Influence of dietary lysine levels and arginine:lysine ratios on performance of broilers exposed to heat or cold stress during the period of three to six weeks of age

Effects of intermittent cold stimulation on growth performance, meat quality, antioxidant capacity and liver lipid metabolism in broiler chickens

Intermittent cold stimulation (ICS) enhances broilers' resistance to cold stress. Nonetheless, further research is needed to investigate the underlying mechanisms that enhance cold stress resistance. A total of 160 one-day-old male Ross 308 broilers were randomly divided into 2 groups (CC and CS5), with the CC group managing temperature according to the standard for broiler growth stages, while the CS5 group were subjected to cold stimulation at a temperature 3℃ lower than the CC group for 5 h, every 2 d from 15 to 35 d. Sampling was conducted at 36 d (36D), 50 d (50D) and after acute cold stress for 24 h (Y24). First, we examined the effects of ICS on broiler growth performance, meat quality, antioxidant capacity, and lipid metabolism. The results demonstrated that ICS enhanced the performance of broilers to a certain degree. Specifically, the average weight gain in the CS5 group was significantly higher than that of the CC group, and the feed conversion ratio significantly decreased compared to CC at 4 W and 6 W (P ≤ 0.05). Compared with the CC group, cold stimulation significantly reduced drip loss, shearing force, and yellowness (a* value) of chicken meat, while significantly increased redness (b* value) (P ≤ 0.05). At Y24, the levels of T-AOC and GSH-PX in the serum of the CS5 group were significantly higher than those of the CC group, while the level of MDA was significantly lower (P ≤ 0.05). The content of TG, FFA, and VLDL in the serum of the CS5 group was significantly elevated, whereas the level of TC and HDL was significantly lower (P ≤ 0.05). In addition, we further explored whether AMPK-mTOR pathway is involved in the regulation of changes in lipid metabolism and the possible regulatory mechanisms downstream of the signaling pathway. The results showed that ICS significantly upregulated the expression levels of AMPK mRNA and protein in the liver of the CS5 group at 36D and Y24, while significantly down-regulating mTOR (P ≤ 0.05). Compared with the CC group, ICS significantly down-regulated the mRNA expression levels of lipid synthesis and endoplasmic reticulum stress-related genes (SREBP1c, FAS, SCD, ACC, GRP78 and PERK) at 36D and Y24, while significantly up-regulating the mRNA expression levels of lipid decomposition and autophagy-related genes (PPAR and LC3) (P ≤ 0.05). In addition, at Y24, the protein expression levels of endoplasmic reticulum stress-related genes (GRP78) in the CS5 group were significantly lower, while autophagy-related genes (LC3 and ATG7) were significantly higher (P ≤ 0.05). ICS can affect meat quality and lipid metabolism in broilers, and when broilers are subjected to acute cold stress, broilers trained with cold stimulation have stronger lipid metabolism capacity.

Intermittent cold stimulation affects energy metabolism and improves stress resistance in broiler heart

To investigate the effect of intermittent cold stimulation on cardiac energy metabolism and cold resistance of broilers, 288 broilers were divided into 3 groups: control group (CC) and 2 cold stimulation groups (CS3 and CS9). The CS3 and CS9 groups received cold stimulation at temperatures of 3°C and 9°C lower than CC group for 5 h from d 15 to 35. Three groups were subjected to acute cold stress (ACS) of 10°C for 12 and 24 h at 44 d. Performance, cardiac histopathological changes, heat shock proteins (HSPs), and lipid metabolism levels were measured. Results showed that the performance was not different among groups at 22 and 29 d (P > 0.05), but the mRNA levels of Acyl CoA synthase long-chain family member 1 (ACSL1) and acyl-coenzyme oxidase (ACO) in CS group were upregulated compared to CC group (P < 0.05). At 36 d, the performance of the CS3 group was better than the other 2 groups, myocardial structure was normal and other lipid metabolism indexes, except for peroxisome proliferator-activated receptor coactivator 1α (PGC-1α) levels, were similar to those of CC group (P > 0.05). The myocardial fiber disorder, Triglyceride (TG), and leptin (LEP) contents were significantly lower in CS9 group than in CC and CS3 groups at 36 d (P < 0.05). The HSP protein levels were significantly higher in CS group than in CC group before ACS (P < 0.05). After 24 h of ACS, the mRNA of lipid metabolism genes, the protein levels of HSP40 and HSP60, and the contents of TG and LEP in the CS3 group were upregulated compared to other groups. The CC and CS9 groups showed myocardial structure was destroyed, with lower TG and LEP levels compared to before ACS (P < 0.05). Therefore, cold stimulation at 3°C lower than the normal feeding temperature for 5 h did not impair performance but can increase the resistance of broilers to ACS by promoting lipid metabolism.

