Effects of DL-2-hydroxy-4-(methylthio) butanoic acid on broilers at different dietary inclusion rates

1. A growth experiment was conducted to determine the effectiveness of liquid analogue, DL-2-hydroxy-4-(methylthio) butanoic acid (HMTBA), compared to powder DL-methionine (DLM), in commercial maize–soybean-meal broiler diets similar to those commonly used in China, on feed conversion ratio (FCR), growth performance and European Production Index (EPI) of broilers.

2. A 4 × 2 + 1 factorial arrangement of treatments was used in which HMTBA or DLM was fed at 4 concentrations (low, medium, high and very-high inclusion rates) of supplementation at 100% equivalence on an equimolar basis. Negative control diets were commercial starter, grower and finisher feeds with no added methionine. A total of 1008 commercial-type Arbor Acres 1-d-old chicks were randomly distributed into 9 groups, with 8 replicates of 14 (7 male + 7 female) birds per treatment.

3. The body weight gain of the control group was significantly lower than that of the others in the starter period but did not show any differences during the other periods. The FCR of the control group was higher than that of the others except for those with HMTBA in the grower period. It was also observed that the FCR dropped as the supplemented concentration of methionine was increased regardless of the source. Some of the treatment groups produced a better breast yield than the control. The EPI between the two products did not show any significant difference.

4. In conclusion, both of the methionine sources were equally effective in ameliorating the effects of a dietary deficiency of total sulphur amino acids.

     

Effect of methionine hydroxy analog-free acid on growth performance and chemical composition of liver of broiler chicks fed a corn–soybean based diet from 0 to 6 weeks of age

The experiment was carried out to determine the effects of liquid DL‐methionine hydroxy analog‐free acid (LMA) and dry DL‐methionine (DLM) on growth performance, carcass quality and chemical composition of the livers of broiler chicks during 0–6 weeks of age. Four hundred and fifty male commercial broiler chicks (Ross strain) were used. The chicks were divided into three groups, and each group consisted of six replicates of 25 chicks each. The chicks were kept in floor pens, and water and feed were supplied ad libitum throughout the experiment. Three experimental diets were provided as follows: (i) corn–soybean‐based diet deficient in methionine; (ii) methionine‐deficient corn–soybean‐based diet supplemented with DLM to meet the methionine requirements of broiler chicks; and (iii) methionine‐deficient corn–soybean‐based diet supplemented with LMA (1.25‐fold (w/w) the amount of DLM supplied to the second group, given an assumption that 100 units of liquid LMA can be replaced by 80 units DLM to give similar performance results). During the starter period, the weight gains of chicks fed LMA or DLM were significantly greater than those in chicks receiving the methionine‐deficient diet (P < 0.05), and the addition of LMA significantly improved weight gain compared with the addition of DLM. Adding DLM or LMA significantly improved the feed conversion ratio (FCR) and percentage of uniformity (P < 0.05). No significant differences between the effects of DLM and LMA on these parameters were found. During the grower period (3–6 weeks of age), weight gain, FCR, uniformity and feed intake of chicks that received diet supplemented with DLM or LMA were superior to those of the methionine‐deficient group (P < 0.05). Chicks fed LMA had the same bodyweight gain and uniformity as those fed DLM. However, adding LMA resulted in a significant increase of FCR resulting from excess feed consumption. Outer breast meat yields were significantly improved and abdominal fat was significantly decreased when methionine sources were added (P < 0.05), and adding LMA tended to promote edible meat growth better than did adding DLM. Although no significant effects of methionine sources on the chemical composition of the liver were seen, adding methionine sources tended to increase liver fat content. In conclusion, it seems that the bioefficacy of LMA relative to DLM is not less than 80%. Therefore, chicks fed with diet supplemented with 1.25‐fold (w/w) as much LMA as DLM might exceed requirements for growth performance, while meeting requirements for meat production. Moreover, the relative bioefficacies of LMA and DLM between the starter and grower periods may perhaps be different.     

