Effects of genetic strain and light intensity on growth performance and carcass characteristics of broilers grown to heavy weights were investigated by USDA, Agricultural Research Service, Poultry Research Unit in Mississippi state, USDA, Agricultural Research Service, Poultry Research Unit, Advanced Animal Eye Care and Mississippi State University.

In a paper in the current issue of Poultry Science, first-named author, Hammed Olanrewaju and co-authors explain that they used a randomised complete block experimental design.

Treatment structure was a 2×5 factorial arrangement with the main factors being strain (Ross × Ross 308, Ross × Ross 708) and light intensity (25, 10, 5, 2.5 and 0.2 lux) with trial as replicates.

In each of the five trials, chicks of two different strains of the same commercial hatchery were equally and randomly distributed into 10 environmentally controlled rooms (five rooms per strain) at one day of age at 50 per cent relative humidity.

Each room was randomly assigned one of five light intensities from 22 to 56 days of age.

Feed and water were provided ad libitum. Birds and feed were weighed on 0, 14, 28, 42 and 56 days of age for growth performance. Humoral immune response was determined on day 28, whereas ocular and blood samples were performed on days 42 and 55, respectively.

On day 56, 20 (10 males and 10 females) birds per strain from each room were processed to determine weights and yields.

Genetic strain was significant (P≤0.05) for most of the examined variables, where Ross × Ross 308 had better growth performance and meat yield than Ross × Ross 708.

Although there was no main effect of light intensity on growth performance and meat yield, results indicated that birds under 10- and 5-lux intensities showed slightly better growth performance and meat yield than those under 25, 2.5 and 0.2 lux in both strains.

There was no effect of strain and light intensity on ocular indices, immune response, plasma corticosterone levels or mortality.

Olanrewaju and co-authors concluded their study shows the positive influence on profits to commercial poultry facilities that are using a low lighting environment to reduce energy cost, optimise feed conversion and maximise production without compromising the welfare of the broilers.

Reference

Olanrewaju H.A., W.W. Miller, W.R. Maslin, S.D. Collier, J.L. Purswell and S.L. Branton. 2014. Effects of strain and light intensity on growth performance and carcass characteristics of broilers grown to heavy weights. Poultry Science. 93(8):1890-1899. doi: 10.3382/ps.2013-03806

July 2014