Effect of dietary supplementation of mannanoligosaccharides on hepatic gene expressions and humoral and cellular immune responses in aflatoxin-contaminated broiler chicks.

The present study was conducted to investigate the effects of dietary supplementation of mannanoligosaccharides (MOS) on expression of hepatic immunological genes and immune responses in aflatoxin-contaminated broiler chicks. A total of 336 seven-day-old Ross broiler chicks were randomly allotted to 7 experimental treatments with 4 replicates and 12 birds per replicate. Experimental treatments consisted of 2 aflatoxin levels (0.5 and 2 ppm) and 3 supplemental MOS levels (0, 1 and 2 g/kg) as a 2 × 3 factorial arrangement in comparison with a control group (unchallenged group). The chicks were challenged with a mix of aflatoxins during 7-28 d of age. Results showed that aflatoxin challenge resulted in the lower antibody titers against infectious bronchitis (IBV) and bursal (IBD) diseases viruses. In addition, aflatoxin-contaminated birds had a lower (P < 0.0001) lymphocyte percentage and a decline in (P < 0.01) interleukin-2 (IL-2) mRNA abundance. Likewise, heterophil proportion, heterophil to lymphocyte ratio and gene expressions of hepatic interleukin-6 (IL-6) and C reactive protein (CRP) were raised (P < 0.001) by increasing dietary aflatoxin level. Dietary inclusion of MOS increased (P < 0.05) antibody titers against IBV, IBD and Newcastle disease virus. Lymphocyte proportion and hepatic IL-2 gene expression were greater (P < 0.0001) in MOS-supplemented birds. Furthermore, supplemental MOS decreased hepatic IL-6 and CRP abundances. Additionally, inclusion of 2 g/kg MOS resulted in the upregulation (P < 0.01) of hepatic IL-2 gene expression in birds contaminated with 0.5 ppm aflatoxin. The present results indicate that supplemental MOS could improve cellular immunity via the upregulation of hepatic IL-2 gene expression in birds challenged with aflatoxins.

Effects of dietary supplementation of choline and carnitine on growth performance, meat oxidative stability and carcass composition of broiler chickens fed diets with different metabolisable energy levels.

1. This study was conducted to investigate the effects of two lipotropic factors (choline and carnitine) on growth performance, oxidative stability of leg and breast muscles and carcass characteristics in broiler chickens fed diets differing in metabolisable energy (ME) levels. 2. A total of 540 one-d-old Ross 308 broiler chicks were allotted to 9 experimental diets, including three ME levels (control, or 0.42 or 0.84 MJ/kg higher ME) and three types of supplemental lipotropic factors (control, 1000 mg/kg of choline or 100 mg/kg of carnitine) as a 3 × 3 factorial arrangement of treatments. Average daily feed intake (ADFI), average daily gain (ADG) and feed conversion ratio (FCR) were recorded during the starter (1-14 d of age), grower (15-28 d of age) and finisher (29-42 d of age) periods. 3. Results showed that the increase in dietary ME level had no impact on ADFI during the starter and grower periods. In the finisher period, increasing dietary ME decreased (P < 0.001) ADFI. Raising dietary ME level by 0.84 MJ/kg resulted in the greater ADG during the grower (P < 0.05) and finisher (P < 0.001) periods. Moreover, an improvement in FCR was observed with feeding the +0.84 MJ/kg diet. Dietary supplementation of lipotropic factors improved FCR values in birds fed the control and +0.84 MJ/kg diets during the grower and finisher periods (P < 0.01). 4. Dietary supplementation of both choline and carnitine increased (P < 0.05) moisture content of leg muscle, although malondialdehyde content of leg muscle was decreased (P < 0.01) in the presence of both lipotropic factors. Dietary supplementation of carnitine decreased (P < 0.01) leg fat content, and this effect was more obvious with higher ME levels, giving a significant ME × lipotrope interaction (P < 0.05). Higher dietary ME level (+0.84 MJ/kg) reduced (P < 0.05) protein content of breast muscle, but this factor was increased (P < 0.05) by dietary supplementation of choline. 5. Although dietary ME level had no marked effect on carcass yield and internal organ weight, supplemental choline increased (P < 0.01) carcass yield. 6. The results from this trial indicated that dietary supplementation with lipotropic factors can improve feed efficiency in high energy diets. In addition, oxidative stability of leg/breast muscles was improved as a result of dietary supplementation with choline or carnitine.

Marginal deficiencies of dietary arginine and methionine could suppress growth performance and immunological responses in broiler chickens.

