Response of broilers to gradual dietary protein reduction with or without an adequate glycine plus serine level

Interaction effects of glycine equivalent and standardized ileal digestible threonine in low protein diets for broiler grower chickens

OBJECTIVE

This study aims to investigate the interactive effect of a glycine equivalent (Glyequi) and standardized ileal digestible threonine (SID Thr) levels in low crude protein diets on performance, blood biochemistry, pectoral muscular creatine content and oxidative stability of meat in broiler chickens from 21 to 42 days.

METHODS

A total of 1,500, twenty-one-day-old Cobb-Vantress male broiler chickens were distributed in a completely randomized 5×3 factorial arrangement of Glyequi×SID Thr with five replicates of 20 birds each. Fifteen dietary treatments of 16.5% CP were formulated to contain five levels of total Glyequi (1.16%, 1.26%, 1.36%, 1.46%, and 1.56%) and three levels of SID Thr (0.58%; 0.68% and 0.78%).

RESULTS

Interaction effects (p<0.05) of Glyequi and SID Thr levels were observed for weight gain, carcass yield, pectoral muscular creatine content and serum uric acid. Higher levels of Glyequi increased (p = 0.040) weight gain in 0.58% and 0.68% SID Thr diets compare to the 0.78% SID Thr diet. The SID Thr level at 0.68% improved (p = 0.040) feed conversion compared to other SID Thr diets. Levels of Glyequi equal to or above 1.26% in diets with 0.78% SID Thr resulted in birds with higher (p = 0.033) pectoral muscular creatine content. The breast meat yield observed in the 0.68% SID Thr diet was higher (p = 0.05) compared to the 0.58% SID Thr diet. There was a quadratic effect of Glyequi levels for pectoral pectoral muscular creatine content (p = 0.008), breast meat yield (p = 0.030), and serum total protein concentrations (p = 0.040), and the optimal levels were estimated to be 1.47%, 1.35%, and 1.40% Glyequi, respectively. The lowest (p = 0.050) concentration of malondialdehyde in the breast meat was found in 0.68% SID Thr diets at 1.36% Glyequi.

CONCLUSION

The minimum dietary level of Glyequi needed to improve performance in low crude protein diets is 1.26% with adequate SID Thr levels for broiler chickens.

Effects of different dietary threonine and glycine supplies in broilers fed low-protein diets

The reduction of crude protein (CP) content of broiler diets with balanced amino acid supply can increase the nitrogen (N) utilization efficiency and reduce ammonia emission, the risk of many health problems in birds. Feeding low protein (LP) diets without the impairment of performance traits needs the optimized dietary levels of threonine (Thr) and the non-essential amino acid (AA) glycine (Gly) and serine (Ser). However, the required concentrations and interactions of Thr and Gly + Ser, expressed as Gly equivalent (Glyequi), in LP diets are not fully understood. Therefore, the aim of this study was to investigate the effects of three LP (LP1-3) grower (11-24 days) and finisher (25-35 days) diets with 2% CP reduction compared to the control (C), differing in standardized ileal digestible (SID) Thr to lysine (Lys) ratio (C, LP1, LP3: 63%, LP2: 72%) and Glyequi levels (C: 15.65 g/kg, LP1: 13.74 g/kg, LP2: 13.70 g/kg, LP3: 15.77). The LP treatments did not impair the performance traits of broilers. The LP2 treatment with increased SID Thr-to-Lys ratio (+9.0%) resulted in significantly higher body weight gain and a more advantageous feed conversion ratio in the whole fattening compared to the control treatment with normal CP level (p < 0.05). The LP3 treatment containing swine meat meal with similar Glyequi levels compared to the normal CP treatment led to the most advantageous feed conversion ratio in the finisher phase and the highest nitrogen retention efficiency (p < 0.05). However, the LP3 treatment with a high starch-to-CP ratio negatively influenced the relative carcass weight and the ratio of abdominal fat of broilers (p < 0.05).

