Influence of dietary calcium level, calcium source, and phytase on bird performance and mineral digestibility during a natural necrotic enteritis episode.

The objective of this study was to determine the influence of Ca source [highly soluble calcified seaweed (HSC) or limestone], phytase supplementation, and dietary levels of Ca on bird performance and mineral digestibility (Ca and P) during a necrotic enteritis (NE) episode. Cobb 500 male broilers were weighed and randomized into 8 treatment groups (9 pens/treatment; 30 birds/pen) at day of hatch. The 21-d trial was designed as a 2 × 2 × 2 factorial, which included 2 dietary levels of Ca (0.6 and 0.9%), 2 Ca sources (limestone or HSC), and 2 levels of an Escherichia coli phytase (0 or 1,000 FTU/kg). One unit of phytase (FTU) is defined as the quantity of enzyme that releases 1 µmol of inorganic phosphorus/min from 0.00015 mol/L of sodium phytate at pH 5.5 at 37° C. Birds were placed on used litter from a previous flock that exhibited clinical signs of NE. Birds and feed were weighed on d 7, 14, and 21, and BW gain, feed intake, and feed conversion were calculated for each of these periods and cumulatively. Mortality was recorded daily and pH of the gizzard and duodenum were measured on d 7, 14, and 21. Ileal digesta (8 birds/pen) was collected on d 7, 14, and 21. Significance is reported at P < 0.05. Birds began exhibiting clinical signs of NE on d 9, and elevated NE-associated mortality persisted until the end of the trial. Significantly higher mortality was observed when broilers were fed diets with 0.9% Ca from HSC compared with birds fed diets with 0.6% Ca, regardless of Ca source. Broilers fed 0.6% Ca diets supplemented with phytase were heavier than the other treatments regardless of Ca source. Broilers fed diets formulated with HSC had significantly higher feed conversion then broilers fed diets formulated with limestone. The gizzard of broilers fed 0.9% Ca in the diet was significantly less acidic than the gizzard of broilers fed 0.6% Ca in the diet. Broilers fed 0.6% Ca in diets supplemented with phytase showed significant improvements in P and Ca digestibility. In conclusion, higher dietary Ca (0.9% vs. 0.6%) had a negative effect on mortality associated with NE and on bird performance.

Extra-phosphoric effects of superdoses of a novel microbial phytase.

An experiment was conducted to evaluate the influence of a novel microbial phytase on broiler performance from d 0 to 42 and tibia ash at d 21. Male Cobb 500 broilers (n = 2,016) were fed 1 of 7 experimental diets: positive control (PC) formulated to meet or exceed nutrient recommendations; PC plus dicalcium phosphate (PC+DCP) formulated to provide Ca and P at 0.10% above the PC; PC plus 500 U/kg of microbial phytase (PC+500); negative control (NC) with Ca and P reduced from the PC by 0.16 and 0.15%, respectively; and NC plus 500 (NC+500), 1,000 (NC+1,000), or 1,500 (NC+1,500) U/kg of microbial phytase. Diets were fed in 3 phases from d 0 to 21, d 22 to 42, and d 43 to 49 to 32 birds/pen and 9 replicate pens/diet. From d 0 to 21, broilers fed the NC diet had decreased (P ≤ 0.05) BW gain and tibia ash compared with broilers fed all other diets, except tibia ash in birds fed PC+500. Phytase supplementation at 500, 1,000, or 1,500 U/kg to the NC improved (P ≤ 0.05) BW gain and tibia ash comparable with the PC. Feed conversion ratio (FCR) was improved (P ≤ 0.05) in broilers fed NC+1,500 compared with broilers fed all other diets. From d 0 to 49, growth performance was not influenced (P > 0.05) by diet. However, FCR was improved (P ≤ 0.05) in broilers fed 1,500 U/kg of microbial phytase compared with broilers fed the PC, PC+DCP, and NC. There were no differences in performance or tibia ash between broilers fed the PC or PC+DCP, which would indicate the PC diet was sufficient in Ca and P. Therefore, the improvements in FCR in the NC+1500 may be associated with mitigation of the antinutrient effects of phytate rather than improved P utilization.

In vitro evaluation of limestone, dicalcium phosphate, and phytase on calcium and phosphorus solubility of corn and soybean meal.

