Effects of citric acid and microbial phytase on amino acid digestibility in broiler chickens

1. Two experiments with growing chickens were carried out to study the effects of the inclusion of a microbial phytase (Natuphos 5000) and citric acid (CA) in maize-soybean-based diets on the performance and apparent ileal digestibility (AID) of crude protein (CP) and amino acids (AA). In both experiments the diets were formulated to contain the same amounts of energy and protein. 2. In the first experiment, data were analysed as a 2 x 2 factorial arrangement with two concentrations of available phosphorus (AP) from one day to 3 weeks of age (3.5 and 2.2 g/kg) and for 3 to 6 weeks (2.7 and 1.4 g/kg), and two inclusions of commercial phytase (0 and 500 FTU/kg) in each period. The AID of CP and dispensable and indispensable AA were not modified by the AP content of the diet. Addition of phytase improved the AID of CP and dispensable and indispensable AA only at low AP levels. 3. In the second experiment, data were analysed as a 3 x 2 factorial arrangement with three concentrations of citric acid (0, 20 and 50 g/kg) and two inclusions of commercial phytase (0 and 750 FTU/kg). Diets were formulated with deficient contents of AP (2.5 g/kg). Performance was not affected by commercial phytase addition. The addition of CA reduced the weight gain but did not modify the feed intake and gain:feed. In general, the AID of CP and dispensable and indispensable AA were not affected by CA addition. Commercial phytase increased the apparent ileal digestibility of crude protein but had no effect on AID of dispensable and indispensable AA. 4. In conclusion, the present work showed that microbial phytase enhanced AA digestibility in maize-soy-based diet only at very low AP concentrations, and that CA had no affect on the AID of CP and dispensable and indispensable AA. No synergism between CA and microbial phytase was detected.     

Effects of increasing dietary concentrations of specific structured triacylglycerides on performance and nitrogen and energy metabolism in broiler chickens

Specific structured triacylglycerides (STG) containing medium chain fatty acids in sn-1,3 positions and a long chain fatty acid in sn-2 position were prepared from rapeseed oil and capric acid (C10:0). A total of 80 female broiler chickens (Ross 208) were randomly allocated into five dietary treatments as two series of 40 chicks: a basal diet with graded levels of STG of 0, 20, 40, 60 and 80 g/kg diet at the expense of rapeseed oil were fed to the chickens in groups of four. At 12 d of age the chickens were placed pair-wise in metabolism cages. The grower period (d 13-36) was divided into four consecutive balance periods each of 6 d. Two 24 h measurements of gas exchange in two open-air circuit respiration chambers were performed during the second and third day of each balance period. During the whole experiment there was a negative effect of the inclusion of STG on average feed intake. However, this only slightly affected average daily weight gain. Feed conversion efficiency improved linearly with the inclusion level of STG. Daily gain adjusted to mean daily feed intake increased linearly with inclusion rate of STG, indicating that the weight gain was affected by both feed intake and the enhancing effect on digestibility of STG. Weight of small intestine and colon decreased with increasing inclusion of STG. Utilisation of dietary protein relative to intake increased while that of retained fat tended to decrease resulting in a decreased utilisation of metabolisable energy (RE/ME) in birds receiving STG. Heat production (HE) was slightly lower in the STG groups. More of the dietary fat was oxidised when more STG was added, although the total amount of fat in the diets was kept constant.     

Effect of amino acid deficiency on precaecal amino acid digestibility in broiler chickens

In this study, we determined whether deficient dietary amino acid (AA) concentrations influence the precaecal (pc) AA digestibility when determined using the regression approach. We mixed two basal diets. Basal diet 1 was deficient in essential AAs, whereas adequate AA concentrations were ensured in basal diet 2 by adding free AAs. Rapeseed cake and full‐fat soya beans as test ingredients were included in the basal diets at levels of 100 and 200, and 150 and 300 g/kg, respectively, at the expense of maize starch. Each diet was tested with six replicates of 10 broiler chickens each. The feed intake of the chickens that were fed diets based on basal diet 2 was similar, whereas the feed intake of the chickens that were fed diets based on basal diet 1 differed considerably. The numerical differences in pc AA digestibility determined with basal diet 1 or 2 ranged from 2.6 percentage points to 20.8 percentage points in rapeseed cake and from 0.5 percentage points to 15.2 percentage points in soya beans. Across all measured AAs, the average differences were 10.1 percentage points and 5.4 percentage points in rapeseed cake and soya beans, respectively. The differences in the estimated pc AA digestibility between the basal diets were probably caused by different basal endogenous AA losses in the digesta between treatments as a consequence of different feed intake. Adequate AA concentrations and test ingredient levels that are specifically adjusted to avoid a negative effect on feed intake are recommended for future studies.     

