The combination of quillaja and yucca saponins in broilers: effects on performance, nutrient digestibility and ileal morphometrics.

1. Two series of studies were conducted to determine the effects of a combination of ground plant material derived from Quillaja saponaria trees and Yucca schidigera plants (QY) as sources of saponin, on performance, productivity, nutrient digestibility and ileal morphology of growing broilers. In each trial, 480 Cobb male birds were allocated equally to 24 pens at one-day-of-age according to body weight2. The studies consisted of two identical floor pen trials in which performance and nutrient digestibility were assessed and two trials where performance and ileal morphology were determined. In each trial, 0, 250 or 500 ppm QY were included in feed given to the broilers from 1-35 or 1-42 d of age, respectively. Eight (digestibility) or 12 (morphology) randomised replicate pens were used.3. In the digestibility trials, two birds per pen were moved to metabolism cages at d 21. Excreta was collected for a five-day period (d 21 to 25) for the determination of apparent total tract digestibility of dry and organic matter, fat and ash and nitrogen retention. For intestinal morphology, ileal segments were collected from four birds/pen on d 21 to determine villus height and crypt depth. Performance data were collected in each trial series.4. Results showed that feeding graded levels of QY produced significant linear improvements in performance and productivity at d 35, and similar linear effects were observed for N retention and all apparent digestibility measurements. Morphology data showed that birds receiving 250 and 500 ppm QY had significantly increased villus height5. These results indicated that QY exerted a positive influence on the intestinal tract by increasing the absorptive surface and improving nutrient digestibility. These effects were considered to be associated with the performance improvements recorded in both experiments.

Effects of nicarbazin on the blood glucose and liver glycogen statuses of male broilers.

Nicarbazin (NCZ), an effective anticoccidial widely used by the global broiler industry, is known to produce some side effects in broilers. Recent field observations have suggested that NCZ could be associated with spiking mortality syndrome, a disease of uncertain etiology that is most commonly characterized by hypoglycemia. In turn, 2 trials were conducted to investigate the effects of NCZ on the blood glucose levels and liver glycogen content of Ross × Ross 708 male broilers. In 6 of 12 pens beginning at 1 d of age, NCZ was added to basal broiler diets at a rate of 125 mg/kg, and the other 6 pens were control pens in which birds received salinomycin instead of NCZ, at a rate of 66 mg/kg. Feed and water were provided ad libitum, feed was closely monitored in all pens to avoid shortages, no coccidial challenge was imposed, and room temperature never exceeded 29.4°C. At the end of the second trial, a photoperiod increase from 8L:16D to 24L:0D was imposed in an effort to induce stress due to feed engorgement. In response to NCZ in trial 1, 0 to 28 d feed conversion and relative liver weights on d 21 and 28 were higher, whereas 0 to 28 d cumulative BW gain was lower. In response to NCZ in trial 2, 0 to 13 d feed conversion was higher, whereas 0 to 13 d cumulative BW gain was lower. The added NCZ increased blood glucose on d 13 in trial 2, but did not affect at any time the liver constituents analyzed in both trials. In conclusion, the uninterrupted feeding of NCZ at 125 mg/kg in the starter and grower diets of male Ross × Ross 708 broilers increased feed conversion and reduced BW gain, but despite an increase in relative liver weight on d 21 and 28 posthatch, liver glucose and glycogen concentrations were not affected.

The effects of a quillaja and yucca combination on performance and carcass traits of coccidia-vaccinated broilers exposed to an enteric disease challenge.

