| The application of low-protein diets can effectively alleviate the shortage of protein feed resources and reduce the nitrogen emissions of livestock in China.However,low-protein diets may negatively impact animal nutrient metabolism and growth performance when crude protein levels in the diet are reduced by more than 3percentage points.Fatty acids with different chain lengths can improve animal metabolism in various ways,which combined with low-protein diets may further promote oxidative metabolism of glucose and fat,thereby eliminating the negative effects of low-protein diets.Therefore,we studied the effect of low-protein diets supplemented with short chain fatty acids(sodium butyrate),medium chain fatty acids and polyunsaturated fatty acids on nutrient metabolism in weaned piglets,aiming to explore the application prospects of low-protein diets supplemented with different chain length fatty acids in weaned piglets,and to provide reference value for the further development and application of low-protein diets.A total of 120 healthy weaned piglets(Duroc × Landrace × Yorkshire)with a body weight of 7.93±0.65 kg were selected and divided into 5 groups according to the randomized complete block design,with 6 replicates in each group and 4 pigs in each replicate.Piglets in the 5 groups were fed the following diets: 20.4% CP(CON group);16.5% CP(LP group);LP + 0.2% sodium butyrate(LP+SB group);LP + 0.2% medium chain fatty acids(LP+MCT group);LP + 0.2% n-3 polyunsaturated fatty acids(LP+PUFA group).The experimental pre-feeding period was 3 days,and the trial period was 28 days.During the test,the initial weight,final weight and feed intake of the piglets were accurately recorded,and feed samples were collected.Piglet feces was collected for three consecutive days on the 21 st,22nd and 23 rd days of the trial period.On the last day of the trial period,one piglet was randomly selected from each replicate in each group to obtain plasma from the anterior vena cava.After the feeding experiment,one piglet from each replicate in each group was randomly selected for slaughter,the organ tissue weight was weighed,the length of the small intestine and the intestinal p H value were measured,and liver samples were collected.The results showed:(1)Growth performance.Compared with the CON group,the final weight and average daily gain of piglets in the other 4 groups decreased significantly(P<0.05),and the feed to meat ratio increased significantly(P<0.05);compared with the LP group,the average daily feed intake of the piglets in the LP+SB group increased significantly(P<0.05).(2)Organ Index.LP,LP+SB,LP+MCT and LP+PUFA significantly increased the liver index and cardiac index of weaned piglets(P<0.05),and had a tendency to increase the kidney index(P=0.078);the pancreas index of piglets in the LP and LP+MCT groups was significantly higher than that in the CON and LP+SB groups(P<0.05),while there was no significant difference in the CON,LP+SB and LP+PUFA groups(P>0.05).(3)Intestinal length and p H.There were no significant difference in the lengths of the duodenum and the p H of the jejunum and colon of piglets among the 5 groups(P>0.05).(4)Apparent digestibility.Compared with the LP group,the apparent digestibility of total phosphorus of piglets in LP+SB group was significantly improved(P<0.05),the apparent digestibility of dry matter and total phosphorus of piglets in LP+MCT group increased significantly(P<0.05),and the apparent digestibility of crude protein had a trend of increasing(P=0.096).(5)Plasma biochemical indicators.The plasma aspartate aminotransferase activity of piglets in the LP+MCT group was significantly higher than that in the other4 groups(P<0.05);the plasma alanine aminotransferase activity of the piglets in the LP+SB,LP+MCT and LP+PUFA groups were significantly higher than that in the CON group(P<0.05);the plasma alanine aminotransferase activity of piglets in the LP+PUFA group was significantly higher than that in the LP group(P<0.05);The plasma cholesterol content of piglets in LP group was significantly higher than that in the other 4 groups(P<0.05);while there was no significant difference among the LP+SB,LP+MCT,LP+PUFA and CON groups(P>0.05).(6)Plasma hormone indicators.The plasma cholecystokinin level of piglets in LP+PUFA group was significantly higher than that in LP,LP+SB and LP+MCT groups(P<0.05),and there was no significant difference with CON group(P>0.05).(7)Liver m RNA relative expression.Compared with the CON group,the relative expressions of acetyl-Co A carboxylase and fatty acid synthase m RNA in the liver of piglets in the LP+MCT and LP+PUFA groups were significantly increased(P<0.05);The relative expression of sterol regulatory element-binding protein 1 gene in the liver of piglets in LP,LP+MCT and LP+PUFA groups was significantly increased(P<0.05);the relative expression of liver serine/threonine protein kinase gene of piglets in LP and LP+SB groups was significantly increased(P<0.05).(8)liver protein levels.Compared with the LP group,the expression of glutamate dehydrogenase in the liver of the LP+MCT group had a tendency to increase(P=0.074);there was no significant difference in the protein expression levels of hepatic adenosine monophosphate-activated protein kinase α2,carnitine palmitoyltransferase 1 and peroxisome proliferator-activated receptor γcoactivator 1α among the 5 groups(P>0.05).(9)Liver metabolomics.Compared with the CON diet,LP diet mainly affected piglet liver oxidative phosphorylation,pentose and glucuronic acid interconversion,and amino sugar and nucleotide sugar metabolism(P<0.05);compared with LP diet,LP+SB diet mainly affected pyrimidine metabolism,galactose metabolism and lysine degradation pathways(P<0.05),while LP+MCT and LP+PUFA diets significantly changed linoleic acid metabolism,glutathione metabolism and arginine metabolism pathways in piglets(P<0.05).In conclusion,the reduction of dietary protein level by more than 3.5% would significantly impaire the growth performance of weaned piglets;supplementing low-protein diets with different chain lengths fatty acids could reduce plasma cholesterol level.Specifically,the addition of sodium butyrate to the low-protein diets can increase the feed intake of piglets,and medium chain fatty acid can significantly improve the apparent digestibility of dry matter and total phosphorus. |
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