Effects of cold stress on growth performance, carcass traits and tibia attributes in broiler chickens with thiram-induced dyschondroplasia

The objective of this study was to investigate the effect of cold stress (CS) on growth performance and tibia attributes in broiler chickens with thiram-induced dyschondroplasia (TD). Four hundred 10-day-old male broilers were randomly allocated into four groups including, NT0: normal temperature (NT) without thiram; NT50: NT + thiram; CS0: CS without thiram; and CS50: CS + thiram in a completely randomised. The birds in CS groups were placed at a constant temperature of 15 ± 1°C during 11-20 days. Thiram (50 mg/kg) was added to the diet during 11-14 days to induce TD. Results showed that main effects of CS and thiram significantly decreased body weight and daily weight gain during 11-42 days (p < 0.05). Feed intake in the thiram50 group was significantly lower than the group thiram0 during 25-42 days (p < 0.05). Feed conversion ratio in CS birds was significantly more than NT group during 25-42 days (p < 0.05). On day 16, tibia width (TW) and TW to tibia length (TL) ratio were significantly higher in CS chicks compared to the NT group. TW was significantly higher in thiram50 group than thiram0 group (p < 0.05). On day 19, TL in CS chicks was significantly shorter than NT (p < 0.05). On day 23, growth plate width (GPW) in thiram50 group was significantly higher than thiram0 birds. In general, thiram increased tibial GPW and CS decreased TD severity as well as decreased growth performance in broilers.

L-Citrulline: A novel hypothermic amino acid promoting thermotolerance in heat-exposed chickens

With global warming becoming of increasing concern, poultry farms are experiencing a concomitant increase in heat stress. Chickens are very sensitive to high ambient temperature (HT), so the development of novel nutrients that will help deal with the challenge posed by heat stress is vital. We revealed that L-citrulline (L-Cit) can reduce body temperature in chickens. Orally administered L-Cit solution has been found to provide heat tolerance in chickens and to result in reduced food intake. Heat exposure and oral administration of L-Cit led to increased levels of plasma insulin, whereas heat stress led to a decline in plasma thyroxine. Dietary administration of L-Cit was also shown to be effective to reduce heat stress in broiler chickens. Moreover, L-Cit was found to be metabolized in the liver within 1 h of its administration, and in L-Cit-treated broiler chicks, the Cit-Arginine cycle and the Krebs cycle were found to be active. L-Cit has not yet been approved for inclusion in the poultry diet, so it is important to find alternative sources of L-Cit. Taken together, these findings suggest that L-Cit may serve as an important novel nutrient with the ability to produce heat tolerance in chickens under HT.

A review of heat stress in chickens. Part II: Insights into protein and energy utilization and feeding

With the growing global demand for animal protein and rising temperatures caused by climate change, heat stress (HS) is one of the main emerging environmental challenges for the poultry industry. Commercially-reared birds are particularly sensitive to hot temperatures, so adopting production systems that mitigate the adverse effects of HS on bird performance is essential and requires a holistic approach. Feeding and nutrition can play important roles in limiting the heat load on birds; therefore, this review aims to describe the effects of HS on feed intake (FI) and nutrient digestibility and to highlight feeding strategies and nutritional solutions to potentially mitigate some of the deleterious effects of HS on broiler chickens. The reduction of FI is one of the main behavioral changes induced by hot temperatures as birds attempt to limit heat production associated with the digestion, absorption, and metabolism of nutrients. Although the intensity and length of the heat period influences the type and magnitude of responses, reduced FI explains most of the performance degradation observed in HS broilers, while reduced nutrient digestibility appears to only explain a small proportion of impaired feed efficiency following HS. Targeted feeding strategies, including feed restriction and withdrawal, dual feeding, and wet feeding, have showed some promising results under hot temperatures, but these can be difficult to implement in intensive rearing systems. Concerning diet composition, feeding increased nutrient and energy diets can potentially compensate for decreased FI during HS. Indeed, high energy and high crude protein diets have both been shown to improve bird performance under HS conditions. Specifically, positive results may be obtained with increased added fat concentrations since lipids have a lower thermogenic effect compared to proteins and carbohydrates. Moreover, increased supplementation of some essential amino acids can help support increased amino acid requirements for maintenance functions caused by HS. Further research to better characterize and advance these nutritional strategies will help establish economically viable solutions to enhance productivity, health, welfare, and meat quality of broilers facing HS.

Environmental Stress in Chickens and the Potential Effectiveness of Dietary Vitamin Supplementation

Environmental stressors can promote the vulnerability of animals to infections; it is therefore, essential to understand how stressors affect the immune system, the adaptive capacity of animals to respond, and effective techniques in managing stress. This review highlights scientific evidence regarding environmental stress challenge models and the potential effectiveness of vitamin supplementation. The major environmental stressors discussed are heat and cold stress, feed restriction, stocking density, and pollutants. Much work has been done to identify the effects of environmental stress in broilers and layers, while few involved other types of poultry. Studies indicated that chickens' performance, health, and welfare are compromised when challenged with environmental stress. These stressors result in physiological alterations, behavioral changes, decreased egg and meat quality, tissue and intestinal damage, and high mortalities. The application of vitamins with other nutritional approaches can help in combating these environmental stressors in chickens. Poultry birds do not synthesize sufficient vitamins during stressful periods. It is therefore suggested that chicken diets are supplemented with vitamins when subjected to environmental stress. Combination of vitamins are considered more efficient than the use of individual vitamins in alleviating environmental stress in chickens.

