MVSc

An experiment was conducted to study the egg weight profile in three strains of White Leghorn viz., IWN, IWP and control population (CP) maintained at the All India Co-ordinated Research Project on Poultry improvement, Mannuthy Centre. One hundred pullets from each strain chosen at random at 18 weeks of age were used for the study. The body weight at 20 and 40 weeks of age, average age at first egg, per cent hen housed production, weekly egg weight, 28-day period-wise egg weight, weight of first egg, magnitude of variation in egg weight, per cent variation in egg weight, distribution of eggs under different weight classes and correlation of egg weight with body weight and production were studied from 19 to 52 weeks of age.

The mean body weight at 20 weeks of age was 1.339, 1.421 and 1.229 kg in IWN, IWP and CP respectively. The corresponding values at 40 weeks of age for the above strains were 1.539, 1.546 and 1.445 kg respectively. The results indicated a statistically significant difference between three strains at both the periods. Mean age at first egg was 149.53, 136.41 and 153.85 days in IWN, IWP and CP respectively. The overall mean hen housed egg production from 19 to 52 weeks of age was 65.48, 60.50 and 64.42 per cent for the above strains respectively which were statistically comparable.

The overall mean egg weight from 19 to 52 weeks of age was 49.02, 48.14 and 45.10 g respectively for the strain IWN, IWP and CP. The difference in egg weight between weeks within each strain was statistically significant. Statistical analysis of period-wise mean egg weight showed a significant difference between strains. It was significantly higher in IWN strain, lower in control population and medium in IWP strain.

The weights of first ranged from 29.8 to 57.1 g in IWN strain, 29.8 to 63.2 g in IWP strain and 29.7 to 51.0 g in CP. The net gain in egg weight from 20 to 52 weeks was 20.5, 15.33 and 18.8 g for strain IWN, IWP and CP respectively. Per cent variation in weekly mean egg weight was higher in the initial period in all the strains. As compared with CP pullets, the IWN and IWP strains laid heavier eggs from 19 to 52 weeks of age.

Per cent marketable eggs were higher in IWN strain, lower in control population and medium with IWP strain. Correlation between egg weight and bodyweight indicated that 20 and 40 week body weight had significant correlation with 40 week egg weight in IWN and CP strain. Weekly egg weights were significantly correlated from 28 to 52 weeks in IWN and CP while from 24 to 36 weeks in IWP strain. Twenty four week egg weight with 24 to 52 week egg number had significant correlation in IWN and CP strain but in IWP, the values were negative.

Considering the overall egg weight profile in the above strains, the ideal period for the measurement of egg weight for selection purpose in IWN strain was found to be 29 to 30 weeks of age and 28 weeks of age in IWP strain.