A series of in vitro trials was conducted to evaluate the influence of limestone, dicalcium phosphate, phytase, and the digestion phase on Ca and P solubility. Experimental samples were arranged as a 2 × 2 × 2 × 2 factorial and contained corn (experiment 1) or soybean meal (experiment 2) plus limestone, dicalcium phosphate, phytase, and all combinations. Calcium and available P in the samples were maintained at 1.0% with limestone and 0.45% with dicalcium phosphate, respectively. Phytase was added to the samples at 1,000 FTU/kg. Samples were exposed to a 2-step in vitro digestion assay to simulate the gastric and the small intestinal (SI) phases of digestion. In experiment 1, dicalcium phosphate improved (P ≤ 0.05) P solubility in the gastric phase, which did not change in the SI phase, except when phytase was supplemented, which reduced (P ≤ 0.05) P solubility in the SI phase. The small amount of Ca present in corn is highly soluble, but limestone, dicalcium phosphate, or phytase reduced (P ≤ 0.05) Ca solubility in the gastric phase. Solubility was further reduced (P ≤ 0.05) in the SI phase in the presence of limestone. In experiment 2, P was more soluble (P ≤ 0.05) in the presence of limestone, dicalcium phosphate, or phytase in the gastric phase and compared with P solubility in the SI phase. Calcium solubility was reduced (P ≤ 0.05) in the SI phase compared with the gastric phase, except when dicalcium phosphate or limestone was supplemented. In conclusion, P and Ca solubility were influenced by the change in pH between the gastric and SI phases, differences in diet composition, and the Ca:P ratio. Limestone, dicalcium phosphate, and phytase increased P solubility in the gastric phase and reduced P solubility in the SI phase. Phytase had more of an effect on P and Ca solubility in soybean meal than in corn, and this is possibly a result of the high amount of phytate in soybean meal.

Influence of limestone and phytase on broiler performance, gastrointestinal pH, and apparent ileal nutrient digestibility.

An experiment was conducted to determine the influence of 2 levels of dietary Ca from limestone and 3 levels of phytase on broiler performance, bone ash, gastrointestinal pH, and apparent ileal digestibility (AID) of Ca, P, and amino acids. Cobb 500 broilers (n = 576) were allowed access to one of 6 corn-soy diets from 0 to 16 d. Experimental diets contained 1.03% or 0.64% Ca from limestone and 0.61% total P. Each diet was supplemented with 0, 500, or 5,000 FTU/kg of phytase to create a 2 × 3 factorial experiment. Broiler feed intake (FI) and BW gain were not affected by dietary Ca or phytase. Feed conversion ratio was improved (P < 0.05) as dietary phytase increased (1.36, 1.34, and 1.31, respectively). Tibia ash percent was reduced (P < 0.05) from 41.4 to 40.0% as dietary Ca decreased but increased with phytase addition (P < 0.05). Gizzard and ileal pH were reduced (P < 0.05) in broilers fed 0.64% Ca compared with broilers fed 1.03% Ca. Phytase at 5,000 FTU/kg increased (P < 0.05) pH in the gizzard, duodenum, jejunum, and ileum. Apparent ileal P digestibility was increased (P < 0.05) in broilers fed 0.64% Ca compared with broilers fed 1.03% Ca (0.68 vs. 0.73, respectively). Apparent ileal Ca digestibility was increased (P < 0.05) in broilers fed 1.03% Ca compared with broilers fed 0.64% Ca (0.67 vs. 0.53, respectively). Phytase improved AID of CP in broilers fed 1.0% Ca but did not have an effect on AID of CP in broilers fed 0.64% Ca, which resulted in a Ca × phytase interaction (P < 0.05). In conclusion, high dietary Ca increased pH in gizzard and ileum and interfered with the AID of P and CP. The interactions between Ca and phytase in the gastrointestinal tract are complex, and feeding phytase at doses above industry recommendations may allow for reduced-Ca diets while maintaining broiler performance, bone ash, and improving amino acid digestibility.

Effects of dietary enzymes on performance and intestinal goblet cell number of broilers exposed to a live coccidia oocyst vaccine.