日粮中添加(-)-羟基柠檬酸对肉鸡脂肪代谢的影响

为探讨(-)-羟基柠檬酸[(-)-HCA]对肉鸡脂肪代谢的影响,120羽21日龄罗氏308肉鸡随机分成4组,每组3个重复,每个重复10羽。分别于基础日粮中添加0、150、300和600 mg/kg的(-)-HCA,饲喂至50日龄,各组分别从每个重复中随机抽取4只肉鸡宰杀,采集血液、肝脏、腹脂、肌肉等样品。试验结果表明,与对照组相比,3个剂量组的(-)-HCA对腹脂率、日采食量、料重比影响虽无统计学上的差异,但3个剂量(-)-HCA的处理均有降低使腹脂率、日采食量,并提高饲料转化率的趋势。与对照组相比,600 mg/kg的(-)-HCA处理能显著降低肉鸡血清中甘油三酯(TG)和总胆固醇(TC)的含量(P0.05),但3个剂量组的(-)-HCA均可显著降低血清中游离脂肪酸(NEFA)的含量显著(P0.05)。与对照组相比,300和600 mg/kg的(-)-HCA处理可显著升高血清中高密度脂蛋白-胆固醇(HDL-C)的含量(P0.05),3个剂量的(-)-HCA处理均可显著降低血清中低密度脂蛋白-胆固醇(LDL-C)的含量(P0.05)。与对照组相比,300 mg/kg的(-)-HCA处理可显著提高肉鸡肝糖元的含量(P0.05),但3个剂量组的(-)-HCA对肌糖元的含量均无显著影响(P0.05)。3个剂量的(-)-HCA处理对肝脂酶活性均无统计学上的差异(P0.05),但不同剂量的(-)-HCA处理均有提高肝脂酶活性的趋势。提示(-)-HCA可通过抑制脂肪酸的合成、加快脂肪的分解,从而减少脂肪在肉鸡体内的沉积。     

Effects of temperature treatments on the energy and nitrogen metabolism of fed chickens

1. Calorimetric measurements were made for 5 d on individual broiler chickens (1 kg) fed ad libitum and acclimated or unacclimated to six temperatures from 2 to 35 °C (constant), or alternated between these temperatures and 22 °G (alternated). For the four treatments, heat production was related to temperatures and the resultant curves were significantly different.

2. Food intake, heat production and maintenance energy requirement all increased linearly with decreasing temperature. Metabolisability of the diet was only 13.8 kJ/g at 35 °C, compared with a mean value for all treatments of 14.1 kJ/g.

3. Energy retention and nitrogen (N) retention (g/d, or % dietary N) were maximal at 22 and 16 °C, however the amount of energy deposited as protein remained relatively constant below 30 °C.

4. Net availability of metabolisable energy was calculated in two ways: by calculating the increase in heat production of fed birds above their starvation values giving a mean value of 0.82; this was similar to the mean regression coefficient which included starvation data, and related ME intake and energy retention; but without these data availabilities ranged from 0.45 at 35 °C to 1.0 in the cold.

5. Acclimation or alternating of temperature had very few significant effects, however there were temperature x acclimation effects on N retention and heat production. Similarly alternating temperature significantly increased food intake and heat production at high temperatures, but decreased metabolisability of the diet to 13.7 kJ/g at 35 °C from an overall mean of 14.1 kJ/g.     

