Dietary non-phytate phosphorus requirements for optimal productive and reproductive performance, and egg and tibial quality in egg-type duck breeders.

Optimal dietary non-phytate phosphorus (NPP) is essential in poultry to maximise productive and reproductive performance, along with indices of egg and bone quality. This study aimed to establish the NPP requirements of egg-type duck breeders aged from 54 to 80 weeks on the following traits: egg production, egg incubation, egg quality, tibial characteristics, reproductive organ, plasma indices, and the expression of genes related to phosphorus absorption. Longyan duck breeders aged 54 weeks (n = 300) were randomly allotted to five treatments, each containing six replicates of 10 individually caged birds. Birds were fed corn-soybean meal-based diets containing 0.18, 0.25, 0.32, 0.38, and 0.45% NPP/kg for 27 weeks. The tested dietary NPP levels did not affect egg production or egg quality indices. The hatchling weight of ducklings increased (quadratic, P < 0.01) as dietary NPP level increased, and the highest value occurred with 0.25% NPP. The number of large yellow follicles (LYF), and the relative weights of LYF and ovary showed linear and quadratic responses to dietary NPP levels; the lowest number and relative weight of LYF occurred with 0.38% NPP, and the lowest ovarian weight was obtained with 0.25% NPP. There were no differences in tibial length, breaking strength, and mineral density in response to dietary NPP levels. In contrast, tibial content of Ca increased (linear, P < 0.01) with dietary NPP levels increasing from 0.18 to 0.45%, and the tibial content of P increased at 0.32% NPP and the higher dietary NPP levels. Plasma concentration of P showed a quadratic (P < 0.05) response to the dietary NPP levels, where the highest value was seen at 0.38% NPP. In conclusion, dietary NPP levels from 0.18 to 0.45% had no effects on egg production, and egg and tibial quality of duck breeders. The duck breeders fed a diet with 0.25% NPP showed the highest hatchling weight of their offspring, while those fed 0.38% NPP had the lowest number and relative weight of LYF. These results indicated that the diet with 0.25% NPP can be used in egg-type duck breeders to improve the hatchling weight of their offspring, without adverse effects on their productivity. The regression model indicated that the maximal hatchling weight of ducklings was obtained from duck breeders fed the diet with 0.30% NPP.

Interactive effects of dietary amino acid density and environmental temperature on growth performance and expression of selected amino acid transporters, water channels, and stress-related transcripts.

Exposure to heat stress (HS) is one of the challenges facing the broiler industry worldwide. Various nutritional strategies have been suggested, such as altering dietary concentrations of some nutrients. Thus, we evaluated feeding different amino acid (AA) densities on live performance, Pectoralis (P.) muscles, and expression of selected AA transporters, water channels, and stress-related transcripts in a fast-growing broiler strain. Ross 308 chicks (n = 576) were randomly assigned to 4 dietary treatments (24 reps, 6 chicks per rep), differing in AA density (110, 100, 90, and 80% of a breeder's AA specifications). During 24 to 36 days of age, half of the birds were kept at a thermoneutral (TN) temperature of 20°C, whereas the other half were subjected to HS at 32° C for 8 h daily, making the treatment design a 4 × 2. The results revealed no interaction between housing temperature and AA density on growth performance or P. muscles weights. Feeding 80% AAs depressed BWG, FCR, and P. muscles at 36 d (P < 0.001). There was an interaction (P < 0.001) between AA density and temperature on the expression of all examined genes. Reducing the AA density beyond 100% upregulated the expression of AA transporter (CAT1, B0AT, b0,+AT, SNAT1, LAT1), HSP70, HSP90, glucocorticoid receptor (GR), and AQP3 in the TN birds' jejunum. Whereas in the HS birds, inconsistent expressions were observed in the jejunum, of which CAT1, B0AT, and LAT1 were markedly downregulated as AA density was reduced. In P. major of TN birds, reducing AA density resulted in upregulating the expression of all AA transporters, HSP70, GR, and AQP1, while downregulating HSP90 and AQP9. In contrast, AA reduction markedly downregulated CAT1, B0AT, and LAT1 in the P. major of HS birds. These findings indicate that the dietary AA level alters the expression of various genes involved in AA uptake, protein folding, and water transport. The magnitude of alteration is also dependent on the housing temperature. Furthermore, the results highlight the importance of adequate AA nutrition for fast-growing chickens under HS.

