A comparative survey on performance of M gallisepticum-Free and M gallisepticum-infected layer flocks in Tabriz area of Iran

Abstract

The aim of this study was to determine the effect of M gallisepticum (MG) on performance of commercial layer flocks in Tabriz, Iran. Eight Hy-line W36-strain commercial layer flocks, 4 MG-Free and 4 MG infected-flocks, from two breeding companies were reared in the same condition and compared for production factors during rearing phase and production period. In rearing period, livability and body weight at the age of 17 weeks in MGinfected group were significantly lower than MG-Free group (PB0.05). These factors in both groups were lower than the standard group. Feed intake in rearing period did not differ between the two groups. At production period (18Á80 weeks), livability, hen housed egg production and peak production rates in MG-infected group were markedly less than MG-Free group. Overall, the result showed that MG-infected group had lower economic performance.Keywords: Mycoplasma gallisepticum; layer flocks; performance IntroductionAvian mycoplasmosis is an important disease in poultry industry of many countries and causing economic loss (Bradbury 2001;Sarkar et al. 2005). The disease is caused by four commonly recognized pathogens; Mycoplasma gallisepticum, Mycoplasma iowae, Mycoplasma meleagridis and Mycoplasma synoviae (Bradbury 2001;Lierz et al. 2008). M gallisepticum (MG) is the most pathogenic and economically significant mycoplasmal pathogen of poultry. The clinical signs associated with MG infection in these avian species include respiratory rales, coughing, nasal discharge, sinusitis, and occasionally conjunctivitis (Murakami et al. 2002;Nascimento et al. 2005). The most prominent pathological findings include inflammatory lesions in the trachea, air sac, lungs, conjunctiva, and other tissue such as the oviduct (Nunoya et al. 1995). In view of the above consideration, the aim of this study was to determine the effect of MG on performance of commercial layer flock during rearing phase and production period. Materials and methodsEight commercial layer flocks (Hy-line W36-strain) were chosen from two breeding companies in Tabriz Performance factors that were investigated in both flocks during growing period (1Á17 weeks) were livability (percent), body weight at 17 weeks (g), and total feed intake (Kg). During production period (18Á80 weeks); livability (percent), total feed intake (Kg), hen housed egg production, and peak production rate (percent) were evaluated. The data from MG-Free and MG-infected groups were analysed statistically using T-test procedure with SPSS version 13 for windows and compared with the result of Hyline W-36 strain that published in Hy-line catalogue (Hy-line International Poblication 2006). Results and discussionDue to substantial performance and production losses, MG has been described as most economically important pathogenic Mycoplasma species affecting poultry (Evans et al. 2005). Mohammad et al. (1987) studied the influence of MG on production rate of 366 commercial layer flocks in California, and reported that MG-infected flocks produced 12 and 5 fewer eggs per hen th...