Table 2. The effect of maternal immunization with purified gametocyte antigens of Eimeria maxima on the development of resistance to Eimeria tenella in offspring chickens.

Age of challenge	Peak numbers of oocysts per gram faeces for vaccine birds (average±S.D.)×10−3 (n = 4 groups of 15 birds)	Peak numbers of oocysts per gram faeces for control birds (average±S.D.)×10−3 (n = 4 groups of 15 birds)	Peak % reduction in oocyst excretion by vaccine birds	Overall numbers of oocysts per gram faeces, days 4–14 post-challenge, for vaccinated birds (average±S.D.)×10−3 (n = 4 groups of 15 birds)	Overall numbers of oocysts per gram faeces, days 4–14 post-challenge, for control birds (average±S.D.)×10−3 (n = 4 groups of 15 birds)	Overall % reduction in oocyst excretion by vaccine birds
4 days	56.2±2.2	175.0±81.7	67.9	115.0±5.5	310.9±53.0	63.0
39 days	48.0±36.9	405.7±214.8	88.2	104.4±92.9	713.6±322.8	85.4
57 days	0.1±0.1	3.6±1.8	98.0	0.1±0.1	6.2±3.6	98.4

Commercial broiler breeder hens (14,532 vaccinated with purified gametocyte antigens and 7,256 control) were vaccinated twice with purified gametocyte antigens, (at 15 and 20 weeks of age). Eggs were collected from groups of vaccinated and unvaccinated 43-week old hens and incubated to hatching. At 4 days of age, four groups of 15 male chicks from vaccinated and unvaccinated hens were challenged with 50 oocysts of E. tenella. At 39 and 57 days of age four groups of 15 chicks from each of vaccinated and unvaccinated hens were challenged with 25,000 oocysts of E. tenella. Faeces were collected from days 4–14 after challenge infection and oocyst counts performed. Oocyst excretion is expressed in two ways: [i] by peak oocyst excretion, which is a measure of the highest number of oocysts per gram of faeces on a single day after challenge infection (generally day 7 post-challenge) for groups of 15 chickens; and [ii] overall oocyst excretion, which is a measure of the number of oocysts per gram faeces found in the total faecal collection for days 4 to 14 post-challenge for groups of 15 chickens. The differences for both the peak and total oocyst counts in the vaccinated and control groups at the three time points are all statistically significant at the p<0.05 level (one-way ANOVA, Student's t-test).