The present study was conducted to investigate the effects of different levels of dietary arginine (Arg) and methionine (Met) on performance, immune responses, and carcass characteristics of broiler chickens. A total of 540 day-old Ross 308 broiler chicks were randomly assigned into the nine experimental diets, consisting five replicates of 12 birds each. Dietary treatments included three different levels (90%, 100%, and 110% of National Research Council [NRC] specifications) of either dietary Arg or Met, which were fed to the birds according to a 3 × 3 factorial arrangement of treatments during a 42 days feeding trial. Results showed that supplementation of Arg and Met into the deficient-diets increased (p < .01) weight gains during all trial periods. Although average daily feed intake (ADFI) was not influenced by dietary treatments, increasing Arg up to 100% of NRC recommendations improved (p < .05) feed conversion ratio (FCR) throughout the trial period. Similarly, supplementation of deficient-diets with Met improved FCR values. There was a significant (p < .01) Arg × Met interaction for ADFI during the starter period; increasing the dietary Arg level increased ADFI when the diets were deficient in Met, while had an opposite effect in diets containing higher dietary Met levels. On the other hand, dietary Met fortification improved (p = .067) FCR values to a greater extent in 110% Arg-diets during the entire trial period. Although different levels of Arg and Met had no marked effects on carcass yield and abdominal fat percentage, supplemental Arg up to 100% of NRC values increased (p < .01) the relative weights of spleen and bursa of Fabricius. Furthermore, bursa weight was affected by Arg × Met interaction (p < .01), so that supplemental Arg level of 100% of NRC increased the relative bursa weight in birds that were fed diets containing 90% and 110% of Met. Serum uric acid level was decreased (p < .05) as a result of dietary Arg fortification up to 110% of NRC recommended values. Supplementation of deficient-diets with Met decreased (p < .05) serum cholesterol level. Although Newcastle antibody titer was not affected by dietary Arg or Met levels, Arg fortification of deficient-diets increased (p < .001) antibody responses against infectious bronchitis (IBV) and bursal (IBD) disease viruses. Similarly, Met supplementation of deficient-diets increased IBD antibody titer. There were significant (p < .05) Arg × Met interactions for IBV and IBD titers; Met fortification of 110% Arg-diets was more effective in increasing antibody titers. An increase in dietary Met level up to 100% of NRC values increased (p < .001) serum concentration of γ-globulins. The present findings imply that supplemental Arg could affect feed efficiency and antibody responses when the diets were already fortified with a sufficient Met level.

Effects of dietary inclusion of silymarin on performance, intestinal morphology and ileal bacterial count in aflatoxin-challenged broiler chicks.

This study was conducted to investigate the effect of dietary supplementation of silymarin on performance, jejunal morphology and ileal bacterial population in broiler chicks intoxicated with a mix of aflatoxins. A total of three hundred thirty six 7-day-old Ross broiler chicks were randomly distributed between seven experimental groups with four replicates of 12 birds each. Experimental treatments consisted of a control group (unchallenged), and a 2 × 3 factorial arrangement, including two aflatoxin levels (0.5 and 2 ppm) and three levels of silymarin (0, 500 and 1000 ppm). Birds were challenged with a mix of aflatoxins from 7 to 28 days of age. Results showed that increasing aflatoxin level resulted in decreased average daily feed intake (ADFI) and weight gain (ADWG), consequently impaired feed conversion ratio (FCR) throughout the trial period. Dietary supplementation of silymarin resulted in the marked increases in ADFI and ADWG, and improved FCR values in aflatoxin-challenged chicks. Ileal bacterial populations at days 28 and 42 of age were increased by incremental levels of aflatoxins. On the other hand, dietary silymarin supplementation suppressed ileal populations of Escherichia coli, Salmonella, Klebsiella and total negative bacteria in aflatoxicated birds. Increase in dietary aflatoxin level resulted in the decreased villi height, villi height-to-crypt depth ratio (VH:CD), villi surface area and apparent villi absorptive area, while it increased crypt depth, goblet cell count and lymphoid follicular diameter. Feeding silymarin at the level of 1000 ppm increased villi height and VH:CD in aflatoxicated birds. Present results indicate that dietary inclusion of silymarin could improve performance by suppressing ileal bacteria and enhancing absorptive surface area in aflatoxin-challenged broiler chicks.

Effect of early feed restriction on physiological responses, performance and ascites incidence in broiler chickens raised in normal or cold environment.