An experiment was conducted to evaluate the effects of dietary enzymes on performance, tibia ash, and intestinal goblet cells of broilers administered a live coccidia oocyst vaccine (Coccivac B, Schering Plough, Kenilworth, NJ). Cobb 500 straight-run broilers were obtained and one-half of the chicks were sprayed with the live coccidia oocyst vaccine. Chicks were weighed and placed in battery brooders with respect to nonvaccinated or vaccinated group according to dietary treatment. The 8 dietary treatments were a positive control (0.90% Ca and 0.45% available P), a negative control (NC; 0.80% Ca and 0.35% available P), NC + phytase (PHY), NC + protease (PRO), NC + xylanase (XYL), NC + PHY+ PRO, NC + PHY + XYL, and NC + PHY + PRO + XYL. A diet × vaccination interaction (P > 0.05) was not observed for feed intake or BW gain. Feed conversion ratio was improved (P ≤ 0.05) in birds fed NC + PHY + XYL compared with NC. Vaccination reduced (P ≤ 0.05) feed intake and BW gain from d 0 to 18. Tibia ash was reduced (P ≤ 0.05) in the NC and PRO or XYL diets. Vaccination increased goblet cell numbers in the duodenum of birds fed XYL, whereas no differences were found in goblet cell numbers between nonvaccinated and vaccinated birds in other dietary treatments, which resulted in a diet × vaccination interaction (P ≤ 0.05). Protease decreased and NC + PHY+ PRO increased goblet cells in the jejunum at d 7, which resulted in a diet × vaccination interaction (P ≤ 0.05). At d 18, NC + PHY + XYL was the only diet in which vaccination decreased goblet cells in the jejunum, resulting in a diet × vaccination interaction (P ≤ 0.05). The data indicate that NC + PHY + XYL improved the feed conversion ratio in broilers fed corn-soybean meal diets. The vaccination × dietary enzyme interaction altered the number of goblet cells in the small intestine. Dietary enzyme supplementation did not alleviate reductions in growth performance associated with the use of a live coccidia oocyst vaccine.

Effect of incubation temperature on nutrient transporters and small intestine morphology of broiler chickens.

This study evaluated the effects of elevated incubation temperature on posthatch nutrient transporter gene expression, integrity of the intestinal epithelium, organ development, and performance in Ross 308 broiler chickens. Ross × Ross 308 fertile eggs (n = 900) were incubated at different eggshell temperatures during development. From embryonic day (ED) 1 to ED12, all eggs were incubated at 37.1°C, whereas from ED13 to ED21, the eggs were divided into 2 groups for incubation at 37.4°C (S) or 39.6°C (H). Performance characteristics were measured at day of hatch (DOH) and d 7, 14, 21, 30, and 42. Small intestine and residual yolk sacs were collected at DOH and d 2, 4, 6, and 10 and weighed individually. Intestinal samples from the duodenum, jejunum, and ileum were evaluated for mucosal morphology and relative nutrient transporter gene expression. No significant differences were found in performance or organ weights. The intestinal morphology results showed a temperature × age interaction in duodenum villus height (P = 0.02) and crypt depth (P = 0.05) and in ileum villus height-to-crypt depth ratios (P = 0.02). There was a main effect of temperature, resulting in deeper crypts (P = 0.02) in the jejunum of chicks incubated at H compared with S. In the nutrient gene expression evaluation, peptide transporter (PepT1) showed a temperature × age interaction. On DOH and d 2, 4, and 10, PepT1 expression was similar between chicks incubated at S and H. However, on d 6, chicks incubated at S had significantly higher expression of PepT1 than those incubated at H. This study presents the effects of elevated incubation temperature on small intestine morphology and relative expression of nutrient transporter mRNA in high-yield broiler chicks, which can be important for the availability of nutrients and distribution of energy.

An antimicrobial peptide is downregulated in the small intestine of Eimeria maxima-infected chickens.

Avian coccidiosis is a major disease of poultry caused by the intestinal protozoa Eimeria. Infection leads to reduced feed efficiency and BW gain, resulting in severe economic losses for the poultry industry. Aviagen line A and line B birds show a differential response to Eimeria infection, with line B birds exhibiting higher lesion scores and mortality. The objective of this study was to examine differential intestinal gene expression between 2-wk-old line A and B chicks in response to a challenge with Eimeria maxima. After challenge with 1 × 10(4) oocysts/chick, more than 40% of line A chicks had lesion scores of 0 to 1 (scale of 0 to 4), similar to control chicks. In contrast, all line B chicks challenged at this same dose had lesion scores of 2 to 4. Total RNA was extracted from the jejunum of control and challenged chicks from both lines A and B. Microarray analysis revealed that liver-expressed antimicrobial peptide 2 (LEAP-2), a component of the innate immune system, was downregulated 20-fold in line A challenged chicks with lesion scores of 2 to 4 compared with line A control chicks, and was downregulated 11- to 71-fold in line B challenged chicks with lesion scores of 2 to 4 compared with line B control chicks. Liver-expressed antimicrobial peptide 2 was downregulated less than 2-fold in line A challenged chicks with lesion scores of 1 compared with line A control chicks, indicating that these chicks were similar to control chicks in their expression level of LEAP-2. Other genes (cytochrome P450, heat shock protein 25, keratin 19, and amino acid transporter ASCT1) showed different patterns of over- or underexpression. The expression of LEAP-2 was verified using real-time PCR, revealing a correlation between lesion score and magnitude of LEAP-2 downregulation for both line A and line B chicks. Thus, LEAP-2 may serve as a useful marker for identification of chickens resistant to E. maxima infection and potentially other Eimeria spp.

