Sporulation of Eimeria maxima oocysts in litter with different moisture contents.

The aim of this study was to determine if the sporulation of Eimeria maxima oocysts was affected by the moisture content of the litter. Fresh feces were collected from chickens experimentally infected with E. maxima. The feces were mixed with dried wood shavings and different amounts of water to obtain final moisture contents of 16, 42, and 62% and a final oocyst concentration of 5,000 per g of mixture. The samples were kept at 23 C and 75% relative humidity and were thoroughly aerated every 12 h. Oocysts kept under ordinary laboratory sporulation conditions in 2% wt/vol aqueous potassium dichromate at 27 C were used as a standard for optimal sporulation. The proportion of sporulated oocysts was determined microscopically every 12 h. Sporulation of E. maxima was most efficient under the driest conditions studied (16% moisture content), and poorest in the samples with the highest moisture content (62%). Even though the differences may not have resulted from a direct effect of humidity on the oocysts, but more likely resulted from limited oxygen in the moister substrates, it is clear that sporulation is not favored by moist litter.

Intestinal digesta viscosity decreases during coccidial infection in broilers.

1. The effect of intestinal digesta viscosity on bird performance in chickens with coccidiosis was compared to those without coccidiosis. 2. Six hundred chicks were divided into five groups: one control group was fed a basal maize/soyabean-based diet and the other groups were fed the basal diet supplemented with 2, 4, 6 or 8 g carboxymethyl cellulose (CMC) per kg of feed. At 14 d of age half the birds were individually inoculated with sporulated oocysts of Eimeria acervulina and Eimeria praecox. 3. Intestinal digesta viscosity increased with increasing inclusion of CMC. This effect was considerably less pronounced in inoculated than in non-inoculated birds. 4. There was a significant negative effect on live weight gain and feed conversion ratio (FCR) with increasing CMC inclusion in non-inoculated birds, but in inoculated birds there was no clear relation between CMC inclusion and performance. Neither intestinal lesion scores, nor numbers of Clostridium pefringens in the caeca, were significantly affected by CMC inclusion. 5. Across all diets inoculation impaired growth rate by 9% and FCR by 8%, but did not affect the amount of C. perfringens in the caeca.

Comparison between a live, attenuated anticoccidial vaccine and an anticoccidial ionophore, on performance of broilers raised with or without a growth promoter, in an initially Eimeria-free environment.

An experiment was carried out to study the effects of vaccination with Paracox, a live, attenuated vaccine against avian coccidiosis, on broilers isolated from extraneous Eimeria parasites. The study involved 3200 broiler chickens raised in floor pens similar to commercial conditions, but in an initially Eimeria-free environment. Forty percent of the chickens were vaccinated at 3 days of age and given either a basal unmedicated feed or a feed supplemented with the feed antibiotic virginiamycin. Unvaccinated birds were given either the basal feed or feed supplemented either with virginiamycin or the anticoccidial ionophore narasin. At slaughter at 36 days of age vaccinated birds had a lower live weight than non-vaccinated birds. The difference was 4.6% in unmedicated, and 6.0% in virginiamycin medicated chickens. Feed conversion ratio at slaughter was 2.5% higher for unmedicated vaccinated birds, and 1.3% higher for virginiamycin medicated vaccinated birds, compared to respective non-vaccinated groups. There was no significant difference in overall performance of unvaccinated birds given narasin as compared to virginiamycin. At 10 days post vaccination vaccinated birds had a higher number of Clostridium perfringens in the caeca, but there was no difference thereafter. Throughout the experiment, caecal clostridial counts were considerably higher in vaccinated unmedicated birds than in unvaccinated birds given narasin. The number of oocysts shed in the vaccinated groups was very low, but during a subsequent challenge with E. maxima and E. tenella the birds' immunity was found to be satisfactory.

Effect of betaine supplement on broiler performance during an experimental coccidial infection.