Impacts of Dietary Lysine and Crude Protein on Performance, Hepatic and Renal Functions, Biochemical Parameters, and Histomorphology of Small Intestine, Liver, and Kidney in Broiler Chickens

The present study aimed to investigate the effects of increasing dietary lysine (Lys) levels with an adequate dietary crude protein (CP) content, as well as the effects of a reduction in dietary CP content with the recommended amino acid (AAs) level, on the performance, blood biochemical parameters, and histomorphology of the duodenum, liver, and kidney in broiler chickens. A total of 500 broiler chickens were randomly distributed into five dietary treatment groups, following a completely randomized design, where, at the beginning, the control group (C) was fed a diet containing the standard CP and Lys levels: 23% CP with 1.44% Lys during the starter period; 21.5% CP with 1.29% Lys during the growing period; and 19.5% CP with 1.16% Lys during the finishing period. The Lys content was increased by 10% above the recommended control basal requirements in the second group (Gr1) and by 20% in the third group (Gr2), while using the same recommended CP percentage as the C group. The fourth group (Gr3) had a 1% lower CP content and the fifth group had a 2% lower CP content than the C group, with the same recommended AA level as the C group. Increasing the Lys content in the Gr1 group improved the broilers' weight gains (p < 0.05) during the starter, growing, and finishing periods. Decreasing dietary CP with the standard AA levels (Gr3 and Gr4) did not significantly affect (p > 0.05) the live weight gain, feed intake, or feed conversion ratio (FCR) of the broilers compared with those fed with the C diet. Blood total bilirubin, direct and indirect bilirubin, triglycerides, cholesterol, low-density lipoprotein (LDL), and very LDL were not different among the experimental groups. However, blood aspartate aminotransferase levels were increased (p < 0.05) in the Gr1 and Gr3 groups compared with the other treatment groups. All dietary treatments decreased the serum creatinine levels (p < 0.05) compared with the C group. The Gr2 broilers had greater serum total protein and globulin (p < 0.05) than those receiving the other treatments. Increasing dietary Lys levels resulted in a significant improvement in duodenum villus height and width (p < 0.05), while the low-CP diets resulted in shorter villi length and width, along with degenerated areas and lymphocytic infiltration. Low dietary CP content induced hepatocyte disorganization and moderate degeneration, along with vacuolated hepatic cells, excessive connective tissue, and lymphocytic infiltration. The cortical regions of the kidney exhibited obvious alterations in the Gr3 and Gr4 groups and large interstitial spaces were found between tubules. Renal tubules in the Gr3 and Gr4 groups were smaller in size and some of these tubules were atrophied. In conclusion, reducing dietary CP levels to 1% or 2% lower than the recommended level did not negatively affect growth performance, inducing minimal influence on the blood metabolic indicators of health status, and resulting in moderate alterations to the histomorphology of the duodenum, liver, and kidney. Furthermore, increasing the Lys content by 10% above the recommended level improved the growth performance, health status, and histomorphology of the duodenum, liver, and kidney in broiler chickens.

Interactive effect of amino acids balanced at ideal lysine ratio and exogenous protease supplemented to low CP diet on growth performance, carcass traits, gut morphology, and serum metabolites in broiler chicken

This study evaluated the effect of amino acids balanced at a specific lysine ratio with exogenous protease supplementation and reduced CP levels in the broiler diet. In total, 480 straight-run broiler chicks (Ross-308) were used for the study. A completely randomized design in the factorial arrangement was applied, with 4 treatments of 6 replicates with 20 birds each. Treatments consisted of 2 lysine ratios (100% and 110%; factor 1) without or with exogenous protease supplementation (200 g/ton; factor 2). Twenty percent reduction of CP from standard requirements of Ross-308 (18.4% vs 23% in starter and 17.2% vs 21.5% in grower phase) was made in all the treatment diets. Growth performance (feed intake, weight gain, feed conversion ratio, livability), carcass traits (live and carcass weight, carcass yield, heart, liver, gizzard, leg quarter, breast weight, and abdominal fat percentage), gut morphology (villus height, crypt depth, and villus height and crypt depth ratio), and serum metabolites (total protein, albumin, and uric acid) were evaluated. A significant interaction (p ≤ 0.05) for lysine ratio and protease was noted in body weight gain, feed conversion ratio, carcass traits, and gut morphology throughout the experimental period yet a non-significant (p > 0.05) influence was observed on serum metabolites. It was concluded that the broiler diet with a net reduction of 20% CP from Ross-308 standards, balanced for amino acids at lysine ratio 110% and supplemented with exogenous protease, could be used to improve growth performance, intestinal health, and carcass traits.