The effect of dietary protein level on performance characteristics of coccidiosis vaccinated and nonvaccinated broilers following mixed-species Eimeria challenge.

A series of experiments were conducted to investigate the effect of starter diet protein levels on the performance of broilers vaccinated with a commercially available live oocyst coccidiosis vaccine before subsequent challenge with a mixed-species Eimeria challenge. Data indicated that an increasing protein concentration in the starter diet improved broiler performance during coccidiosis vaccination. Prechallenge performance data indicated that vaccination could decrease BW and increase feed conversion ratio. The time period most important for the observed effects appeared to be between 13 and 17 d of age. This reduction in performance parameters of vaccinated broilers compared with nonvaccinated broilers was eliminated by the conclusion of the experiments (27 d) in the diet groups with higher protein. Vaccination was effective at generating protective immunity against Eimeria challenge, as evidenced by increased (P < 0.05) BW gain, improved feed conversion, reduced postchallenge mortality, and reduced lesion development in vaccinated broilers compared with nonvaccinated broilers. These observations support numerous other reports that confirm live oocyst vaccination can be used effectively as a preventive against avian coccidiosis in commercially reared broilers. More important, these findings suggest that reduced protein concentration of starter diets can lead to significant losses in broiler performance when using a vaccination program to prevent coccidiosis.

Performance and immune responses to dietary beta-glucan in broiler chicks.

During the first week posthatch, the avian immune system is immature and inefficient at protecting chicks from invading pathogens. Among immunomodulators, beta-glucans are known as biological response modifiers due to their ability to activate the immune system. Current research suggests that beta-glucans may enhance avian immunity; however, very little is known about their influence on regulation of immune function. A study was performed to evaluate the effects of dietary beta-glucan on growth performance, immune organ weights, peripheral blood cell profiles, and immune-related gene expression in the intestine. One-day-old chicks were fed a diet containing 0, 0.02, or 0.1% yeast beta-glucan (n = 30/treatment). On d 7 and 14 posthatch, body and relative immune organ weights were measured and small intestinal sections were collected to evaluate gene expression by quantitative real-time PCR. Peripheral blood samples were also collected to determine heterophil:lymphocyte ratios. Supplementation of beta-glucan did not significantly affect BW gains, and no significant differences were observed among groups for relative immune organ weights or heterophil:lymphocyte ratios. Compared with controls, expression of interleukin (IL)-8 was downregulated in the beta-glucan-treated groups on d 7 and 14. On d 14, beta-glucan inclusion resulted in increased inducible nitric oxide synthase expression. Expression of IL-18 was upregulated on d 7 but reduced on d 14 due to beta-glucan supplementation. On d 7, interferon-gamma and IL-4 expression decreased in the beta-glucan-treated groups. However, on d 14, IL-4 expression was upregulated in the supplemented groups. Intestinal expression of IL-13 was also downregulated in the beta-glucan-treated birds on d 7. These results suggest that dietary inclusion of beta-glucans altered the cytokine-chemokine balance; however, it did not elicit a robust immune response in the absence of a challenge, resulting in no deleterious effects on performance.

Immune responses to dietary beta-glucan in broiler chicks during an Eimeria challenge.