Protein and energy metabolism in broiler chickens selected for either body weight gain or feed efficiency

1. Correlated responses in protein and energy metabolism were studied in 2 lines of meat-type chickens selected during 6 generations for improved efficiency of food utilisation (line A) or greater body weight (line B). 2. Daily gain was 18% higher in line B but efficiency was 15% better in line A. 3. Metabolisability (ME/GE) was 0.752 in line A and 0.725 in line B. 4. Retained nitrogen as a fraction of nitrogen intake was 0.51 for line A and 0.46 for line B. 5. Energy retention as a fraction of metabolisable energy was 0.38 in line A and 0.43 in line B the difference being primarily attributable to greater fat retention in line B. 6. Selecting for improved efficiency of food utilisation in meat-type chickens having a growth capacity of 50 to 60 g was very effective and produced a lean bird with higher metabolisability of the diet.     

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.     

柠檬酸对西门塔尔牛日粮能量平衡和氮平衡的影响

选用4头年龄4岁、体况良好、平均体重500kg,装有永久性瘤胃瘘管的中国西门塔尔牛阉牛,采用4×4拉丁方设计．以混合精料和玉米秸秆为基础日粮,研究柠檬酸（0、100、200和300g／d）对日粮养分表观消化率的影响。结果表明：日粮添加柠檬酸200州组代谢能、沉积能、代谢能／总能、沉积能／消化能和沉积氮较对照组显著提高（P〈0．05）,沉积氮／消化氮较对照组极显著提高（P〈0．01）。根据试验结果推断日粮中柠檬酸的适宜添加水平为200g/d。     

Effects of rumen-protected amino acids on ruminant nitrogen balance, plasma amino acid concentrations and performance

A series of trials was conducted to determine the effects of supplemental rumen-protected methionine (RPMet) and lysine (RPLys) on nutrient metabolism and performance. In situ RPMet N disappearance was less than 4% following 48 h of incubation and was not affected (P greater than .05) by diet or resultant ruminal pH differences, indicating that RPMet was well protected from ruminal microbial degradation. Thirty-five Dorset-sired crossbred wether lambs (avg wt 28 kg) fed ground corn-soybean hull diets supplemented with urea were randomly assigned to one of the following treatments: 1) 0% RPMet, 2) .03% RPMet, 3) .06% RPMet, 4) .09% RPMet or 5) .12% RPMet. Dry matter, fiber and N digestibilities and N retention were not affected (P greater than .05) by treatment. Plasma methionine concentration tended to increase linearly (P less than .07) with dietary RPMet level. Six Simmental X Angus steers (avg wt 427 kg) were fed a corn grain-corn silage diet supplemented with urea and five levels of RPMet: 1) 0%, 2) .04%, 3) .08%, 4) .12% and 5) .16%. The plasma methionine concentration increased linearly (P less than .01) with dietary RPMet level. In a steer performance trial, no improvements in feedlot performance resulted due to these RPMet levels (P greater than .05), suggesting that the control diet (0% RPMet) was meeting the methionine requirement of these steers. The effects of RPMet and RPLys on growing and finishing steer feedlot performance also were evaluated. Treatments were 1) urea control, 2) soybean meal positive control, 3) .09% RPMet + .06% RPLys, 4) .12% RPMet + .08% RPLys and 5) .15% RPMet + .10% RPLys. In the growing trial, added RPMet and RPLys did not improve steer feedlot performance. In the finishing trial, only steers fed .09% RPMet + .06% RPLys had higher (P less than .05) gains than those fed the urea control diet. These trials indicate that postruminal methionine and lysine supplies were not limiting feedlot steer performance.     

