SummaryThis study was performed in Ross 308 chickens aged 1-21 days and aimed to evaluate
K E Y W O R D S25-hydroxycholecalciferol, broiler chicken, immunity, production parameters
Ten infectious bronchitis virus (IBV) isolates were recovered from broiler chickens in the states of Queretaro and Guanajuato in Mexico. The viruses were isolated from trachea, lung, kidney, and cecal tonsils of birds that showed respiratory signs in spite of vaccination with Massachusetts (Mass) and Connecticut strains of IBV. Each isolate was identified by an accession number from 1 to 10. Six of the isolates were neutralized by Mass monoclonal antibodies, whereas the other four were not. In addition, these four isolates did not produce lesions in embryos in the first five to seven passes. These four isolates were further characterized by the reverse transcriptase-polymerase chain reaction and restriction fragment length polymorphism techniques. The electrophoretic patterns for the four isolates were identical but were different from other known IBV isolates.
This study was conducted (at high altitude [1969 meters]) to determine whether chicks predisposed to cardiac failure and ascites could be identified and followed during growout with non-invasive electrocardiographic (ECG) techniques. ECG recordings were made on 40 chicks at 1 week of age. All recordings were analyzed by quantifying the amplitude in millivolts of the R-, S-, and T-waves in each of the recordings. During the study, ascites-related mortality was 40%, with the majority of the deaths occurring between 5 and 8 weeks of age. Chicks exhibiting moderate-to-severe right ventricular hypertrophy, as identified by ECG analysis at 1 week of age, were predisposed to development of ascites. Thus, the variability in ascites-related mortality observed in field cases may be directly related to the number of predisposed chicks at the time of placement in the broiler house.
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