Effects of Cold Exposure on Performance and Skeletal Muscle Fiber in Weaned Piglets

Low-temperature is one of the most significant risks for the animal industry. In light of this, the present study aimed to explore the effects of low-temperature on growth performance, nutrient digestibility, myofiber types and mitochondrial function in weaned piglets. A total of sixteen 21-day-old male Duroc × Landrace × Yorkshire (DLY) piglets were randomly divided into a control group (CON, 26 ± 1 °C) and a low-temperature group (LT, 15 ± 1 °C), with eight duplicate piglets in each group. The trial period lasted for 21 days. We showed that LT not only increased the ADFI (p < 0.05), as well as increasing the diarrhea incidence and diarrhea index of weaned piglets in the early stage of the experiment (p < 0.01), but it also decreased the apparent digestibility of crude protein (CP), organic matter (OM) and dry matter (DM) (p < 0.05). Meanwhile, in the LT group, the mRNA expression of MyHC IIa (p < 0.05) in longissimus dorsi muscle (LM) and MyHC I (p < 0.01) in psoas muscle (PM) were increased, while the mRNA expression of MyHC IIx in PM was decreased (p < 0.05). In addition, LT increased the mRNA expression of mitochondrial function-related genes citrate synthase (CS) and succinate dehydrogenase-b (SDHB) in LM, as well as increased the mRNA expression of CS (p < 0.05) and carnitine palmitoyl transferase-1b (CPT-1b) (p < 0.01) in PM. Furthermore, LT increased the T-AOC activity in serum and LM (p < 0.01), as well as increased the T-SOD activity in PM (p < 0.05). Taken together, these findings showed that low-temperature could negatively affect the growth performance and nutrient digestibility, but resulted in a shift toward oxidative muscle fibers, which may occur through mitochondrial function regulation.

Potential Role of Amino Acids in the Adaptation of Chicks and Market-Age Broilers to Heat Stress

Increased average air temperatures and more frequent and prolonged periods of high ambient temperature (HT) associated with global warming will increasingly affect worldwide poultry production. It is thus important to understand how HT impacts poultry physiology and to identify novel approaches to facilitate improved adaptation and thereby maximize poultry growth, health and welfare. Amino acids play a role in many physiological functions, including stress responses, and their relative demand and metabolism are altered tissue-specifically during exposure to HT. For instance, HT decreases plasma citrulline (Cit) in chicks and leucine (Leu) in the embryonic brain and liver. The physiological significance of these changes in amino acids may involve protection of the body from heat stress. Thus, numerous studies have focused on evaluating the effects of dietary administration of amino acids. It was found that oral l-Cit lowered body temperature and increased thermotolerance in layer chicks. When l-Leu was injected into fertile broiler eggs to examine the cause of reduction of Leu in embryos exposed to HT, in ovo feeding of l-Leu improved thermotolerance in broiler chicks. In ovo injection of l-Leu was also found to inhibit weight loss in market-age broilers exposed to chronic HT, giving rise to the possibility of developing a novel biotechnology aimed at minimizing the economic losses to poultry producers during summer heat stress. These findings and the significance of amino acid metabolism in chicks and market-age broilers under HT are summarized and discussed in this review.

Proper cold stimulation starting at an earlier age can enhance immunity and improve adaptability to cold stress in broilers

The effects of long-term cold stimulation on the immune function of ileum and adaptability to cold stress in broilers were examined. A total of 360 Arbor Acres broilers was divided into 3 groups and four replicates per group. C (control) was reared in normal thermal environment. C-3 and C-12 (treatments) were kept in cold condition of 3 or 12°C lower than the temperature of C from days 8 to 42. At day 42, all the groups were exposed to an acute cold stress challenge, designated as S, S-3, and S-12. The mRNA levels of immune molecules and heat shock proteins as well as oxidative stress-related indicators in ileum tissues, and immunoglobulins contents in serum were examined at 14, 42, and 43 d of age. The C-3 regimen had no adverse effect on production performance, whereas the C-12 regimen reduced the production performance relative to C (P < 0.05). At day 42, C-3 had higher levels of immune indexes (P < 0.05), whereas C-12 had lower levels than C (P < 0.05). No differences in levels of oxidative stress-related indicators were found between C and C-3 at day 42 (P > 0.05). S-3 had higher levels of immune indexes and lower levels of oxidative stress-related indicators (P < 0.05), as compared to S and S-12. The results suggest that 34 d of cold stimulation at 3°C lower than the normal temperature had no adverse impacts on production performance but enhanced the immunity of ileum and adaptability to acute cold challenge in broilers.