α-酮戊二酸对免疫应激仔猪肝脏氨基酸代谢的影响

试验研究了α-酮戊二酸(AKG)对免疫应激下仔猪氨基酸代谢的影响。将24头(24±1)日龄仔猪[杜×长×大,体重(7.25±0.23)kg]随机分为3个处理组,每个处理组设8个重复,每个重复1头猪。3个处理组分别为:对照组、应激对照组(LPS组)、试验组(AKG组)。各组基础日粮一致,空白对照组和应激对照组饲喂基础日粮+1%淀粉,AKG组饲喂基础日粮+1%AKG。试验期为17d。在试验第10、12、14和16d分别在LPS组和AKG组仔猪的腹膜注射80μg/kgBW脂多糖(LPS),对照组注射相应剂量的灭菌生理盐水。第17d清晨屠宰空腹仔猪,取肝组织样品,分析游离氨基酸含量。结果显示:免疫应激导致仔猪肝脏酪氨酸(Tyr)含量显著下降了81.82%(P0.05),赖氨酸(Lys)的含量有下降的趋势(P0.1),AKG组仔猪肝脏的Tyr、Lys含量与LPS组和对照组差异均不显著;丙氨酸(Ala)的含量较LPS组有升高的趋势(P0.1),谷氨酸(Glu)的含量较对照组和LPS组均有上升的趋势(P0.1)。以上结果表明:AKG能在一定程度上缓解免疫应激对仔猪氨基酸代谢的影响,减轻LPS刺激对仔猪肝脏损伤。     

Relationship between monensin and sulphur amino acid requirements IN broiler chickens

1. Diets containing 80, 100, 125, 150, 175 or 200 mg monensin/kg were fed to broiler chickens from 0 to 28 d in cages that prevented access to excreta.

2. Growth was depressed with 125 mg monensin or more/kg and food intake tended to decrease. Feathering was adversely affected with 175 mg or more/kg.

3. In a similar experiment, diets containing 8.8, 9.1, 9.4, 9.7 or 10.1 g total sulphur amino acids (SAA)/kg were supplemented with 125 or 80 mg monensin/kg and compared with a diet containing 8.8 g SAA and 33 mg robenidine/kg.

4. With 125 mg monensin/kg, body‐weight gain was significantly less than that of birds receiving robenidine if dietary SAA content was 9.4 g or less/kg. With 9.7 g SAA or more/kg, gain in birds receiving monensin was similar to that of birds receiving robenidine.

5. Monensin at 125 mg/kg therefore appears to increase the SAA requirement.     

Linear regression approach to study amino acid digestibility in broiler chickens

1. An experiment was conducted to investigate whether a linear regression approach is a suitable tool for determining the amino acid (AA) digestibility up to the terminal ileum of broiler chickens. Solvent-extracted rapeseed meal (RSM) was used as the model ingredient. 2. Ten diets with 5 different inclusion rates of RSM (60, 120, 180, 240 and 300 g/kg, corresponding to crude protein concentrations from 170 to 250 g/kg in the diet), each without or with a supplementation of phytase (500 U/kg), were fed ad libitum to broiler chickens between 14 and 21 d of age. Seven pens of 12 chickens were allocated to each treatment. Digesta were sampled on a pen basis from the section of the gastrointestinal tract between Meckel's diverticulum and 2 cm anterior to the ileo-caeco-colonic junction. Titanium dioxide was included as an indigestible marker. 3. The amounts of crude protein and AAs digested up to the terminal ileum constantly increased with increasing AA intake over the entire range of intakes. When the amount of an AA digested at the terminal ileum is linearly regressed against its intake, the deviation of the slope from 1 is caused by both the unabsorbed AA from RSM and from specific endogenous losses related to RSM. These slopes varied between 0.68 and 0.88 for individual AAs, and the slopes were unaffected by phytase supplementation. 4. It is suggested that a linear regression approach be adopted to study the AA digestibility of raw materials in chickens. Digestibility determined this way does not need any correction for basal endogenous loss.     

不同形式米渣蛋白对断奶鼠氮平衡和能量代谢的影响

选用20只体重相近的28日龄断奶Sprague-Dawley(SD)鼠,以豆粕蛋白(SB)为对照,采用4×4拉丁方设计对米渣(RD)、米渣蛋白酶解物(RD-H)、壁材型米渣蛋白酶解物(MF)进行28d的代谢试验。结果表明:米渣蛋白较大豆蛋白能显著提高氮沉积、促进脂肪的消化吸收(P0.01),SB、RD、RD-H、MF各组氮沉积分别为0.538、0.590、0.605、0.625g/d;米渣蛋白的体外低度预消化、脂肪的体外预乳化对其在试验鼠体内的消化吸收无影响(P0.05)。     