Intensive selection of broilers for faster growth and better feed efficiency resulted in greater susceptibility to metabolic disorders such as ascites syndrome, which is one of the major causes of mortality and economic loss in broiler industry. Whereas cool temperature is one of the primary triggers for ascites, early feed restriction (FDR) significantly alleviates its incidence and mortality. However, little is known about effects of FDR, cold environmental temperature and their interaction on physiological responses in broiler chickens. For this purpose, 320 one-day-old male broilers were divided into two treatment groups of Ad libitum (Ad) and feed restricted (FR) with eight pen replicates each. Chickens in FR group underwent feed access limitation from days 7 to 14 of age. On day 21 half of the birds (four pens) in each group exposed to the cold temperature (CT) and the other half (four pens) continued at normal temperature (NT). Average daily feed intake, average daily weight gain and feed conversion ratio (FCR) were measured at days 7, 14, 21, 28 and 42. At 39 and 46 days of age two chicks with a BW around the pen average were selected from each pen and slaughtered after collecting blood samples. Then, relative weight of internal organs and right ventricle weight per total ventricle weight (RV : TV) ratio were calculated. Compared with NT group, CT birds had higher daily feed intake and FCR (P<0.05) from day 28 to 42. Cumulative ascites mortality in CT chickens was higher (P<0.001) than NT chicks. Within the CT group, ascites mortality in FR chickens was reduced (P<0.001) to 1.25% compared with 8.75% in Ad chicks. Birds in CT group had significantly (P<0.05) thicker right ventricle and greater relative weight of heart, hematocrit and triiodothyronine concentration. However, none of these parameters were affected by FDR. Under cold stress conditions, FDR reduced activity of alanine aminotransferase and aspartate aminotransferase (P<0.05). Serum triglyceride, cholesterol, high-density lipoprotein and total protein were not influenced by either temperature or feeding regimen. In conclusion, these findings suggest that FDR reduces ascites incidence mainly by allowing better development of internal organs, which helps them to cope with the high metabolic pressure and suffer less damage.

Effects of dietary fat source and supplemental lysophosphatidylcholine on performance, immune responses, and ileal nutrient digestibility in broilers fed corn/soybean meal- or corn/wheat/soybean meal-based diets.

Two separate experiments were conducted to investigate the effect of different fat sources and a supplemental exogenous emulsifier (lysophosphatidylcholine, LPC) on growth performance, antibody production titers, and ileal nutrient digestibility in broiler chicks fed with different basal diets. A total of 288 one-day-old Ross 308 chicks were used for each trial (6 dietary treatments based on 3 × 2 factorial arrangements of treatments in both trials) with 4 replicates of 12 birds each. Dietary treatments consisted of 3 different fat sources (soy oil, SO; soy free fatty acids, SFFA; and palm fat powder, PFP) and 2 LPC levels (0 and 0.1% of diet), which were evaluated with 2 different basal diets (corn/soybean meal-based diets in Exp. 1, or corn/wheat/soybean meal-based diets in Exp. 2). In Exp. 1, average daily feed intake (ADFI) was increased (P < 0.01) in birds fed PFP diets compared with those fed SO or SFFA diets. Although supplemental LPC decreased (P < 0.01) ADFI, the birds fed SFFA diets had the greater ADFI at the presence of LPC (fat source × LPC, P < 0.01). Dietary supplementation of LPC caused a 4.6% improvement (P < 0.001) in average daily weight gain (ADWG) and consequently improved (P < 0.01) feed conversion ratio (FCR). Supplemental LPC was more effective in increasing ADWG in SFFA-containing diets, resulted in a significant (P < 0.01) dietary fat source × LPC interaction. Dietary inclusion of LPC increased (P < 0.01) bursa weight and improved (P < 0.05) antibody production titers against sheep red blood cells and Newcastle disease virus during primary responses. Ileal digestibility of ether extract (EE) was improved (P < 0.05) in birds fed diets containing SO as compared with those fed PFP diets; dietary LPC supplementation, however, had no marked effect on ileal nutrient digestibility. In Exp. 2, ADWG was greater (P < 0.05) in birds fed SO-containing diets compared with PFP-supplemented broiler chicks. Furthermore, dietary supplementation with LPC improved (P < 0.05) FCR value by 2.1%. Relative thymus weight was greater (P < 0.05) in birds fed LPC-supplemented diets than those fed unsupplemented diets. Supplemental LPC increased (P < 0.05) Gumboro antibody titer, and the lowest antibody response was allotted to the birds fed PFP diets. The greatest (P < 0.05) EE digestibility was assigned to the birds fed SO and SFFA diets. The present findings showed that birds fed SFFA-containing diets had similar performance as SO birds, and supplemental LPC improved overall performance especially in SFFA-fed birds.

Effect of extrusion processing of soybean meal on ileal amino acid digestibility and growth performance of broiler chicks.