Heat stress management in poultry farms: A comprehensive overview

Heat stress causes significant economic losses in poultry production, especially in tropical and arid regions of the world. Several studies have investigated the effects of heat stress on the welfare and productivity of poultry. The harmful impacts of heat stress on different poultry types include decreased growth rates, appetites, feed utilization and laying and impaired meat and egg qualities. Recent studies have focused on the deleterious influences of heat stress on bird behaviour, welfare and reproduction. The primary strategies for mitigating heat stress in poultry farms have included feed supplements and management, but the results have not been consistent. This review article discusses the physiological effects of heat stress on poultry health and production and various management and nutritional approaches to cope with it.

Heat Stress Biomarker Amino Acids and Neuropeptide Afford Thermotolerance in Chicks

With global warming, heat stress is becoming a pressing concern worldwide. In chickens, heat stress reduces food intake and growth, and increases body temperature and stress responses. Although it is believed that young chicks do not experience heat stress as they need a higher ambient temperature to survive, our series of studies in young chicks showed that they are sensitive to heat stress. This review summarizes current knowledge on amino acid metabolisms during heat stress, with special emphasis on the hypothermic functions of l-citrulline (l-Cit) and l-leucine (l-Leu), and the functions of neuropeptide Y (NPY) in terms of body temperature and heat stress regulation in chicks. Amino acid metabolism is severely affected by heat stress. For example, prolonged heat stress reduces plasma l-Cit in chicks and l-Leu in the brain and liver of embryos. l-Cit and l-Leu supplementation affords thermotolerance in young chicks. NPY expression is increased in the brains of heat-exposed chicks. NPY has a hypothermic action under control thermoneutral temperature and heat stress in chicks. The NPY-sub-receptor Y5 is a partial mediator of the hypothermic action of NPY. Further, NPY stimulates brain dopamine concentrations and acts as an anti-stress agent in heat-exposed fasted, but not fed chicks. In conclusion, young chicks can serve as a model animal for the study of heat stress in chickens. l-Cit, l-Leu, and NPY were identified as biomarkers of heat stress, with the potential to afford thermotolerance in chicks.

Determination of the optimum arginine : lysine ratio in broiler diets

The study was conducted to determine the optimum dietary concentration of arginine relative to lysine on the basis of the performance, carcass traits and blood characteristics of 1–35-day-old broilers using a randomised complete block design. One-day-old broilers (n = 1200) were allocated to five dietary treatment groups receiving different arginine:lysine (Arg:Lys) ratios, where the proportion of Arg was progressively increased by increments of 10%, and the concentration of lysine was kept constant; the final ratios were 0.85, 0.95, 1.05, 1.16 and 1.26. Each diet treatment was composed of eight replicates (4 males and 4 females), with 30 chickens each replicate. All broilers were fed in three phases, namely starter, grower and finisher, at 1–10, 11–24 and 25–35 days of age respectively. An increase in the Arg:Lys ratio in the diet from 0.85 to 1.26 linearly (P &lt; 0.001) increased bodyweight gain by 7% and improved feed conversion ratio by 6%. Feed intake and mortality were not significantly (P &gt; 0.05) different among the treatments. Increasing the Arg:Lys ratio in the diet linearly (P &lt; 0.0001) and quadratically (P &lt; 0.05) improved the carcass yield and relative chilled carcass weight respectively. The percentages of breast meat and creatinine and insulin-like growth factor-1 concentrations also linearly (P &lt; 0.0001) increased by 5.5%, 23.0% and 18.0% respectively, with an increasing dietary Arg:Lys ratio. The results of the present study indicated that the highest dietary Arg:Lys ratio (1.26) improved bodyweight gain, feed conversion ratio, breast meat, creatinine and insulin-like growth factor-1. However, the optimum dietary Arg:Lys ratio to improve carcass yield and weight gain in the grower phase (Days 11–24 of age) was at 1.05.

