Amino Acids Fortification of Low-protein Diet for Broilers Under Tropical Climate. 2. Nonessential Amino Acids and Increasing Essential Amino Acids

Effect of black soldier fly larvae as substitutes for fishmeal in broiler diet

This study investigated the effect of processed forms (defatted or hydrolyzed) of black soldier fly larvae (Hermetia illucens L., BSFL) as a protein substitute on broilers. Experiment 1 was a feeding experiment, and Experiment 2 was a metabolism experiment. In Experiment 1, a total of 120 day-old Arbor Acres broilers (initial body weight 39.52 ± 0.24 g) were used for 28 days. There were 8 replicate pens, and 5 broilers were assigned to each pen. In Experiment 2, a total of 36 day-old broilers (initial body weight 39.49 ± 0.21 g) were used for the metabolism trial. There were 2 broilers in a metabolism cage and six replicate cages per treatment. The dietary treatments were as follows: a basal diet (CON), a basal diet without fishmeal and substitute with defatted BSFL (T1), a basal diet without fishmeal and a substitute with hydrolyzed BSFL (T2). In Experiment 1, during the entire experimental period, the T2 group significantly increased (p < 0.05) body weight gain and feed intake compared to the CON and T1 groups. The feed conversion ratio showed a lower tendency (p = 0.057) in the T2 group than in the CON and T1 groups. At 2 weeks, the CON and T2 groups were significantly higher (p < 0.05) crude protein (CP) digestibility than the T1 group. At 4 weeks, the total protein level significantly increased (p < 0.05) in the CON and T2 groups compared to the T1 group. In Experiment 2, the CP digestibility significantly increased (p < 0.05) in the T2 group compared to the CON and T1 group at weeks 2 and 4. At week 4 amino acid digestibility, the T2 group significantly increased (p < 0.05) lysine, methionine, tryptophan, and glycine digestibility compared to the T1 group. There was no difference in fecal microbiota among the treatment groups. In conclusion, feeding hydrolyzed BSFL as a fishmeal substitute in broiler diets improved growth performance, CP digestibility, and specific amino acid digestibility. Therefore, it is considered that hydrolyzed BSFL in broiler diets can be sufficiently used as a new protein source.

Heat Shock Protein Response to Stress in Poultry: A Review

Compared to other animal species, production has dramatically increased in the poultry sector. However, in intensive production systems, poultry are subjected to stress conditions that may compromise their well-being. Much like other living organisms, poultry respond to various stressors by synthesising a group of evolutionarily conserved polypeptides named heat shock proteins (HSPs) to maintain homeostasis. These proteins, as chaperones, play a pivotal role in protecting animals against stress by re-establishing normal protein conformation and, thus, cellular homeostasis. In the last few decades, many advances have been made in ascertaining the HSP response to thermal and non-thermal stressors in poultry. The present review focuses on what is currently known about the HSP response to thermal and non-thermal stressors in poultry and discusses the factors that modulate its induction and regulatory mechanisms. The development of practical strategies to alleviate the detrimental effects of environmental stresses on poultry will benefit from detailed studies that describe the mechanisms of stress resilience and enhance our understanding of the nature of heat shock signalling proteins and gene expression.

Research Note: Effects of dietary L-arginine on the production performance and gene expression of reproductive hormones in laying hens fed low crude protein diets

The present study was designed to investigate whether L-arginine (Arg) supplementation would influence the production performance and reproductive traits of laying hens fed low crude protein (LCP) diets. Hy-Line brown laying hens were randomly assigned to dietary treatments of control, LCP, and LCP supplemented with 0.05, 0.10, 0.15, or 0.20% Arg for 7 wk. The results showed no significant variations on the production performance, and relative organ indexes of hens. However, significant transcriptional and structural changes were evident along the HPG axis of hens. Arg supplementation linearly upregulated (P < 0.05) the gonadotropin-releasing hormone 1 (GnRH1), and gonadotropin inhibitory hormone in the hypothalamus. The pituitary growth hormone, GnRH receptor, and follicle-stimulating hormone (FSHβ) were also increased (P < 0.05). In the ovary, GnRH1, and estrogen receptor β were linearly increased by Arg, and the ovarian morphology revealed that LCP induced structural alterations which were minimally recovered by Arg supplementation. Serum insulin-like growth factor 1 (IGF-1) and nitric oxide (NO) were increased (P < 0.05) at higher levels of Arg supplementation. Therefore, supplementing high Arg (0.20%) to LCP hens influenced the ovarian morphology and modulated the gene expression of reproductive hormones in the hypothalamic-pituitary-gonadal axis of laying hens via actions that may be related to NO and IGF-1 activity.

