Effect of Supplementing Synthetic Amino Acids in Low-protein Diet and Subsequent Re-feeding on Growth Performance, Serum Lipid Profile and Chemical Body Composition of Broiler Chickens

Encapsulated crystalline lysine and DL-methionine have higher efficiency than the crystalline form in broilers

Crystalline amino acids (AAs) exhibit high nutritional values when supplemented AA-deficient diets. However, the AAs in crystalline form in the diet are absorbed quickly than protein-bound AAs, which may take an effect on AA utilization efficiency. In this study, 2 experiments were conducted to investigate the effect of encapsulated lysine-HCl (Lys) and DL-methionine (DL-Met) on the growth performance of broiler chickens. In experiment 1, a total of 432 one-day-old male Arbor Acres broilers were subjected to 3 dietary treatments (27 pens; 16 birds per pen) for 42 d. The control group was basal diets supplemented with crystalline Lys and DL-Met, and treatment groups had basal diets supplemented with encapsulated Lys and DL-Met at the levels of 80% and 60% of control diets (80CLM, 60CLM), respectively. The growth performance, intestinal development, and transcription of AA transporters were determined. In experiment 2, 24 broiler chickens were subjected to the same treatments as in experiment 1. The plasma concentrations of free AAs were measured 0, 2, 4, and 6 h after feeding. The results showed that 80CLM treatment had no significant influence on production performance, carcass characteristics, and plasma free AAs content during the experiment compared with the control group (P > 0.05). In addition, the 80CLM group moderately enhanced gut morphology development and increased AAs' absorption capacity. However, broilers fed the 60CLM diet had lower production performance and breast muscle weight than the control group (P < 0.05), but increased villi height and B⁰AT mRNA expression level (P < 0.05). At h 4 after feeding, the 60CLM broilers exhibited higher concentration of Ala, Cys, and total dispensable AAs than the control group (P < 0.05). In conclusion, the result suggests that the supplemental levels of crystalline Lys and DL-Met can be effectively saved approximately for 20% by using the encapsulated form in broilers, with improvements to AAs utilization efficiency, while posing no detrimental effects on production performance. Encapsulated Lys and DL-Met would have greater potential for application when replacing crystalline AAs in broiler chickens.

Supplementation of a low-protein diet with tryptophan, threonine, and valine and its impact on growth performance, blood biochemical constituents, immune parameters, and carcass traits in broiler chickens

AIM

This study aimed to investigate the effects of protein reduction with supplementation of limiting amino acids (AA, tryptophan, threonine, and valine) on growth performance, blood biochemical, immunity parameters, and carcass traits in broiler chickens.

MATERIALS AND METHODS

Three hundred one-day-old broiler chicks were randomly allotted into three treatment groups, with five replicates per treatment and 20 broiler chickens per replicate. The three experimental diets were formulated with different dietary crude protein (CP) %, (control [CON] and CON with 1% [CP-1%] or 2% [CP-2%] less CP units) during the starter, grower, and finisher phases. The CP of the experimental diets were 22, 21, and 20% for the starting period (day 1-14); 20, 19, and 18% CP for the growing period (day 15-28); and 18, 17, and 16% CP for the finishing period (day 29-35) in CON, CP-1%, and CP-2%, respectively. The low-CP diets (CP-1% and CP-2%) were supplemented with combined AA, threonine+tryptophan+valine, to meet the respective levels of the CON diet.

RESULTS

The CP-2% group had greater (p<0.05; linear, p<0.05) final body weight and gain and better feed conversion ratio. The combined AA inclusion in the low-CP diet (CP-1% and CP-2%) increased (p<0.001; linear, p<0.001) carcass and breast meat yield as well as CP% of breast meat. The reduction of CP% with AA supplementation (CP-2%) decreased (p<0.05; linear, p<0.05) serum triglycerides, glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, and alkaline phosphatase, while increased (p<0.01; linear, p<0.01) phagocytic activity and phagocytic index. The mRNA expression of splenic and cecal tonsil interleukin 4 and interferon gamma was upregulated (p<0.001; linear, p<0.001) in the low-CP diets supplemented with AA (CP-1% and CP-2%). Dietary supplementation with AA to low-protein diets improved (p<0.01; linear, p<0.01) the economic returns of broiler chickens.

CONCLUSION

A reduction of dietary CP and increased synthetic AA such as threonine, valine, and tryptophan should be considered to improve performance, health, and immunity in broiler chickens.

Effects of low-protein diet on the intestinal morphology, digestive enzyme activity, blood urea nitrogen, and gut microbiota and metabolites in weaned pigs

