Growth and haematological response of indigenous Venda chickens aged 8 to 13 weeks to varying dietary lysine to energy ratios

The effect of feeding varying dietary lysine to energy levels on growth and haematological values of indigenous Venda chickens aged 8 – 13 weeks was evaluated. Four hundred and twenty Venda chickens (BW 362 ± 10 g) were allocated to four dietary treatments in a completely randomized design. Each treatment was replicated seven times, and each replicate had fifteen chickens. Four maize–soya beans‐based diets were formulated. Each diet had similar CP (150 g/kg DM) and lysine (8 g lysine/kg DM) but varying energy levels (11, 12, 13 and 14 MJ ME/kg DM). The birds were reared in a deep litter house; feed and water were provided ad libitum. Data on growth and haematological values were collected and analysed using one‐way analysis of variance. Duncan's test for multiple comparisons was used to test the significant difference between treatment means (p < 0.05). A quadratic equation was used to determine dietary lysine to energy ratios for optimum parameters which were significant difference. Results showed that dietary energy level influenced (p < 0.05) feed intake, feed conversion ratio, live weight, haemoglobin and pack cell volume values of chickens. Dry matter digestibility, metabolizable energy and nitrogen retention not influenced by dietary lysine to energy ratio. Also, white blood cell, red blood cell, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration in female Venda chickens aged 91 days were not influenced by dietary lysine to energy ratio. It is concluded that dietary lysine to energy ratios of 0.672, 0.646, 0.639 and 0.649 optimized feed intake, growth rate, FCR and live weight in indigenous female Venda chickens fed diets containing 8 g of lysine/kg DM, 150 g of CP/kg DM and 11 MJ of ME/kg DM. This has implications in diet formulation for indigenous female Venda chickens.     

Methodologic studies on the metabolism-oriented determination of methionine requirements of broiler chickens

In a preliminary experiment the time course of 35S-excretion following a single injection of 35S-methionine in male broiler chickens was measured for 5 days. Within 2 days 65 to 69% of the amount of 35S excreted during the whole 5-day-period were recovered. Therefore, in the main experiment excrements for 35S measurement were collected only 2 days. During the main experiment starting 7 days posthatching 48 male broiler chickens received diets based on peas and wheat. The basal diet was supplemented with DL-methionine at 8 levels increasing the methionine content from 3.3 to 7.5 g/kg DM or 1,51 to 3.42 g/16 g N and the content of sulphur containing amino acids varied from 6.8 to 11.8 g/kg DM or 3.11 to 5.02 g/16 g N, respectively. Daily body weight gain was followed up to day 30 posthatching and N-balance was estimated during the 21st to 26th day posthatching. Up to day 26 a methionine content of 3.9 g/kg DM was sufficient for maximum weight gain. However, during the last period of the experiment highest weight gains were observed in animals receiving diets with 4.5 or more methionine/kg DM. Highest N-retention (1.2 g N/d) was measured if the diet contained 3.9 g methionine/kg DM or more. At day 28 posthatching 35S-methionine was injected intravenously and the subsequent 35S-excretion was measured. The 35S-excretion started to increase at a methionine content in the diet of 4.5 g/kg DM and continued to rise up to the highest methionine content of 7.5 g/kg DM. The metabolism oriented methionine requirement determination indicates for male broiler chickens at the beginning of the 5th week posthatching a methionine requirement of 3.9 to 4.5 g/kg DM (1.78 to 2.05 g/16 g N) and a requirement of S-containing amino acids of 7.4 to 8.0 g/kg DM (3.38 to 3.65 g/16 g N). The method used is potential in studying the age-dependent changes in methionine requirement.     

Determination of lysine requirement in growing rats as based on the catabolism rate of 14-C- and 15-N-labeled lysine

Male Wistar rats (weighing some 80 g at the start of the experiment) were fed diets containing maize gluten as protein carrier and which was supplemented with amino acids (except lysine) in such way that their concentrations came up to the requirement norms. Lysine was gradually supplemented this resulting in 10 diets of different lysine content (1.6-10.6 g lysine/16 g N). On the 7th experimental day, 4 animals of each group were labelled with 14C-lysine and subjected to 2-hour measuring of 14CO2-excretion. On the following day, the animals were injected i.p. 15N-lysine, the urine being collected over 24 hours to determine 15N-frequency in urine. Both 14CO2-excretion and 15N-frequency in urine were found to remain constant at a lysine content of the diet up to 4.5 g/16 g N and rose steeply from 5.8 g lysine/16 N on. Under the experimental conditions chosen the lysine requirement is deduced to be 5 g/16 g N. This method of lysine requirement determination is highly sensitive and exact because it covers the catabolization of the amino acids under study and not so parameters that are known to be influenced by other factors such as growth, N-balance, total N-conversion or CO2-formation. The method can also be applied to metabolic situations not connected with productive performances.     

