on any baseline values (P > 0.1), but decreased overall insulin AUC (P < 0.05) and glucose maximal values (P < 0.05) and increased morning FFA AUC (P < 0.05). Compared to one daily meal, twice daily feeding increased afternoon baseline cortisol (P < 0.05) and decreased morning cortisol AUC and baseline FFA (P < 0.001). It also increased afternoon insulin maximal values and AUC (P < 0.05) as well as morning and afternoon maximal glucose (P < 0.05) and decreased morning maximal FFA (P < 0.05). Insulin was the only variable affected by the fiber intake x number of meals interaction with twice daily feeding lowering morning maximal (P < 0.05) and AUC (P < 0.001) values in concentrate-fed gilts while not altering those values in gilts fed a high-fiber diet. Addition of fiber to the diet of pregnant gilts altered their hormonal response to meals, while once daily feeding created a post-absorptive state in the morning and increased cortisol concentrations postprandially.