The response of Ross 308 and Hybro broiler chickens to early and late skip-a-day feed restriction

The effects of skip-a-day feeding for 14 days during the starter or grower period or for 28 days during both periods followed by ad libitum feeding to market age on the growth performance of two strains of broiler chickens, Ross 308 and Hybro, were studied over 7 weeks. Ross was superior to Hybro in weight gain, final body weight and feed conversion but consumed more feed. Overall, feed restriction reduced feed intake, weight gain and body weight in all feed - restricted birds. Also, the 14-day feed-restricted birds gained more weight and were heavier than the 28-day restricted ones. Feed restriction neither improved feed conversion nor reduced abdominal fat but decreased mortality rate. Strain | treatment interaction significantly affected only feed intake. It is suggested that for broiler chicken production in the tropics Ross 308 could be used and feed restricted for 14 days during the starter or grower period.     

2‐Hydroxy‐4‐methylthio butanoic acid and DL‐methionine for Japanese quails in production

An experiment was performed using 1,000 laying Japanese quails to assess the availability of two alternative dietary methionine sources. Treatment 01 = Basal Feed that is deficient in digestible methionine + cystine (Met + Cys). The other treatments were constituted by Met + Cys levels of 0.8, 1.60 and 2.40 g/kg, supplemented with DL‐Methionine‐99%, HMTBA‐88% and HMTBA‐84%, being 10 treatments in total. The following characteristics were studied: feed intake (g/bird/day), egg production (egg/day × 100), egg weight (g/egg), egg mass (g/egg), feed conversion per egg dozen (kg feed/dozen eggs), feed conversion per egg mass (kg feed/kg eggs), relative yolk weight (g/100 g of egg), relative albumen weight (g/100 g of egg), relative shell weight (g/100 g of egg), shell thickness (mm) and specific gravity (g/cm³). In general result comment, supplemental methionine sources must be included in the poultry diet. The different methionine sources affect the performance of quails, and the increase in the levels within each source improves the performance variables. Significant effect was observable on performance variables and egg quality variables, being that DLM‐99% is superior to the other sources. The HMTBA‐88% source is superior to the HMTBA‐84% source for the same aforementioned variables. In conclusion, the bioefficacy values of the HMTBA‐88% and HMTBA‐84% sources compared to the DLM‐99% source on an equimolar basis were 81 and 79%, respectively, for the performance variables, and 83 and 74 while the methionine sources were equivalent for the variables related to egg quality.     

蛋氨酸形式和饲粮蛋白质水平对黄羽肉鸡生产性能的影响

选用1日龄快长型岭南黄羽肉鸡公雏1500只,随机分为5个处理,每处理6个重复,每重复50只鸡,分别饲喂以下5种饲粮:正常蛋白质加Alimet饲粮(处理1)、正常蛋白质加DLM饲粮(处理2)、低蛋白质(比正常水平降低约1.5个百分点)加Alimet饲粮(处理3)、低蛋白质加DLM组饲粮(处理4)、正常蛋白质未加蛋氨酸饲粮(处理5)。结果表明,在等摩尔量有效成分添加基础上,Alimet比DLM更有利于提高黄羽肉鸡生长性能,降低饲料成本和死亡率;饲粮蛋白质水平和蛋氨酸形式对43～63日龄和0～63日龄黄羽肉鸡生长性能的影响存在互作效应,表现为在正常蛋白质水平时添加Alimet对黄羽肉鸡生长性能的改善效果优于DLM,且更有利于降低饲料成本,而在低蛋白质水平时添加Alimet和DLM则无显著差异;在本试验条件下,降低饲粮蛋白质水平会对黄羽肉鸡的生长性能、饲料成本和成活率产生不利影响。     