Fatty acid and energy metabolism in broiler chickens fed diets containing either beef tallow or an oil blend

The hypothesis tested was that the feeding of n‐6 polyunsaturated fatty acids (PUFA) results in more whole‐body fatty acid oxidation than the feeding of saturated fatty acids (SFA). It was reasoned that the increased fatty acid oxidation would be associated with enhanced whole‐body energy expenditure and stimulated de novo fatty acid synthesis. To put the hypothesis to the test, broiler chickens were fed diets containing either beef tallow as source of SFA or an oil blend as source of n‐6 PUFA. The broilers either had free access to their diet or were fed a restricted amount. Seven‐day‐old, male broiler chickens were used; they were kept individually in cages from 1 to 4 weeks of age. In the birds fed ad libitum, the n‐6 PUFA diet reduced average daily feed intake (ADFI), but did not significantly affect average daily weight gain (ADG) and the feed:conversion ratio (FCR). The lower ADFI on the n‐6 PUFA diet was associated with a higher apparent digestibility of total fatty acids. The ratio of deposition in the body to intake of digestible total PUFA, which reflected n‐6 PUFA, was significantly decreased by the n‐6 PUFA diet, pointing at preferentially increased n‐6 PUFA oxidation on the n‐6 PUFA diet. The ratio for n‐9 monounsaturated fatty acids (MUFA) was higher than 1.0, which agrees with net de novo synthesis, but the n‐6 PUFA diet induced a lower value than did the SFA diet. Feeding either the n‐6 PUFA or SFA diet did not influence energy expenditure expressed as percentage of energy intake. This study supports the idea that dietary n‐6 PUFA instead of SFA are preferentially oxidized, but no proof was obtained for enhanced energy expenditure and contrary to the hypothesis put forward, the n‐6 PUFA diet depressed de‐novo fatty acid synthesis.     

Effects of chitosan on growth performance and energy and protein utilisation in broiler chickens

1. Two experiments were conducted to investigate the effects of dietary chitosan on growth performance, energy availability and protein retention in broilers. 2. Experiment 1 was a 42-d growth assay, in which 294 1-d-old male broilers were given one of 7 dietary treatments. A control feed was supplemented with 5 levels of chitosan (0.2, 0.5, 1.0, 3.0 and 5.0 g/kg) or 50 mg/kg chlortetracycline (CTC). 3. Increasing chitosan inclusion gave a nonlinear increase (P< 0.001) in feed conversion efficiency (FCE). Optimal growth and feed conversion were obtained with 0.5-1.0 g/kg chitosan. 4. In experiment 2, 42 1-d-old male broilers (6/treatment) were individually housed but fed on the same diets as in experiment 1. Excreta were collected from d 19-21 and d 40-42. 5. The addition of 0.5-1.0 g/kg chitosan increased nitrogen retention compared with the control group (P< 0.01), while apparent metabolisable energy in the diets was not altered.     

Evaluation of xylanase and a fermentable xylo-oligosaccharide on performance and ileal digestibility of broiler chickens fed energy and amino acid deficient diets

The objective of this study was to evaluate the effect of a product consisting of a combination of xylanase and xylo-oligosaccharide (STBIO) on performance and ileal digestibility of broiler chickens fed energy and amino acid (AA) deficient diets. Day-old male Ross 308 broiler chicks were randomly allocated to 8 pens per treatment, with 25 chicks per pen. Treatments based on wheat-corn-soybean meal diets were arranged in a 3 × 2 factorial design: a positive control that met or exceeded nutrient recommendations (PC), a negative control diet with a 50 kcal/kg apparent metabolizable energy (AME) reduction (NC1) and NC1 with a 3% reduction in AA content (NC2), each with or without supplementation of 100 g/t of the STBIO. Body weight gain (BWG), feed intake, feed conversion ratio corrected for mortality (FCR) and the European production efficiency factor (EPEF) were recorded from 0 to 42 d. On d 42, ileal samples were collected to determine dry matter (DM), organic matter (OM), ash, protein and energy digestibility. A significant interaction was observed for BWG and feed intake (P < 0.001). The energy and AA reduction reduced (P < 0.05) BWG when compared to the PC. The effect of STBIO on BWG was greater in NC1 (+451 g/bird) than in NC2 (+314 g/bird) or PC (+176 g/bird) diets (P < 0.05), and that in NC2 with STBIO was equal to that in PC without STBIO, and that in NC1 with STBIO was equal to that in PC with STBIO. No interactions were observed on the EPEF or FCR; however, STBIO improved EPEF (P < 0.001) and FCR (P < 0.001) irrespective of the energy reduction or AA density. The intake of digestible DM, OM, ash and energy for the finisher period was increased with STBIO supplementation (P < 0.01). A significant interaction was observed for the intake of digestible protein. NC1 and NC2 reduced the intake of digestible protein; however, when STBIO was supplemented, it was improved in both diets to similar levels to the PC. The stimbiotic supplementation improved performance of broiler chickens fed all diets, particularly those deficient in AME and AA.     