The present experiments were conducted to investigate the efficacy of extrusion of inadequately processed soybean meal (SBM) on amino acid (AA) digestibility and performance of broiler chicks. In Exp. 1, 180 day-old Ross broiler chicks were randomly distributed between 6 pen replicates (15 chicks each) of 2 dietary treatments; diets based on SBM or extruded SBM (ESBM) as the main protein sources. Based on the results of Exp. 1 and AA digestibility assay, Exp. 2 was designed using 216 day-old Ross broiler chicks (6 replicates of 18 chicks each), in which dietary SBM content was replaced by 86% using ESBM. This replacement caused about a 9% decrease in dietary crude protein (CP) level. Results showed that coefficients of CP and AA digestibility were greater (P < 0.05) for ESBM than those of SBM. Extrusion processing of SBM increased digestibility coefficients of Lys, Thr, Cys, Leu, Phe, Tyr, Pro, Ser, and Gly. Except during the starter period, dietary inclusion of ESBM increased (P < 0.05) average daily feed intake (ADFI) in Exp. 1 and caused increases (P < 0.01) in average daily weight gains (ADWG) throughout the trial period. Also, using ESBM improved the (P < 0.01) feed conversion ratio (FCR) during starter and finisher periods. In Exp. 2, reducing dietary CP level using ESBM decreased both ADFI (P < 0.05) and ADWG (P < 0.01) in the starter period. During grower, finisher, and entire trial periods, however, ADFI and ADWG were not influenced by dietary treatments. Dietary inclusion of ESBM improved (P < 0.05) FCR value in the finisher period. Although carcass yield was not affected by dietary treatments, reducing dietary CP level resulted in an increase (P < 0.05) in abdominal fat percentage. Moreover, a decrease in dietary CP level reduced (P = 0.08) breast yield. The present findings indicate that extrusion of SBM could improve its nutritive value for broiler chicks. Using ESBM, one can reduce dietary CP level by about 9% without any detrimental effect on performance parameters of broiler chicks.

Dietary chromium methionine supplementation could alleviate immunosuppressive effects of heat stress in broiler chicks.

The present study was conducted to investigate the effects of dietary supplementation of chromium methionine (CrMet) on performance, immune responses, and stress status of broiler chicks subjected to heat-stress conditions. A total of 450 day-old Ross 308 broiler chicks were randomly distributed between 5 replicate pens (15 birds each) of 6 experimental treatments according to a 2 × 3 factorial arrangement of treatments including 2 temperature conditions (thermoneutral and heat stress) and 3 supplemental Cr levels (0, 500, and 1,000 µg/kg as CrMet). For induction of heat stress, the house temperature was set at 35 ± 2°C from 15 to 42 d of age. Results showed that the chicks subjected to heat-stress condition had lower (P < 0.01) feed intake, BW gain, and deteriorated (P < 0.05) feed conversion values compared with those kept in the thermoneutral house. Dietary supplementation with CrMet increased (P < 0.01) feed intake and improved (P < 0.01) weight gain and feed efficiency. There were significant Cr level × temperature interactions, so that inclusion of CrMet into the diets was more effective in heat-stressed chicks. Exposure to heat stress suppressed (P < 0.01) cutaneous hypersensivity response to phytohemagglutinin-P injection at 30 d of age, and dietary supplementation of 500 µg Cr/kg induced (P < 0.05) this response, with the greater impacts in heat-stressed chicks, resulting in a significant (P < 0.01) Cr × temperature interaction. Antibody responses against Newcastle and infectious bronchitis disease viruses were diminished (P < 0.01) in heat-stressed chicks. Dietary inclusion of CrMet improved (P < 0.05) antibody responses to different immunostimulants, and this effect was more pronounced in heat-stressed chicks. Exposure to heat stress caused a significant (P < 0.05) decrease in the proportion of helper (CD4+) T lymphocytes and increased cytotoxic (CD8+) T lymphocytes, resulting in a decreased (P < 0.01) CD4+ to CD8+ ratio in peripheral blood circulation. Supplementation of CrMet to heat-stressed chicks modulated (P < 0.01) plasma corticosterone level. The present findings indicate that dietary CrMet supplementation could alleviate heat-stress-induced growth retardation in broiler chicks. Moreover, supplemental CrMet modulated suppressive effects of heat stress on cellular and humoral immune responses.

Effect of dietary supplementation of mannan-oligosaccharides on performance, blood metabolites, ileal nutrient digestibility, and gut microflora in Escherichia coli-challenged laying hens.