Escalating consumer concerns regarding pathogen resistance have placed the poultry industry under mounting pressure to eliminate the use of chemotherapeutic agents as feed additives. One possible alternative receiving increased attention is the use of immunomodulators such as ß-glucan. A study was conducted to investigate the effects of a yeast-derived ß-glucan (Auxoferm YGT) on broiler chick performance, lesion scores, and immune-related gene expression during a mixed Eimeria infection. Day-old chicks were fed diets containing 0, 0.02, or 0.1% YGT. On d 8 posthatch, one-half of the replicate pens were challenged with a mixed inoculum of Eimeria acervulina, Eimeria maxima, and Eimeria tenella. Measurements were taken and samples collected on d 4, 10, 14, and 21 posthatch. Dietary supplementation had no effect on performance or mortality. On d 14, 3 birds per pen (n = 24/treatment) were scored for intestinal coccidia lesions. Gross lesion severity was significantly reduced in birds supplemented with 0.1% YGT. On d 10, inducible nitric oxide synthase (iNOS) expression was downregulated in the jejunum of challenged birds fed 0.1% YGT. Expression of iNOS in the ileum was downregulated in the nonchallenged birds, but upregulated in the challenged birds fed 0.1% YGT on d 14. Interleukin (IL)-18 was upregulated in the jejunum of 0.1% YGT-treated birds. Interferon (IFN)-γ expression was decreased in challenged and nonchallenged birds fed 0.1% YGT. The IL-4 expression was downregulated in the nonchallenged birds with 0.1% YGT diet supplementation. The IL-13 and mucin-1 levels were also reduced due to ß-glucan supplementation. Mucin-2 expression was increased in the nonchallenged birds, but decreased in the infected birds fed 0.1% YGT. These results suggest that although Auxoferm YGT at doses of 0.02 and 0.1% does not influence performance, it significantly reduces lesion severity and is capable of altering immune-related gene expression profiles, favoring an enhanced T helper type-1 cell response during coccidiosis.

Supplementation of Avizyme 1502 to corn-soybean meal-wheat diets fed to turkey tom poults: the first fifty-six days of age.

A study was designed to determine the effects of enzyme supplementation on poults fed commercially based diets that included corn, soybean meal, and ground wheat with meat and bone meal (0 to 21 d) or Pro-Pak (22 to 56 d). Day-old turkey poults (n = 3,850) were divided into 35 pens and fed 1 of 5 dietary treatments for 56 d. Treatments were a positive control, a negative control (corn matrix adjustment of 140 kcal), and negative control diets supplemented with Avizyme 1502 at 250, 500, or 750 g/tonne. Feed intake, live weight gain, feed conversion ratio, and mortality were measured for the periods 0 to 21 d, 21 to 42 d, and 42 to 56 d, as well as for the cumulative 0 to 56 d. The 0- to 21-d period was further divided into subperiods (0 to 4 d, 4 to 8 d, 8 to 12 d, 12 to 16 d, 16 to 21 d) to evaluate early nutritional development. Ileal contents along with duodenal, jejunal, and ileal sections (n = 7/treatment) were sampled to determine apparent digestibility and morphology. In most instances, production response differences between the positive and negative controls were not significant, making definitive interpretation of enzyme addition difficult. Energy and protein ileal digestibilities of the negative control diets were lower than those of the positive control diet at 4, 8, 12, 16, and 42 d. Enzyme supplementation significantly improved energy and protein beyond that of the PC diet on d 42. Villus height and crypt depth did not respond to dietary treatment, although there was a significant interaction of age by treatment on jejunal villus height. The similarity between the controls, as well as the high inclusion of CuSO(4), may be responsible for the low response with enzyme inclusion.

Influence of orally administered CpG-ODNs on the humoral response to bovine serum albumin (BSA) in chickens.

Synthetic oligodeoxynucleotides containing CpG motifs (CpG-ODNs) have been reported to be effective mucosal adjuvants in mice when given orally. Studies on their effectiveness in chickens are currently very limited. This study investigated whether CpG-ODNs could adjuvant the immune response to BSA when given orally to a commercial line of SCWL chickens. In two experiments, performed over time, chickens were given selected concentrations of CpG-ODNs with BSA followed by 6 consecutive days of ad libitum access to drinking water containing 1.4 mg/ml BSA. Serum responses, and in some cases intestinal specific antibodies, were measured out to 33 days post-immunization. Birds receiving a single dose of CpG-ODN had consistently higher IgG, IgM, and IgA titers in the serum, dependent upon dose, and in specific areas of the intestine when compared to the non-immunized and BSA only groups. These findings suggest that a single oral CpG-ODN administration can accelerate the kinetics of antigen specific antibodies of all three isotypes in commercial-strain chickens immunized via the drinking water using common protein antigen.

Comparison of prophylactic or therapeutic dietary administration of capsaicin for reduction of Salmonella in broiler chickens.

