Effects Of Excessive Feed Fluorine On Growth Of Piglets And Approach To Mechanism Of The Effects

Experiments were conducted to study the effects of fluorine on the growth of piglets, and approach to the mechanism of the effects by histopathological changes, main organs metabolism enzymes activities, hormonal synthesis and secretion, free radicals metabolism and antioxidation system function, apoptosis and its key enzymes activities, SOD gene expression and nephrocytes culture.Ninety-six piglets (Duroc × Landrace × Yorkshire) with an average initial body weight of 17.17 ± 1.01 kg were randomly allotted to four groups by weight and sex. Every group included three pens (replicates) of eight pigs each. The groups received the same corn-soybean based diet (DE 13.22MJ/kg , CP 17.75%, Fluorine 26.18 mg/kg) supplemented with 0, 100, 250, 400mg/kg fluorine as sodium fluoride. All piglets were given adequate diets and free access to water. The feeding experiment lasted for fifty days after seven days of adaptation period. Seven days before finishing the feeding trail, eight pigs (sex balanced) were chosen from each group and kept in individual pens for digestion experiment by outside indicator as Cr₂O₃ method. At the end of the feeding trial, eight pigs of each group (sex balanced) were randomly selected based on the similar body weight for slaughter experiment and anatomy observation. Meanwhile, the samples of serum, duodenum, pancreas, liver, kidney and thyroid gland were collected for laboratory analysis. In vitro trial, cultural nephrocytes were used to study the effects of NaF with different concentration grades on cell proliferation and metabolism function. The main results were as follows:1. The results of feeding experiment indicated that excessive fluorine decreased average daily gain (p< 0.05) and average daily feed intake (p > 0.05), also did 400 mg/kg fluorine feed gain ratio (p< 0.05). Meanwhile, it was observed that piglets of fluorine treated groups showed anorexia and reluctant moving at earlier trial period, and disorder hair coat, paleness skin, emaciating figure and claudication at later trial period compared with the control group.2. The results of digestion experiment showed that excessive fluorine reducedapparent digestibility of dry matter and crude protein (p< 0.02), also did 250mg/kg and 400mg/kg fluorine that of ester extract (p< 0.02).3. The results of slaughter experiment indicated that 250mg/kg and 400mg/kg fluorine increased the percentage of liver weight to live weight (p< 0.02), also did 400mg/kg fluorine the percentage of heart weight to live weight (p< 0.03). Meanwhile, it was observed that fluorine treated piglets showed fluorine-spot teeth, swollen and locally necrotic liver, swollen and fat denaturalization kidney and hydronephrosis compared with the control group.4. In fluorine treated piglets, histopathological examination revealed denaturalization and necroses hepatocytes and nephrocytes, crimpling nephric spherules, diminishing thyroid follicles and reducing colloids. Cellular ultrastructure observation of liver, kidney and thyroid revealed crimpling nucleolus and condensation chromatin, swollen and enlarging mitochondria and broken mitochondrial cristaes with rupturing or disintegrating membrane, swollen and anamorphic endoplasm reticulum with falling off ribosome. In addition, duodenum villus height was decreased (p< 0.01) while crypt depth increased (p< 0.01).5. Results from main metabolic organs function examination indicated that excessive fluorine: (1) decreased the total protelytic enzyme, lipase, amylase activities in duodenal content and the total protelytic enzyme, lipase activities in pancreas; (2) reduced SDH activities in mitochondria of hepatocytes; (3) lowered AKP and GPT activities while increased LDH activities in kidney; (4) decreased Na+-K+-ATPase, TPO activities and iodine content in thyroid gland; (5) reduced creatinine, Na+ concentration while elevated GPT activities and urea nitrogen concentration in serum; (6) decreased T4 and FT4 level while improved TSH level in serum.6. Results from free radical metabolism and antioxidation system function examination showed that excessive fluorine decreased T-AOC level and CAT activities in serum, GSH-Px and SOD activities in serum, liver, kidney and thyroid gland, and GSH content in liver, elevated NO, MDA level in serum and MDA content in liver, kidney and thyroid gland.7. The phenomenon of apoptosis increase was found in liver and kidney tissues with fluorine dosage increase, especially in 250mg/kg and 400 mg/kg fluorine treated groups. Furthermore, hepatocytes DNA of 250 mg/kg fluorine treated piglets were extracted for electrophoresis and showed the ladder-strap shape, as indicated that DNA happened fragmentation rupture. In addition, compared with the control group, 250mg/kg and 400mg/kg fluorine improved caspase-9 activities (p< 0.03).8. Results from gene expression experiment showed that 250mg/kg fluorine decreased Cu,Zn-SOD mRNA abundance in liver (p< 0.03) in comparison with the control group.9. Results from cultural nephrocytes treated with different concentration grade NaF manifested that nephrocytes happened shrinkage, diminishing, anamorphosis and rupture. The percentage of denaturalization and necroses nephrocytes increased and proliferation reaction was inhibited with NaF concentration increase. Meanwhile, T-AOC level and GSH-Px activities decreased, yet GPT and GOT activities and MDA concentration elevated in cultural nephrocytes.Results above implicated: (1) excessive fluorine could decrease growth and feed conversion efficiency in piglets. (2) excessive fluorine could interference digestive enzymes secretion of duodenum and pancreas, hormonal secretion of thyroid gland, matter and energy metabolism of liver and kidney, further inhibit digestion, absorption and utilization of feed nutrients, result in adverse influence to growth performance of piglets. (3) excessive fluorine could inhibit antioxidase gene expression, further decrease antioxidation capacity of the body, induce disorder of free radical metabolism, improve apoptosis, finally result in damage of soft-tissues structure and metabolism function widely.