胍基乙酸对肉鸡的适用阶段及饲粮蛋氨酸配套强化效果研究

本研究基于生长性能和肉品质,评价胍基乙酸(GAA)对肉鸡的适用阶段和饲粮蛋氨酸(Met)配套强化效果。选取1日龄雄性爱拔益加肉仔鸡1920只,随机分为16组,每组设6个重复,每个重复20只鸡。试验分前期(1~21日龄)和后期(22~42日龄)2个饲养阶段,1组为对照组,饲喂常规饲粮(Met水平前期为0.50%,后期为0.40%)。2~6组仅在前期设置Met或GAA处理,其中,2组只把饲粮Met的水平提高至0.65%;3~6组采用双因素完全随机设计,2个饲粮Met水平分别为0.50%和0.65%,2个GAA添加量分别为300和600 mg/kg。7~11组仅在后期设置Met或GAA处理,其中,7组只把饲粮Met水平提高至0.55%;8~11组采用双因素完全随机设计,2个饲粮Met水平分别为0.40%和0.55%,2个GAA添加量分别为400和800 mg/kg。12~16组在全期(1~42日龄)设置Met或GAA处理,前期和后期饲粮设置分别同2~6组和7~11组。试验期42 d。结果发现:1)与对照组相比,只在前期饲喂高剂量GAA并强化Met供应能够显著提高1~21日龄平均日增重和21日龄体重(P<0.05),显著降低1~21日龄料重比(P<0.05);仅在后期饲喂高剂量GAA能够显著提高22~42日龄平均日增重,显著降低22~42日龄料重比(P<0.05),同时强化Met供应还可显著提高1~42日龄平均日增重及42日龄体重、胸肌指数(P<0.05),显著降低22~42日龄和1~42日龄料重比及42日龄腹脂指数(P<0.05);全期饲喂高剂量GAA能够提高22~42日龄和1~42日龄平均日增重及42日龄体重和胸肌指数(P<0.05),显著降低22~42日龄和1~42日龄料重比及42日龄腹脂指数(P<0.05),同时强化Met供应还可显著提高1~21日龄平均日增重和21日龄体重(P<0.05),显著降低1~21日龄、22~42日龄和1~42日龄料重比(P<0.05)。2)与对照组相比,全期单独强化饲粮Met或联合添加低剂量GAA可以显著降低42日龄胸肌、腿肌亮度(L^∗)值和剪切力(P<0.05),提高红度(a^∗)值和24 h pH(pHu)(P<0.05);单独饲喂GAA对肉品质无显著影响(P>0.05)。由此可见,当全程饲喂高剂量GAA时,无需额外补充Met就可使肉鸡终末体重和胴体质量达到最佳;若要阶段性使用GAA,宜在后期高剂量添加且同时补充Met。     

Effect of 2‐hydroxy‐4‐(methylthio) butanoic acid and acidifier on the performance,chyme pH,and microbiota of broilers

This study was aimed to explore the comparative acidifying properties of 2‐hydroxy‐4‐(methylthio) butanoic acid (HMTBA) and a combination of DL‐methionine (DLM) and acidifier in male broiler production. A total of 480 1‐day‐old broiler chicks were randomly divided into four treatments: A (low HMTBA, 0.057% HMTBA); B (low acidifier, 0.05% DLM + 0.057% acidifier); C (high HMTBA, 0.284% HMTBA); and D (high acidifier, 0.25% DLM + 0.284% acidifier). At 21 d, growth performance, chyme pH, digestive enzyme activities, and intestinal microflora were measured. The pH of crop, gizzard, and ileum contents was higher in the HMTBA treatment group than in DLM + acidifier treatment group. Furthermore, acidifier supplementation promoted growth of butyrate‐producing bacteria such as Faecalibacterium, whereas high HMTBA (0.284%) inhibited the proliferation of acid‐producing bacteria including Roseburia and Collinsella. The chymotrypsin activity was lower in the HMTBA group than in the DLM + acidifier group. In contrast, high‐level HMTBA group showed higher average daily gain and average daily feed intake than the DLM + acidifier group. These results suggested that HMTBA work through different pathways with DLM plus acidifier.     