In three experiments the effects of prophylactic or therapeutic dietary inclusion of capsaicin, the pungent component of peppers, were evaluated as a nonantibiotic alternative for reduction of Salmonella in broiler chickens through culture and morphologic assessment of cecal tissue. Expt. 1 evaluated the effects of 0 or 10 ppm purified capsaicin (CAP) in the starter phase (days 1-16) on chicks challenged with Salmonella Enteritidis (SE) on day of age. Therapeutic inclusion of 10 ppm purified CAP increased (P < 0.05) liver/spleen (L/S) and ceca positive results for SE. In Expt. 2, capsaicin oleoresin (CO) was included in the finisher diet (days 30-37) at 0, 5, or 20 ppm with SE challenge on day 31. Inclusion of 5 ppm CO increased ceca positive results for SE, and a linear decrease in cecal lamina propria thickness of SE-challenged birds was observed with increased CO concentration in the diet. Expt. 3 evaluated prophylactic CO treatment at 0, 5, or 20 ppm in starter, grower, and finisher diets for resistance to SE or Salmonella Typhimurium (ST) challenge on day 14 or 29. With challenge on day 14, 5 and 20 ppm prophylactic CO feeding reduced ceca SE positive results by 37% and 26%, respectively, and ST culture rate was reduced similarly with 5 ppm CO. Lamina propria thickness of the ceca increased with 5 ppm CO feeding in SE-challenged birds, whereas a decrease was observed in nonchallenged birds fed 5 ppm CO. Challenge on day 29 of birds fed 20 ppm CO resulted in reduced L/S positive results for SE. Lamina propria thickness decreased with 5 ppm CO and SE or ST challenge compared with nonchallenged birds fed 5 ppm. An increase was observed in ST- or SE-challenged birds fed 20 ppm CO compared with nonchallenged birds fed 20 ppm CO. No differences were observed in mast cell number in either Expt. 2 or 3. These data provide evidence that prophylactic or therapeutic dietary capsaisin differentially affects broiler susceptibility to Salmonella.

BASP-induced suppression of mitogenesis in chicken, rat and human PBL.

The purpose of the present investigation was to extend previous research conducted by our laboratory which demonstrated the suppressive effects of chicken bursa of Fabricius-derived bursal anti-steroidogenic peptide (BASP) on neonatal-chick B-lymphocyte mitogenesis. To test these anti-proliferative effects on lymphocytes derived from older animals, and to evaluate the phylogenetic applicability of these findings to other species, we evaluated the ability of BASP to alter proliferative indices in peripheral blood lymphocytes derived from adult chickens, rats and humans. Data from the present series of experiments confirm and extend our previous findings and suggest an anti-proliferative effect, exerted by BASP, on pools of isolated PBL from chickens, rats and humans, when measuring 3H-thymidine incorporation following mitogenic stimulation. While the present data was derived from limited numbers of pooled PBL, these findings may be indicative of a potential extra-bursal function of BASP on lymphocyte function.

Antimicrobial residue detection in chicken yolk samples following administration to egg-producing chickens and effects of residue detection on competitive exclusion culture (PREEMPT) establishment.

Competitive exclusion (CE) cultures may offer alternatives to antimicrobial agents for disease prophylaxis in poultry. To avoid potential transfer of antibiotic resistance, safe and effective CE cultures must, by necessity, be highly sensitive to antimicrobial residues. The following studies evaluated the effect of maternal administration of selected antibiotics on the establishment of a licensed CE culture, PREEMPT. Selected antibiotics were administered to actively laying hens for a period of 7 days (experiment 1) or 9 days (experiment 2) in drinking water [sulfadimethoxine (0.05%), enrofloxacin (0.005%), and tylosin tartrate (0.05%)] or feed (sulfadimethoxine with ormetoprim, 250 ppm). In experiment 1, fertile eggs were collected daily and subjected to bioassay for detectable antimicrobial residues in yolk. Antimicrobial residues were not detected during the 7 days of treatment or the subsequent 3 days following cessation of treatment in the control, sulfadimethoxine, sulfadimethoxine with ormetoprim, or tylosin treatment groups. However, detectable residues were observed in eggs derived from enrofloxacin-treated hens on days 6 and 7 during antibiotic administration and also on days 2 and 3 post-antibiotic administration. In experiment 2, antimicrobial residues were also only detected in yolks from hens treated with enrofloxacin. Residue detection occurred on days 2-6 of antibiotic administration, on day 9 of antibiotic administration, on days 1-3 post-antibiotic administration, and also on day 7 post-antibiotic administration. A subset of eggs from each experimental group, corresponding to days 2-6 of antibiotic administration, days 4-6 post-antibiotic administration, and days 14-16 post-antibiotic administration, were pooled for incubation, and chicks hatched from these pools of fertile eggs were treated with PREEMPT at hatch. When 48-h cecal propionate concentrations were used as an index of culture establishment, reduced (P < 0.05) efficacy was observed only in chicks derived from enrofloxacin-treated hens at either collection period. Although several antibiotics do not appear to produce detectable egg residues or interfere with CE culture establishment, these data suggest that chicks derived from enrofloxacin-treated hens may not be candidates for safe and effective CE culture treatment.