The efficiency of energy retention of broiler chickens and turkeys fed on diets with different lysine concentrations

1.?An experiment determined the effect of 6 different lysine concentrations (40, 52, 58, 65, 90 and 130 g/kg CP) in two protein concentrations (210 and 260 g/kg) on the efficiency of energy utilisation of broiler chickens and turkeys. Ninety-six male Ross 308 broiler chicks and 96 male BUT Big 6 turkey poults were fed at 90% of ad libitum during a 12 d bioassay period. At the end of the bioassay, birds were slaughtered and carcase crude protein, fat and gross energy were measured and nutrient metabolisability determined.

2.?Broiler chickens had lower AME and AME_N than turkeys. AME was higher in the 260 g/kg than in the 210 g/kg protein diet; however, no difference was evident in AME_N between any of the diets in both species. A significant species × lysine interaction indicated that the decrease in AME and AME_N with increasing lysine was greater in turkeys than in broiler chickens.

3.?Turkeys had lower weight gains and efficiencies of energy retention than broiler chickens. The effects of different lysine concentrations on growth and the efficiency of energy retention were significant and growth responses were quadratic but there were negative linear responses in the efficiency of energy retention in both species at both crude protein concentrations. The efficiency of energy retention was increased with decreasing lysine concentrations throughout the wide range of concentrations used in the experiment.     

Effects of feed withdrawal on the weight, fecal excretion and Salmonella status of market age broiler chickens.

The withdrawal of feed from the pens of broiler chickens for several hours before they are shipped for slaughter is an increasingly common practice, whose objective is to decrease fecal contamination of birds during processing. In this study, Salmonella typhimurium-infected market age broiler chickens were subjected to feed withdrawal for eight hours, then placed in crates for 18 hours before they were killed and weighed. The intestines, ceca, and cloacal feces were weighed and cultured for salmonellae. The feces deposited in the crates were also weighed and cultured. The results were compared with those of control birds whose feed was not withdrawn before they were placed in crates. The withdrawal of feed did not significantly affect the total liver weights of the birds, but reduced the weights of the intestines in 7/10 groups, and of the ceca in 5/11 groups, and dramatically reduced the amount of feces deposited in the crates. There was no consistent effect on excretion of salmonellae. These results indicated that feed withdrawal for eight hours before broilers are shipped for slaughter should be effective in reducing the spread of fecal contamination and of salmonellae during transport and processing, and in improving the effectiveness of crate washing procedures.     

Studies on methods for the determination of amino acid requirements for metabolic balance based on the oxidation rate of 14C labeled lysine to 14CO2]

Male experimental rats (100 gm liveweight) were distributed into 10 groups of 8 animals each and received balanced diets, with the exception of lysine which was added to the diets in graded amounts in such a way that the lysine content of the diets ranged from 2.44 to 5.92 gm/16 gm N. After a feeding period of 7 days the animals received 3H- and 14C lysine injected intraperitoneally, 4 animals of each group were investigated for the total CO2 excretion and 14CO2 excretion during the first 2 hrs after the injection and for the urinary excretion of radioactivity (48 hours). The remaining animals in each group were used for determining the plasma amino acids and for establishing the specific radioactivity of free lysine in the liver and muscles after an 1-hour incorporation period. Total CO2 excretion was not found to be influenced by the lysine contents while the level of excretion of 14C activity through CO2 and that of specific 14C activity of CO2 increased with increasing lysine concentrations. This produced a broken curve pattern, showing an increased release of 14CO2 (under maintenance conditions) if the diet contained 4 gm lysine/16 gm N and more. Investigations for the specific 14C activity of free lysine in the liver, the main site of lysine oxidation, showed that the increase in 14CO2 release was due to an enhanced rate of lysine catabolism and was not brought about by changes in the pool volume or in specific radioactivity. The levels of urinary 14C excretion were not found to be related to the lysine content of the diets, whereas the curve pattern of 3H excretion observed 5 to 8 hrs after injection was similar to that of 14CO2 excretion. The lysine content of blood plasma and the content of free lysine in the liver increased continuously with increasing levels of dietary lysine. The methodological studies made in the present paper showed that in scientific research a determination of amino acid requirements on the basis of CO2 oxidation data may be a very exact and sensitive method. It will also yield values for maintenance requirements.     