Nutritional value of quality protein maize and food corn for starter and growth pigs

Growth traits with starter and grower pigs and a digestion trial were conducted to compare the nutritional value of Quality Protein Maize (QPM), food corn and conventional feed corn. The QPM, food and feed corn contained .45, .31 and .29% lysine, respectively. The growth trials evaluated a QPM-soybean meal diet formulated on a lysine basis (.96% in starter and .7% in grower diets) and four diets arranged in a 2 (food corn vs feed corn) X 2 (low vs high soybean meal) factorial. Soybean meal was either added in the same amount as in the QPM diet or was added to provide the lysine content of the QPM diet. Performance was similar for pigs fed food corn and feed corn in both trials. The QPM diets resulted in greater performance than food and feed corn diets containing the same level of soybean meal supplementation; starter pigs were more (P less than .10) efficient and grower pigs had a higher (P less than .01) rate and efficiency of gain. However, performance of pigs fed the QPM diets was not equal to that of pigs fed isolysinic food and feed corn diets; growth rate was lower (P less than .05) in starter pigs and gain:feed was lower (P less than .05) in grower pigs. Diets in the digestion trial consisted of the corns plus 3.25% casein. Energy digestibility was similar for all diets. Ileal N and amino acid digestibilities were highest for QPM, intermediate for food corn and lowest for feed corn. In most instances, these differences were significant (P less than .05). Apparent biological value was highest (P less than .05) for QPM. These trials indicate that food corn and feed corn have similar nutritional value, and that starter and grower pigs can benefit from the higher protein quality of QPM.     

DL-羟基蛋氨酸钙相对于DL-蛋氨酸的生物学效价

试验采用肉仔鸡生产性能和胴体品质指标结合回归模型比较了DL-羟基蛋氨酸钙(DL-MHA-Ca)相对于DL-蛋氨酸(DLM)的生物学效价。选取792只体重相近且健康的AA肉仔鸡,随机分为11个处理,每个处理6个重复。DLM或DL-MHA-Ca按照等摩尔水平(0.03%、0.06%、0.10%、0.15%和0.21%)添加到仅缺乏蛋氨酸的基础日粮中。试验期35 d,分为7~21 d和22~42 d 2个阶段。结果表明:7~21 d和7~42 d,添加蛋氨酸源显著改善了肉仔鸡的体增重、饲料/增重、屠体重、胸肉重、胸肉率、腿肉重和全净膛重(P0.05);在等摩尔基础上,DL-MHA-Ca相对于DLM的生物学效价,7~21 d分别是71%(增重)和66%(饲料/增重);7~42 d则分别为63%(增重)、58%(饲料/增重)、74%(屠体重)、60%(胸肉重)、49%(胸肉率)、71%(腿肉重)和72%(全净膛重)。     

The site of intestinal disappearance of DL-methionine and methionine hydroxy analog differs in pigs

A study was conducted with pigs to determine the sites of and the influence of dietary wheat middlings (WM) as a fiber source on the absorption of dl-Met (DLM) and dl-2-hydroxy-4-methylthio butanoic acid (HMTBA). Twelve 25-kg barrows were used in a replicated 6 × 4 incomplete Latin-square design with 6 diets and 4 periods per pig. Each pig was surgically fitted with simple T-cannulas in the terminal duodenum and ileum 2 wk before the initiation of the experiment and housed in a stainless-steel metabolism crate. The 6 diets were arranged in a 2 × 3 factorial of WM at 0 (CON) or 8% and Met source including none, DLM, or HMTBA. Supplemental DLM doubled the duodenal free Met concentration from 9.6 to 19.6 g/100 g of DMI. Supplemental DLM also increased the apparent ileal digestibility (AID) of free Met from 52 to 92% (P < 0.05). Adding 8% WM increased (P < 0.01) duodenal NDF concentrations by 2 g/100 g of DMI and decreased (P < 0.05) AID of free Met. No HMTBA was detected in digesta collected from the duodenum or ileum of pigs fed the CON + HMTBA or the WM + HMTBA diets, indicating complete absorption before the terminal duodenum regardless of WM inclusion. Interactions between Met supplementation and WM were observed for the digestibility of all other nutrients (P < 0.05). Fiber and AA digestibility in the ileum were the greatest for the CON + HMTBA diet, and least for the WM + HMTBA diet. The CON + HMTBA diet had greater AID of ADF, NDF, CP, and Thr, and greater AID of ADF, NDF, ash, Arg, Ile, Gly, and Pro when compared with the CON and CON + DLM diets, respectively (P < 0.05). The WM + HMTBA had less AID of ADF, CP, and all AA with the exception of Lys, Trp, and Val when compared with the CON + HMTBA (P < 0.05). In summary, absorption of HMTBA in the pig is complete by the end of the duodenum, but negative interaction between HMTBA and WM can decrease the AID of most AA.     