Effect of dietary lysine to crude protein ratio on performance of male Ross 308 broiler chickens

Two experiments were conducted to determine the effect of dietary lysine to crude protein ratio on performance of male Ross 308 broiler chickens. In each experiment the diets were isocaloric and isonitrogenous but with different lysine to crude protein ratios. A complete randomized design was used in both experiments, the starter (1–21 days) and grower (22–42 days) experiments. The three starter diets, based on lysine to crude protein ratios, were L₀ (0.055), L₁ (0.066) and L₂ (0.077), while grower diets were L₃(0.047), L₄(0.061) and L₅(0.074). A quadratic type equation was used to determine ratios for optimum growth rate, feed conversion ratio, breast meat yield and breast meat nitrogen content. Dietary lysine to crude protein ratios of 0.066 and 0.077 supported optimum growth rate and feed conversion ratio, respectively, during the starter period. Dietary lysine to crude protein ratios of 0.073, 0.073, 0.069 and 0.079 supported optimum growth rate, feed conversion and breast meat yield and nitrogen content during the grower phase. Dietary lysine to crude protein ratio had no effect on diet intake and digestibility. The results indicate that at each phase a single dietary lysine to crude protein optimized both growth rate and feed conversion ratio. However, the ratio for optimum breast meat yield was lower than that for optimum growth rate and feed conversion ratio. These findings have implications on ration formulation for broiler chickens.     

Influence of dietary conjugated linoleic acid isomers on early inflammatory responses in male broiler chickens

1. The influence of dietary conjugated linoleic acid isomer (CLA, 0 and 10 g/kg) on the metabolic and physiological responses to immune stimulation induced by a single injection of Salmonella enteritidis lipopolysaccharide (LPS) or repeated injections of LPS and Sephadex G-50 was determined in male broiler chicks. 2. In experiment 1, 10-d-old chicks were fed on experimental diets for 14 d and half of the birds fed on each diet were injected intraperitoneally with LPS (1.5 mg/kg body weight). In experiment 2,7-d-old chicks were fed on experimental diets for 18 d. Immune stimulation was started at 19 d old and continued for 5 d. Half of the birds fed on each diet were injected intraperitoneally with 0.25 mg/kg body weight of LPS at 19, 21 and 23 d of age, and with 250 mg/kg body weight of Sephadex at 20 and 22 d of age to stimulate the immune system. 3. In experiment 1, giving CLA prevented an increase in blood heterophil to lymphocyte ratio 7 h after a single injection of LPS, and increases in plasma ceruloplasmin and alpha 1 acid glycoprotein (AGP) 24 h after the injection, but not 7 h after the injection. CLA also prevented a decrease in food intake for 24 h after LPS injection. 4. In experiment 2, the CLA diet partially prevented reductions in body weight gain and weight gain to feed intake ratio caused by repeated injections of LPS and Sephadex. Feeding CLA prevented increases in plasma ceruloplasmin and AGP at 24 d of age caused by repeated injections of LPS and Sephadex, but not at 20 d of age. 5. These results suggest that feeding CLA alleviates some undesirable metabolic and physiological changes induced by immunological stimulation in male broiler chicks.