Estimation of calcium requirements for optimal productive and reproductive performance, eggshell and tibial quality in egg-type duck breeders.

Optimizing the dietary calcium (Ca) level is essential to maximize the eggshell quality, egg production and bone formation in poultry. This study aimed to establish the Ca requirements of egg-type duck breeders from 23 to 57 weeks of age on egg production, eggshell, incubation, tibial, plasma and ovary-related indices, as well as the expression of matrix protein-related genes. Totally, 450 Longyan duck breeders aged 21 weeks of age were allotted randomly into five treatments, each with six replicates of 15 individually caged birds. The data collection started from 23 weeks of age and continued over the following 35 weeks. The five groups corresponded to five dietary treatments containing either 2.8%, 3.2%, 3.6%, 4.0% or 4.4% Ca. The tested dietary Ca levels increased (linear, P <0.01) egg production and egg mass, and linearly improved (P <0.01) the feed conversion ratio (FCR). Increasing the dietary Ca levels from 2.8% to 4.4% increased (P <0.01) the eggshell thickness and eggshell content. The tested Ca levels showed a quadratic effect on eggshell thickness and ovarian weight (P <0.01); the highest values were obtained with the Ca levels 4.0% and 3.6%, respectively. Dietary Ca levels affected the small yellow follicles (SYF) number and SYF weight/ovarian weight, and the linear response (P <0.01) was significant vis-à-vis SYF number. In addition, dietary Ca levels increased (P <0.05) the tibial dry weight, breaking strength, mineral density and ash content. Plasma and tibial phosphorus concentration exhibited a quadratic (P <0.01) response to dietary Ca levels. Plasma calcitonin concentration linearly (P <0.01) increased as dietary Ca levels increased. The relative expression of carbonic anhydrase 2 in the uterus rose (P <0.01) with the increment of dietary Ca levels, and the highest value was obtained with 3.2% Ca. In conclusion, Longyan duck breeders fed a diet with 4.0% Ca had superior eggshell and tibial quality, while those fed a diet with 3.6% Ca had the heaviest ovarian weights. The regression model indicated that the dietary Ca levels 3.86%, 3.48% and 4.00% are optimal levels to obtain maximum eggshell thickness, ovarian weight and tibial mineral density, respectively.

Sodium and chloride requirements of yellow-feathered chickens between 22 and 42 days of age.

Sodium and chloride are the key factors maintaining normal osmotic pressure (OSM) and volume of the extracellular fluid, and influencing the acid-base balance of body fluids. The experiment was conducted to investigate the effects of dietary Na+ and Cl- level on growth performance, excreta moisture, blood biochemical parameters, intestinal Na+-glucose transporter 1 (SGLT1) messenger RNA (mRNA), and Na+-H+ exchanger 2 (NHE2) mRNA, and to estimate the optimal dietary sodium and chlorine level for yellow-feathered chickens from 22 to 42days. A total of 900 22-day-old Lingnan yellow-feathered male chickens were randomly allotted to five treatments, each of which included six replicates of 30 chickens per floor pen. The basal control diet was based on corn and soybean meal (without added NaCl and NaHCO3). Treatments 2 to 5 consisted of the basal diet supplemented with equal weights of Na+ and Cl-, constituting 0.1%, 0.2%, 0.3% and 0.4% of the diets. Supplemental dietary Na+ and Cl- improved the growth performance (P<0.05). Average daily gain (ADG) showed a quadratic broken-line regression to increasing dietary Na+ and Cl- (R2=0.979, P<0.001), and reached a plateau at 0.1%. Supplemental Na+ and Cl- increased (P<0.05) serum Na+ and OSM in serum and showed a quadratic broken-line regression (R2=0.997, P=0.004) at 0.11%. However, supplemental Na+ and Cl- decreased (P<0.05) serum levels of K+, glucose (GLU) and triglyceride. Higher levels of Na+and Cl- decreased duodenal NHE2 transcripts (P<0.05), but had no effect on ileal SGLT1 transcripts. The activity of Na+ /K+-ATPase in the duodenum decreased (P<0.05) with higher levels of dietary Na+ and Cl-. In conclusion, the optimal dietary Na+ and Cl- requirements for yellow-feathered chickens in the grower phase, from 22 to 42 days of age, to optimize ADG, serum Na+, OSM, K+ and GLU were 0.10%, 0.11%, 0.11%,0.17% and 0.16%, respectively, by regression analysis.