Effects of protein concentration on responses to dietary lysine by chicks

Chicks were fed on diets varying in crude protein (CP) content (140 to 280 g/kg diet) in either 8 steps, experiment 1, or 6 steps, experiment 2. Protein composition was held constant in each experiment. At each protein concentration, 5 (experiment 1) or 6 (experiment 2) concentrations of lysine were tested, ranging from 40 to 60 g/kg CP. Growth rate and efficiency of food utilisation to 21 d of age responded to increasing dietary protein contents up to about 230 g CP/kg. An estimate of lysine requirement at each protein concentration was obtained by fitting a quadratic curve to the response data and calculating the dose of lysine (g/kg CP) needed to maximise either growth rate or gain/food ratio. Although no growth response to dietary protein was obtained between 240 and 280 g CP/kg, the amount of lysine needed to maximise growth and gain/food ratio over this range increased systematically when expressed as g/kg diet, but remained constant if expressed as g/kg CP. The regression of lysine required (g/kg diet) for maximum performance (growth or food efficiency) on CP (g/kg diet) was strictly linear for both responses in both experiments throughout the entire range studied (140 g CP/kg to 280 g CP/kg). The estimated lysine requirement was 0.053 of the CP in experiment 1 and 0.055 of the CP in experiment 2. It is concluded that a fixed ratio of lysine to protein should be specified in practical diet formulation, rather than a minimum dietary concentration of lysine. This would ensure that, if the dietary protein content rises above a prescribed minimum value in least-cost formulation, an appropriate adjustment will automatically be made to the lysine content of the solution.     

木薯型日粮添加复合酶对肉鸡生长性能、组织器官重量及养分消化的影响

文章旨在评估日粮用木薯粉替代玉米同时补充外源复合酶对肉鸡生长性能、组织器官重量及养分表观消化率的影响。试验选择平均初始体重（44.15±0.76）g的肉鸡576只,随机分为4组,每组4个重复,每个重复36只。试验日粮采用2×2因子设计,即2种原料（玉米和木薯）和酶添加量（0和100?mg/kg复合酶）,其中T1组和T2组分别饲喂玉米、木薯型日粮,T3和T4组分别在T1和T2基础日粮中添加100?mg/kg复合酶,试验为期3周。结果：玉米型日粮组肉鸡末重较木薯型日粮组显著提高6.65%（P＜0.05）,但料重比显著降低2.10%（P＜0.05）。无论日粮类型如何,添加复合酶较未添加组肉鸡料重比显著降低2.10%（P＜0.05）。日粮类型及复合酶对肉鸡平均日增重和料重比的影响具有显著交互作用（P＜0.05）。与T2组相比,T3组肉鸡脾脏相对重量显著提高50%（P＜0.05）。无论日粮是玉米型还是木薯型,补充100?mg/kg复合酶较未补充组淀粉表观消化系数显著提高5.59%（P＜0.05）。结论：在本研究条件下,日粮中添加50%木薯粉完全替代玉米同时补充100?mg/kg复合酶可以改善肉鸡饲料效率,提高淀粉表观消化率。 [关键词]木薯|复合酶|肉鸡|生长性能|养分消化     

Effect of dietary lysine level and environmental temperature during the finishing phase on the intramuscular fat content of pork