Effect of prolonged heat stress in single-comb white leghorn hens on progeny resistance to Salmonella enteritidis organ invasion.

In our laboratory, we have often had difficulty infecting neonatal chickens with invasive salmonellae when ambient temperatures exceed 30 C. We hypothesized that this increased resistance in chicks during warmer months may be associated with heat stress-associated maternal factors. Presently, single-comb white leghorn hens were separated into a non-heat-stressed group, reared under temperatures from approximately 10 to 24 C, and a heat-stressed group, in which environmental temperature was incrementally elevated to near 37 C and maintained for the duration of the 13-wk study. For Expt. 1, eggs from heat-stressed or control hens, collected on days 8-14 of the study, were pooled respective to treatment and incubated. At the time of egg collection, mean hen-day egg production was 51.83% or 65% for heat-stressed or control hens, respectively. On day of hatch, progeny from hens in each group were orally challenged with 0.9 x 10(4) colony-forming units (CFU) Salmonella enteritidis (SE). Rates of SE organ invasion of 97.3% or 94.4% were obtained in progeny from heat-stressed or control hens, respectively. In Expt. 2, eggs from heat-stressed or control hens from days 30-42 of the study were collected and pooled by treatment for incubation. Mean hen-day egg production was 46.5% or 72.85% for heat-stressed or control hens, respectively. On day of hatch, progeny were orally challenged with either 2.2 x 10(3) or 2.2 x 10(4) CFU SE. A 100% incidence in SE organ invasion was observed in all groups. In Expt. 3, eggs were collected from days 43 through 56 of the study. Mean hen-day egg production was 19.8% or 76.8% for heat-stressed or control hens, respectively. On day of hatch, progeny were orally challenged with 2 x 10(3) CFU SE. Rates of SE organ invasion of 95.8% or 95.6% were obtained in progeny from heat-stressed or control hens, respectively. These data suggest that factors other than elevated temperature may be responsible for seasonal resistance to invasive salmonellae infection in neonatal chickens observed in our laboratory during warmer months in Texas.

Effect of prolonged administration of dietary capsaicin on broiler growth and Salmonella enteritidis susceptibility.

The effect of continuous (42 days) dietary administration of 5 or 20 ppm capsaicin to broiler chickens on Salmonella enteritidis susceptibility, body weight, and feed efficiency was investigated. Chickens were weighed at 1, 21, and 42 days of age. No significant differences in body weight or feed efficiency were observed. Chickens were challenged with 1 x 10(8) colony-forming units of S. enteritidis at 21, 28, or 42 days of age. The S. enteritidispositive culture rate for cecal tonsils was significantly lower (P < 0.05) in the treatment groups receiving 5 ppm or 20 ppm dietary capsaicin than in the untreated control group at all challenge times. Dietary capsaicin (5 and 20 ppm) resulted in protection against S. enteritidis organ invasion at 28 days in one experiment and at both 21 and 42 days in the other. These results indicate that continual dietary capsaicin administration increases resistance to S. enteritidis colonization and organ invasion throughout the normal growth period without detrimental effects on growth in broiler chickens.

In vivo biologic effects of recombinant-turkey interferon-gamma in neonatal leghorn chicks: protection against Salmonella enteritidis organ invasion.