Productivity, reproductive performance, and fat deposition of laying duck breeders in response to concentrations of dietary energy and protein.

This study evaluated the optimal concentrations of dietary ME and CP for the productivity, reproductive performance, and fat deposition in laying duck breeders aged from 29 to 45 wk. Using a 3 × 3 factorial arrangement of treatments, 648 Longyan laying duck breeders with similar BW were randomly assigned to experimental diets of 2,600 (HME = high ME), 2,500 (MME = medium ME), or 2,400 (LME = low ME) kcal of ME/kg, each containing 19% (HCP = high CP), 18% (MCP = medium CP), or 17% (LCP = low CP) CP. Each dietary treatment contained 6 replicates of 12 birds each. Compared with birds fed the LCP diet, the egg production and egg mass were higher in birds fed HCP and MCP (P < 0.01), with better feed conversion (P < 0.01). Interactions were detected between ME and CP levels in egg production, egg mass, and feed conversion ratio as the LMEMCP diet was the best (P < 0.05). The birds fed MME (P < 0.05) had the lowest abdominal fat. The percentage of healthy ducklings was affected by maternal dietary CP (P < 0.05) with the HCP being the highest. The weight of large yellow follicles/ovarian weight was higher in birds fed HCP and MCP (P < 0.05), whereas the weight of small yellow follicles/ovarian weight was higher in birds fed HCP and LCP (P < 0.05). The hepatic transcript abundances of genes for very low density apolipoprotein-II and carnitine palmitoyltransferase-1A (CPT-1A) were lowest in birds fed MCP, whereas the highest abundance of CPT-1A transcripts was found in birds fed MME. These results revealed that the diets containing ME of 12.9 kcal/g protein optimized both egg production and egg mass, while the feed conversion was optimized at 12.8 kcal ME/g protein. Using ME to CP ratio of 12.9 kcal/g protein, i.e., 2,451 kcal ME/kg at 19% CP, maximized the reproductive performance and hatchling outcome of Longyan laying duck breeders.

Effects of dietary threonine supplementation on intestinal barrier function and gut microbiota of laying hens.

The effects of supplemental dietary threonine (Thr) on laying performance, expression of intestinal mucin 2 (MUC2) and secretory IgA (sIgA), and intestinal microbiota of laying hens fed a low CP diet were investigated. A total of 240 Lohmann Brown laying hens, 28 wk of age, was allocated to 3 dietary treatments, each of which included 5 replicates of 16 hens. Hens were fed a control diet (16% CP), a low CP diet (14% CP), or a low CP diet supplemented with 0.3% L-Thr for 12 weeks. Chemical analyses of the diets for Thr are 0.49, 0.45, and 0.69%, respectively. Lowering dietary CP impaired egg production and egg mass of laying hens. Dietary Thr supplementation to the low CP diet increased (P < 0.05) egg production and egg mass. In addition, ileal sIgA contents and MUC2 and sIgA mRNA expression were increased (P < 0.05) by dietary Thr addition. Dietary CP reduction reduced (P < 0.05) intestinal bacterial diversity, whereas dietary Thr supplementation to the low CP diet recovered the bacteria diversity and significantly increased the abundance of potential beneficial bacteria. In conclusion, dietary Thr supplementation to a low CP diet could affect intestinal health and hence productivity via regulating intestinal mucin and sIgA expression, and microbial population of laying hens.