This study was designed to investigate the effects of dietary lysine level on the intramuscular fat content of the longissimus in finishing pigs reared at two environmental temperatures. Seventy-two hybrid gilts were individually penned and given ad libitum access to either a diet formulated to meet their lysine requirement (6.4 g/kg lysine) or a lysine-deficient diet (4.8 g/kg). Pigs were held at one of two environmental temperatures (thermoneutral [18 degrees C] or hot [32 degrees C]). The study was carried out between approximately 90 and 126 kg live weight; pigs in the thermoneutral and hot environments were on test for 5 and 7 wk, respectively. There were no interactions between dietary lysine level and environmental temperature. Dietary lysine content did not influence feed intake or average daily gain; however, pigs on the lysine-deficient diet had a poorer gain:feed ratio than those fed to requirement (P < .01). High environmental temperature decreased feed intake (P < .001) and average daily gain (P < .01) but improved gain:feed ratio (P < .01). Backfat at the 10th rib was increased and loin eye area and estimated percentage lean in the carcass were decreased for pigs on the lysine-deficient diet. The higher environmental temperature resulted in an increase in carcass length but had no effect on other carcass measurements or intramuscular fat. Feeding the lysine-deficient diet resulted in an increase of .55 percentage unit in longissimus intramuscular fat content (P < .01); however, there was no difference in subjective marbling scores between the diets. Warner-Bratzler shear force values were not affected by dietary lysine level or environmental temperature. Results from this study suggest that feeding of lysine-deficient diets at the end of the finishing period can increase intramuscular fat deposition under thermoneutral and hot conditions.     

Effect of the amount of food provided on the utilization of synthetic lysine (alpha-15N labelled) in broiler chickens

A total of 15 broiler chickens was fed with a diet of wheat/wheat gluten supplemented with lysine on three N-intake levels (I: 1,500; II: 2,100; III: 3,000 mgN/LW0, 67kg) between their 11th and 20th day of life and tested with regard to the characteristic data of N-metabolisation (N-balance experiment) and 15N-incorporation in selected tissues and the complete body of the chickens. While N-metabolisation did not show any differences of procedure, the results of 15N-incorporation indicated slightly more favourable utilisation conditions for synthetic lysine in III in the complete body and the liver. One can derive from the results that the level of feed intake cannot be excluded as one variable in the utilisation of synthetic lysine, the problems in connection with this, however, cannot completely be explained with this. For the restrictions of N-intake effective in the N-balance experiment no negative influence is to be expected with regard to the utilisation of synthetic lysine in comparison to ad libitum feeding.     

Effect of formic acid on performance, digestibility, intestinal histomorphology and plasma metabolite levels of broiler chickens

1. The effect of dietary formic acid on performance, digestibility, intestinal histomorphology and plasma metabolite levels of broiler chickens was studied. 2. An experiment with 120 Ross male broiler chickens was conducted from 1 to 42 d of age at the laboratory. There were 4 treatment groups: control (C), 10 mg/kg feed avilamycin (AV) and formic acid at two concentrations, 5 and 10 g/kg feed (FA5 and FA10, respectively). 3. No differences in weight gain, feed intake or feed conversion ratio were observed in male broiler chickens fed on the different diets. 4. An effect of the additives on ileal dry matter (DM) digestibility at 42 d of age was detected with the finisher diets; AV and 10 g/kg of feed formic acid slightly improved ileal DM digestibility compared to the other treatment groups. 5. Jejunum pH was not affected when 5 or 10 g/kg formic acid was added, and the results do not clearly show a positive effect of formic acid on the intestinal histomorphology. 6. No differences were noticed for blood metabolites in the different diets, and the levels of calcium and phosphorus in the plasma were not altered by formic acid addition. 7. In conclusion, when using broiler chickens under conditions of good hygiene, dietary formic acid did not have a clear positive effect on performance, intestinal histomorphology or plasma metabolite levels; however, there was a slight positive effect on the ileal digestibility of nutrients.     

