Rate and course of sporulation of oocysts of Eimeria acervulina under different environmental conditions.

An experiment was conducted to determine the rate and maximum percentage of sporulation of Eimeria acervulina oocysts at various environmental conditions relating to temperature (21 versus 33 degrees C) and relative humidity (RH) (40 versus 80%). Measurements were made during 44 h after excretion of oocysts in 3 substrates: dry litter, clammy litter and pure faeces respectively. Maximum sporulation percentage in both dry (22.6%) and clammy litter (19.5%) was higher (P < 0.005) than in pure faeces (11.6%). Neither temperature nor RH had a significant influence on percentage of oocysts that sporulated. Under these simulated practical conditions approximately 25% of all oocysts sporulated, whereas sporulation under optimal conditions (29 degrees C, aeration, 2% K2Cr2O) showed a higher (68%) sporulation ability of oocysts. At 33 degrees C sporulation proceeded at a faster pace than at 21 degrees C (P < 0.005). With respect to RH and substrate, once sporulation started, the rate of increase to maximum percentage was not different. Time of onset of sporulation was influenced by temperature (P < 0.0001) and RH (P < 0.001). Time of onset occurred 15 h later at 21 degrees C compared with 33 degrees C and 5 h later at 40% RH compared with 80%. Also, an interaction effect (P < 0.01) was found with effect of RH being stronger at 21 degrees C compared with 33 degrees C. It was concluded that the most important aspect in the epidemiology of E. acervulina during a flock cycle is the time of onset of sporulation with temperature being the most important factor.

Multivariate epidemiological approach to coccidiosis in broilers.

A retrospective, case-control study into risk factors of coccidiosis was undertaken using data from 189 broiler flocks. A case flock was defined as a flock in which at least one bird had intestinal lesions on 1 of 6 wk in a 42-day cycle. Flocks wherein such birds could not be detected were defined as controls. There were 187 variables, measured or derived. These were assigned to subsets of data, each subset being a group of variables representing related information. Uni- and bivariate analyses were performed in each subset. Variables and interactions that were significant in these analyses were entered into a multivariate model across subsets. In the final model, seven variables appeared to be significantly associated with detecting lesions in birds of a flock. Differences among breeds covered a range of about an 80-fold change in risk of being a case. At intermittent lighting, the risk of being a case increased about sevenfold compared with continuous lighting. A higher initial (Week 1) environmental temperature decreased the risk of finding lesions in a flock (about .8-fold per degree Celsius). This risk was also lower at a lower average aerial ammonia content (below versus above 14 ppm) and higher maximum carbon dioxide content (above versus below .4 vol%) changing the risk about .3- and .4-fold, respectively. The risk of being among cases increased with more litter (about twofold per kilogram of litter per square meter). Flocks in houses of 600 to 800 m2 were about 9.8 times more at risk of being scored as lesion-positive than those in smaller houses.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of claw clipping, stocking density and feeding space on the incidence of scabby hips in broilers.

1. The aetiology of scabby hips was studied in broilers by scratching the skin with chicken claws, clipping the birds' claws and varying the effects of stocking density and food trough allocation. 2. Gentle scratching twice a week resulted in skin lesions that could not be distinguished from clinical scabby hips at slaughter. Interaction between birds appeared to be a prerequisite for the skin condition to develop. 3. Clipping of the claws at day 25 could almost completely prevent scabby hips at day 45 when the birds were slaughtered. 4. No positive correlation was found between feather condition and the severity of scabby hips at slaughter at day 45. 5. Decrease in stocking density and an increase in feeding space resulted in a reduction of skin lesions at day 25 and resultant scabby hips after slaughter.

Efficacy of toltrazuril in broilers and development of a laboratory model for sensitivity testing of Eimeria field isolates.

(1) The efficacy of toltrazuril (Baycox) against coccidiosis was established on a broiler farm in an intermittent application during five consecutive growing periods. Treated birds were fed a broiler ration without anticoccidials. The efficacy of Baycox was compared with the nicarbazin-salinomycin shuttle. It was concluded that Baycox retarded the onset of Eimeria infection for several weeks. During the fifth rearing period coccidiosis problems emerged on the farm in all birds during medication, suggesting development of resistance. (2) During a laboratory experiment the efficacy of Baycox was studied in birds after inoculation with different numbers of oocysts at 7, 10 or 15 days of age. Baycox was applied at 10 and 11 days of age. In all cases medication with Baycox protected birds from coccidiosis during a period of at least 7 days. This effect of Baycox could be due to the long-existing tissue levels of the product and its metabolites as well as its specific effect on the second generation of schizonts. (3) In another laboratory experiment coccidia obtained from field trials were tested for sensitivity to Baycox in conjunction with two strains obtained from farms were coccidiosis emerged during application. The inoculation model developed in this study was used for sensitivity testing. One of the Eimeria strains tested was resistant to the product, one strain was tolerant and the remaining two strains, including the control strain, were fully sensitive to Baycox.

Contribution to the aetiology of synovitis in chickens, with special reference to non-infective factors. V. Extractability of glucosaminoglycans/mucoproteins from tendon tissue.

A comparative study was undertaken regarding the extractability of glucosaminoglycans and mucoproteins in the tendon tissue of birds highly susceptible to synovitis, viz.broiler breed cocks (BB cocks), and of birds highly resistant to synovitis. viz. White Leghorn hens (WL hens). It was shown that in ;the case of WL hens this extractability decreased in accordance with ageing. In the case of BB cocks such a decrease was not observed. This observation is in support of a working hypothesis which supposes a relatively high degree of interaction between the several components of tendon components of tendon tissue (e.g. collagen and glucosaminoglycans/mucoproteins) in the case of WL hens, and a relatively low degree of this interaction in the case of BB cocks. Moreover the results of this study account for the observation that the tendon tissue of WL hens is more resistant to tensile stress than that of BB cocks, and they indicate that the above interaction is a determinant in the aetiology of synovitis.