Feeding broiler breeders represents a challenging balance from the welfare point of view as birds' feed intake and bodyweight need to be restricted for optimum production of hatchable eggs and minimum mortality.

A recent study at the Prestage Department of Poultry Science at North Carolina State University to examine how two feeder space allocations during the rearing period followed by two feeder space allocations after photostimulation and two female feeding to peak programmes (fast or slow) affected female broiler breeder reproductive performance and mortality.

The researchers, led by Professor John Brake, explain in their paper in Poultry Science that standard commercial practice across much of the world is for a single brood-grow-lay housing system in which broiler breeders reside for 65 weeks in a single facility. However, in the United States, a more popular system has been for separate systems for the brood-grow and laying periods, with broiler breeders moved from growing quarters to laying quarters and photostimulated at about 21 weeks of age. The latter system has the economic advantage that fewer houses are required.

Production results, however, tend to favour the brood-grow-lay system. A major difference between the two systems is in the feeding systems and feeder space in the growing versus laying houses, according to the researchers.

Primary breeders suggest that feeder space should be sufficient to ensure that all birds have access to the feed at the same time and that feeder space should increase as the birds age. Insufficient feeder space has been associated with poor uniformity of flock bodyweight.

At sexual maturity, which follows movement to the laying quarters and photostimulation, the ovary and oviduct develop rapidly, according to Professor Brake and his team, and others have shown that these organs are sensitive to the feeding programme at the time of photostimulation during sexual maturation.

Overfeeding during reproductive development has been found to interfere with the orderly formation of ovarian follicles, which may permanently reduce fertility and hatchability.

To investigate the effects of and interactions between feeding space during rearing and laying and the rateof increase of feed allocation from photostimulation to peak production, the researchers at Raleigh used 16 pens, each of 76 breeder females. Each pen was equipped with either four tube feeders with a 132-cm circumference pan (7.0cm per female) or six feeders (10.4cm per female) to 21 weeks of age.

Thereafter, 64 females were moved to breeding pens, photostimulated and fed sex-separate from either three (6.2cm per female) or five (10.3cm per female) feeders with either fast or slow feeding to peak feeding programmes applied to complete a 2×2×2 factorial design.

Seven males that were separately reared in a similar manner were added per pen.

Individual female bodyweights were determined at six, 20 and 32 weeks of age and bodyweight uniformity assessed.

Greater feeder space during rearing increased bodyweight at 32 weeks of age, whereas greater feeder space during lay or slow feeding to peak decreased bodyweight at 32 weeks.

There were no differences in bodyweight uniformity.

Hens from the 10.4 to 10.3cm per female combination produced a significantly greater number of eggs than the females with the combinations of 7.0 to 10.3cm or with 10.4 to 6.2cm; 7.0 to 6.2cm per bird combination was intermediate.

Percentage hen-day egg production of the 10.4 to 10.3cm per female combination hens was significantly greater than all other combinations.

Livability was improved in the 10.4 to 10.3cm per female combination relative to the 7.0 to 10.3cm combination with the others intermediate.

The fast feeding to peak programme increased yolk weight as well as yolk:albumen ratio at 28 and 30 weeks of age but egg weight did not differ.

The Raleigh-based researchers concluded that breeder hens that were given the most similar feeder space (10.4 to 10.3cm per female) between the rearing and laying periods produced the most eggs as well as exhibited the greatest hen-day egg production with the lowest mortality.

Their data indicate that increased or decreased feeder space between the growing and laying periods did not affect broiler breeder female bodyweight, uniformity, egg weight, fertility or hatchability.

The 10.3cm per female laying feeder space resulted in the highest hen-day egg production in combination with 10.4cm per pullet rearing but not with 7.0cm per pullet rearing space.

In a similar manner, they added, hen mortality was greater in the 7.0 to 10.3cm per female feeder space combination than the combination of 10.4 to 10.3cm per female.

Reference

Leksrisompong N., H. Romero-Sanchez, E.O. Oviedo-Rondón and J. Brake. 2014. Effect of feeder space during the growing and laying periods and the rate of feed increase at the onset of lay on broiler breeder female reproductive function. Poultry Science. 93:1599-1607. doi: 10.3382/ps.2013-03277

September 2014