Effect of liquid feeding weaned pigs on growth performance to harvest

Four experiments were undertaken to examine the effect of feeding postweaning diets as dry pelleted feed, fresh liquid feed, acidified liquid feed, and fermented liquid feed on pig performance from weaning (26 d) to harvest. In Exp. 1 (n = 12 replicates) and 2 (n = 10 replicates), the treatments were 1) dry pelleted feed and 2) fresh liquid feed. In Exp. 1, 2 kg of starter diet (16.7 MJ of DE/kg and 1.6% lysine) per pig and 5 kg of transition diet (16.7 MJ of DE/kg and 1.5% lysine) per pig followed by a weaner diet (14.0 MJ of DE/kg and 1.36% lysine) were offered to 27 d after weaning. In Exp. 3 (n = 8 replicates), the treatments were 1) dry pelleted feed, 2) fresh liquid feed, and 3) acidified liquid feed. In Exp. 4 (n = 8 replicates), the treatments were 1) dry pelleted feed, 2) acidified liquid feed, and 3) fermented liquid feed. In Exp. 2, 3, and 4, 3 kg of starter diet (16.1 MJ of DE/kg and 1.74% lysine) per pig and 6 kg of transition diet (15.3 MJ of DE/kg and 1.5% lysine) per pig followed by a weaner diet (14.0 MJ of DE/kg and 1.36% lysine) was offered to 27 d after weaning. All treatments were balanced for boars and gilts and diets were offered for ad libitum consumption. Acidified liquid feed was produced by adding lactic acid to the liquid feed so that its pH was decreased to 4.0. Fermented liquid feed was produced by adding an inoculum of Lactococcus lactis subsp. cremoris 303 (1.3%, vol/wt) to the first mix. In Exp. 1, ADG from weaning to d 27 after weaning was 338 and 286 g/d (SEM = 10; P < 0.01) and DM gain/feed in the same period was 888 and 594 g/kg (SEM = 23.1; P < 0.001) for dry pelleted feed and fresh liquid feed, respectively. In Exp. 2, ADG was 391 and 352 g/d (SEM = 6.4; P < 0.01) and DM gain/feed was 856 and 642 g/kg (SEM = 9.9; P < 0.001) for dry pelleted feed and fresh liquid feed, respectively, during the period from weaning to d 27 after weaning. In Exp. 3, ADG was 408, 416, and 433 g/d (SEM = 12.7; P > 0.05) and DM gain/feed was 865, 755, and 789 g/ kg (SEM = 14.5; P < 0.001) for dry pelleted feed, fresh liquid feed, and acidified liquid feed, respectively. In Exp. 4, ADG was 361, 389, and 347 g/d (SEM = 13.2; P = 0.11) and DM gain/feed was 888, 749, and 733 g/ kg (SEM = 15.8; P < 0.001) for dry pelleted feed, acidified liquid feed, and fermented liquid feed, respectively, during the period from weaning to d 27 after weaning. It is concluded that although feeding acidified liquid feed may have some merit in the first 27 d after weaning, this benefit is lost in the subsequent period. No benefit arose from feeding fresh liquid feed or fermented liquid feed. Growth performance from d 28 after weaning to harvest was not improved by any liquid feed treatment.     

The effect of dietary lysine deficiency on the immune response to Newcastle disease vaccination in chickens

The effect of lysine deficiency on chicken immune function was evaluated using broiler chickens fed a diet with lysine at 67% of the control diet (1.24% lysine). The evaluation of humoral immune function was conducted by measuring the antibody production to a live Newcastle disease virus (NDV) vaccination using the hemagglutination inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA). The cellular immune function was evaluated through the use of cutaneous basophil hypersensitivity test. The antibody response to NDV vaccination was reduced in broiler chickens fed a lysine-deficient diet when measured by ELISA but not when measured by HI. The cell-mediated immune response was also reduced by lysine deficiency.     

Effect of glutamic acid content of the diet on isotope-labeled glutamic acid catabolism in rats. 1. The course of 14CO excretion following intragastric administration of 14C-glutamic acid

Male rats received in 8 groups of 10 animals each for a period of 7 days 7 synthetic diets and one semisynthetic diet on maintenance requirement level. A L-amino acid mixture corresponding to the pattern of egg protein without glutamic acid was the protein source of the synthetic diets. Glutamic acid was supplemented successively from 0 to 58 mol-% of the total amino acid content. The crude protein source of diet 8 was whole egg powder. On the 8th day of experiment 5 animals per group were labelled by intragastric infusion (i.g.) with 14C-U-glutamic acid. During the following 24 hours the excretion of CO2 and 14CO2 was measured. Throughout the experimental feeding body weight was relative constant, however, when the synthetic diets were fed it was necessary to increase the daily amount of energy from 460 to 480 kJ/kg0,67. The relative 14CO2-excretion within 24 hours was 68-75% of the dose. However, the main part of the amount of radioactivity excreted during 24 hours was found after 4 to 6 hours already. Exponential functions calculated from the data of cumulative 14CO2-excretion suggest the existence of a fast process of 14CO2-formation directly from 14C-glutamic acid, reaching a plateau within 2 hours and a slow process of oxidation of intermediates of glutamic acid metabolism, causing a continued 14CO2-formation even after 24 hours. The oxidation of 14C-glutamic acid to CO2 decreased 2 to 14 hours after i.g. labelling if the glutamic acid content of the diet increased. The same was found for the specific radioactivity of 14CO2. A storage of intermediates of glutamic acid before degradation was assumed.     

