Dietary stimulation of the endogenous somatotropic axis in weaner and grower-finisher pigs using medium chain triglycerides and cysteamine hydrochloride.

Three experiments were conducted to examine the overall hypothesis that addition of medium chain triglycerides (MCT) and cysteamine hydrochloride (CSH) into the diets of young and growing pigs would stimulate the endogenous somatotropic axis to improve growth and performance. In Experiment 1, weaner pigs were given either a 5 d dietary supplement of 5 % MCT (n = 8) or a control diet (n = 8). MCT increased the plasma concentration of growth hormone (GH; P < 0.05) and the GH secretagogue, ghrelin (P < 0.05). Additionally, the MCT treatment reduced scouring (P < 0.05), maintained villous height in the small intestine (P < 0.05) and stabilised daily weight gain (P < 0.05), compared to the controls. Experiment 2 compared the effects of 4 levels (0, 1, 3 and 6 % v/v) of MCT supplementation in grower-finisher male pigs, of approximately 35 kg live weight (n = 15 per treatment). Blood samples taken after 7 wk of treatment showed that the MCT supplementation increased circulating ghrelin (P < 0.001), GH (P < 0.01) and insulin (P < 0.05) concentrations in a dose-dependent manner. Daily weight gain, feed intake and feed conversion ratio were not affected by the MCT diets. In Experiment 3, 64 female pigs of approximately 60 kg live weight were allocated to one of three dietary treatments: control (n = 20); 6 % MCT (n = 21); and 70 mg/kg CSH (n = 21). After 3 wk of supplementation, the MCT treated pigs had a higher plasma concentration of ghrelin compared to the control and CSH pigs (P < 0.05). Plasma concentrations of GH and weight were not affected by any of the dietary treatments. Evidence is provided in Experiment 1 to support the use of dietary MCT supplements, perhaps acting via stimulation of somatotropic endocrine pathways, to minimise weaning-associated disorders such as slowing of growth and diarrhoea. In Experiments 2 and 3, although there was no effect on weight gain or feed conversion ratio in either experiment, MCT and CSH increased endocrine components of the somatotropic axis.