Effect of dietary threonine on laying performance and intestinal immunity of laying hens fed low-crude-protein diets during the peak production period.

Threonine (Thr) may be a limiting amino acid for laying hens fed diets with lowered protein level. An experiment was conducted to examine laying performance, and the intestinal immune function of laying hens provided diets varying in digestible Thr levels. Lohmann Brown laying hens (n = 480), 28 weeks of age, were allocated to six dietary treatments, each of which included five replicates of 16 hens. Dietary crude protein (CP) 16.18% diet was offered as the positive control diet. L-Thr was added to the negative diet (14.16% CP) by 0, 1.0, 2.0, 3.0 and 4.0 g/kg, corresponding 0.44%, 0.43%, 0.49%, 0.57%, 0.66% and 0.74% digestible Thr. At 40 weeks, a reduction in CP level decreased laying performance (p < 0.05). In the low CP, increasing dietary Thr increased (p < 0.05) egg production and egg mass and rose to a plateau between 0.57% and 0.66%. The hens fed 0.66% Thr showed the lowest value (p < 0.05) of feed conversion ratio (FCR). Serum level of uric acid showed the lowest values (p < 0.05) at 0.57-0.66%. In addition, serum-free Thr maximized (p < 0.05) between 0.66% and 0.74%. Digestive trypsin activity decreased (p < 0.05) when hens fed the low-CP diet compared with hens fed CP (16.18%) and hens fed 0.57-0.66%. Expressions of ileal MUC2 mRNA maximized (p < 0.05) at 0.66% Thr. Occludin mRNA increased with increasing Thr level (p < 0.05). sIgA mRNA reached to the maximum level (p < 0.05) at 0.66% and 0.74% Thr. INF-γ mRNA reached to the lowest level (p < 0.05) at 0.65%. Expressions of ileal IL-2, IL-6, IL-1ß mRNA decreased with increasing Thr level (p < 0.05). In conclusion, Thr supplementation resulting in optimal laying performance and stimulated the mucosal immune system, suggesting that it is a limiting amino acid in the low-crude-protein diet of laying hens during the peak production period.

Effects of dietary L-isoleucine on laying performance and immunomodulation of laying hens.

Isoleucine may be a limiting amino acid for laying hens fed diets with a lowered protein level. An experiment was conducted to examine laying performance and the immune function of laying hens provided diets varying in digestible isoleucine levels during the peak production period. A total number of 400 Lohmann Brown laying hens, 28 wk of age, were allocated to 5 dietary treatment groups, each of which included 5 replicates of 16 hens per replicate (4 cages / replicate; 80 hens / treatment). L-isoleucine was added to the experimental diet (14% CP) containing synthetic amino (methionine, lysine, threonine, tryptophan, and valine) by zero, 1.0, 2.0, 3.0, and 4.0 g/kg, corresponding to 0.54%, 0.64%, 0.74%, 0.84, and 0.94% digestible isoleucine, respectively. At the end of the experiment (wk 40), dietary isoleucine did not affect laying performance or egg quality. Serum albumin concentration increased quadratically (P < 0.05) in response to digestible dietary isoleucine at 0.74%. Serum free isoleucine and lysine increased (P < 0.05) in response to digestible dietary isoleucine at 0.74%. Digestible dietary isoleucine levels did not affect the serum concentrations of total antioxidative capability (T-AOC), total superoxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA), and CuZn-superoxide dismutase (CuZn-SOD). There was no significant (P > 0.05) response of excess digestible isoleucine level on the serum level of IgG, IgA, or IgM. In addition, dietary isoleucine levels did not affect the concentrations of secretory immunoglobulin A (sIgA), tumor necrosis factor alpha (TNFα), or interleukin (IL-2 and IL-6) in the ileum. Also, expressions of ileal MUC2 mRNA, sIgA mRNA, and IL-1ß mRNA were not changed (P > 0.05) by excess digestible isoleucine level. Furthermore, excess digestible isoleucine level did not change mRNA expression of ileal tight junction protein (claudin-1 and occludin). No effect occurred when isoleucine was supplemented, suggesting that it is not a limiting amino acid in the low crude protein diet on laying performance and intestinal mucosal immune.

