| The topic chose of 18 head 20 ± 1.1 kg body weight, healthy and castrated Duroc×Landrace×Yorkshire piglets, which were fed 14%, 17%, 20% three different crude protein(CP) diets, whose lysine(Lys), methionine(Met), threonine(Thr), tryptophan(Trp) were balanced. Then hepatic vein-portal vein-mesenteric vein-carotid artery catheters were respectively implanted. Before the feeding 0.5 h to after the start of feeding 0.5,1.5,3,5,7.5 h,the hepatic vein, portal vein and carotid artery blood were collected, respectively, researching the dynamic metabolic rule of amino aicds liver and metabolism efficiency in pigs fed three different CP diets, thus to procide theoretical basis for the CP diet.The main results were as follows:1. The study was aimed to establish techniques for implanting arterial and vein catheters in piglets used to investigate liver nutrient metabolism to provide technical support. Choice of 18 head 20 ± 1.1 kg body weight, healthy and castrated Duroc×Landrace×Yorkshire piglets, hepatic vein-portal vein-mesenteric vein-carotid artery catheters were respectively implanted. After 5 days recovery period, a 1% solution of p-aminohippurate(PAH) was infused continuously into the mesenteric catheters. Then before the feeding 0.5 h to after the start of feeding 0.5, 1.5, 3, 5, 7.5 h, hepatic vein, portal vein and carotid artery blood were collected, respectively, to detect hepatic vein and portal vein blood flow. The results showed that hepatic vein and portal vein blood flow velocity increased post-feeding. Portal vein flowed up to 2.80 L/h/kg and 981.40 m L/min. Hepatic vein flowed rate of 4.04L/h/kg and 1 414.65 m L/min. And the installation can keep blood flowing 16 d, suggesting that the duct system is feasibilited. Twelve of the eighteen test piglets can be successfully used in the study of the liver nutrient metabolism.2. The study aims to use three different CP level diet fed piglets, researching the metabolic rule of amino aicds in the liver. The concentration of free amino aicd in the hepatic vein, portal vein and carotid artery plasma were analyzed by amino acid analyzer. And the ratio of portal vein metabolism of amino acids in the liver of piglets were calculated by areriocenous concentration difference method. The results showed:(1)43%-60% of Lys、25%-45% of Thr and 15%-55% of Arg in the piglet portal were metabolized by the liver, respectively. But for branched-chain amino aicds(BCAAs), we found that the proportion of less metabolism in the liver, valine(Val)(4.07%, 8.95%, 9.52%), isoleucine(Ile)(3.49%, 3.61%, 7.92%) and leucine(Leu)(4.34%, 5.40%, 13.39%) were metabolized in the piglet liver among the three levels of CP group(14%, 17%, 20%), respectively.(2) It is noteworthy that the phenylalanine(Phe) metabolism in the liver reached 79.39%, 74.13%, 63.00%, and tyrosine(Tyr) reached 92.30%, 87.34%, 77.41%, a lot of Phe and Tyr in the piglet liver were metabolized. And glutamate(Glu) and aspartate(Asp) has a net produce in the liver, little was metabolized.(3) Compared with 20% CP diet, 14%CP diet increased the metabolism ratio of TAAs, TEAAs, Lys, Val, Phe, glysine(Gly), serine(Ser) in the piglet liver(P<0.05), but no difference with 17% CP diet(P>0.05). Meanwhile, the synthesis of Glu and Asp in the liver were highest in the 14% CP group. And the metabolism of Thr, Leu, Ile by the piget liver in 17% CP group were significantly lower to 14% CP group((P<0.05).(4) The metabolism of Val(48.94% vs. 7.51%), Ile(37.29% vs. 5.01%) and Leu(56.56% vs. 7.71%) were different between piglet gut and liver, larger proportion of BCAAs were hardly metabolized by the liver. It is worth noting that Tyr(139.34%) and Ala(135.9%) were synthesize by the intestine, but Tyr(85.68%) and alanine(Ala)(77.22%) were metabolized by the liver, respectively. Additionally, almost all of Glu and Asp were metabolized by the intestina, but there were a large number of synthesis in the liver.According to the above test can be concluded that:1. The piglets fed on a low CP diets, only supplemented with Lys, Met, Thr and Trp, had a increasing for hepatic EAAs metabolism. Interestingly, the hepatic production of glutamate and aspartate were increased as the dietary CP level reduced. This may suggest an important conversion between EAAs and NEAAs response to low CP diets.2. The number of amino acids metabolism were equal both in the liver and intestinal, such as Lys, Thr, etc; The amino acids were less metabolized in the liver, such as Val, Ile, ect; The amino acids, which mainly were synthesized, were both synthesized and degradated in the liver, such as Glu, Asp, ect; The amino acids, which mainly were degradated, were both synthesized and degradated in the liver, such as Phe, Tyr, ect; Therefore, the liver and intestinal metabolism of the amino acids were different and the amino acids metabolism in the liver were affected by the dierary CP levels and types of amino acids. |
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