Effect Of Apramycin On Protein Nutrition, Endocrine And Cold Stress Of Piglets

This dissertation consisted of five experiments. It was designed to study apramycin growth-promoting action and effects of apramycin on protein nutrition, intestinal flora, endocrine response, immune function and cold stress of piglets for revealing the mode of action of antibacterial growth promoters. They are summarized as follows: Experiment 1. Effect of Dietary Crude Protein and Lysine on Growth- Promoting action of Apramycin in Piglets In order to determine the effect of apramycin on improving growth performance and to investigate the relationships among apramycin, crude protein and lysine, 4 trials were conducted in this experiment. In trial 1, seventy-two Large White X Landrace X Beijing Black piglets weaned at 28 days were fed a basal diet containing 20% crude protein supplemented with apramycin at 0, 20 ,and 90 mg/kg for a period of 4 weeks. In trial 2, using a 3 X 3 factorial design, one hundred and sixty-two Large White X Landrace X Beijing Black piglets weaned at 28 days were given 9 diets which contained apramycin at 0,20, and 90 mg/kg and crude protein at 1 8%,20%, and 23% for 4 weeks. In trial 3, using a 3 X 2 X 2 factorial design, one hundred and forty-four Large White X Landrace X Beijing Black piglets weaned at 28 days were fed 12 diets supplemented with apramycin at 0,20, and 90 mg/kg , crude protein at 18% and 20%, and lysine at 1.15% and 1.35% for 4 weeks. In trial 4, twenty Large White X Landrace X Beijing Black male piglets weaned at 28 days were randomly divided into 4 groups with 5 piglets each, and were individually housed in plastic-coated metabolism crates under different temperature(28 ,15 ). The piglets were fed a basal diet containing 20% crude protein supplemented with apramycin at 0, 90, and 150 mg/kg for a period of 2 weeks. During the last week, metabolic trial was conducted to study the effect of apramycin on the apparent metabolizablity of dry matter and protein and the nitrogen retention of piglets. In all trials, average daily gain (ADO), average daily feed intake (ADFI), feed conversion rate (FCR) and diarrhoea rate were measured. The results are as follows: 1. Dietary apramycin supplementation markedly decreased the diarrhoea rate of piglets and significantly promoted the piglet growth. Administration of 90 mg/kg apramycin in feed improved ADO by 19.1%?-24.6%(P<0.05), FCR by 7.7%--- 8.5%(P<0.05) and ADFI by 8.4%----?13.1%. Meantime, it was discovered that the promoting effect of apramycin was clearer at the first two weeks than at the latter two weeks after weaning. 2. There were significant relationships among apraniycin, crude protein and lysine (P<0.05). The growth-promoting action of apramycin was no significant while the piglets were fed a low protein diet containing a low or high lysine level. With the increasing of dietary proteil1 level, the growth-promoting action of apramycin was more and more obvious. However, too high protein or lysine level had no further benefits for the growth-promoting action of apramycin. The performance of piglets fed a diet supplemented with 90mg/kg apramycin, 20% protein and 1.15% lysine was best. Additionally, dietary apramycin supplementation could decrease the requirements of protein and lysine for per unit weight gain of piglets. 3. Under low temperature condition, dietary apramycin supplementation could effectively alleviate cold stress. The treatments of 90 and 1 50mg/kg improved the apparent protein metabolizablity by 26.4%, 18.7% and daily nitrogen...