L-arginine upregulates the gene expression of target of rapamycin signaling pathway and stimulates protein synthesis in chicken intestinal epithelial cells.

L-arginine (Arg) is an indispensable amino acid in avians and is required for growth. The aim of this study was to investigate the effects of L-Arg on protein synthesis and genes expression involved in target of rapamycin (TOR) signaling pathway in chicken enterocytes. Cells were cultured for 4 days in L-Arg-free Dulbecco's modified Eagle's medium containing 10, 100, 200, 400, or 600 µM L-Arg. Cell growth, cell cycle, protein synthesis, and protein degradation as well as mRNA expression levels of TOR, ribosomal protein S6 kinase 1 (S6K1), and eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) were determined. The results showed that cell viability was enhanced by L-Arg with a maximal response at 10 to 400 µM. Increasing extracellular concentrations of L-Arg from 10 to 400 µM increased the cells in S and G2/M phase to a significant extent and decreased cell numbers in G0/G1 phase. Further more, addition of 100, 200, or 400 µM L-Arg to culture medium increased protein synthesis and reduced protein degradation in chicken intestinal epithelial cells. Consistent with the data on cell growth and protein turnover, supplementation of 100, 200, or 400 µM L-Arg increased the mRNA abundances of TOR, 4E-BP1, and S6K1. It was concluded the action of L-Arg involves in upregulating the genes expression of TOR cell signaling pathway which increases protein synthesis and reduces protein degradation.

Effect of excess dietary L-valine on laying hen performance, egg quality, serum free amino acids, immune function and antioxidant enzyme activity.

1. The aim of this study was to evaluate the tolerance of laying hens for an excessive L-valine (L-val) supply on laying performance, egg quality, serum free amino acids, immune function and antioxidant enzyme activities of laying hens. 2. A total of 720 HyLine Brown hens were allocated to 5 dietary treatment groups, each of which included 6 replicates of 24 hens, from 40 to 47 weeks of age. Graded amounts of L-val were added to the basal diet to achieve concentrations of 0 (control), 1, 2, 3 and 4 g/kg, respectively, in the experimental diets. 3. Supplementing the diet with L-val did not affect egg production, egg mass, egg weight, feed conversion ratio (FCR) or egg quality. The average daily feed intake response to supplemental L-val was quadratic and was maximised at 2.0 g L-val/kg diet. No differences were observed for total protein, total amino acids, blood urea nitrogen (BUN), uric acid, lactate dehydrogenase (LDH), alkaline phosphatase (AKP), Ca and P concentrations among the treatments. 4. Serum albumin concentration increased significantly in response to supplemental L-val and was also maximised at 2.0 g/kg. In addition, serum glucose increased quadratically to peak at 2.0 g L-val/kg diet. Serum free valine increased as L-val concentration increased to 2.0 g/kg diet and then decreased linearly. 5. Supplementation of L-val did not affect the serum concentrations of total antioxidative capability (T-AOC), superoxide dismutase (SOD) and malondialdehyde (MDA). L-val supplementation did not affect the concentrations of immunoglobulins IgG, IgA, IgM and complements (C3 and C4). Serum concentration of triiodothyronine (T3) increased significantly at 2.0 g L-val/kg diet. 6. It is concluded that high concentrations of L-val are tolerated and can be successfully supplemented into diets without detrimental effects on laying performance or immune function of laying hens.

