It was evaluated the effects of using milk protein or supplemental zinc in the diet on performance, relative weights of small intestine and liver, intestine morphology and IGF-I (insulin-like growth factor) serum concentrations, growth hormone and zinc in piglets. The experiment lasted 14 days and it was carried out using 60 piglets weaned at 21 days of age (5.43 ± 0.46 kg) in a complete random design, in a 2 x 2 factorial composed of two levels of milk protein (with and without, 4%) and two levels of zinc (with or without, 2,250 ppm) in the diet. In the 1-7 day experiment period, zinc provided better feed conversion and the in the 1-14 day experiment period, it promoted higher body weight at 14 days and higher weight gain. Supply of milk protein in the diet worsened feed conversion in the two phases (from 1 to 7 days and from 1 to 14 days of the experiment) and it resulted in a lower crypts depth in the jejunum and a higher villous height on day 14 of the experiment. On the 7th day of the experiment, there was an interaction among milk protein and supplemental zinc for villous height:crypts depth relationship, which was also higher for animals fed milk protein. The addition of zinc in the diet reduced insuline-like growth factor concentration and the average weight of the liver on day 14 of the experiment while the use of milk protein increased IGF-I concentrations. The inclusion of milk protein improves feed conversion, affects intestine morphology and increases IGF-I concentration, but supplementation of zinc is not efficient to affect levels of growth hormone in the organism.
dairy product; IGF-I; intestine morphology; organs; villi