Impact of dietary chitosan oligosaccharide and its effects on coccidia challenge in broiler chickens

ABSTRACT

1. Two experiments were conducted, the first to determine the optimum inclusion of chitosan oligosaccharide (COS) in broiler diets to support growth performance, digestive functions, intestinal morphology, and immune organs. The second experiment evaluated the immune-protective properties of COS on broiler chickens during coccidia challenge (CC).

2. Experiment 1 investigated the effect of graded dietary concentration of COS in the diets of broiler chickens using eight cage replicates for each of the six diets. A corn-soybean meal-based diet was used as the basal diet and supplemented with 0.0, 0.5, 1.0, 1.5, 2.0, or 2.5 g of COS/kg feed to form the six treatments.

3. The diet supplemented with 1.0 g COS/kg of feed provided the optimal inclusion level for broiler chickens regarding body weight (BW) gain, jejunal villus height, villus height to crypt depth ratio, and ileal energy digestibility at d 22 of age.

4. Experiment 2 investigated the immune-protective properties of COS in broiler chickens during CC. A total of 224 male broiler chicks were randomly assigned to eight replicate cages in a 2 × 2 factorial arrangement of treatments with two COS concentrations (0 or 1 g of COS/kg of diet), with or without CC.

5. On d 18 of age, birds in the CC group received twice the recommended coccidia vaccine dose of 30 doses/kg BW.

6. Coccidia challenge reduced (P < 0.05) and dietary COS increased (P < 0.05) BW gain, and feed intake. Dietary COS mitigated (P < 0.05) the CC-induced effects on gain:feed. Dietary COS supplementation attenuated the CC-induced effects (P < 0.05) on the expression of occludin genes.

7. In conclusion, dietary COS improved performance, and the immune-related beneficial impact of COS supplementation was associated with reduced expression of pro-inflammatory cytokine genes.     

Ileal starch digestibility in growing broiler chickens fed on a wheat-based diet is improved by mash feeding, dilution with cellulose or whole wheat inclusion.

1. An experiment was conducted to study causes of low ileal starch digestibilities when broiler chickens were fed on wheat-based diets. Each of 5 cold-pelleted diets containing 771 g/kg DM wheat and one cold-pelleted diet containing 694 g/kg DM wheat were fed to 24 male broiler chickens in 8 cages from 10 to 21 d of age. 2. Feed intake and weight gain were significantly reduced when the wheat diet was crushed and fed in a mash form. 3. Ileal starch digestibility increased significantly from 0.79 to 0.95, 0.93 and 0.91, respectively, when the diet was crushed and fed in a mash form, was diluted with cellulose prior to pelleting, or when parts of the wheat were fed as whole grains. Correspondingly, random variation between individual birds was reduced. 4. These results indicate that an overload of wheat starch in the digestive tract may be the cause of poor digestibility for some broilers in a flock. Grinding of the wheat may also influence starch digestibility.     

Influence of Dietary Metformin on the Growth Performance and Plasma Concentrations of Amino Acids and Advanced Glycation End Products in Two Types of Chickens

Glycation is a non-enzymatic reaction inducing the bonding of glucose to amino acids and proteins. Glycated amino acids are not useful for protein synthesis, suggesting that glycation reduces the utilization of amino acids. Metformin (MF) is well known as a therapeutic drug for type II diabetes that inhibits glycation. It is possible that treatment with MF raises the utilization of amino acids by the inhibition of glycation, thereby improving the growth performance of chickens. In the present study, therefore, we investigated the influence of dietary MF on the growth performance, and plasma concentrations of free amino acids and N^ε-(Carboxymethyl)lysine (CML), which is an advanced glycation end product, in layer (Experiment 1) and broiler (Experiment 2) chickens. From 7 d of age, chicks were allowed free access to one of the experimental diets containing MF at 3 supplementation levels (0, 150, and 300 mg/kg diet) for 14 days. Body weight and feed intake were measured every week. At the end of the experiments, blood and breast muscle (M. pectoralis major) were collected for further analysis. Dietary MF did not affect weight gain, feed intake, or feed efficiency in both layer and broiler chickens. Dietary MF at the level of 150 mg/kg diet increased breast muscle weight in both layer and broiler chickens. Dietary MF increased plasma concentrations of branched chain amino acids and decreased concentrations of CML in layer chickens, although it did not affect plasma concentrations of glucose. The present study suggested that dietary MF might have the potency to increase breast muscle weight of layer chickens with an increment in plasma concentrations of branched-chain amino acids.     