Interferon-gamma (IFNgamma) has been demonstrated to have potent stimulatory effects on parameters of cell-mediated immunity in chickens (11). Protection of neonatal leghorn chickens against infection by invasive salmonellae has been associated with enhanced cell-mediated indices of immunity (5). The present investigation evaluated the effect of recombinant-turkey (rt) IFN-gamma on protection of neonatal leghorn chicks from Salmonella enteritidis (SE) organ invasion after experimental challenge in three experiments. In Expt. 1, intraperitoneal (i.p.) administration of 25 microg rtIFNgamma per chick 30 min prior to per os SE challenge resulted in a 35% reduction (P < 0.01) in SE organ invasion when compared with control (vehicle injected) chicks 24 hr post-SE challenge. However, i.p. administration of 2.5 microg rtIFNy per chick was not efficacious in reducing SE organ invasion. In Expt. 2 and Expt. 3, i.p. administration of 13.75 microg rtIFNgamma per chick 30 min prior to per os SE challenge resulted in significant reductions of 38.4% (P < 0.025) and 31.58% (P < 0.01), respectively, in SE organ invasion as compared with control chicks 24 hr post-SE challenge. Administration of 2.5 or 25 microg rtIFNgamma per chick i.p. had no effect on SE organ invasion in either Expt. 2 or Expt. 3 24 hr post-SE challenge. Additionally, i.p. administration of rtIFNgamma 30 min prior to SE challenge in Expt. 2 and Expt. 3 was not associated with protection against SE organ invasion when organ culture was performed 72 hr postchallenge. Further, the oral administration of 25 microg rtIFNgamma per chick was not efficacious in conferring protection against SE organ invasion at 24 or 72 hr postchallenge when this route of administration was evaluated in Expt. 2. Similarly, the subcutaneous administration of a potential repository injection of 13.75 or 25 microg rtIFNgamma per chick did not protect chicks against SE organ invasion when evaluated 72 hr postchallenge. These data indicate a potential acute immunostimulatory activity of rtIFNgamma in chickens experimentally challenged with SE. Further, these experiments, although preliminary, are suggestive of the potential involvement of IFNgamma in cell-mediated or innate mechanisms of protective immunity against salmonellosis in chickens.

Effect of bursal antisteroidogenic peptide (BASP) on chicken embryonic pituitary secretion of growth hormone (GH) and prolactin (PRL): evaluation in a reverse hemolytic plaque assay (RHPA).

Using the reverse hemolytic plaque assay described in the present investigation, a secretagogue activity of bursal antisteroidogenic peptide (BASP) for growth hormone (GH) or prolactin (PRL) secretion was observed in chicken Day 20e pituitary cell monolayers. Partially purified BASP (ppBASP), at all concentrations evaluated (0.25 BEQ/ml, 0.75 BEQ/ml, or 1.5 BEQ/ml), induced PRL secretion by isolated lactotrophs above (P < 0.05) basal levels during the 2- and 6-hr incubation. At the 18-hr time point, neither ppBASP nor vasoactive intestinal polypeptide (VIP) was efficacious (P < 0.05) in causing an elevation in PRL-secreting cells above basal levels. ppBASP, at all concentrations evaluated (0.25 BEQ/ml, 0.75 BEQ/ml, or 1.5 BEQ/ml), caused an increase in the percentage of GH-secreting cells above (P < 0.05) basal levels during the 18-hr incubation. When evaluating the 2-hr time point alone, ppBASP, at 0.75 or 1.5 BEQ/ml, significantly (P < 0.05) elevated the percentage of GH-secreting cells to above basal levels. After the 6-hr incubation, ppBASP at 0.25 or 0.75 BEQ/ml, was efficacious in causing elevated (P < 0.05) GH secretion above basal levels. The present study indicates a secretagogue activity of BASP on PRL or GH secretion by chicken embryonic anterior pituitary cells in vitro.

Intestinal mucosal mast cell immune response and pathogenesis of two Eimeria acervulina isolates in broiler chickens.

Four experiments were conducted comparing intestinal immune responses to 2 isolates of Eimeria acervulina (EA), EA1 and EA2. In experiments 1 and 2, broiler chicks of 2 commercial breeds were divided into control (nonchallenged), EA1-, or EA2-challenged groups. On d 6 postchallenge (PC), changes in BW were determined, intestinal lesions were scored, and duodenal tissue was evaluated for morphometric alterations and mucosal mast cell numbers. EA1 produced classical duodenal lesions and reduced villus height to crypt depth ratios compared with controls; however, no differences were found in mast cell counts. EA2 produced different results, and observed data were suggestive of an anaphylactic-like intestinal secretory response compared with EA1 or controls. In experiment 3, tissues were analyzed from d 2 through 6 PC. Villus atrophy and crypt hyperplasia were increased on d 5 PC in both challenged groups. Mast cell counts were significantly greater on d 3 and 4 PC in EA1-challenged birds. In experiment 4, EA2 oocysts were cleaned with 5.25% sodium hypochlorite to evaluate the possibility of a bacterial contaminant contributing to the pathogenesis of intestinal alterations. No evidence of a bacterial contaminant contributing to the pathology was observed. These data are indicative of differential host response and immunovariability between different isolates of the same Eimeria species in 2 breeds of commercial broiler chickens.