A series of 6 floor pen trials was conducted to determine the effects of a quillaja and yucca combination product on the performance and carcass traits of growing broiler chickens vaccinated for coccidiosis at the hatchery. In each of the trials graded levels (0, 250, and 500 ppm) of a quillaja and yucca combination (QY) were fed to Ross 708 broilers for the duration of each 42 d test. Trials were arranged in completely randomized block designs involving a minimum of 11 blocks per trial. At the start of each trial, pens contained 55 broilers. In order to provide each bird with an enteric disease challenge, 5 kg commercial broiler litter containing 104 CFU Clostridium perfringens per gram was placed in each pen. In addition, the sporulated oocysts of Eimeria acervulina and E. maxima were added to each pen at the outset of each test. At d 21 of the trials, coccidial lesion scores, mortality and performance were determined; final performance and total mortality were assessed at 42 d. At the completion of each test, 10 birds of average body weight per pen were selected for carcass evaluations; whole and chilled carcass yield were determined, and pre- and post-chill breast measurements were made. A combined analysis of the results of the 6 trials (75 replications per treatment) was used to determine treatment effects and each variable was assessed by linear regression analysis. Results indicated that QY significantly reduced mortality and coccidial lesions scores at d 21 (P < 0.05). Performance was significantly improved by both levels of QY at 21 and 42 d, and significant linear effects were observed for these variables (P < 0.05). All carcass characteristics were significantly improved by QY administration and significant linear responses were observed for each carcass variable (P < 0.05). These results indicate that by reducing intestinal disease challenge, QY provided linear improvements in performance. In addition, QY positively affected carcass parameters as each variable responded linearly to QY feeding (P < 0.05).

Concurrent use of saponins and live coccidiosis vaccines: the influence of a quillaja and yucca combination on anticoccidial effects and performance results of coccidia-vaccinated broilers.

A series of studies was conducted to determine the effects of a quillaja and yucca (saponin) combination (QY) product on postvaccination oocyst production, development of coccidial immunity, and final bird performance of broilers administered live coccidiosis vaccines. In all, 3 groups of tests were carried out. Study 1 evaluated the effects of QY (0 and 250 ppm) on oocyst per gram of feces (OPG) following vaccination at day-of-age; OPG were measured from 5 to 12 d postvaccination. Study 2 determined the effects of QY (250 ppm) in the presence of 3 commercial coccidiosis vaccines in floor pens. OPG were measured weekly for birds receiving each vaccine and for each corresponding vaccine group fed QY. To determine whether QY influenced the development of coccidial immunity induced by the 3 vaccines, 5 birds were removed from each pen at 28 d and challenged with pathogenic levels of Eimeria spp. At 6 d post challenge, lesion scores were used to evaluate the effects of QY on immune protection provided by each vaccine. In addition, comparisons of final bird performance were made between birds given each vaccine and their corresponding vaccinates fed QY. Study 3 comprised a meta-analysis of 15 floor pen trials in which 21- and 42-d body weight, feed conversions, and total mortality were compared between coccidiosis-vaccinated broilers and similarly vaccinated broilers fed QY (250 ppm). Results of these experiments indicated that feeding QY to vaccinated broilers did not significantly affect OPG from days 5 through 12 postvaccination (P > 0.05). For each vaccine tested in study 2, OPG values were the highest at 14 and 21 d postvaccination. QY significantly reduced OPG at 14 d postvaccination for 2 of the vaccines tested, and produced a similar effect in 1 vaccine at 21 d postvaccination. The remaining vaccine was not affected by QY in the postvaccination OPG results. Despite these changes in OPG, significant differences in lesion scores following the Eimeria challenge were not observed for any vaccinated groups receiving QY. Irrespective of the vaccine, both interim and final feed conversion values were significantly improved when QY was fed (P < 0.01). Similarly, results of a 15-trial meta-analysis indicated that QY-fed vaccinated broilers had higher body weights, improved feed conversions, and lower mortality than their vaccinated controls. Results show that while QY may induce changes in OPG following vaccination, coccidia-vaccinated broilers fed QY develop immunity equivalent to that of controls and show significant improvements in performance and mortality.

The Effects of a Combination of Quillaja saponaria and Yucca schidigera on Eimeria spp. in Broiler Chickens.

