NUTRITION ▶▶▶


Figure 3 - Plasma free amino acids concentrations of pigs after feeding diets supplemented with L‐Met or DL‐Met for four weeks.


1400 L-Met


1200 1000


800 P > 0.19


600 400


200 0


DL-Met


0.107% and 0.147% DL-Met or L-Met on equimolar basis for three weeks (33 pens; three pigs per pen). Feed intake, body weight gain and feed:gain were similar among DL-Met and L-Met groups. Based on body weight gain and feed:gain, basi- cally 100% bioavailability was estimated for L-Met relative to DL-Met (Figure 2). Overall, these results indicate that the conversion of D-Met to L-Met is not a limiting factor because, as reported by the Mis- sissippi State study, substantial activity of enzyme that con- verts D-Met to L-Met (D-amino acid oxidase) is present in dif- ferent tissues, such as the kidney, liver, stomach, duo denum, jejunum, and ileum of pigs resulting in similar pig performance.


Source: Yang and others (2019).


Figure 4 - Concentrations of selected metabolites in plasma of pigs after feeding diets with L‐Met or DL‐Met for four weeks.


Urea N, mg/dL


6.3 6.4


Total protein, g/dL


5.5 5.7


Albumin, g/dL


3.4 3.5


Glucose, mg/dL Triglycerides, mgdL


Source: Yang and others (2019). 0


20 40


47.5 51.3


60 80 100 120 115 111 L-Met DL-Met P > 0.09


Effect on plasma concentrations After feeding either L-Met or DL-Met diets for four weeks, the researchers at Mississippi State University did not observe any differences (P>0.19) in plasma concentrations of free amino acids (Figure 3), urea nitrogen (N), total protein, albu- min, glucose, and triglycerides (Figure 4) indicating that ami- no acids, lipid, and energy metabolism were not affected by adding L-Met or DL-Met. Similarly, the team at the University of Giessen reported that plasma concentrations of L-Met were similar, and those of D-Met and total methionine were higher in piglets fed DL- Met compared with those fed L-Met (data not shown).


Figure 5 - Concentrations of total glutathione (GSH), glutathione peroxidase enzyme (GPx), trolox equivalent antioxidant capacity (TEAC) and thiobarbituric acid reactive substances (TBARS) in liver and jejunum of weaned pigs fed diets with DL‐Met or L‐Met.


100.0 120.0


P > 0.10


20.0 40.0 60.0 80.0


0.0 DL-Met Liver Source: Zeitz and others (2019). 28 ▶PIG PROGRESS | Volume 35, No. 6, 2019 L-Met DL-Met Jejunum References available on request. L-Met


GSH, nmol/100 mg TEAC, nmol/g


P > 0.10


Effects are the same Overall, these data consistently indicate that the effects of die- tary L-Met and DL-Met supplementation are not different in terms of pig performance, expression of myogenesis genes, plasma concentrations of amino acids and metabolites and parameters of gut morphology and the antioxidant status in the gut and liver of young pigs. In conclusion, DL-Met and L-Met are equally bioavailable as methionine sources to opti- mise performance, gut integrity and antioxidant status of pigs.


GPx, U/g TBARS, nmol/g


Effect on gut morphology After feeding for three weeks, the team at the University of Giessen observed no differences in gut morphology parame- ters such as villi height, crypt depth, the villi height:crypt depth ratio in duodenum and jejunum and gene expression of tight junction proteins in the jejunum of pigs fed DL-Met or L-Met diet (see Table 2). Furthermore, they found similar concentrations of the antiox- idant total glutathione (GSH), the trolox equivalent antioxi- dant capacity (TEAC), the activity of antioxidant enzyme glutathione peroxidase (GPx) and concentrations of thiobar- bituric acid reactive substances (TBARS) which are markers for oxidative damage of lipids in liver and jejunum mucosa of weaned pigs fed DL-Met or L-Met diet (see Figure 5).


mmol/mL


Lys


Met Leu His Phe Ile


Thr Val


Trp Arg Cit


Ala Glu Gly Asg Asp


B-Ala Glun Orm Ser


Taur Tyr


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