Meta-analysis of the effects of intensive rearing environments on the performance and welfare of broiler chickens

To better understand how relevant intensive systems’ characteristics simultaneously affect the performance and welfare of broiler chickens, a meta-analysis of recent literature was carried out. The study determined the effects of gender, genetics, experimental initial age (EIA, d), stocking density (SD; kg/m²), group size (GS; n), bedding material (yes/no), duration of photoperiod (DP; h), divided scotoperiod (yes/no), feeding phases (1/2/3/>3), environmental control (EC; yes/no), environmental enrichment (yes/no), use of vaccines and other medications (yes/no), experimental duration (d), and relevant 2-way interactions on average daily gain (g/d), average daily feed intake (g/d), FCR (g: g), mortality (%), behavior (%), and gait score (mean value). Predictive equations for response variables were calculated using multiple regression models including a random experiment effect. Among other results, EIA × SD interaction indicated that relatively high SD may improve FCR at older ages, but parallel increased mortality would pose concerns about the actual productive benefits and welfare. Combining large GS and relatively low SD seem to improve performance and decrease flock disturbance. They would also increase leg problems, and so their actual benefits on welfare remain unclear. A gradual increase in FCR seems to occur with longer DP at older EIA (EIA × DP interaction), highlighting the importance of adapting light programs to flock age to optimize performance. The SD × DP and GS × DP interactions predicted increased FCR for longer DP at low SD or large GS, that is, with more effective space available. Longer DP combined with low SD or large GS would overall promote enhanced leg conditions, and therefore welfare. Predictions would not support scotoperiod division from both performance and welfare perspectives. The SD × EC interaction indicated that EC would benefit chicken performance at low SD, although EC would seem to increase leg problems. Our study highlights the complex, interactive nature of production systems’ characteristics on broiler chicken performance and welfare.

Factors affecting adipose tissue development in chickens: A review

The intense genetic selection for rapid growth in broilers has resulted in an increase in voluntary feed intake and growth rate, accompanied by increased fat deposition in adipose tissue depots throughout the body. Adipose tissue expansion is a result of the formation of adipocytes (several processes collectively referred to as adipogenesis) and cellular accumulation of triacylglycerols inside lipid droplets. In mammals, different anatomical depots are metabolically distinct. The molecular and cellular mechanisms underlying adipose tissue development have been characterized in mammalian models, whereas information in avian species is scarce. The purpose of this review is to describe factors regulating adipogenesis in chickens, with an emphasis on dietary factors and the broiler. Results from many studies have demonstrated effects of dietary nutrient composition on adipose tissue development and lipid metabolism. Transcription factors, such as peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding proteins α and β, and sterol regulatory element binding proteins orchestrate a series of cellular events that lead to an increase in activity of fatty acid transport proteins and enzymes that are responsible for triacylglycerol synthesis. Understanding the mechanisms underlying adipose tissue development may provide a practical strategy to affect body composition of the commercial broiler while providing insights on diets that maximize conversion into muscle rather than fat and affect depot-dependent deposition of lipids. Because of the propensity to overeat and become obese, the broiler chicken also represents an attractive biomedical model for eating disorders and obesity in humans.

Orally Administered D-Aspartate Depresses Rectal Temperature and Alters Plasma Triacylglycerol and Glucose Concentrations in Broiler Chicks

L-Aspartate (L-Asp), D-aspartate (D-Asp) or their chemical conjugates plays important physiological roles in regulating food intake, plasma metabolites and thermoregulation in animals. However, there are very few studies available in layers and no reports have been found in broilers. Broilers are very important commercial birds for meat production, so effects of L- or D-Asp in broilers would provide new physiological insight of this strain. Therefore, the purpose of this study was to determine the effect of oral administration of L- or D-Asp on feed intake, rectal temperature and some plasma metabolites in broiler chicks. Broiler chicks (5 days old) were orally administered with different doses (0, 3.75, 7.5 and 15 mmol/kg body weight) of L- or D-Asp. At 120 min after administration of L- or D-Asp, the blood was immediately collected through the jugular vein. The rectal temperature of chicks was measured at 30, 60 and 120 min after administration using a digital thermometer with an accuracy of ±0.1°C, by inserting the thermistor probe in the rectum to a depth of 2 cm. A repeated-measures two-way ANOVA was applied for the analysis of feed intake and rectal temperature. Plasma metabolites were statistically analyzed by one-way ANOVA and regression equations. The study showed that oral administration of both L- and D-Asp did not alter feed intake. However, D-Asp, but not L-Asp, dose-dependently decreased the rectal temperature in chicks. It was also found that D-Asp increased plasma glucose and decreased triacylglycerol concentrations. The changes in plasma metabolites further indicate that D-Asp treatment modulates the energy metabolism in broiler chicks. In conclusion, D-Asp may be a beneficial nutrient not only for layers but also for broilers, since orally administered D-Asp lowered rectal temperature without reducing feed intake.

