In this trial, we assessed the effects of 2 different ages of breeders and of 2 periods of fasting posthatching on the performance of broilers up to 42 d of age. Male broilers from breeders of different ages (30 and 60 wk) were subjected to an experimental design with 4 treatments: 1) T1, chicks not subjected to fasting, from 30-wk-old breeders; 2) T2, chicks not subjected to fasting, from 60-wk-old breeders; 3) T3, chicks subjected to a 12-h fast, from 30-wk-old breeders; and 4) T4, chicks subjected to a 12-h fast, from 60-wk-old breeders. At the end of the trial, feed intake was greater for the chicks from older breeders. Fasting had a negative influence on feed intake in the period from 0 to 10 d of age. The birds from older breeders had a greater BW gain from 21 to 35 d of age when they were not subjected to a fasting period, but when birds were subjected to a fasting period, no differences between broiler breeder ages were observed on BW gain. Fasting did not exert a significant effect on the BW of the birds. Feed conversion was not influenced by the age of the breeders or by fasting.

In this trial fertile eggs from two different flocks of breeders (aged 30 and 60 weeks) from the same commercial line were incubated under commercial conditions. After hatching, birds were feathersexed and selected. Birds were allocated in four groups. Two of these groups were fed just after placement, while the other two were fed only after 12 hours of housed. Blood samples were collected weekly, starting at day one, and antibodies against Newcastle disease, Infectious Bronchitis and Infectious Bursal Disease virus were measured. The effect of these two variables on the local reaction after a subcutaneous injection with an oil vaccine adjuvant, and the presence and severity of macroscopic lesions in the digestive system organs, at 19 and 30 days of age were also evaluated. The 12 hours fasting period had affected negatively only the Newcastle disease virus antibodies titles at 7 days of age. Both variables had no effect on the severity of macroscopic lesions in the respiratory system and in the digestive system at 19 and 30 days old.Key words: antibodies; immune response;Newcastle R RE ES SU UM MO ONeste experimento ovos férteis oriundos de matrizes de uma mesma linhagem genética, mas com idades distintas (30 e 60 semanas), foram incubados sob condições rotineiras. Após a eclosão, as aves foram sexadas, selecionadas, e alocadas em quatro grupos. Dois destes grupos receberam ração logo após o alojamento, enquanto os outros grupos foram submetidos a jejum de 12 horas. Foram realizadas colheitas de sangue no momento do alojamento e semanalmente no decorrer do experimento. Os títulos de anticorpos para as doenças de Newcastle, Gumboro e Bronquite Infecciosa foram avaliados. Também foi avaliado o efeito destas duas variáveis sobre a resposta local à aplicação subcutânea de um veículo vacinal oleoso e sobre a presença e severidade de lesões macroscópicas nos órgãos do sistema digestório aos 19 e 30 dias de idade. Somente os títulos de anticorpos contra a doença de Newcastle, medidos aos sete dias, foram afetados pelo período de jejum de 12 horas. Nem o período de jejum nem a idade de matrizes afetaram a severidade das lesões macroscópicas no sistema respiratório e digestório aos 19 e 30 dias de idade.Palavras-chave: anticorpos; Newcastle; resposta imune 164 Breeder ages and periods of post-hatching fasting on immunity of broilers ________________________________________________________________________ ________________________________________________________________________