Study of broiler chicken responses to dietary protein and lysine using neural network and response surface models

1. In this study, neural network (NN) and response surface (RS) models were developed to investigate the response [average daily gain (ADG) and feed efficiency (FE)] of young broiler chickens to dietary protein and lysine. For this purpose, data on their responses to dietary protein and lysine were extracted from the literature and separate NN and RS models were constructed.

2. Comparison between the NN and RS models revealed higher accuracy of prediction with the NN models compared to the RS models. In terms of R ² values, the NN models developed for both ADG (R ² = 0.923) and FE (R ² = 0.904) were far superior to the RS models (R ² for ADG = 0.511; R ² for FE = 0.67). This suggests that the NN models can serve as an alternative option to conventional regression approaches including use of RS models.

3. Optimisation of the NN models developed for response to protein and lysine showed that diets containing 220.7 (g/kg of diet) protein and 12.85 (g/kg of diet) lysine maximise ADG, whereas maximum FE is achieved with diets containing 241.3 and 13.12 (g/kg) protein and lysine, respectively. Based on the optimisation results, optimal dietary protein and lysine concentrations for maximum FE in broiler chickens during the starting period are higher than for ADG.     

Effect of casein phosphopeptide and 25-hydroxycholecalciferol on tibial dyschondroplasia in growing broiler chickens

1. An experiment was conducted to investigate the influence of dietary casein phosphopeptides and 25-hydroxycholecalciferol on the incidence of tibial dyschondroplasia (TD) in 14-d-old commercial broiler chickens. 2. Three hundred and twenty broiler chicks (one day old) were randomly allocated to one of 4 dietary treatments. A standard broiler diet was used as the control with the three experimental treatments receiving the control diet supplemented with 10 g casein phosphopeptide/kg, 14 g casein phosphopeptide/kg or 69 microg 25-hydroxycholecalciferol/kg. 3. Those birds fed the diets supplemented with 14g casein phosphopeptide/kg or 25-hydroxycholecalciferol had a lower incidence of TD than both the control and 10g casein phosphopeptide/kg treatments when assessed grossly. 4. The body weight of birds fed the 10 g casein phosphopeptide/kg diet or the 25-hydroxycholecalciferol diet was higher than birds fed the control diet. Although not significant, the body weight of birds fed the 14 g casein phosphopeptide/kg diet was also greater than the control birds. 5. The current experiment demonstrated that both casein phosphopeptide and 25-hydroxycholecalciferol can reduce the incidence of TD in the young broiler chicken. More research is required to explain the unexpected increase in body weight described above.     

Voluntary food intake variation in chickens on lysine-free diet is attributed to the plasma lysine concentration

1. Growing chickens decrease their voluntary food intake when they receive a diet deficient in a single essential amino acid. Our previous studies suggest that the decreased food intake was associated with some metabolic changes.

2. In order to reveal the involvement of plasma lysine fluctuations in the reduction of food intake, we examined whether maintaining the plasma lysine concentration in chickens on a lysine-free diet (the purified diet contained no lysine) restored the food intake to that of the control (lysine hydrochloride 11.9 g/kg) group.

3. Male egg-type chickens at 21 d of age were injected with lysine at doses of 0.1 g/ml one hour after presenting the lysine-free diet. This injection increased the plasma lysine concentration one hour later and kept it similar to that of the control group for the following 2 h. Chickens ate the lysine-free diet as much as the control diet when their plasma lysine concentration was kept at a similar level to the control group. Injection of saline or alanine (0.12 g, isonitrogenous to lysine 0.1 g) into the crop of chickens on the lysine-free diet did not bring about the variations of food intake and plasma lysine concentrations as observed in those with lysine.

4. These findings show that the food intake variation was attributed to the plasma lysine concentration in the chickens on the lysine-free diet.