Effects of L-arginine and L-citrulline supplementation in reduced protein diets for broilers under normal and cyclic warm temperature

Heat stress causes significant economic losses in the broiler industry. Dietary supplementation of arginine (Arg) and citrulline (Cit) might increase the performance of broilers raised under warm temperature due to vasodilation effects. This study investigated the effects of L-Arg or L-Cit supplementation in broilers fed a reduced protein wheat-based diet deficient in Arg under thermoneutral (NT) and cyclic warm temperature (WT). Ross 308 cockerels (n = 720) were randomly allocated to 4 dietary treatments with 12 replicates of 15 birds per pen from d 7 to 21. The 4 treatments were: normal protein (NP), i.e., 22.3% and 20.9% crude protein in grower and finisher, respectively; reduced protein (RP), i.e., 2.5% lower protein and deficient in Arg; and RP supplemented with 0.28% Arg (RP-Arg) or 0.28% Cit (RP-Cit). A factorial arrangement of treatments was applied during the finisher phase (21 to 35 d). Factors were: diet (4 diets above); and temperature, NT (24 °C) or cyclic WT (33 ± 1 °C for 6 h per day) with 6 replicate pens per treatment. During 7 to 35 d and 21 to 35 d, the birds fed the RP diet had lower body weight gain (BWG) and higher FCR compared to the NP diet (P < 0.01). The addition of Arg or Cit to RP decreased FCR compared to RP (P < 0.01). During 21 to 35 d, the birds exposed to WT had lower feed intake (FI), lower BWG (P < 0.001) but similar FCR (P > 0.05) compared to birds exposed to NT. Diet by temperature interactions were not observed for performance parameters during the period of WT (P > 0.05). On d 35, the RP-fed birds had a lower yield of thigh and drumstick, higher fat pad, lower femur ash, and breaking strength but similar serum uric acid level and higher nitrogen digestibility on d 21 compared to those offered NP (P < 0.05). Supplementation of Arg or Cit to RP resulted in increased femur ash on d 35 (P < 0.05). Thus, feeding the NP diets is necessary to maintain growth performance in broilers regardless of the temperature conditions.

Recovery of Gelatin from Bovine Skin with the Aid of Pepsin and Its Effects on the Characteristics of the Extracted Gelatin

Pepsin enzyme was used to pretreat the bovine skin at the rate of 5, 15, and 25 units of enzyme/g of skin to recover gelatin, and the recovered gelatins were referred to as Pe5, Pe15, and Pe25, respectively. The gelatin yield increased significantly (p < 0.05) from 18.17% for Pe5 to 24.67% for Pe25 as the level of pepsin increased, but the corresponding gel strength and viscosity decreased significantly (p < 0.05) from 215.49 to 56.06 g and 9.17 to 8.17 mPa·s for Pe5 and Pe25, respectively. β- and α1- and α2-chains were degraded entirely in all the gelatins samples as observed in protein pattern elaborated by gel electrophoresis. ¹H nuclear magnetic resonance (¹H NMR) analysis indicated the coiled structure of gelatin protein chains. The lowest amide III amplitude of Pe25 as found by Fourier transform infrared (FTIR) spectroscopy indicated that α-helix structure of protein chains were lost to more irregular coiled structure. Thus, it could be summarized that pepsin might be used at the lower level (5 units/g of wet skin) to extract gelatin from bovine skin with good functional properties and at higher level (15/25 units/g of wet skin) to obtain gelatin of industrial grade with high yield.

Broiler production challenges in the tropics: A review

Under tropical climate, broiler production is encumbered by several constraints which make it difficult for them to attain their genetic potential. The scarcity and high price of poultry feed and veterinary services and the harsh environmental conditions with respect to thermal stress are some of the challenges that hinder optimal growth of the birds. Limited availability of feedstuffs, including crucial feed ingredients like maize and oil seedcakes, is an important challenge to the sector, since feed still represents a major cost of producing broiler chickens. Additionally, the problem of climate change, which has become a global concern, is the main problem in broiler production under hot and humid climate. Under high ambient temperature, feed intake decreases, carbohydrates metabolism and protein synthesis efficiency are disturbed. Lipid utilization is lower and glucose or insulin homeostasis is altered while fat deposition and oxidative stress increases. Several strategies are used to ameliorate the effect of heat stress in poultry. The objective of this review was to summarize the challenge in broiler production under hot and humid climate and different approaches to fight heat stress in poultry.