A trial was conducted to investigate the effects of betaine as a feed supplement, given singly and in combination with the ionophore coccidiostat narasin, on broiler performance during an experimental coccidial infection. Five hundred and sixty female Ross broiler chickens were kept in floor pens and given a wheat-based diet. At 10 d of age, 420 chickens were individually inoculated with a mixture of Swedish chicken Eimeria isolates containing E. acervtulina, E. praecox, E. maxima, and E. tenella. Remaining birds were kept as uninoculated controls. The effects of betaine (0 or 1.0 g/kg) and narasin (0 or 70 ppm) added to the basal diet were evaluated. Overall, betaine as a single feed supplement improved live weight by 5.7, 5.4, and 5.6% at 22, 29, and 36 d, respectively, but had no positive effect in combination with narasin. A longer withdrawal period of the coccidiostat (10 vs 5 d) did not affect live weight, but significantly increased feed intake by 9.6% and feed conversion ratio by 12.6%, irrespective of betaine supplement. Inoculated birds had a 10% lower live weight than uninoculated chickens. Performance of uninoculated birds was similar to that of inoculated birds treated with narasin, except at 7 d after inoculation, when live weights of uninoculated birds were significantly higher. Chickens given coccidiostat had less Clostridium perfringens in their ceca, but the prevalence was not altered by betaine supplement. There was no difference in intestinal lesion scores between inoculated chickens given coccidiostat or not, despite the better performance of chickens given coccidiostat. Betaine did not affect Eimeria oocyst output or intestinal lesion scores.

Effect of antibiotic growth promoters and anticoccidials on growth of Clostridium perfringens in the caeca and on performance of broiler chickens.

The effects of the growth promoters avoparcin and avilamycin and the ionophore anticoccidials maduramicin, narasin and monensin on the growth of Clostridium perfringens (Cp) in the caeca and on performance of broiler chickens were tested in 2 experiments. The supplements were fed as single feed additives or in some combinations. No clinical signs or lesions caused by coccidia were observed in any of the studies. All supplements had an antibacterial effect on Cp and improved growth rate significantly. Carcass yield of birds fed growth promoters avilamycin or avoparcin was significantly higher compared with birds fed anticoccidials. These data indicate that, what concerns bird performance, during good hygienic conditions supplementation with antibiotic growth promoters may not be necessary when the diet is supplemented with an anticoccidial with antibacterial effects.

Comparison between effects of standard feed and whole wheat supplemented diet on experimental Eimeria tenella and Eimeria maxima infections in broiler chickens.

The effects of experimental infections with Eimeria tenella (Experiment 1, n = 144) or E. maxima (Experiment 2, n = 216) in broiler chickens fed whole wheat, with or without access to grit, as compared to a standard pelleted feed were studied. Inclusion of whole wheat was gradually increased up to 30% at 3 weeks of age. Grit was given separately. The chickens were kept on litter in a parasite-free environment with free access to water and feed. At 3 weeks of age half the number of chickens were individually inoculated with 500 sporulated oocysts of E. tenella (Experiment 1) or 3,000 sporulated oocysts of Eimeria maxima (Experiment 2), and the remaining birds were kept separate as uninfected controls. Neither coccidiostats nor growth enhancers were used. Oocyst concentration was determined from each group separately. Intestinal lesions were scored on 6 birds per feed regime 7 d postinoculation, and on the remaining birds at slaughter. Diet had no significant effect or bird performance during infection. However, there was an indication that the E. maxima infection had more negative effect on weight gain in birds given standard feed than in those given whole wheat supplement, but the difference was not significant (p < 0.09). The number of oocysts shed or mean intestinal lesion scores did not differ between diets in either experiment. In both experiments, the number of Clostridium perfringens was higher in the caeca of inoculated birds, but there were no differences between diets.

Retrograde flow of urine from cloaca to caeca in laying hens in relation to different levels of nitrogen intake.

Retrograde flow of urine into the caeca provides a more efficient recovery of nutrients and supplies a nitrogen source for the caecal microbes. 30 laying hens of Leghorn type were used in the present experiments. Hens were randomly divided into three treatment groups and fed a high nitrogen (19.8% crude protein in dry matter), medium (15.0% crude protein in dry matter), or low (10.6% crude protein in dry matter) isocaloric diet for fourteen days prior to and during the experimental period (8 h). Results from the study show that the retrograde flow of urine from cloaca to caeca is significantly higher in birds given a low protein diet compared to medium or high levels. It also shows that the produced amount of urine is significantly higher in hens given a low protein diet compared to the medium level diet.