Effects of methionine and guanidinoacetic acid supplementation on performance and energy metabolites in breast muscle of male broiler chickens fed corn-soybean diets

ABSTRACT

1. Guanidinoacetic acid (GAA) is the single endogenous precursor of creatine, which plays a critical role in energy homeostasis of cells. Since GAA is endogenously converted to creatine by methylation, it was hypothesised that the effects of dietary GAA supplementation might determine the methionine (Met) availability in corn-soybean based diets.

2. A total of 540, one-day-old male Ross 308 broilers were allocated to nine dietary treatments with six replicates (10 birds each) in a 3 × 3 factorial arrangement with three graded levels of supplementary Met (+0.4 g/kg per level), whilst cystine was equal across groups, resulting in a low, medium and high level of total sulphur amino acids, and with three levels of GAA (0, 0.6 and 1.2 g/kg). Birds were fed for 42 days.

3. Increasing levels of supplemental Met enhanced performance indices in all rearing periods, although there was no effect on feed conversion ratio in the grower or feed intake in the finisher periods. Final body weight was 8.8% and 14.6% higher in the birds fed medium and high Met diets, respectively, compared to the low Met level. Relative breast weight and protein content in muscle on d 25 linearly increased with higher levels of Met. At low and high Met levels, growth in the finisher phase was negatively affected by supplementing GAA at 1.2 g/kg. It was suggested that disturbances in methylation homeostasis and/or changes in Arg metabolism might explain these findings. At the end of the grower phase, muscle creatine content was higher when feeding GAA at 0.6 and 1.2 g/kg (4464 and 4472, respectively, vs. 4054 mg/kg fresh muscle in the control group).

4. The effects of dietary GAA supplementation were influenced by the dietary Met level only in the finisher period, which indicates the need for proper sulphur amino acid formulation in diets when feeding GAA.     

Effects of dietary protein and energy concentrations on performance and carcase characteristics of chukar partridge (Alectoris chukar) raised in captivity

1. This study was conducted to determine the effects of starter and grower diets with differing crude protein (CP) and metabolisable energy (ME) concentrations on the body weight (BW), live weight gain (LWG), feed consumption (FC), feed conversion ratio (FCR), and carcase, breast+back, rump, wing, neck and abdominal fat weights of chukar partridge raised in captivity. 2. Chukar partridges were fed on starter diets containing 4 concentrations of CP (160, 200, 240, 280 g/kg) and 4 concentrations of ME (10.9, 11.7, 12.6, 13.4 MJ/kg) from hatch to 8 weeks of age; they were fed on grower diets containing 4 concentrations of CP (150, 175, 200, 225 g/kg) and 4 concentrations of ME (11.9, 12.6, 13.2, 13.8 MJ/kg) from 9 to 16 weeks of age. All diets contained at least 5.5 g/kg methionine, 15 g/kg lysine and 10 g/kg methionine+cystine. Sixteen starter and 16 grower diets were arranged in a 4 x 4 factorial design with 4 levels of CP and 4 levels of ME. Each treatment was replicated three times with each replicate consisting of 5 males and 5 females. 3. Partridges fed on a starter diet containing 160 g CP/kg were significantly lighter at 8 weeks of age than those in groups given diets containing a higher CP. However, at 16 weeks of age, the differences in BW among treatments had disappeared. Throughout, there were no significant effects of ME concentration on BW and LWG. 4. The daily mean FC for the 0 to 8 week and 0 to 16 week periods was not affected by dietary CP concentration. For the 9 to 16 week period, the partridges fed on a grower diet containing 225 g CP/kg consumed more feed than those given a diet containing 175 g CP/kg. 5. The highest FCR for the 0 to 8 week period was in partridges fed on a starter diet containing 160 g CP/kg. For the 9 to 16 week period, the lowest FCR was in partridges fed on a grower diet containing 150 g CP/kg. For the 0 to 16 week period, there was not a significant effect of dietary CP concentration on FCR. The daily mean FC and the FCR for the 0 to 8, 9 to 16 and 0 to 16 week periods decreased when the ME concentration of the starter and grower diets increased. 6. The carcase, rump and breast+back weights of the male partridges increased when the ME content of the diets increased. Weights of all carcase components of the male partridges were significantly greater than those of the carcase components of the females. 7. There were no significant interactions between CP and ME concentrations on BW, LWG, FC, FCR and carcase characteristics. 8. We conclude that the starter diet for chukar partridges raised for meat production should contain at least 200 g CP/kg, 11.7 MJ ME/kg, and the grower diet should contain 150 g CP/kg, 12.6 MJ ME/kg.     