The present study was carried out to investigate the effect of dietary supplementation of different levels of mannan-oligosaccharides (MOS) on performance, egg quality, immune responses, and gut microflora in laying hens exposed to Escherichia coli (E. coli) challenge. A total of 180 Hy-Line W-36 laying hens, 55 wk of age, were randomly distributed among 5 dietary treatments with 6 replicates of 6 hens each. Experimental diets consisted of 5 graded levels of MOS (0, 0.05, 0.1, 0.15, and 0.2% of diet). The study lasted 77 d including 7 d for adaptation and 70 d as the main experimental period subdivided into two 35-d periods. The results showed increases (P<0.05) in egg production percentage and egg mass, and a decrease (P<0.05) in feed conversion ratio (FCR) in birds fed the diets containing 0.1 and 0.15% MOS compared with control birds during the first 35-d period. In addition, there were significant differences between dietary treatments for egg mass and FCR during the second 35-d, with the best (P<0.05) values observed for hens fed on 0.1% MOS-supplemented diet. Feed intake and egg weight, however, were not influenced by dietary treatments throughout the experimental period. Compared to control birds, supplemental MOS resulted in 9.8% (P<0.01) and 8.1% (P<0.05) increases in hen-day egg production and egg mass, respectively, during the entire experimental period. Dietary supplementation with 0.1 to 0.2% MOS decreased (P<0.01) serum triglycerides concentration compared with control birds. In addition, serum concentration of low-density lipoproteins was reduced (P<0.001) by all supplemental MOS levels. In contrast to Newcastle antibody titer, primary antibody response against sheep red blood cell was significantly (P<0.05) affected by supplemental MOS. Supplementation of MOS into the diet caused increases in digestibility coefficients of DM (P<0.05) and CP (P<0.01). In addition, there was a significant (P<0.01) difference between dietary treatments for ileal ether extract digestibility, with the highest digestibility values assigned to the hens supplemented with 0.05% MOS. Although dietary MOS supplementation had no effect on ileal E. coli and total bacteria enumerations, it resulted in a decrease (P<0.01) in Salmonella count and increased Lactobacillus. The present findings indicate that MOS supplementation of laying hens under bacterial challenge could improve productive performance probably through modification of intestinal bacterial populations and improving nutrient digestibility.

Improved performance and immunological responses as the result of dietary genistein supplementation of broiler chicks.

The present study aimed to investigate the effect of supplemental genistein (an isoflavonoid) on performance, lymphoid organs' development, and cellular and humoral immune responses in broiler chicks. A total of 675-day-old male broiler chicks (Ross 308) were randomly assigned to the five replicate pens (15 chicks each) of nine experimental diets. Dietary treatments included a negative (not-supplemented) control diet, two positive control groups (virginiamycin or zinc-bacitracin, 20 mg/kg), and diets containing 10, 20, 40, 80, 160 and 320 mg/kg of genistein. The cutaneous basophil hypersensivity (CBH) test was measured at day 10 of age after toe web injection with phytohemagglutinin-P. In addition, sera samples were collected after different antigen inoculations to investigate antibody responses. At day 28 of age, three randomly selected birds from each pen were euthanized to evaluate the relative weights of lymphoid organs. Results showed that dietary supplementation of both antibiotics increased (P<0.01) feed intake during 1 to 42 days of age. Furthermore, daily weight gain was influenced (P<0.01) by dietary treatments throughout the trial, so that the birds fed on antibiotics and 20 to 80 mg/kg genistein diets revealed the greater weight gains compared with other experimental groups. The best (P<0.05) feed conversion ratio assigned to the birds fed on diets containing antibiotics and moderate levels (40 to 80 mg/kg) of genistein. Although the relative weights of thymus (P<0.05) and bursa of Fabricius (P<0.01) were greater in birds fed on genistein-supplemented diets compared with antibiotics-supplemented birds, the spleen weight was not affected by experimental diets. Similarly, CBH response and antibody titers against Newcastle and infectious bronchitis disease viruses were markedly (P<0.05) greater in chicks fed on diets supplemented with 20 to 80 mg/kg of genistein. Interestingly, the higher dosages of genistein suppressed CBH and antibody responses to the levels seen by control and antibiotics chicks. Dietary inclusion of genistein increased (P<0.05) lymphocytes and subsequently reduced (P<0.01) heterophil to lymphocyte ratio. The present findings indicate that dietary genistein supplementation at the levels of 20 to 80 mg/kg not only improves growth performance, but also could beneficially affect immunological responses in broiler chicks.

Dietary supplementation of organic selenium could improve performance, antibody response, and yolk oxidative stability in laying hens fed on diets containing oxidized fat.