A series of studies was carried out to determine the anticoccidial effects of a product derived from plant material sourced from Quillaja saponaria and Yucca schidigera. These plants are known to contain high concentrations of triterpenoid and steroidal saponins, substances that are known to display an array of biological effects. Battery tests involving individual Eimeria acervulina, Eimeria maxima, and Eimeria tenella infections and graded levels of a quillaja/yucca combination (QY) (0, 200, 250, and 300 ppm) were conducted. Body weight gain, coccidial lesion scores, and total oocysts per gram of feces (OPG) were used to evaluate anticoccidial effects. In addition, three floor pen trials evaluated the effects of 250 ppm QY in the control coccidial infections. The first pen trial measured the effects of 250 ppm QY, both alone and in combination with 66 ppm salinomycin (Sal), in a 2 3 2 factorial treatment arrangement. Two additional 42-day pen studies assessed the effects 250 ppm QY in birds vaccinated for coccidiosis. Data from the three battery trials indicated that at doses of 250 ppm QY or more, weight gain was improved, E. acervulina and E. tenella lesion scores were reduced, and OPG was lowered. In general, OPG was reduced by about 50% across all species by 250 and 300 ppm QY. Results of the pen study indicated that 250 ppm QY and Sal, when fed individually, reduced OPG and lesion scores and improved final performance. However, when QY and Sal were administered concurrently, further significant reductions in OPG occurred. The final performance of broilers vaccinated for coccidiosis was also improved at 250 ppm QY, as was OPG at both 21 and 28 days. Thus, at QY doses of 250 ppm or more, anticoccidial activity was evident but lacked the potency exhibited by many standard anticoccidials. When combined with either Sal or a live coccidiosis vaccine, QY improved the anticoccidial effects and performance of these anticoccidial methods.

Sensitivity of Eimeria field isolates in the United States: responses of nicarbazin-containing anticoccidials.

A series of studies were conducted to assess the drug sensitivity of 26 coccidial field isolates to the anticoccidial effects of nicarbazin (NIC) and narasin + NIC (NAR + NIC). Isolates were collected from typical broiler farms in the United States from 2003 to 2006, propagated once in the absence of anticoccidial medication, and then used to inoculate broilers that were fed nonmedicated rations or those containing NIC 125 ppm or NAR + NIC 80 ppm. Results of these sensitivity trials indicated that 81% of these coccidial isolates were sensitive to the effects of NIC, but only 22% of these coccidia were controlled by NAR + NIC. Studies conducted to evaluate performance responses to these drugs demonstrated that birds fed NIC gained more weight and utilized feed more efficiently than those receiving NAR + NIC. The results of 2 floor pen tests, conducted to confirm the results of the above sensitivity trials, demonstrated that NIC provided a greater level of protection from coccidiosis than NAR + NIC. Lower lesion scores and improved performance were recorded for birds receiving NIC compared with NAR + NIC. Results of these studies revealed that changes in the susceptibility of Eimeria spp. to the activity of NAR + NIC are evident. These changes appear to be associated with the reduction in ionophore sensitivity that has been documented in most areas of the world.

Blood Glucose Concentrations in Nicarbazin-Fed Broiler Chickens.

Four floor pen studies were carried out to evaluate the effects of nicarbazin (NIC) administration on blood glucose concentrations and the onset of hypoglycemia in broiler chickens. All tests involved continuous NIC feeding at 0, 100, or 125 ppm to 28 days of age. In each study, birds were reared at both standard environmental temperatures and at 3 C below this level. In addition, two studies were conducted in the presence of coccidial infection and two were carried out in noninfected broilers. At 26 days of age in each test, two birds per pen were bled by puncture of the brachial vein, and whole blood glucose concentrations were determined. Results indicated that the administration of NIC to broilers for 26 days had no effect on blood glucose concentrations, although graded levels of NIC tended to increase these values. In addition, no evidence of hypoglycemia was recorded in any of the trials. In a similar fashion, blood glucose was unaffected by environmental temperature and coccidial challenge. These findings support previous work showing that NIC administration does not influence blood glucose levels and indicate that the product is not involved when field diagnoses use reduced blood glucose and hypoglycemia as indicators of production anomalies.

Performance and anticoccidial effects of nicarbazin-fed broilers reared at standard or reduced environmental temperatures.