Effects of step-up and step-down phytase regimens on performance and processing yields of male broilers from 1 to 35 d of age

An experiment was conducted to evaluate increasing or decreasing concentrations of dietary phytase on growth performance and processing yields of male broilers from 1 to 35 d of age. Treatments consisted of a positive control, a negative control (NC; less 0.14% Ca, 0.13% nonphytate P, and 0.03% Na), and 6 additional treatments based on the NC supplemented with phytase. Treatments 3 through 5 consisted of the NC diet supplemented with 500 phytase units (FTU)/kg of phytase in the starter phase that was either continued throughout the remainder of the study (treatment 3) or increased to 1,500 FTU/kg beginning in the finisher (treatment 4) or grower (treatment 5) phases. Treatment 6 had 1,500 FTU/kg of phytase throughout the study. Treatments 7 and 8 had 1,500 FTU/kg in the starter and decreased to 500 FTU/kg in the finisher or grower phases, respectively. At 35 d of age, broilers fed diets containing 1,500 FTU/kg of phytase had increased BW gain compared with birds fed diets formulated to contain 500 FTU/kg of phytase. Increasing phytase concentration between the starter and grower phases or decreasing phytase concentration between the grower and finisher phases negatively affected FCR from 1 to 35 d of age. Phytase supplementation did not affect weight and yield of carcass characteristics. Therefore, dietary phytase concentration should not be varied throughout production for optimum growth performance.     

Chemical composition and nutritive value of kapok seed meal for broiler chickens

1. Mechanically extracted kapok (Ceiba pentandra) seed meal (KSM) contained 324 g crude protein, 97 g ether extract, 289 g fibre, 94 g ash, 128 g available carbohydrates, 3-8 g calcium, 11 g phosphorus, 10.4 g cyclopropenoid fatty acids and 15 g tannins per kg. 2. In a 4 x 2 factorial experiment, KSM was incorporated in broiler starter and finisher feeds at 0, 30, 60 and 90 g/kg, replacing sunflower meal (SFM) w/w; without and with multi-enzyme supplementation. 3. No significant differences were noticed between treatments in body weight gain, feed consumption, feed conversion efficiency, mortality or carcase yields. 4. Multi-enzyme (amylase, endoxylanase, hemicellulase, beta-glucanase, pectinase, phytase and protease) supplementation did not improve the growth performance of broilers fed on the KSM diets.     