The present study was carried out to investigate the effect of dietary supplementation of organic selenium (Se) on performance, egg quality indices, and yolk oxidative stability in laying hens fed diets with different fat sources. A total of 270 Hy-line W-36 Leghorn hens of 47 weeks of age were randomly distributed into the 5 replicate cages of 9 dietary treatments. Experimental diets consisted of a 3 × 3 factorial arrangement of treatments with three different fat sources (soybean oil, SO; yellow grease, YG; and palm fat powder, PFP) and three different levels of supplemental Se (0, 0.2, and 0.4 mg/kg of diet) as supplied by zinc-L-selenomethionine (ZnSeMet) complex, which fed during a 77-day feeding trial including 7 days for adaptation and 70 days as the main recording period. Results showed that the highest (P < 0.05) egg weights assigned to the hens fed on SO-supplemented diets. Hen-day egg production was affected by both dietary fat source (P < 0.01) and Se level (P < 0.05) throughout the trial period. Regardless of dietary fat source, dietary supplementation of ZnSeMet improved (P < 0.05) egg mass during all trial periods. Moreover, the significant (P < 0.05) fat source× Se interactions were observed for egg mass, so that dietary supplementation with 0.4 mg/kg Se was more effective in diets supplemented with YG. Although feed intake was not affected by experimental diets during the first 35-day period, dietary inclusion of PFP reduced feed intake during both second 35-day (P < 0.01) and entire trial period (P < 0.05). The best (P < 0.01) feed conversion ratio during the first 35-day period was assigned to the birds fed on SO-diets, followed by those fed YG-diets. Dietary supplementation of ZnSeMet improved (P < 0.05) feed efficiency during the first 35-day period. Supplementation of ZnSeMet into the diets increased yolk index, with more impact in hens fed on YG-diets. The highest concentration of yolk malondialdehyde was observed in YG-fed groups, and ZnSeMet supplementation of diets decreased (P < 0.05) yolk malondialdehyde. The highest (P<0.01) glutathione peroxidase activity was observed for hens fed on diets supplemented by YG, followed by those on SO-diets. Although different fat sources had no effect on antibody titer against Newcastle disease virus, supplemental ZnSeMet improved (P < 0.05) antibody response. The present findings indicate that dietary supplementation of ZnSeMet could improve performance parameters and egg oxidative stability in laying hens, with the highest impact in diets containing oxidized (high peroxide values) fat sources.

Effects of dietary organic chromium and vitamin C supplementation on performance, immune responses, blood metabolites, and stress status of laying hens subjected to high stocking density.

The present study was carried out to investigate the effects of dietary supplementation of chromium-methionine (CrMet) and vitamin C (VC) on performance, immune response, and stress status of laying hens subjected to high stocking density. A total of 360 Hy-Line W-36 leghorn hens (at 26 wk old) were used in a 2×3×2 factorial arrangement that had 2 cage densities (5 and 7 hens per cage), 3 Cr levels (0, 500, and 1,000 ppb as CrMet), and 2 dietary VC levels (0 and 500 ppm as L-ascorbic acid). The trial lasted for 12 wk. The first 2 wk were for adaptation (26 to 28 wk of age), and the remaining 10 wk served as the main recording period. In addition to performance, immune response to Newcastle disease virus (NDV) was assessed at d 7 and 14 postvaccination. Also, the birds' stress status was evaluated by analyzing appropriate plasma metabolites. The results showed that hens in cages with higher stocking density had lower hen-day egg production, egg mass, and feed intake compared with those in normal density cages (P<0.05). Dietary CrMet supplementation caused significant increases in egg production and egg mass (P<0.01). There were significant Cr × VC interactions related to egg production and feed conversion efficiency (P<0.01); dietary CrMet supplementation was more effective in improving egg production and feed conversion ratio in VC-unsupplemented diets. Although plasma concentrations of triglycerides and high-density lipoproteins were not influenced by dietary treatments, supplemental CrMet decreased plasma cholesterol levels (P<0.05). Plasma insulin and glucose levels of hens kept at a density of 7 hens/cage were significantly higher than those of hens in normal cage density (P<0.01), and dietary CrMet supplementation decreased plasma concentrations of insulin (P<0.001) and glucose (P<0.01), with higher impacts in high stocking density-challenged hens. While high stocking density caused a marked increase in plasma corticosterone (P<0.01), both supplemental CrMet and VC decreased it to near normal levels. There were significant stocking density×Cr interactions related to plasma insulin and corticosterone concentrations (P<0.01); supplemental CrMet was more effective in lowering these hormones in high stocking density-challenged hens. The high stocking density challenge suppressed NDV antibody response (P<0.001), while dietary supplementation of CrMet improved antibody titers against NDV at d 14 post vaccination particularly in hens kept at a density of 7 hens/cage (P<0.01). From the present observations, it can be concluded that CrMet can improve laying performance largely because it alleviates harmful responses to stressful conditions.

Effects of dietary substitution of zinc-methionine for inorganic zinc sources on growth performance, tissue zinc accumulation and some blood parameters in broiler chicks.

