Genotype and breeder flock age impact on broiler performance in suboptimal conditions

A comparative study of production traits was performed between COBB 500 broilers from a 52-week-old breeder flock and a ROSS 308 from two breeder flocks of different ages (52 weeks and molted flock 79-week-old) in equal, relatively suboptimal ambiental (temperature oscillations) and nutritional conditions (market feed of average quality). The experiment was performed on a total of 720 day-old chicks of both sexes in 4 experimental groups (Cobb; Ross 52; Ross 79; Ross mix - a mixture of Ross broilers from two breeder ages), with 6 replications per group and 30 chickens in each replication. Mortality, body weight (days 0, 7, 21 and 42), weight gain, feed conversion and production index (EPEF) were monitored in 42 days of fattening. It was determined that heavier day-old chickens (p<0.01) with better gain in the first week of production, were obtained from the older breeder flock. Except in the first week, Cobb generally had the highest (p<0.05) body weights and gains in the experiment, aside from in mid and the end of the test, where did not differ significantly from the body weight of the Ross 79 and Ross mix group of broilers, respectively. Results also indicate that genetics (used hybrid) may have a greater influence on the final body weight and daily gain in suboptimal test conditions than the breeder age. Cobb 500 broilers also had significantly higher mortality under test conditions (p<0.05). Feed conversion and the achieved EPEF production index did not vary significantly in the test in chickens of different genotypes or parents. In general, suboptimal conditions in our research constrained realisation of the genetic production potential, with a suppressive effect on both hybrids, higher on the growth in Ross 308, and on the resistance measured by mortality in Cobb 500 hybrids.