Effect of arginine supplementation of broiler breeder hens on progeny performance

Fernandes, J. I. M., Murakami, A. E., Gomes de Souza, L. M., Ospina-Rojas, I. C. and Rossi, R. M. 2014. Effect of arginine supplementation of broiler breeder hens on progeny performance. Can. J. Anim. Sci. 94: 313–321. Two experiments were conducted to determine the effects of arginine (Arg) supplementation of broiler breeder hens on the performance, carcass yield, and bone measurements of their progeny. In both experiments, the maternal diet was supplemented with five levels of digestible Arg (0.94, 1.09, 1.24, 1.39 and 1.54%). In exp. 1, a total progeny of 1050 chicks were housed in pens according to maternal diet and fed a typical diet without L-Arg supplementation. In exp. 2, a total progeny of 960 chicks were kept in pens according to maternal diet and fed diets containing supplemental L-Arg from 1.30 to 1.90% in the starter phase and from 1.15 to 1.75% in the grower phase. The data obtained in both experiments were deployed in orthogonal polynomials to allow for an analysis of variance and a regression analysis. In the starter phase, there was a quadratic effect (P<0.05) of Arg level in the maternal diet on the feed:gain ratio of the non-supplemented progeny. In the Arg-supplemented progeny, there was a quadratic effect (P<0.05) of Arg level on the feed intake and feed:gain ratio and a linear increase (P<0.05) in body weight gain, and carcass and breast yields (P<0.05). Femur length, tibia diameter, and the Seedor index of both bones increased linearly (P<0.05) in broilers fed the Arg-supplemented diet. Arg supplementation in the broiler breeder hen diets had little positive effect on the non-supplemented progeny; thus, Arg supplementation in the progeny diet is necessary to optimize performance, carcass yield, and bone quality of these hens’ progeny.

Oral administration of D-aspartate, but not L-aspartate, depresses rectal temperature and alters plasma metabolites in chicks

AIMS

L-Aspartate (L-Asp) and D-aspartate (D-Asp) are physiologically important amino acids in mammals and birds. However, the functions of these amino acids have not yet been fully understood. In this study, we therefore examined the effects of L-Asp and D-Asp in terms of regulating body temperature, plasma metabolites and catecholamines in chicks.

MAIN METHODS

Chicks were first orally administered with different doses (0, 3.75, 7.5 and 15 mmol/kg body weight) of L- or D-Asp to monitor the effects of these amino acids on rectal temperature during 120 min of the experimental period.

KEY FINDINGS

Oral administration of D-Asp, but not of L-Asp, linearly decreased the rectal temperature in chicks. Importantly, orally administered D-Asp led to a significant reduction in body temperature in chicks even under high ambient temperature (HT) conditions. However, centrally administered D-Asp did not significantly influence the body temperature in chicks. As for plasma metabolites and catecholamines, orally administered D-Asp led to decreased triacylglycerol and uric acid concentrations and increased glucose and chlorine concentrations but did not alter plasma catecholamines.

SIGNIFICANCE

These results suggest that oral administration of D-Asp may play a potent role in reducing body temperature under both normal and HT conditions. The alteration of plasma metabolites further indicates that D-Asp may contribute to the regulation of metabolic activity in chicks.

Growth performance and intestinal morphology in broiler chickens produced from hyperthyroid breeder hens

An association between induced maternal hyperthyroidism and a decreased incidence of cold-induced ascites in broiler chickens has been reported recently. There are also reports suggesting that thyroid hormones have an effect on intestine, a high oxygen-demanding organ. The present study aimed to determine whether the ascites-attenuating effect of maternal hyperthyroidism is associated with morphological changes in intestine and with probable adverse effects on growth performance in progeny chicks. Eighty-eight broiler breeder hens were allotted to control or hyperthyroid [HYPER; thyroxine-treated] groups, and artificially inseminated. Hatching eggs (n = 924) were incubated and day-old male chicks (n = 288) were reared for 42 days under standard or low ambient temperature. Plasma thyroxine was higher in the HYPER hens and their embryos at internal pipping. Maternal hyperthyroidism did not adversely affect the feed : gain ratio and carcass weight, whereas cold stress impaired them. A higher relative weight was found at 42 days of age for all intestinal regions at low ambient temperature. The duodenal and jejunal crypt depths (CD) were lower in HYPER group at 7 days of age. Cold exposure decreased the duodenal and jejunal villus height and CD, and increased the ileal goblet cell number at 21 days. On Day 42, higher values were recorded for CD, goblet cell number, and epithelial thickness of different intestinal regions in cold-exposed birds. In conclusion, growth performance was not adversely influenced by maternal hyperthyroidism and its minimal early effect on intestinal morphology does not appear to be the underlying mechanism for decreased incidence of ascites in broilers.