This study was designed to evaluate the effects of dietary inclusion of zinc-methionine (ZnMet) as a replacement for conventional inorganic zinc sources on performance, tissue zinc accumulation and some plasma indices in broiler chicks. A total of 450-day-old Ross male broiler chicks were randomly assigned to five pen replicates of nine experimental diets. Dietary treatments consisted of two basal diets supplemented with 40 mg/kg added Zn as feed-grade Zn sulphate or Zn oxide in which, Zn was replaced with that supplied from ZnMet complex by 25, 50, 75 or 100%. At 42 days of age, three randomly selected birds from each pen were bled to measure plasma metabolites; then, the chicks were slaughtered to evaluate carcass characteristics. Results showed that dietary treatments affected (p < 0.05) feed intake during the starter period, and chicks on Zn oxide diets consumed more feed than sulphate counterparts. Furthermore, dietary substitution of inorganic Zn sources by ZnMet caused improvements (p < 0.01) in body weight gain during all experimental periods. Dietary supplementation of ZnMet improved feed conversion efficiency during 1-21 and 1-42, but not in 21-42 days of age. Complete replacement of inorganic Zn by that supplied from ZnMet caused an increase (p < 0.05) in relative liver weight. Similarly, dietary inclusion of ZnMet increased breast meat and carcass yields and reduced abdominal fat percentage (p < 0.05). Incremental levels of ZnMet increased (p < 0.05) zinc concentrations in liver and thymus, and the highest zinc accumulations were seen in 100% ZnMet-supplemented birds. Interestingly, introduction of ZnMet into the diets partially in place of inorganic sources resulted in decreases (p < 0.01) in plasma uric acid and triglycerides concentrations. The present findings indicated that dietary ZnMet inclusion in replacement of inorganic sources in addition to improving growth performance, reduced plasma uric acid and triglycerides concentrations, consequently decreased abdominal fat pad and increased carcass meat yield.

Effects of decreasing metabolizable protein and rumen-undegradable protein on milk production and composition and blood metabolites of Holstein dairy cows in early lactation.

This study was conducted to evaluate the effects of decreasing dietary protein and rumen-undegradable protein (RUP) on production performance, nitrogen retention, and nutrient digestibility in high-producing Holstein cows in early lactation. Twelve multiparous Holstein lactating cows (2 lactations; 50 ± 7 d in milk; 47 kg/d of milk production) were used in a Latin square design with 4 treatments and 3 replicates (cows). Treatments 1 to 4 consisted of diets containing 18, 17.2, 16.4, and 15.6% crude protein (CP), respectively, with the 18% CP diet considered the control group. Rumen-degradable protein levels were constant across the treatments (approximately 10.9% on a dry matter basis), whereas RUP was gradually decreased. All diets were calculated to supply a postruminal Lys:Met ratio of about 3:1. Dietary CP had no significant effects on milk production or milk composition. In fact, 16.4% dietary CP compared with 18% dietary CP led to higher milk production; however, this effect was not significant. Feed intake was higher for 16.4% CP than for 18% CP (25.7 vs. 24.3 kg/d). Control cows had greater CP and RUP intakes, which resulted in higher concentrations of plasma urea nitrogen and milk urea nitrogen; cows receiving 16.4 and 15.6% CP, respectively, exhibited lower concentrations of milk urea nitrogen (15.2 and 15.1 vs. 17.3 mg/dL). The control diet had a significant effect on predicted urinary N. Higher CP digestibility was recorded for 18% CP compared with the other diets. Decreasing CP and RUP to 15.6 and 4.6% of dietary dry matter, respectively, had no negative effects on milk production or composition when the amounts of Lys and Met and the Lys:Met ratio were balanced. Furthermore, decreasing CP and RUP to 16.4 and 5.4%, respectively, increased dry matter intake.

Effect of different levels of black cumin (Nigella sativa L.) on performance, intestinal Escherichia coli colonization and jejunal morphology in laying hens.

This study was conducted to investigate the effects of different levels of black cumin seeds (Nigella sativa L.) on performance, intestinal Escherichia coli count and morphology of jejunal epithelial cells in laying hens. A total of 100 Leghorn laying hens (Hy-Line W-36) of 49 weeks old were randomly distributed among five cage replicates of five birds each. Experimental diets consisted of different levels (0%, 1%, 2% and 3% of diet) of dietary black cumin inclusion. The experimental period lasted for a total of 10 weeks, and egg quality indexes and laying hens' performance were measured as two 35-day trial periods. At the final day, two hens per replicate were slaughtered to investigate the influence of dietary treatments on intestinal E. coli colonization and morphology of jejunal cells. Although dietary black cumin in all supplementation levels decreased (p < 0.05) the enumeration of ileal E. coli, the morphological and histological alterations in small intestine such as enhancement of villus height to crypt depth ratio, increased goblet cell numbers and proliferation of lamina propria lymphatic follicles were observed after dietary supplementation with at least 2% black cumin. Dietary treatments decreased (p < 0.05) the concentration of serum cholesterol and triglycerides and increased (p < 0.05) serum HDL concentration and relative weight of pancreas; however, the egg yolk cholesterol was not influenced by dietary treatments. In addition, dietary supplementation with black cumin improved (p < 0.05) eggshell quality and Haugh unit. The best feed conversion ratio was obtained when diets were supplemented with 2% black cumin. This improvement was due to the increase (p < 0.05) in egg mass and contemporaneous decrease (p < 0.01) in feed consumption. The present results indicated that regardless of supplementation level, dietary inclusion of black cumin decreased E. coli enumeration in ileal digesta and improved serum lipid profile and eggshell quality, whereas the best intestinal health indices and haying hens' performance were obtained by at least 2% black cumin seeds.

