Nutritional And Physiological Effects Of Different Protein Sources In Low Protein Diets Fed To Piglets And As Alternatives To Fish Meal

In the swine nutrition,values for available energy and amino acid digestibility in diets and ingredients were mainly obtained from digestive and metabolic experiments of growing-finishing pigs.Piglets’ diets preparation based on these data might overestimate their digestive ability and cause unscientific nutrition supply,which can’t meet the current precise nutrition requirements of livestock and poultry.To precisely determine the nutritional value of feed ingredients fed to piglets will fill the gap of related nutrient parameters in feeding standard for piglets and promote the development of piglets’ precision rearing.Additionally,researches on piglet protein nutrition mainly focus on the protein level and amino acids,but ignore the functional characteristics of protein ingredients.The study of nutritional and physiological effects of the sole protein source fed to piglets will help further optimize the dietary protein composition.Piglets’ diets preparation has a high standard in selecting protein sources,and high-quality animal proteins such as fish meal are often used.However,these proteins are expensive and limited resources,and might exist potential biosecsafe problems.Therefore,it is urgent to optimize the diet formula in piglets’ production to reduce the utilization of fish meal.Part one: Estimation of nutritional value in different protein sources fed to piglets.Exp.1,36 barrows with average initial body weight of 10.19 ± 1.35 kg housed individually in metabolism crates were randomly divided into 6 diets with 6pigs per diet.A basal diet,and 5 diets containing 800 g/kg basal diet and 200 g/kg of each test protein ingredient(S50,HP300,CDCP,P50 or FM)were prepared.Urine and fecal samples were collected for 5 d following 7 d of adaptation to the diets.In Exp.2,38 barrows(12.61 ± 1.45 kg BW)housed individually in metabolism crates were randomly allotted to 1 of 6 diets with 6 pigs except for N-free diet(n = 8).Five isoenergetic and isonitrogen diets containing each of test protein ingredient(S50,HP300,CDCP,P50 or FM)as the sole source of AA and a N-free diet were formulated.The experimental period last for 9 d,on the d 10,all piglets were slaughtered under anesthesia to collect ileal digesta.Results indicated that S50 contained more DE(16.28 MJ/kg)(P < 0.05)than CDCP(15.79 MJ/kg)and P50(15.16 MJ/kg),but less(P < 0.05)than HP300(16.53 MJ/kg)and fish meal(16.59MJ/kg).The ME content in CDCP(14.68 MJ/kg)was less(P < 0.05)than in S50(14.47 MJ/kg),HP300(15.77 MJ/kg)and fish meal(15.63 MJ/kg),but greater(P <0.05)than in P50(13.11 MJ/kg).P50 had lower(P < 0.05)AID or SID of CP and most indispensable AA compared with other protein ingredients.AID or SID of CP and most indispensable AA in HP300 and CDCP were no differences,but greater(P <0.05)than in other protein ingredients.S50 and fish meal had similar AID or SID of CP and most indispensable AA.Part two: Study on the nutritional and physiological effects of different protein sources fed to piglets.Piglets from S50,CDCP,P50 and FM groups in the Exp.2 were slaughtered to collect and analyse the samples to investigate the effects of different sources on tissular amino acid transport and protein synthesis,and colonic microecological environment of piglets.Protein sources greatly affected the jejunal digestive enzyme activity and m RNA expression of peptide and amino acid transporters,plasm amino acid profile in hepatic portal vein and vena cava anterior,and protein expression of key proteins in m TOR signal way in liver and longissimus dorsi of piglets.However,the amino acid profile in longissimus dorsi and ADG of piglets were slightly changed by dietary protein sources.Colonic α-diversity indices among groups were no differences,but Venn analysis identified unique OTUs in the P50(13),CDCP(74),FM(39),and S50(31)groups.High Escherichia abundance in the P50 and FM,great abundant of Lactobacillus in the CDCP,and high Gemmiger abundance in the S50 were found.S50 and CDCP increased the amount of mixed neutral-acidic mucins relative to P50.The CDCP tended to elevate valeric acid and branched chain fatty acid(BCFA)concentrations compared with the other diets.The P50 and FM groups had greater ammonia nitrogen and methylamine contents than the S50 and CDCP groups.There was a positive correlation between the Escherichia and ammonia nitrogen,the Lactobacillus and short chain fatty acid(SCFA),and a negative correlation between the Gemmige and BCFA.Part three: Study on the effects of different protein sources replacing fish meal in the low protein diets fed to piglets.A total of 330 weaned pigs with similar initial weight(9.90 ± 0.62 kg)were randomly divided into one of five reduced CP,amino acid(AA)-supplemented diets containing 4 % of either S50,HP300,CDCP,P50,or FM diets for a 28-day study period,and each group had six pens with 11 pigs.Compared with fish meal,dietary proteins did not affect growth performance,apparent total tract digestibility(ATTD)of nutrients,serum hormone levels and biochemical parameters,apparent ileal digestibility(AID)of CP and most AA,colonic short-chain fatty acid(SCFA)contents,duodenal and ileal morphology,digestive enzyme activity,and p H in small intestine of piglets.CDCP decreased the Desulfovibrio abundance but increased the Parabacteroides abundance.S50 elevated the Bacteroides and CF231 abundance.P50 and FM reduced the Clostridium and Ruminococcus abundance.CDCP upregulated the Occludin m RNA expression and tended to increase the amount of mixed neutral-acidic mucins in the colon.FM and CDCP declined the serum DAO and endotoxin contents.S50 and CDCP decreased the levels of serum IL-1α,and P50 lowered the serum IL-8 content.In summary,(1)S50,HP300 and CDCP had promising potential to replace fish meal in piglet diet after adding appropriate amount of fat and crystalline AA.(2)Short-term feeding of different dietary protein sources greatly affected jejunal protein digestion and amino acid transport,plasm free amino acid profile and tissular protein synthesis,but had little effect on the ADG and free amino acid profile in muscle of piglet.Potential pathogenic bacteria and detrimental metabolites appeared in the colons of piglets fed P50 and FM,whereas,beneficial effects were conferred upon piglets fed CDCP and S50,thus indicating that available plant proteins added to the diets of piglets enhanced colon health by reducing protein fermentation.(3)The selected proteins could completely replace fish meal in low-protein diet without impairing piglets’ growth via maintaining intestinal digestive physiology,and nitrogen digestion and metabolism.Plant protein(CDCP and S50)had advantages over animal protein(P50 and FM)in maintaining the colonic health via the regulation of colonic microbiota and barrier function.