低蛋白质饲粮添加甘氨酸对肉仔鸡生长性能、胴体组成和血液生化指标的影响

本试验旨在研究在低粗蛋白质(CP)饲粮中添加甘氨酸(Gly)对肉仔鸡生长性能、胴体组成和血液生化指标的影响。选用180只1日龄健康爱拔益加(AA)肉仔鸡(公雏),随机分为3组,每组6个重复,每个重复10只。3组分别为:正对照(PC)组,前期和后期饲粮CP水平分别为22.0%和20.0%;负对照组,前期和后期饲粮CP水平分别为18.0%和15.5%;Gly组,在负对照组基础上添加Gly,使饲粮Gly和丝氨酸水平为2.32%。试验期42 d,分为前期(1~21 d)和后期(22~42 d)2个阶段。结果表明:1)饲粮CP水平降低4.0~4.5个百分点,试验1~21 d的料重比(F/G)显著升高(P0.05),22~42 d的平均日增重(ADG)显著降低(P0.05);添加Gly后,1~21 d F/G显著降低(P0.05),22~42 d ADG显著升高(P0.05),达到了与PC组相似的生长性能。2)CP水平降低,肉仔鸡42日龄胸肌率降低了9.5%(P0.05)、腹脂率提高了60.3%(P0.05);添加Gly后,胸肌率提高了17.6%(P0.05),腹脂率降低了34.6%(P0.05),获得了与PC组相似的胴体组成。CP水平降低、添加Gly均未显著影响屠宰率、全净膛率和腿肌率(P0.05)。3)各组间血液生化指标均无显著差异(P0.05)。可见,低CP饲粮中添加Gly可以改善生长性能和胴体组成,结果提示了Gly在肉仔鸡低CP饲粮中的可应用性。     

Effect of dietary protein content on growth and body composition of fast and slow feathering broiler chickens

1. Broilers were produced from two lines of breeders selected for three generations for fast and slow feather growth. The base population foundation stock originated from a commercial pedigree female line, which carried only the dominant sex‐linked late feathering gene K. Three isoenergetic (12.7 MJ AME/kg) starter and grower diets were formulated to contain 280, 240 and 200, and 260, 220 and 180 g/kg protein, respectively, and fed to 156 broilers of each sex to give three starter‐grower combinations.

2. Broiler performance in terms of growth, food conversion ratio, carcase meat, fat and protein content was optimised on the 240 to 220 g/kg protein starter‐grower series of diets.

3. Birds of the slow line were significantly (P<0.05) heavier at 48 d of age and had the same food intake and food conversion ratio as birds of the fast feathering line.

4. The slow line birds had significantly (P<0.01) shorter feathers and less total plumage weight at 48 d. The slow line birds had significantly (P<0.001) less carcase fat and significantly (P<0.05) more carcase protein than the fast line. The slow line had significantly more carcase meat (P<0.01) within which a greater breast meat yield was evident (P<0.001).     

Effects of breed and dietary nutrient density on the growth performance,blood metabolite,and genes expression of target of rapamycin (TOR) signalling pathway of female broiler chickens

This study was conducted to compare the effects of exchanged diets with identical energy level on characteristics of slow‐growing (WENs Yellow‐Feathered Chicken, WYFC) and fast‐growing (White Recessive Rock Chicken, WRRC) female chickens. A total of 1450 WYFC and 1150 WRRC 1‐day‐old female hatchlings were used. A high‐nutrient‐density (HND) diet and a low‐nutrient‐density (LND) diet were formulated for three phases. A completely randomized experimental design with a 2 × 2 factorial arrangement (diet and breed), each with five replicates of 145 and 115 birds, was applied. The results showed that WRRC had a higher body weight (BW), average daily feed intake and average daily gain than WYFC throughout the experiment (p < 0.05). WYFC that were provided with HND groups had a higher BW only in the starter and grower phases, whereas WRRC had a higher BW in the HND group than in LND groups throughout the experiment. The feed:gain ratio and protein efficiency ratio (PER) were better for WRRC in the starter and grower phases; however, these ratios were better for WYFC in the finisher period. The LND groups had a higher PER throughout the experiment for both breeds (p < 0.05). The breast and leg muscle weights were higher for WRRC compared with WYFC during the grower and finisher phases (p < 0.05). WRRC had a lower liver index but higher serum UA and alkaline phosphatase (ALP) concentrations than WYFC (p < 0.05). No diet effect was observed on organ indices, muscle yields or blood responses. The gene expressions of Rheb, TOR, S6K1 and 4E‐BP1 in gastrocnemius muscle were the highest in the WYFC‐LND groups at 63 and 105 days (p < 0.05). These findings suggested that different genotypes respond differently to changes in dietary nutrient density and that lower‐nutrient‐density diets are optimal for the long‐term housing of broiler chickens.     