Dietary glycine equivalent and standardized ileal digestible methionine + cysteine levels for male broiler chickens fed low-crude-protein diets

This study was conducted to determine the optimum dietary glycine equivalent (Glyequi) level in low-crude-protein diets of 181 g·kg−1 containing varied concentrations of standardized ileal digestible (SID) methionine + cysteine (Met + Cys) for broiler chicks (1–21 d old). A total of 1275, 1-d-old Cobb-Vantress® male broilers were distributed in a 5 × 3 factorial arrangement with a completely randomized design of 15 treatments with five replicates of 17 birds each. Treatments consisted of five levels of dietary Glyequi (14.9, 16.4, 17.9, 19.4, and 20.6 g·kg−1) and three concentrations of SID Met + Cys (7.70, 9.0, and 10.3 g·kg−1). Interactions between Glyequi and SID Met + Cys levels were observed for feed:gain (P = 0.055) and breast meat yield (BMY) (P = 0.017). In 7.7 and 9.0 g SID Met + Cys·kg−1 diets, optimal feed:gain and increased BMY were observed at Glyequi levels not lower than 17.9 g·kg−1. In 10.3 g SID Met + Cys·kg−1 diet, a lower feed:gain was achieved at 19.4 g Glyequi·kg−1. Therefore, a minimum dietary level of 17.9 g Glyequi·kg−1 is needed to increase growth of broilers fed diets containing 7.7 or 9.0 g·kg−1 SID Met + Cys, whereas 19.4 g·kg−1 Glyequi is necessary in diets containing 10.3 g·kg−1 SID Met + Cys for optimum growth.

Cyst(e)ine fortification in low crude protein diet improves growth performance of broilers by modulating serum metabolite profile

This study was aimed to explore the metabolomical mechanisms for the potentially ameliorative effect of cyst(e)ine (Cys) fortification on growth performance of broilers fed low crude protein (CP) diet. A total of 432 1-d-old broilers were randomly divided into 6 groups, each of which received one of the following diets: normal-CP diet (positive control, PC), low-CP diet (negative control, NC), NC diet fortified with 0.05%, 0.1%, 0.15% or 0.2% of Cys. Samples were collected on d 42. Results showed that increasing Cys fortification quadratically elevated (P < 0.05) the accumulative growth performance and leg muscle yield of broilers fed NC diet, with 0.1% being the optimal dose. Thus, samples from PC, NC and NC plus 0.1% Cys (NCC) groups were selected for further analysis. Both dietary CP reduction and fortification of 0.1% Cys in NC diet caused complex changes (P < 0.05) in serum amino acids and some other metabolites primarily involved in lipid metabolism. Multiple lipogenesis-related pathways were regulated (P < 0.05) following Cys fortification in NC diet, which could at least partially interpret the benefit of Cys fortification in NC diet on broiler performance. In conclusion, fortifying low-CP diet with 0.1% Cys promoted the growth performance of broilers probably through modulating serum metabolite profile.

The Response of Broiler Chickens to Dietary Soybean Meal Reduction with Glycine and Cysteine Inclusion at Marginal Sulfur Amino Acids (SAA) Deficiency

Simple Summary

Climate change, resource shrinkage, and greenhouse gasses emission are becoming a major issue that could be confronted by using reducing protein levels in poultry diet. Reduced protein with amino acids supplementation improved the overall performance of broiler chickens. Reduced protein diets with glycine supplementation could be the potential solution to maintain the growth performance of the chicken, thus reducing feed cost and nitrogen excretion.