A series of 4 floor pen studies was conducted to evaluate the effects of environmental temperature modification on nicarbazin (NIC) responses in broiler chickens raised to 28 d of age. Birds were reared at either standard temperatures (recommended by the primary breeder for ages zero to 28 d) or at 3°C below this level. From placement to 28 d, birds were provided feeds containing zero, 100, or 125 ppm NIC, comprising a 2 × 3 factorial arrangement in each test. Two of the trials were conducted in the presence of an imposed coccidial challenge and 2 were conducted in healthy animals. At 18 and 28 d of age, performance was recorded; cloacal temperatures were measured at 7, 14, 21, and 26 days. Mortality data were collected daily and coccidial lesions were scored at 6 d post challenge. Results of these studies revealed that NIC improved coccidial lesion scores regardless of environmental temperature. In the absence of coccidial challenge, NIC depressed performance, but reductions in environmental temperature diminished the magnitude of these responses. Under conditions of coccidial challenge, NIC significantly improved body weight gains in both temperature environments. Compared to standard temperature conditions, lower environmental temperatures exerted a positive effect on feed conversion rates of NIC-fed broilers. Birds reared in the low temperature environment exhibited lower cloacal temperatures than standard environment groups throughout the test period. Irrespective of coccidial challenge, lower environmental temperatures significantly reduced nicarbazin mortality compared to standard temperature groups, resulting in a significant nicarbazin x temperature interaction. This finding indicates that temperature modification is a practical method for minimizing mortality over the course of 28-day nicarbazin usage.

Tiamulin and semduramicin: effects of simultaneous administration on performance and health of growing broiler chickens.

The pleuromutilin antibiotic tiamulin (TIA) is known to produce a variety of negative interactive effects when it is administered in combination with several anticoccidial ionophores. A 35-d growth study was performed in cages to evaluate the compatibility of TIA when it was administered concurrently with the poly-ether ionophore anticoccidial semduramicin (SEM). Tiamulin and SEM, both alone and in combination, were administered to 10 replicates of female broilers arranged in a completely randomized block design. Tiamulin was administered in drinking water (250 mg of TIA/kg of water) from d 15 through 19 of the study, whereas SEM was incorporated in feed (25 mg/kg) from placement to the conclusion of the test. Water consumption was determined during the period of concurrent administration of the drugs and weekly measurements of feed intake and bird performance were recorded. In addition, hematocrit, blood cell counts, serum protein, albumin, glucose, uric acid, electrolytes, and activities of several enzymes were determined from blood samples taken at d 35. Results indicated that simultaneous administration of TIA and SEM during the third week of the trial reduced water and feed intake resulting in a temporary growth depression. Feed efficiency was transiently affected during the period of coadministration. However, during the fourth week of the test, negative effects in body weight were not observed for any treatment and feed conversion improved for birds concurrently receiving TIA + SEM. By the termination of the experiment, no adverse effects were observed in final performance for any treatment. Histopathological and hematological parameters were unaffected by treatment at d 35 of the test. These results demonstrated that simultaneous administration of TIA and SEM produced only temporary impairments of water and feed consumption that transiently influenced performance. Neither mortality nor long-term effects on performance variables occurred in broilers.

Development of immunity in broilers continuously exposed to Eimeria sp.

A series of experiments was conducted to determine the time required to induce absolute immunity to three species of Eimeria in young broiler chickens continuously exposed to the parasite. Acquisition of immunity was measured by cessation of oocyst production in each bird. Initial experiments were performed in broilers beginning at age 7 days with continuous oocyst administration for 28 days with E. tenella, E. maxima, or E. acervulina. Evaluation of oocyst production demonstrated a major decline in oocyst output of E. maxima and E. tenella by 2 weeks, with cessation by 25 days. Exposure to E. acervulina caused cessation of oocyst production by day 16. To study whether chickens of different ages varied in their capacity to immunize within this time frame, 1-day-old birds also were studied. For E. tenella, exposures also were initiated in 14- and 21-day-old birds. This study demonstrated that regardless of the age of the broiler, all were capable of establishing complete protective immunity to E. tenella, E. maxima, and E. acervulina under continuous exposure within 25, 24, and 16 days, respectively.

