Assessment of the Level of Protection against Coccidiosis in Broiler Breeders Conferred by a Live Anticoccidial Vaccine, and its Influence on Early Growth and Development.

摘要

Coccidiosis continues to be a great challenge to the poultry industry all over the world and in broiler breeders vaccination with live oocysts of Eimeria has been widely adopted as a control measure. Broiler breeders are usually subjected to feed restriction during their early growth however no studies have been undertaken on the effects of vaccination in birds whose feed has been restricted in this manner. The objective of this study was to assess the level of protection acquired by broiler breeder chickens when immunized at day-old with live eimerian oocysts and given a restricted diet. Effects upon growth and development were measured. In the first experiment, 220 vaccinated and unvaccinated broiler breeder chickens were raised in separate pens on new litter. At 4 weeks of age, and every week thereafter until 8 weeks of age, 40 of the vaccinated and unvaccinated birds were assigned to 4 treatment groups in cages and challenged with 100,000 oocysts of Eimeria tenella. The 4 groups were 1) vaccinated and challenged (VC), 2) unvaccinated and challenged (UC), 3) vaccinated and unchallenged (VU), and 4) unvaccinated and unchallenged (UU). The level of protection acquired was assessed by the presence of lesions in the ceca and dropping pan scores 6 days after challenge. In the second experiment one group of birds was infected orally with 500 oocysts each of E. acervulina, E. maxima and E. tenella at day old and a second group was kept as uninfected controls. Doses were intended to simulate those provided in commercial coccidiosis vaccines. Body weight, chest girth, shank length, and keel length were used as criteria to judge the effect of infection on growth and development. In the first experiment, lesions and dropping pan scores were significantly reduced in the VC (P < 0.05) birds compared to UC birds at 4, 5, 6, 7, and 8 weeks of age indicating that birds have developed sufficient immunity to protect them from the pathology caused by E. tenella. In the second experiment, infected birds showed significantly reduced (P < 0.05) body weights and chest girths compared to the control birds. This indicates that infection affects body growth and development of these birds. Results were inconclusive with shank length and keel length measurements.