Effects of starter diet supplementation with arginine on broiler production performance and on small intestine morphometry

The effects of starter diet (days 1 to 21) supplemented with arginine (Arg) on the production performance and duodenum and jejunum mucosa morphometry of broilers were studied. Male Cobb broiler chickens (990) were randomly assigned to one of five treatments in a complete random design. Measurements of 33 chicks per treatment were made in six repetitions. The treatments consisted of a basal diet with 1.390% digestible Arg (no supplementation) and four dietary levels (1.490%, 1.590%, 1.690%, and 1.790%), providing a relationship with lysine of 1.103; 1.183; 1.262; 1.341 and 1.421%, respectively. From the age of 22 days on, all birds received conventional grower diet. The data were submitted to regression analysis by polynomial decomposition of the degrees of freedom in relation to the levels of Arg. The Arg supplementation increased (P<0.05) the live weight and the feed conversion ratio without increasing the feed intake of the birds. However, no effect was observed (P>0.05) in the growth phase (days 22 to 42) in the absence of the Arg supplementation. The supplementation of Arg over of NRC recommendation during the starter phase may be necessary for the expression of the maximal weight gain potential in birds. No effect (P<0.05) of Arg dietary supplementation was observed either on small intestine weight and length at any age. However, the duodenum villus:crypt ratio increased and the crypt depth decreased in the first week in response to increasing dietary Arg. It is concluded that broiler Arg dietary supplementation in the starter diet improved production performance and small intestine morphometry, especially in the first week.

Effect of ascorbic acid or increasing metabolizable energy level with or without supplementation of some essential amino acids on productive and physiological traits of slow-growing chicks exposed to chronic heat stress

Four hundred and twenty, 21-day-old slow-growing chicks were divided randomly into seven treatments, each containing five replicates. Each replicate was kept in a 1 × 1-m floor pen. One treatment was kept under thermo-neutral conditions in a semi-open house and fed a corn-soybean meal diet (positive control). The other six groups were kept under chronic heat stress (CHS) at 38 °C and 60% RH for 4 h from 12:00 to 16:00 pm for three successive days per week. Chicks in CHS treatments were fed a corn-soybean meal diet without (negative control) or with increasing metabolizable energy (ME) level by oil supplementation alone, or also with increasing some essential amino acids (EAA) such as methionine (Met), methionine and lysine (Met+Lys) or methionine, lysine and arginine (Met+Lys+Arg) or supplemented with 250 mg of ascorbic acid (AA)/kg. CHS impaired (p < 0.05) growth performance, increased plasma triglycerides and total serum Ca while decreasing (p < 0.05) plasma glucose and total serum protein. Meanwhile 250 mg AA/kg diet or an increasing ME without or with some EAA partially alleviated (p < 0.0001) the negative effect of CHS on growth while increasing (p < 0.05) feed intake and improving (p < 0.05) feed:gain ratio (F:G) and crude protein (CP) digestibility (p < 0.05). AA or increasing ME with or without EAA increased (p < 0.05) percentage dressing, liver and giblets to those of the positive control. AA or increasing ME with or without EAA partially alleviated the negative effect of CHS on blood pH, packed cell volume (PCV), haemoglobin (Hgb), total serum protein and total Ca, plasma glucose and triglyceride, rectal temperature and respiration rate. Increasing ME level improved chickens' tolerance to CHS without a significant difference from those supplemented with AA. However, increasing Met, Lys and Arg concentration did not improve performance over that recorded with increasing ME level alone. Under CHS, 250 mg AA/kg diet or increasing ME level by addition of 3% vegetable oil could be an useful approach to improve productive and physiological traits of slow-growing chicks, which may be applicable also to fast-growing one.

Relação entre os níveis de lisina da dieta e as características de desempenho de codornas de corte EV2, durante o período de crescimento

Estudou-se a exigência de lisina total para a linha EV2 de codornas de corte na fase de crescimento. Foram utilizadas 312 codornas de corte EV2, de ambos os sexos, em delineamento experimental inteiramente ao acaso, cujos tratamentos consistiram de dietas com seis níveis lisina total - 1,4; 1,5; 1,6; 1,7; 1,8 e 1,9% - e quatro repetições de 13 codornas por unidade experimental. Para avaliação do desempenho, estudaram-se peso corporal ao final de cada período (g), ganho de peso (g), consumo alimentar (g) e conversão alimentar (g de alimento/g de peso) durante os períodos experimentais inicial (nascimento ao 21º) e total (nascimento ao 42º dia de idade). No período inicial, houve efeito significativo dos níveis de lisina total da dieta sobre o peso corporal, ganho de peso, consumo e conversão alimentar, com máximo desempenho das codornas nos níveis de 1,66; 1,66; 1,40 e 1,59% de lisina total, respectivamente. Para o período total de criação, houve também efeito quadrático dos níveis de lisina da dieta sobre o peso corporal ao 42º dia, ganho de peso, consumo e conversão alimentar, com os pontos de máximo desempenho estimados em 1,62; 1,62; 1,60 e 1,61%, respectivamente. A exigência de lisina total para o máximo ganho de peso de machos e fêmeas de codornas de corte do nascimento ao 21º dia é estimada em 1,66% e do nascimento ao 42º dia de idade, em 1,62% da dieta.