Geographic variation in helminth parasites from the digestive tract of Tennessee raccoons, Procyon lotor.

The stomachs and intestinal tracts of 253 raccoons, Procyon lotor, were examined for helminth parasites. Sixteen species of helminths were found including eight trematodes, two cestodes, five nematodes, and one acanthocephalan. Fourteen of these helminths are new geographic records for the state of Tennessee. Multivariate statistical techniques were used to analyze two-state and multistate character sets. Matrices of correlation among characters were computed and the first three principal components were extracted, accounting for 79.7% and 66.5% of the variation in the respective character sets. Three-dimensional projections of Tennessee's eight geographic localities onto two-state and multistate principal components demonstrated that raccoons in western localities were parasitized most heavily by Atriotaenia procyonis. Mesocestoides variabilis, Gnathostoma procyonis, and Pharyngostomoides procyonis. Parallelorchis diglossus, Euparyphium beaveri. Eurytrema procyonis, Euryhelmis squamala, Molineus barbatus, and Macracanthorhynchus ingens were most common to P. lotor from eastern areas.

Effect of nicarbazin and narasin-nicarbazin combinations on broiler pigmentation.

An experiment was conducted with young battery-reared chickens to evaluate the effects of graded levels of nicarbazin (0, 40, 80, 120, and 160 ppm) on plasma pigmentation in the presence and absence of coccidial infection. A second experiment was also performed to determine whether nicarbazin (50 ppm) and the narasin nicarbazin combination anticoccidial (50 ppm each) affected pigmentation values in coccidia-infected and healthy chicks. Pigmentation values were expressed as micrograms beta-carotenoid equivalents per milliliter of plasma (beta-CE). Results of these studies indicated that nicarbazin improved beta-CE in both parasitized and coccidia-free chicks, but the magnitude of improvement was greater in coccidia-infected animals. Linear responses to nicarbazin additions were observed in both groups. The second experiment revealed that the effects produced in healthy chicks receiving the narasin nicarbazin combination were equivalent to those which received nicarbazin alone, indicating that the nicarbazin response in beta-CE is manifested with the combination anticoccidial as well.

Monensin efficacy in rations containing suboptimal energy or protein.

Experiments were performed with growing chicks to assess the effects of rations deficient in energy and protein on feed intake, quantity of monensin ingested, and overall anticoccidial efficacy. Experiment 1 employed a 4 X 2 X 2 factorial design where four levels of monensin (0, 70, 90, and 110 ppm) were added to rations containing either 17 or 23.5% crude protein. In Experiment 2, identical levels of monensin were added to diets containing either 2600 or 3200 kcal metabolizable energy/kg. Both studies were conducted in the presence and the absence of infections produced by Eimeria acervulina, E. maxima, and E tenella. Chicks fed diets deficient in protein consumed significantly more feed and gained less weight than those fed rations adequate in protein. Likewise, protein-deficient chicks consumed more monensin per kilogram of body weight gain. In Experiment 2, weight gain and feed intake were greater in birds fed adequate energy, but the quantity of monensin consumed per kilogram of weight gain was greatest in energy-deficient chicks. In both experiments coccidial lesions and oocyst output were controlled more effectively as monensin dosage was increased. Neither protein nor energy interacted significantly with monensin when lesion scores and oocyst output were evaluated. Thus, these studies indicate that coccidiosis control offered by the monensin concentrations studies is independent of the protein or energy content of the ration.

Selection for resistance to monensin, nicarbazin, and the monensin plus nicarbazin combination.