Effects of methionine and betaine supplementation on growth performance, carcase composition and metabolism of lipids in male broilers

1. This study was conducted to investigate the effects of methionine and betaine supplementation on growth performance, carcase composition and lipid metabolism in growing broilers. 2. A total of 450 commercial broilers, 22 d of age, were randomly allocated to three groups, each of which included three replicates (50 birds per replicate). The groups received the same methionine-deficient diet supplemented with 0 or 1 g/kg methionine, or 0.5 g/kg betaine, respectively. 3. Methionine and betaine supplementation significantly improved weight gain and feed conversion. Supplemental methionine and betaine also significantly increased breast muscle yield and decreased abdominal fat content. Meanwhile, addition of methionine and betaine significantly increased the contents of creatine and free carnitine in liver, the activity of hormone-sensitive lipase in abdominal fat and the concentration of free fatty acid in serum, whereas uric acid concentration in serum was significantly decreased. 4. The results of this study suggest that betaine can spare methionine in its function as an essential amino acid and is as effective as methionine in improving performance and carcase quality of growing broilers if the diet is moderately deficient in methionine. The decrease in abdominal fat may be due to the increased carnitine synthesis in liver and hormone-sensitive lipase activity in abdominal fat.     

Dietary L-arginine supplementation beneficially regulates body fat deposition of meat-type ducks

1. Unlike mammals, uricotelic species, such as the duck, cannot synthesise endogenous arginine (Arg). This study was conducted to test the hypothesis that dietary L-Arg supplementation might regulate body fat deposition in ducks without affecting their fast growth rate. 2. A total of 160 21-d-old male and female White Pekin ducks were assigned randomly to two treatments: a non-supplemented control and supplementation at 10 g/kg L-Arg of a maize and soybean meal-based diet. 3. The 3-week feeding trial showed that the addition of L-Arg had no significant effect on feed intake, but significantly increased body weight gain by 5·2 %, breast muscle weight relative to live body weight by 9·9%, carcase crude protein content by 9·2%, ether extract content in breast muscle by 11·9%. Arg supplementation significantly decreased skin with fat and abdominal fat pad contents by 7·6% and 4·9% respectively and the ether extract content of carcase by 7·2%. 4. The results of this study indicate that a diet with 10 g/kg supplemental L-Arg could reduce the fat deposition of carcase and abdominal adipose cell size (diameter and volume), enhance intramuscular fat in breast muscles, as well as increase muscle and protein gain. The decreased fat depot in the carcase may be attributed to a reduction of hepatic lipogenic enzyme activity.     

Dietary methionine source and level affect hepatic sulfur amino acid metabolism of broiler breeder hens

A study was carried out to investigate the effects of dietary methionine source and level on plasma free amino acids patterns and the expression of genes involved in hepatic methionine metabolism in broiler breeders. A total of 2184 broiler breeders were assigned to 13 dietary treatments, with eight replicates per treatment. The 13 treatments included one control group and 12 additional treatments employing two sources and six levels (0.05, 0.10, 0.15, 0.20, 0.25 and 1.00%). Higher plasma methionine concentration was measured for DL‐methionine (DLM) treated hens. Plasma alanine concentration was linearly increased as DLM or 2‐hydroxy‐4‐(methylthio) butanoic acid (HMTBA) supplementation level increased. There was a linear increase in concentrations of tyrosine, valine, glycine and serine as dietary DLM supplementation level increased. Hens treated with DLM had higher relative expression of ADA than those fed HMTBA. The expression of MS, ADA, SAHH and MAT2A changed quadratically as HMTBA supplementation level increased, while the expression of GNMT and SAHH changed quadratically as DLM supplementation level increased. In conclusion, the effects of HMTBA on plasma free amino acid patterns and the expression of hepatic genes involved with methionine are different from DLM.