This study investigated the effects of low-protein diet supplemented with Lysine (Lys), Methionine (Met), Threonine (Thr), and Tryptophan (Trp) on small intestine morphology, enzyme activity, blood urea nitrogen, and gut microbiota and metabolites in weaned piglets. Eighteen weaned pigs weighing an average of 9.57 kg received one of three treatments: a normal protein diet with 20% crude protein (CP, diet [NP]), a moderately reduced protein diet with 17% CP (MP), or a low-protein diet with 14% CP (LP). All three diets were supplemented with Lys, Met, Thr and Trp to meet essential amino acid requirements for post-weaned piglets according to the NRC (2012). Following a 45 d study period, piglets on the LP and MP diets demonstrated atrophic small intestinal morphology, with decreased villus heights and lower ratios of villus height to crypt depth (p < 0.05); pepsin activity in the stomach was also reduced in these two groups (p < 0.05). Increased plasma cholesterol and decreased blood urea nitrogen presented in the MP and LP groups compared with the NP group (p < 0.05). Overall, gastrointestinal hormones were not affected by dietary protein levels with the exception of reduced somatostatin levels in the MP and LP groups. Jejunum and colon microbiota were not affected at either the phyla or genera level in any of the diets. Colonic ammonia nitrogen concentration was reduced in MP and LP groups. Dietary protein level had no effect on short chain fatty acids or biogenic amines. Our data suggest that reducing dietary protein levels by 3% (MP) or 6% (LP) in weaned pigs has the potential to decrease nitrogen emissions and impaired digestive capacity. Therefore, dietary protein level cannot be reduced by more than 3% in consideration of maladaptive changes to small intestinal morphology and pepsin activity in weaned piglets.

Methionine supplementation of low-protein diet and subsequent feeding of low-energy diet on the performance and blood chemical profile of broiler chickens

The effects were investigated of supplementing methionine (Met) in a low-crude protein diet (Low-CP+Met) during Days 11–24 post-hatch and subsequent feeding with a low-metabolisable energy diet (Low-ME; –0.31 MJ/kg) during Days 25–42 on the productive performance and blood chemistry profile of broiler chickens. The 1600 broiler chicks were divided into four groups and fed as follows: (1) Control diet; (2) Low-CP (Met deficiency) diet during Days 11–24, then re-feeding with conventional diet; (3) Low-CP+Met diet during days 11–24, then re-feeding with conventional diet; and (4) Low-CP+Met+Low-ME diet (Low-CP+Met diet during Days 11–24, then re-feeding with Low-ME diet). During Days 11–24, the growth performance of the Control group was better than the other groups (P < 0.01), although the Low-CP+Met diet improved bodyweight, feed conversion ratio and improved the protein conversion ratio compare to the Low-CP group (P < 0.01). During the re-feeding phase (Days 25–42), reducing the dietary energy resulted in better growth performance and a better protein conversion ratio and energy conversion ratio than in the Control group (P < 0.05). Triglyceride, very low-density lipoprotein, low-density lipoprotein-cholesterol and total cholesterol in serum were higher, and non-esterified fatty acid was lower in the Control group than those of the Low-CP+Met+Low-ME group (P < 0.05). In conclusion, reducing dietary protein with balanced amino acids during the grower period and subsequent feeding with a low-energy diet promoted productive performance, improved protein utilisation and reduced fat accumulation via increasing lipolysis and/or disruption of the triglyceride transportation in broiler chickens.

The Protein and Energy Metabolic Response of Skeletal Muscle to the Low-Protein Diets in Growing Pigs

This study was conducted to determine the effect of low-protein diets on protein and energy metabolism in skeletal muscle, and to elucidate the underlying mechanism. A total of 18 growing pigs (average initial body weight = 36.47 kg) were individually penned and assigned to three treatments; each treatment was fed one of three diets containing either 18%, 15%, or 12% CP. The results showed that reducing dietary CP contents decreased (P < 0.05) the weight of half Longissimus dorsi (LD) muscle and serum concentration of insulin-like growth factor 1 (IGF-1). Compared with the 18% and 15% CP treatments, the 12% CP treatment suppressed (P < 0.05) the components of mammalian target of rapamycin complex 1 (mTORC1) pathway, but upregulated (P < 0.05) the mRNA levels for proteolysis-related genes, and concomitantly caused an increase (P < 0.05) in the percentage of apoptotic cells in LD muscle. Along with lower (P < 0.05) AMP/ATP ratio and greater (P < 0.05) energy charge value in LD muscle of the 12% CP treatment, there was a concurrent decrease (P < 0.05) in the proteins for AMP-activated protein kinase α (AMPKα) pathway. Likewise, these results were also observed in the Biceps femoris muscle with slightly different degree of impacts. These results indicate that the retardation effect of low-protein supply on muscle growth of growing pigs could be likely regulated by inhibiting IGF-1/mTORC1 protein synthesis cascade, along with strong alterations in energy status and AMPKα pathway.

Effects of Low-Protein Diets Supplemented with Branched-Chain Amino Acid on Lipid Metabolism in White Adipose Tissue of Piglets

This study evaluated the effect of branched-chain amino acid (BCAA) supplementation in low-protein diets on lipid metabolism in dorsal subcutaneous adipose (DSA), abdominal subcutaneous adipose (ASA), and perirenal adipose (PRA) tissues. A total of 24 piglets were allotted to four treatments, and each group was fed the adequate protein (AP) diet, low-protein (LP) diet, LP diet supplemented with BCAA (LP + B), or LP diet supplemented with twice BCAA (LP + 2B). Serum concentrations of leptin in the BCAA-supplemented treatments were higher (P < 0.01) than in the AP treatment, but lower (P < 0.01) than in the LP treatment. In DSA, the mRNA and protein levels for lipogenic-related genes were highest in the LP treatment and lowest in the LP + 2B treatment. However, in ASA and PRA, the expression levels for those genes were significantly elevated in the LP + 2B treatment. In conclusion, BCAA supplementation could alter the body fat condition, and this effect was likely modulated by the expression of lipid metabolic regulators in DSA, ASA, and PRA in a depot-specific manner.