Two series of experiments were conducted to assess the relative ability of strains of Eimeria acervulina and Eimeria tenella to develop resistance to monensin (MON), nicarbazin (NIC), and the monensin plus nicarbazin combination (MON plus NIC). The studies were designed so that drug concentrations in the selection experiments were increased whenever possible. During selection, E. acervulina increased its reproductive index in the presence of NIC or MON plus NIC, equivalent selection in the presence of MON resulted in only a slight increase in reproductive ability. Eimeria tenella, however, was unable to increase its reproductive capacity to the respective drugs. Sensitivity tests after 60 generations of selection revealed that patterns of resistance development for E. acervulina and E. tenella corresponded with the changes in reproductive indices established in the selection experiments. Thus, results of these tests indicate that E. acervulina possesses the ability to develop resistance to NIC and MON plus NIC. Under essentially the same conditions of selection, E. tenella developed only partial resistance to the respective drugs.

Anticoccidial effect of monensin against Eimeria mitis and Eimeria dispersa.

Four chick and five poult trials were conducted in order to investigate the anticoccidial efficacy of monensin against Eimeria mitis in chickens and Eimeria dispersa in turkeys. The chicks were fed a basal diet with either 0 or 100 ppm of monensin. The poults were fed a basal diet with either 0 or 60 ppm of monensin. Two days after the initiation of each experiment, the chicks and poults were crop-intubated with oocysts of E. mitis and E. dispersa, respectively. A group was also included that was not infected and not medicated. Growth and feed intake were recorded. At 6 or 7 days postinoculation, the birds were killed by cervical dislocation and were scored for the incidence and severity of intestinal abnormalities. The Eimeria mitis infection reduced (P less than .01) gain and the feed:gain ratio, compared with uninfected birds; the E. dispersa infection only reduced (P less than .05) gain. Although well-defined, discrete lesions were not observed, marked intestinal abnormalities were noted in birds infected with either E. mitis or E. dispersa. Also, the infected, unmedicated birds had increased (P less than .01) intestinal scores compared with uninfected birds or those with infection but treated with monensin. Monensin eliminated the reduction in gain and feed efficiency seen in the infected birds. The infected birds fed monensin had intestinal scores, gain, and feed:gain ratios similar (P greater than .10) to those for the birds that were not infected and that did not receive medication.

Effects of the ionophore anticoccidial semduramicin on broiler breeders.

Three experiments were conducted to assess the effects on broiler breeders of contamination of feed with the ionophore anticoccidial semduramicin. In Experiment 1, individually caged females received 0, 12.5, or 25 mg/kg diet for 3 wk from 48 to 50 wk of age. In Experiment 2, males and females in floor pens received 0, 12.5, or 25 mg/kg diet for 3 wk from 63 to 65 wk of age. In Experiment 3, individually caged males and females received 0, 3, 6, or 25 mg/kg diet for 1 wk at 31 wk of age and were mated by artificial insemination. There was a dose-related decrease in cumulative egg production and percentage shell in Experiment 1 after more than 1 wk exposure, but these effects were not observed in the other experiments. There was a decrease in cumulative fertile hatchability and a dose-related decrease after 3 wk exposure due to an increase in early embryonic mortality in Experiment 2, but these changes were not observed during the 1-wk exposure in Experiment 3. The data show that adverse effects of semduramicin require greater than 1 wk of exposure to be evident.

Lead toxicity in the chick as affected by excess copper and zinc and by Eimeria acervulina infection.

Several experiments were performed with young chicks to evaluate lead (Pb) toxicity and its effect upon copper (Cu) and zinc (Zn) toxicosis in the presence or absence of Eimeria acervulina infection. Toxic levels of Pb (3300 mg/kg) and Cu (500 mg/kg) or Zn (2000 and 4000 mg/kg) were added to completely adequate corn-soybean meal diets, while duodenal coccidiosis was produced by multiple crop inoculations of 4 X 10(5) sporulated E. acervulina oocysts. Both Pb and Cu depressed gain and feed efficiency while concomitant coccidial infection reduced these parameters further. Moreover, E. acervulina increased the concentration of liver Cu and kidney Pb. Although Pb supplementation slightly decreased the accumulation of liver Cu, additional Cu tended to increase the deposition of Pb in the kidney in both infected and uninfected birds. Similarly, chick performance was significantly reduced by excess dietary Pb or Zn, although coccidiosis slightly ameliorated the growth depression caused by toxic levels (4000 mg/kg) of Zn. Although 4000 ppm Zn and coccidial infection reduced the deposition of Pb in the kidney, this interaction was not evident when 2000 mg/kg Zn was fed to infected chicks. It is evident that Pb toxicosis in the chick is affected little by excess dietary levels of either Cu or Zn.

