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).

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.

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.

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.

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.

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.

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.

The influence of withdrawal time on the performance of broiler chickens fed semduramicin.

Three 49-d experiments, with a total of 6,528 male broiler chicks in floor pens, were conducted to test the hypothesis that Semduramicin feeding-time affects the body weight gain, feed consumption, and feed conversion ratio of broilers. Semduramicin ionophore was added to corn and soybean meal-based diets at the recommended level, 25 mg/kg for 0,34,39, or 42 d. Thus, three withdrawal times were employed (7, 10, and 15 d) during each experiment. Significant differences among experiments were observed for body weight gain, feed intake, and feed conversion ratio, but no significant differences due to Semduramicin were noted in body weight or feed intake. There was only one treatment by experiment interaction found for 0-to-34-d feed intake (P = 0.028), but it was not evident for 0 to 39 d (P = 0.818) or any other times. Feeding Semduramicin with a 10- or 15-d withdrawal period resulted in an improvement in feed conversion of about 0.04 units.

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.

Studies on semduramicin and nutritional responses: 3. Electrolyte balance.

Four experiments were conducted to determine whether fluctuations in dietary electrolyte level (milliequivalents Na+K-Cl per kilogram) or different dietary sodium chloride levels would affect performance, water intake, or excreta moisture of chickens fed semduramicin vs nonmedicated controls. In all experiments, male commercial broiler chicks were used, and all diets were fed with and without 25 mg semduramicin/kg diet. The basal diets were based on corn, soybean meal, and poultry oil. Experiments 1, 3, and 4 were conducted using male broiler chicks in battery brooders to 18 d of age. In Experiment 1, six electrolyte levels were fed [basal (0.2% Na, 0.33% Cl, 1.10% K); basal plus 0.1% Na (from sodium chloride); basal plus 0.1% K (from potassium chloride); basal plus 0.2% Na (from sodium carbonate); basal plus 0.34% K (from potassium chloride); basal plus 0.15% Cl (from ammonium chloride)]. There were no significant changes in BW gain, feed consumption, or feed conversion ratio caused by any dietary treatment. Water consumption was not affected by the inclusion of Na, Cl, K, or electrolyte levels, but excreta moisture was affected. The highest and lowest excreta moisture levels came from chicks fed the lowest chloride levels. There were no significant dietary effects on serum Na, Cl, or K by dietary electrolytes or semduramicin. Experiment 2 was conducted with triplicate floor pens of 33 male broilers each for 42 d with four electrolyte levels [basal (0.2% Na, 0.34% Cl, 1.03% K); basal plus 0.1% Na (from sodium carbonate); basal plus 0.1% Cl (from ammonium chloride); basal plus 0.18% K (from potassium carbonate)]. Increasing electrolyte level had a significant effect on BW gain at 35 d but not at 42 d [mainly because of differences in K (1.943 kg at 35 d) vs Cl (2.013 kg at 35 d)]. At 42 d, there were no differences in growth because of N, K, Cl, or semduramicin. Potassium supplementation caused a significant increase in litter moisture (P = 0.031). Semduramicin did not affect litter moisture (P = 0.892), nor were there significant semduramicin interactions with Na, K, Cl, or semduramicin. The basal diets in Experiments 3 and 4 were identical to the basal diet in Experiment 1 except there was no sodium chloride added. The diets fed in Experiment 3 contained 0, 0.1, 0.2, 0.3, or 0.4% added sodium chloride. The diets fed in Experiment 4 contained 0.1, 0.3, 0.5, 0.7, and 0.9% added sodium chloride. The results of Experiments 3 and 4 show that about 0.4% added sodium chloride is necessary to achieve maximum growth and feed conversion. It is clear that semduramicin had no significant effect upon the variation observed in any of the variables measured.

Studies on semduramicin and nutritional responses: 2. methionine levels.

Three experiments were conducted to determine whether feeding semduramicin at recommended levels would affect the broiler chicken's response to dietary methionine. In Experiment 1, three levels of methionine (0, 0.15, 0.30%) were fed to chicks in battery brooders. In Experiment 2, two levels of protein (18 and 22%) and three levels of methionine (0, 0.15, 0.30%) were fed to chicks in floor pens from 18 to 44 d. In Experiment 3, two methionine supplements were fed during each of the starter (0 and 0.21%, 0 to 18 d) and grower (0 and 0.10%, 18 to 35 d) periods to chicks in floor pens. In all experiments, male commercial broiler chicks were used, and all diets were fed with and without 25 mg/kg diet of semduramicin. The basal diets were based on corn, soybean meal, and poultry oil. In Experiment 1, there was a growth and feed conversion ratio response to methionine supplements, but there was no effect of semduramicin on growth nor any semduramicin by methionine supplement interaction. In Experiment 2, at 44 d, protein and methionine levels both influenced feed conversion ratios, but semduramicin did not. Feeding 22 vs 18% protein increased carcass and breast muscle yields and decreased abdominal fat pad weights. The results of Experiments 2 and 3 were very similar. Overall, the effects of semduramicin on growth and processing parameters were small and not significant, but considerable benefits in performance and carcass parameters could be realized by feeding the higher levels of protein or methionine.

Studies on semduramicin and nutritional responses. 1. Level and source of protein.

An experiment was conducted to determine whether feeding semduramicin at recommended levels (25 mg/kg) would affect the broiler chicken's response to dietary protein; and to determine whether protein source (all vegetable, corn and soybean meal, vs 12% high animal protein ingredients) would affect the response to semduramicin. Semduramicin was fed to half of 1,584 male Ross x Ross broilers in floor pens during the growing phase (18 to 35 d). Three protein fortification levels were also fed with protein and amino acid minimum restrictions at 80, 100, and 120% of NRC (1994) recommendations. At 35 d, semduramicin was found to cause a slight growth depression in body weight gain only when low protein levels were fed (P = 0.051). After a 7-d withdrawal period, compensatory gains occurred (P = 0.006) such that there was no interaction effect of semduramicin by protein level for 42-d body weight (P = 0.75). Birds fed the diets containing high animal protein were slightly heavier than those fed control diets containing all-vegetable protein (2.40+/-0.02 vs 2.36+/-0.01 kg/bird; P = 0.059). Semduramicin feeding did not affect feed consumption (2.43+/-0.03 vs 2.40+/-0.02 kg per bird during the growing period when it was fed) so that overall feed conversion ratios were identical to two decimal places (1.90+/-0.02 vs 1.90+0.02). Neither did semduramicin affect feathering score or weight of the No. 8 primary feather, except that feather weight tended to be improved by semduramicin feeding with the diets containing ingredients high in animal protein (P = 0.067).

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.

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.

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.

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.