Effects of dietary egg yolk antibody powder on growth performance, intestinal Escherichia coli colonization, and immunocompetence of challenged broiler chicks.

The present study aimed to investigate the effects of dietary supplementation of different levels of specific IgY (sIgY) and nonspecific IgY (nsIgY) egg yolk antibody powder on growth performance, immune functions, and intestinal morphology of Escherichia coli O78:K80-challenged broiler chicks. Lyophilized antibody isolated by the water-dilution method was obtained from the eggs of laying hens hyperimmunized with E. coli O78:K80. A total of 392 broiler chicks were randomly assigned to 7 dietary treatments with 4 replicates of 14 chicks (7 males and 7 females) each. Before offering the experimental diets, 7-d-old broiler chicks (except the negative control) were challenged orally with 0.5 mL (10(9) cfu/mL) of E. coli O78:K80 suspension. The challenge was continued for an additional 7 d from d 14 to 21 with 1.0 mL of a late log phase culture (10(9) cfu/mL) until the level of E. coli in feces reached 10(5) cfu/g. The 6 challenged groups received a basal diet supplemented with 0 (as positive control), 0.1, 0.2, or 0.4% (wt/wt) sIgY from eggs of immunized hens or levels of 0.2 or 0.4% (wt/wt) nsIgY from eggs laid by the nonimmunized hens. The negative control group was fed with the same unsupplemented diet. Oral infection caused an increase in ileal E. coli enumeration, total blood leukocytes, heterophil:lymphocyte ratio, the concentration of serum and intestinal secretory IgA, and the numbers of jejunal goblet cells and lamina propria lymphatic follicles. After 3 wk of feeding, the levels of 0.2 and 0.4% sIgY and 0.4% nsIgY had the most suppressive effects (P < 0.01) on the ileal E. coli enumeration and secretory IgA concentration. However, serum IgA concentration was slightly decreased only at the presence of 0.4% sIgY and nsIgY. Dietary supplementation with at least 0.2% sIgY decreased (P < 0.05) the circulating heterophil:lymphocyte ratio. Inclusion of both sIgY and nsIgY increased the villus height:crypt depth ratio and decreased the jejunal goblet cells and lamina propria lymphatic follicle numbers, with the most pronounced effects assigned to sIgY-supplemented groups. The best feed conversion ratio was obtained when the dietary inclusion of at least 0.2% sIgY continued for 3 wk. The present results indicate that dietary administration of at least 0.2% sIgY for 3 wk improved the intestinal health indices and immunological responses of broiler chicks orally challenged by E. coli O78:K80.

Immunological responses as affected by dietary protein and arginine concentrations in starting broiler chicks.

The study presented here aimed to investigate the effect of dietary protein content on Arg needs and immunological responses of broiler chicks during the starter period. A total of 715 one-day-old male Ross broiler chicks were randomly assigned to 5 replicate pens for each of 11 experimental diets during a 21-d feeding trial. The dietary treatments included a corn-soybean meal control diet or experimental diets (corn-soybean meal-corn gluten meal) containing 5 dietary Arg levels of 80, 90, 100, 110, or 120% of NRC recommendations and 2 dietary protein levels of 19 and 22.35% of diet. Increasing dietary CP content significantly (P<0.001) increased daily feed consumption and weight gain. Also, feeding diets deficient in Arg to the chicks led to a noticeable decline in feed intake, and dietary Arg supplementation overcame decreased feed consumption and weight gain observed in Arg-deficient chicks. Feed efficiency was affected only by dietary Arg concentration so that chicks on Arg-deficient diets markedly (P<0.001) increased feed conversion ratio. Contrast comparisons showed that the highly variable responses of chicks to dietary Arg level were mainly attributed to dietary protein concentration: more dietary protein content and higher Arg demands. Among lymphoid organs, thymus (P<0.001) and spleen (P<0.05) were affected by dietary Arg deficiency, whereas diets low in CP content decreased (P<0.001) relative weights of thymus and bursa of Fabricius. Increase in dietary CP level from 19 to 22.35% caused an increase (P<0.001) in the proportion of lymphocytes and consequently lower (P<0.05) heterophil-to-lymphocyte ratio. Broiler chicks on Arg-deficient diets decreased the proportion of heterophils in peripheral blood. Furthermore, skin reaction to phytohemagglutinin P was impaired when the diets were low in CP and Arg contents. Similarly, a decrease in dietary CP and Arg levels diminished the antibody production response to Newcastle disease virus. The broken-line analysis indicate that the Arg requirements of starting broiler chicks for optimal immune functions (107% of NRC values) are higher than those for maximum growth performance (101%) or feed efficiency (103%) and are dependent on dietary protein concentration.