Zinc utilization in the chick as influenced by dietary concentrations of calcium and phytate and by Eimeria acervulina infection.

Experiments were performed to investigate the effects of Eimeria acervulina infection (duodenal coccidiosis) on the zinc (Zn)-calcium (Ca)-phytate interrelationship in the chick. Three supplemental levels of Ca (0, .91, and 1.82%), two of Zn (0 or 52 mg/kg), and two of sodium phytate (0 or 1.2%) were evaluated as to their effects when added to completely adequate corn-soybean meal diets. Duodenal coccidiosis was produced by multiple crop inoculations of 4 X 10(5) sporulated E. acervulina oocysts. Calcium supplementation depressed gain and efficiency of feed utilization, while Zn content of tissue and plasma was also lowered. Coccidial infection tended to reduce these values further. The addition of dietary phytate also depressed performance and deposition of Zn in tissue. Both excess dietary Ca and phytate addition to the diet markedly reduced plasma Zn concentration of birds fed corn-soybean meal diets unsupplemented with Zn. Addition of 52 mg/kg Zn, however, prevented excess Ca or phytate from exerting this effect. Parasitized chicks responded markedly with increased gain and gain/feed ratios when 52 mg/kg supplemental Zn was added to a 24% protein corn-soybean meal diet containing 1.82% total dietary Ca. It is evident, therefore, that the Zn-antagonizing effect of excess Ca (in the presence of phytate) is exacerbated by duodenal coccidiosis.

Eimeria acervulina infection and the zinc-cadmium interrelationship in the chick.

The purpose of this study was to evaluate the effects of Eimeria acervulina infection (duodenal coccidiosis) on cadmium (Cd) toxicity and zinc (Zn) status in the young chick. Additions of Cd (45 mg/kg) were made to diets that contained either 0 or 52 mg/kg supplemental Zn (from ZnCO3). Duodenal coccidiosis was produced by multiple crop inoculations of 4 X 10(5) sporulated E. acervulina oocysts. Growth and efficiency of feed utilization were reduced by dietary Cd addition while concurrent coccidial infection reduced these parameters further. Addition of Cd also increased Cd content of liver and kidney and depressed hemoglobin, hematocrit, and plasma Zn content. Coccidial infection exacerbated tissue Cd deposition and depressed hematological parameters further. Although dietary Zn addition ameliorated some of the adverse effects of Cd toxicity, Cd administration tended to enhance tissue Zn deposition. Administration of Cd enhanced synthesis of metallothionein.

Effect of narasin and roxarsone combinations on Eimeria tenella infections in floor pen-raised broilers.

A series of four floor pen trials was conducted to evaluate the effects of narasin and roxarsone, both alone and in combination, on their capacity to control severe Eimeria tenella infections in broilers. Three levels of narasin (0, 60, and 80 ppm) were fed to chickens receiving either 0, 25, or 50 ppm roxarsone in a factorial design. Cecal coccidiosis was induced by seeding the litter with ionophore-tolerant and ionophore-sensitive strains of E. tenella. After 8 days, 10 birds/pen were killed and their cecal lesions scored. Performance (body weight and feed consumption) and mortality were measured at the termination of the trials. Narasin reduced the severity of cecal coccidiosis as measured by a reduction in cecal lesions and an improvement in bird performance. Roxarsone also reduced cecal lesion scores. The highest level of roxarsone (50 ppm) in combination with 60 or 80 ppm narasin produced additive responses in the control of E. tenella infections. Maximum performance was obtained when narasin alone was fed at 80 ppm; drug combinations improved performance when compared with that of nontreated or roxarsone only-medicated groups.