Interorgan Metabolism, Nutritional Impacts, and Safety of Dietary L-Glutamate and L-Glutamine in Poultry

L-glutamine (Gln) is the most abundant amino acid (AA) in the plasma and skeletal muscle of poultry, and L-glutamate (Glu) is among the most abundant AAs in the whole bodies of all avian tissues. During the first-pass through the small intestine into the portal circulation, dietary Glu is extensively oxidized to CO₂, but dietary Gln undergoes limited catabolism in birds. Their extra-intestinal tissues (e.g., skeletal muscle, kidneys, and lymphoid organs) have a high capacity to degrade Gln. To maintain Glu and Gln homeostasis in the body, they are actively synthesized from branched-chain AAs (abundant AAs in both plant and animal proteins) and glucose via interorgan metabolism involving primarily the skeletal muscle, heart, adipose tissue, and brain. In addition, ammonia (produced from the general catabolism of AAs) and α-ketoglutarate (α-KG, derived primarily from glucose) serve as substrates for the synthesis of Glu and Gln in avian tissues, particularly the liver. Over the past 20 years, there has been growing interest in Glu and Gln metabolism in the chicken, which is an agriculturally important species and also a useful model for studying some aspects of human physiology and diseases. Increasing evidence shows that the adequate supply of dietary Glu and Gln is crucial for the optimum growth, anti-oxidative responses, productivity, and health of chickens, ducklings, turkeys, and laying fowl, particularly under stress conditions. Like mammals, poultry have dietary requirements for both Glu and Gln. Based on feed intake, tissue integrity, growth performance, and health status, birds can tolerate up to 12% Glu and 3.5% Gln in diets (on the dry matter basis). Glu and Gln are quantitatively major nutrients for chickens and other avian species to support their maximum growth, production, and feed efficiency, as well as their optimum health and well-being.

Amino Acid Nutrition and Metabolism in Chickens

Both poultry meat and eggs provide high-quality animal protein [containing sufficient amounts and proper ratios of amino acids (AAs)] for human consumption and, therefore, play an important role in the growth, development, and health of all individuals. Because there are growing concerns about the suboptimal efficiencies of poultry production and its impact on environmental sustainability, much attention has been paid to the formulation of low-protein diets and precision nutrition through the addition of low-cost crystalline AAs or alternative sources of animal-protein feedstuffs. This necessitates a better understanding of AA nutrition and metabolism in chickens. Although historic nutrition research has focused on nutritionally essential amino acids (EAAs) that are not synthesized or are inadequately synthesized in the body, increasing evidence shows that the traditionally classified nutritionally nonessential amino acids (NEAAs), such as glutamine and glutamate, have physiological and regulatory roles other than protein synthesis in chicken growth and egg production. In addition, like other avian species, chickens do not synthesize adequately glycine or proline (the most abundant AAs in the body but present in plant-source feedstuffs at low content) relative to their nutritional and physiological needs. Therefore, these two AAs must be sufficient in poultry diets. Animal proteins (including ruminant meat & bone meal and hydrolyzed feather meal) are abundant sources of both glycine and proline in chicken nutrition. Clearly, chickens (including broilers and laying hens) have dietary requirements for all proteinogenic AAs to achieve their maximum productivity and maintain optimum health particularly under adverse conditions such as heat stress and disease. This is a paradigm shift in poultry nutrition from the 70-year-old "ideal protein" concept that concerned only about EAAs to the focus of functional AAs that include both EAAs and NEAAs.

Autolysis of bovine skin, its endogenous proteases, protease inhibitors and their effects on quality characteristics of extracted gelatin

The autolysis of pretreated bovine skin (PBS) (treated with 0.1 M NaOH and 1% HCl), its endogenous proteases, inhibitors and their effects on quality attributes of gelatin were examined. PBS was subjected to different temperatures (20-90 °C) and pH (2-9) and treated with different protease inhibitors. Maximum autolytic activity of PBS was observed at 40 °C and pH 5. Ethylene-bis (oxyethylenenitrilo) tetraacetic acid (EGTA) was the most effective in impeding the degradation of γ-, β- and α- chains of PBS protein indicating that metallocollagenases were the predominant endogenous proteases in bovine skin. Gelatin was extracted in the absence (GAE) and presence (GPE) of EGTA, and EGTA with papain enzyme (GPEP). GPEP had a higher yield and lower gel strength than GEA and GPE. Metallocollagenases partook in the degradation of gelatin thereby affecting its functional properties. Pretreating PBS with or without EGTA, and papain influenced the quality attributes of gelatin.

