At the beginning of the experiment (28 days), the weight of each group of pigs was measured, and the initial weight of each pig was recorded. Subsequently, the pigs were weighed at 42 and 56 days of age, with a fasting period of 12 hours before weighing. Daily feed intake was recorded, and the incidence of disease, diarrhea, and death was observed and recorded. The average weight, average daily weight gain, average daily feed intake, feed conversion rate (feed consumption/weight gain), and diarrhea rate (diarrhea rate=diarrhea head days/total experiment head days. Each pig having diarrhea once or more per day counts as one diarrheal head day; each pig participating in the experiment for one day counts as one experimental day) were calculated.
Serum biochemical and hormone indexes related to immunity were determined in the mid (42-day-old) and final (56-day-old) stages of the experiment, and 3 pigs with similar weights were selected from each group (12 in total) for peripheral blood lymphocyte proliferation transformation test. In addition, 9 pigs with average weight were taken from each group (3 pigs per replicate group, 36 in total), and blood samples of about 10 ml were collected from the anterior vena cava to prepare serum, and the following indexes were measured in the serum:
(1) Total protein, albumin, and globulin content (biuret method, dye-binding method)
At 42 days of age, the IL-2 concentration in the blood of Group C was the highest, and at 56 days of age, the IL-2 concentration in the blood of Group C was significantly higher than that of the control group. The IL-6 concentration in the blood was the highest in Group D at both 42 and 56 days of age, but the difference was not significant compared to the other groups.
At 42 days of age, the T lymphocyte proliferation transformation rate induced by ConA was the highest in Group B at both 24 and 48 hours, and the lowest in Group D. The B lymphocyte proliferation transformation rate induced by LPS was consistent with the T lymphocyte proliferation transformation rate induced by ConA. At 56 days of age, the T lymphocyte proliferation transformation rate induced by ConA was the highest in Group C and D at both 24 and 48 hours, and the B lymphocyte proliferation transformation rate induced by LPS was consistent with the T lymphocyte proliferation transformation rate induced by ConA.
Replacing 3% plasma protein in the piglet diet with 3.5% or 5% solpro can significantly increase the IL-2, IL-6, and globulin concentrations in the blood of piglets at 56 days of age, and also significantly improve the T lymphocyte and B lymphocyte proliferation transformation rates in the blood of piglets at 56 days of age, indicating that replacing 3% plasma protein in the diet with 3.5% or 5% solpro can significantly improve piglet immunity.