Evaluating the impact of excess dietary tryptophan on laying performance and immune function of laying hens reared under hot and humid summer conditions.

1. Tryptophan (Trp), besides its role as an essential amino acid in protein synthesis, may also have other important effects on laying hens under summer conditions. 2. Babcock Brown layers (n = 768), 40 weeks of age, were allocated to 4 treatment groups, each of which included 6 replicates of 32 hens. Each group received the same basal diet, formulated with maize and soybean meal, for 8 weeks. Hens were fed on the basal diet with 0·0, 0·2, 0·4, and 0·8 g/kg L-Trp to achieve dietary concentrations of 1·7, 1·9 g/kg, 2·1 g/kg or 2·5 g/kg of Trp, respectively. 3. Supplementing L-Trp had no affect on laying performance. Adding 0·2 or 0·4 g/kg L-Trp improved egg shell strength compared with those fed on the control diet. Serum albumin concentration increased at 0·4 g/kg compared with those receiving 0·0 or 0·8 g/kg Trp. The addition of Trp at 0·4 g/kg increased serum IgM concentration quadratically. Serum superoxide dismutase (T-SOD) increased linearly and quadratically at 0·4 g/kg. 4. In conclusion, we suggest that 0·2 to 0·4 g/kg Trp may have beneficial effects on laying hens under conditions of high temperature and humidity.

Posthatch development of intestinal morphology and digestive enzyme activities in domestic pigeons (Columba livia).

The gastrointestinal tract plays an important role in studies of avian ontogenies because of its key function in nutrient intake. The pattern of intestinal development during postnatal growth in domestic pigeons (Columba livia), as an altricial bird, would be different from the pattern observed in precocial poultry. In this study, the intestinal morphology, mucosal enzyme activities, and pancreatic enzyme activities were determined from hatch to 14 d of age in pigeons. Rapid morphological development was observed immediately after hatching. Villus area and crypt depth increased in parallel in the duodenum and jejunum and more slowly in the ileum. Mucosal enzyme activities per gram of duodenum, jejunum, and ileum varied significantly with segment and age. There were also intestinal segment × age interactions, in which enzyme activity increased most dramatically in the jejunum as compared with the duodenum and ileum for sucrase and maltase activity from day of hatch to 8 d, and for alkaline phosphatase activity through 14 d. However, aminopeptidase-N activity increased most dramatically from day of hatch to 3 d in the ileum as compared with the duodenum and jejunum. Changes in carbohydrate-digesting enzymes activity in duodenum, jejunum, ileum, and pancreas are more pronounced than for protein-digesting enzymes activity from 3 d after hatching. Intestinal total enzyme activities exhibited a steady increase, which was highly correlated with BW. Pancreatic enzymes indicated patterns somewhat similar to those for intestinal enzymes. It was concluded that development of the absorptive area and the capacity for hydrolysis in the duodenum, jejunum, and ileum was rapid immediately after hatching, although rates of development were different in the 3 segments. Young pigeons differ from poultry, in whom intestinal and pancreatic digestive enzyme activities per gram of tissue are generally constant or decline during postnatal development. Also, the data seem consistent with the idea that intestinal hydrolysis may be a determining step in digestion and hence growth.

Molecular cloning, characterization, and expression analysis of fatty acid translocase (FAT/CD36) in the pigeon (Columba livia domestica).