Effects of Ultrasound Assisted Extraction in Conjugation with Aid of Actinidin on the Molecular and Physicochemical Properties of Bovine Hide Gelatin

Actinidin was used to pretreat the bovine hide and ultrasonic wave (53 kHz and 500 W) was used for the time durations of 2, 4 and 6 h at 60 °C to extract gelatin samples (UA2, UA4 and UA6, respectively). Control (UAC) gelatin was extracted using ultrasound for 6 h at 60 °C without enzyme pretreatment. There was significant (p < 0.05) increase in gelatin yield as the time duration of ultrasound treatment increased with UA6 giving the highest yield of 19.65%. Gel strength and viscosity of UAC and UA6 extracted gelatin samples were 627.53 and 502.16 g and 16.33 and 15.60 mPa.s, respectively. Longer duration of ultrasound treatment increased amino acids content of the extracted gelatin and UAC exhibited the highest content of amino acids. Progressive degradation of polypeptide chains was observed in the protein pattern of the extracted gelatin as the time duration of ultrasound extraction increased. Fourier transform infrared (FTIR) spectroscopy depicted loss of molecular order and degradation in UA6. Scanning electron microscopy (SEM) revealed protein aggregation and network formation in the gelatin samples with increasing time of ultrasound treatment. The study indicated that ultrasound assisted gelatin extraction using actinidin exhibited high yield with good quality gelatin.

Growth performance, duodenal morphology and the caecal microbial population in female broiler chickens fed glycine-fortified low protein diets under heat stress conditions

1. This study was undertaken to examine the effect of feeding glycine (Gly)-fortified low protein (LP) diets on the growth performance, duodenal morphology and caecal microbial populations of broiler chickens raised under unheated, cyclic or constant heat stress environmental conditions. 2. From d 1 to 21 (starter phase), an equivalent number of birds were fed either a normal protein (NP) diet or a LP diet fortified with Gly. From d 22 to 42 (grower phase), an equivalent number of birds from each starter diet were distributed to one of the following dietary groups: (i) an NP diet during the starter and grower phases (NPNP), (ii) an NP diet during the starter phase and a LP diet during the grower phase (NPLP), (iii) an LP diet during the starter phase and an NP diet during the grower phase (LPNP) or (iv) LP diets during both phases (LPLP). 3. Commencing from d 22, an equivalent number of birds from each dietary group were exposed to (i) 23 ± 1°C throughout (unheated), (ii) 34 ± 1°C for 7 h each day from 10:00 to 17:00 (cyclic heat) or (iii) 34 ± 1°C throughout (constant heat). 4. Feeding the LP diet during the starter phase resulted in feed intake (FI), weight gain (WG), feed conversion ratios (FCR) and energy efficiency ratios (EER) similar to those for the NP diet. The birds fed the LP diet had a significantly higher protein efficiency ratio (PER) compared with the birds fed the NP diet. 5. During the grower phase, there were significant diet × temperature interactions for F, WG, FCR, PER, EER, villus height, crypt depth and caecal Clostridia. The birds fed the NPLP and LPLP diets had lower FI, WG and EER, higher FCR, shorter villus height and crypt depth and higher caecal Clostridia compared with the birds fed LPNP and NPNP diets under constant heat stress. However, feeding birds the NPLP and LPLP diets resulted in FI, WG, EER, FCR, morphology parameters and caecal Clostridia equivalent to the birds fed LPNP and NPNP diets, as well as improved PER, under unheated and cyclic heat stress conditions. 6. In conclusion, our results indicate that Gly-fortified LP diets can be fed to broilers under normal and acute heat stress environmental conditions without any adverse effects on performance. However, the use of such LP diets can be detrimental to broilers under chronic heat stress conditions.

Endogenous Synthesis of Amino Acids Limits Growth, Lactation, and Reproduction in Animals

Amino acids (AAs) are building blocks of protein. Eight AAs (Ala, Asn, Asp, Glu, Gln, Gly, Pro, and Ser) are formed by all animals, whereas de novo synthesis of Arg occurs in a species-specific manner in most mammals (e.g., humans, pigs, and rats). Synthesizable AAs were traditionally classified as nutritionally nonessential for animals, because they were thought to be formed in sufficient amounts. However, this assumption is not supported by evidence showing that 1) rats grow slowly when their diets do not contain Arg, Glu, or Gln despite adequate provision of all other proteinogenous AAs; 2) pigs cannot achieve maximum growth, lactation, or reproduction performance when fed corn- and soybean meal-based diets meeting National Research Council-recommended requirements of protein and AAs without supplemental Arg, Glu, Gln, Gly, or Pro; 3) chickens exhibit increases in lean tissue gain and feed efficiency when their diets are supplemented with Glu, Gln, Gly, and Pro; 4) lactating cows cannot obtain maximum milk protein production without a postruminal supply of Gln or Pro; 5) fish cannot achieve maximum growth when diets do not contain Gln or Pro; and 6) men fail to sustain spermatogenesis when fed an Arg-deficient diet. Quantitative analysis of nitrogen metabolism showed that AA synthesis in animals is constrained by both precursor availability and enzyme activity. Taken together, these findings support the conclusion that the endogenous synthesis of AAs limits growth, lactation, and reproduction in animals. This new knowledge can guide the optimization of human nutrition for improving health and well-being.