Methionine+cystine requirement of broiler chickens fed low-density diets under tropical conditions

Two experiments were conducted to determine the M+C requirement of straight-run broiler chickens (Hubbard x Hubbard) during the period 4-21 (Exp. 1) and 21-40 (Exp. 2) days of age. Experiments were conducted during summer months (July-August) in open-sided houses, thus exposing chicks to chronic heat stress. Daily min-max temperature averaged 26-37C (Exp. 1) and 23-36C (Exp. 2). M+C deficient basal diets were formulated to contain low-nutrient-density, i.e., 2750 kcal per kg ME, 20.1% CP (Exp. 1), and 2780 kcal per kg ME, 17.0% CP (Exp. 2). Diets were supplemented with DL-methionine to provide total M+C level ranging from 0.64 to 0.89 % (six increments) and 0.54 to 0.79% (six increments), respectively in experiment 1 and 2. Requirements (0.95 of the maximum quadratic response) were found to be 0.77 and 0.75% total M+C, respectively for gain and feed efficiency, during 4-21 days; and 0.67% total M+C for both gain and feed efficiency during 21-40 days of age. Calculated on the digestible M+C basis, the estimates were 0.67 and 0.65% respectively for gain and feed efficiency during 4-21 days of age; and 0.60% for gain and feed efficiency during 21-40 days of age.

Effects of Temperature During Rearing and Crating on Stress Parameters and Meat Quality of Broilers

Two trials were conducted to study the effects of heat stress during rearing (trial 1) and crating (trial 2) on broiler stress parameters and fear, breast meat quality, and nutrient composition. The relationships between stress parameters and meat quality traits were also determined. Trial 1 consisted of 3 temperature treatments from 3 to 7 wk: control (temperature was 22 degrees C); diurnal cyclic temperature (temperature was 28 degrees C from 1000 to 1700 h and 22 degrees C from 1700 to 1000 h); and constant high temperature (34 degrees C; temperature was 34 degrees C). In trial 2, broilers from the control and 34 degrees C groups in trial 1 were used. Broilers in each group were placed in transport cages. The 9 cages from the control group were divided into 3 groups and placed into 3 rooms at 15, 22, or 34 degrees C for 2 h. The 3 cages from the 34 degrees C group were also held in the room at 34 degrees C (34-34 degrees C). Diurnal cyclic temperature had no effect on BW up to 5 wk of age. The effect of 34 degrees C constant temperature on BW of broilers increased with age. Plasma levels of glucose and albumin increased by 34 degrees C, but no dramatic change in levels occurred when those broilers were crated at 34 degrees C. The heterophil:lymphocyte (H:L) was higher for the 34-34 degrees C broilers and the control broilers in the 34 degrees C room than those from the 22 and 15 degrees C room. Breast muscle glycogen level decreased in broilers reared under diurnal cyclic or high temperatures. A lower pH and higher lightness (L*) and redness values and redness:yellowness were found in meat for broilers from both 34 degrees C and 34-34 degrees C groups. Higher H:L was associated with breast muscle pH according to first-order polynomial regression. The H:L had a significant effect on L* values, which were described by a second-order polynomial regression. Blood glucose level was positively correlated with L* and redness values. Duration of tonic immobility was neither influenced by rearing and crating temperatures nor associated with meat quality parameters.

Dietary arginine silicate inositol complex during the late laying period of quail at different environmental temperatures

Arginine silicate inositol complex (ASIdagger; arginine 49.5%, silicon 8.2%, inositol 25%) is a novel material which is a bioavailable source of silicon and arginine. ASI offers potential benefits for vascular and bone health. Poor eggshell quality has been a major economic concern to commercial egg producers. Poor egg quality, skeletal abnormalities and architectural deterioration of bone tissue are common problems under hot conditions and in older birds. The effects of ASI supplementation on egg production, egg quality, levels of osteocalcin (OC) and bone mineral content were investigated in heat-stressed Japanese quail during the later part of the laying period. The birds were randomly assigned to six treatment groups consisting of six replicates of five birds each in a 2 x 3 factorial arrangement of treatments (temperatures, ASI levels). The birds were kept in wire cages in a temperature-controlled room at either 22 degrees C (TN) or 34 degrees C (HS) for 8 h/d and fed either a basal (control) diet or the basal diet supplemented with either 500 or 1000 g of ASI/kg. Heat exposure reduced egg production, egg quality and bone mineralisation when the basal diet was fed. ASI supplementation had no effect on feed intake or egg production under TN or HS conditions. However, ASI supplementation increased egg weight, shell thickness, shell weight and Haugh unit in both TN and HS groups during the late laying period. Bone mineral density (BMD) was significantly improved by ASI supplementation in both TN and HS groups. Serum osteocalcin (OC) concentrations and alkaline phosphatase (ALP) activity increased linearly with dietary ASI supplementation during the late laying period. The amount of calcium and phosphorus in the excreta decreased, while ash, mineral content, calcium and phosphorus concentrations in tibia increased in ASI-supplemented quail in both TN and HS groups during the late laying period. ASI supplementation significantly improved egg quality and bone mineralisation in quail during the late laying period and did not affect feed consumption or egg production.