Fatty acid translocase (FAT/CD36) is a transmembrane glycoprotein that plays an important role in transporting long-chain fatty acids. In the current study, a full-length cDNA of FAT/CD36 was first cloned from the intestine of White King pigeon by rapid amplification of cDNA ends (RACE) method. The full-length cDNA of pigeon FAT/CD36 was 2,282 bp, including a 5'-untranslated region of 224 bp, a 3'-untranslated region of 642 bp, and an open reading frame of 1,416 bp encoding a protein of 471 amino acids with the predicted molecular weight of 52.7 kDa. Sequence comparison indicated that FAT/CD36 of pigeon had high identity with other avian FAT/CD36. Using quantitative real-time PCR, expression of FAT/CD36 was the greatest in the duodenum at 28 d posthatch, and in the jejunum, the expression of FAT/CD36 at 14 d posthatch was greater than at 8 d but the same as 28 d posthatch. However, in the ileum, expression of FAT/CD36 peaked at embryonic d 15 and 8 d posthatch. The effects of long-chain fatty acids on pigeon FAT/CD36 and peroxisome proliferator activated receptor γ (PPARγ) mRNA expression were also investigated in vitro. It showed that a low concentration (5 µM) of oleic acid, palmitic acid, and linoleic acid can significantly increase FAT/CD36 and PPARγ mRNA level in pigeon jejunum. However, for linolenic acid or arachidonic acid, the induction of both gene expressions needed a higher concentration (50 µM or 250 µM). Two hundred and 50 µM palmitic acid was shown to suppress FAT/CD36 gene expression. The results suggest that FAT/CD36 may be a representative of intestine development in pigeon, and it could be regulated by long-chain fatty acids via PPARγ pathway.

Influence of L-threonine supplementation on goblet cell numbers, histological structure and antioxidant enzyme activities of laying hens reared in a hot and humid climate.

1. A previous experiment in our laboratory found that L-threonine supplementation at 0.2 and 0.3% increased egg production and the concentration of serum IgG, respectively. The objective of this current trial was to determine if both supplementation levels can positively influence histological structure, goblet cell numbers, or antioxidant enzyme activities. 2. Babcock Brown layers (n=576), 40 weeks of age, were allocated to three treatment groups, each of which included 6 replicates of 32 hens. Each group received the same basal diet formulated with maize, peanut meal and crystalline amino acids. L-threonine was added to the basal diet at 0 (control), 0.2, and 0.3%, respectively for 8 weeks. Chemical analysis of the diets for threonine values were 0.47, 0.66 and 0.74 %, respectively. 3. The numbers of goblet cells did not change due to L-threonine supplementation. Also, L-threonine had no affect on the villus height and mucosal thickness. No differences were found due to treatments among groups in the activity of alkaline phosphatase (ALP) in jejunum or ileum. L-threonine supplementation at 0.2% maximised the concentration of superoxide dismutases (SOD) in both serum and liver. 4. In conclusion, L-threonine supplementation had no affect on gut morphology but may have an antioxidant function at 0.2%.

Effect of supplemental L-threonine on mucin 2 gene expression and intestine mucosal immune and digestive enzymes activities of laying hens in environments with high temperature and humidity.

In addition to being an essential amino acid in protein synthesis, threonine is an integral component of gut function. To verify the effects of l-threonine on gut function, Babcock Brown layers (n = 960; 40 wk of age) were allocated to 5 dietary treatment groups, each of which included 6 replicates of 32 hens. Each group received the same basal diet formulated with corn, peanut meal, and crystalline amino acids. l-Threonine was added to the basal diet at 0 (control), 0.1, 0.2, 0.3, and 0.4% for 8 wk to achieve 0.47 (NRC), 0.57, 0.67, 0.77, and 0.87% threonine, respectively. Expressions of jejunal and ileal mucin 2 mRNA were increased linearly by increasing l-threonine (P < 0.01). At 0.4% l-threonine, the concentrations of IgA antibody in the mucosa of the ileum increased linearly (P < 0.01). No differences attributable to treatment were found among groups in the activity of digestive enzymes in the jejunum or ileum. It was concluded that dietary threonine requirements as reported in current NRC recommendations are insufficient for modern commercial laying hens raised in summer climates. The results suggest that threonine might function as a nutrient immunomodulator in maintaining intestinal barrier function.