Abstract

The responses of broiler chickens to dietary protein reduction were investigated in the presence of glycine and cysteine inclusion at the marginal deficiency of sulfur-containing amino acids. A total of 432 broiler chickens were allotted to six dietary treatments; SP1 is standard protein diet with 100% total sulfur amino acids (TSAA), SP2 is standard protein diet with 85% TSAA, RP is reduced protein diet without glycine and cysteine supplementation, RPC is reduced protein diet with cysteine supplementation at 0.1%, and RPG is reduced protein diet with 1% glycine supplementation, while RPGC is reduced protein diet with 0.1% cysteine and 1% glycine supplementation. In this study, 4.5% protein is reduced in diets—thus, 17.5% CP (crude protein) for starter phase and 15.5% CP for the grower phase. Reduced protein diets contained 85% TSAA. Broiler chickens fed standard protein diet SP2 had superior bodyweight (BW) (p ≤ 0.05) in the starter and grower phase, average daily gain (ADG) (p ≤ 0.05) in the starter and entire feeding period, average daily feed intake (ADFI) (p ≤ 0.05) in the starter phase, and better feed conversion ratio (FCR) (p ≤ 0.05) in the starter, grower and entire feeding period; however, RPGC showed higher ADG (p ≤ 0.05) in the grower phase, and ADFI (p ≤ 0.05) in the grower and entire feeding period. RPC and RPG diet improved BW (p ≤ 0.05), ADG (p ≤ 0.05), ADFI (p ≤ 0.05), and better FCR (p ≤ 0.05) in starter, grower, entire feeding period compared to RP. The RPGC group had higher BW (p ≤ 0.05), ADG (p ≤ 0.05), ADFI (p ≤ 0.05) and better FCR (p ≤ 0.05) compared to the RPC group. Blood biochemical parameters showed that Broiler chickens fed on the SP2 diet had higher levels of total protein (TP) (p ≤ 0.05), albumin (ALB) (p ≤ 0.05), creatinine (CRE) (p ≤ 0.05), and aspartate aminotransferase (AST) (p ≤ 0.05) and, lower level of uric acid (UA) (p ≤ 0.05), blood urea nitrogen (BUN) (p ≤ 0.05), glucose (GLU) (p ≤ 0.05), and alanine aminotransferase (ALT) (p ≤ 0.05) in the starter phase; however, higher level of TP (p ≤ 0.05), GLU (p ≤ 0.05), CRE (p ≤ 0.05), and AST (p ≤ 0.05), and lower level of ALB (p ≤ 0.05), UA (p ≤ 0.05), and ALT (p ≤ 0.05) in the grower phase; RPGC had higher level of TP (p ≤ 0.05), UA (p ≤ 0.05), GLU (p ≤ 0.05), ALT (p ≤ 0.05) and AST (p ≤ 0.05), and lower level of ALB (p ≤ 0.05), BUN (p ≤ 0.05), and CRE (p ≤ 0.05) in the starter phase; however, in grower phase, RPGC had higher level of TP (p ≤ 0.05), and ALB (p ≤ 0.05), and lower level of UA (p ≤ 0.05), CRE (p ≤ 0.05), ALT (p ≤ 0.05), and AST (p ≤ 0.05). Free amino acids profile showed that broiler fed on standard protein diet SP2 had reduced the methionine (p ≤ 0.05) concentration; RPC increased the concentrations of taurine (p ≤ 0.05), phosphoethanolamine (p ≤ 0.05), threonine (p ≤ 0.05), valine (p ≤ 0.05), isoleucine (p ≤ 0.05), phenylalanine (p ≤ 0.05), ornithine (p ≤ 0.05), and lysine (p ≤ 0.05) and reduced the citrulline (p ≤ 0.05) concentration; RPG increased the concentration of glutamate (p ≤ 0.05), glycine (p ≤ 0.05), cysteine (p ≤ 0.05), and arginine (p ≤ 0.05), and decreased the concentration of tyrosine (p ≤ 0.05); and RPGC increased the concentration of serine (p ≤ 0.05) and reduced the concentration of hydroxyproline (p ≤ 0.05). Serum metabolites analysis showed that reduced protein downregulated the 54 metabolites; however, glycine fortification up-regulated the Benzamide, Pro-Ser, N-Carbamylglutamate, D-gluconate, and Gamma-Glutamylcysteine. Carcass quality showed that SP2 decreased the abdominal fat percentage (p ≤ 0.05). Nitrogen digestibility was higher by the diet RP (p ≤ 0.05). This study demonstrated that protein content could be reduced up to 4.5% with 1% glycine and 0.1% cysteine fortification in diet, which has the potential to inhibit the adverse effect of reduced protein and attain the standard growth performance.