Egg characteristics and hatch performance of Athens Canadian Random Bred 1955 meat-type chickens and 2013 Cobb 500 broilers.

Athens Canadian Random Bred (ACRB) chickens, a 1955 meat-type control strain, were incubated with the 2013 Cobb 500 broiler to determine differences in egg composition, conductance values, incubation duration, hatch performance, and yolk utilization. Unincubated ACRB eggs had greater percentage solids than Cobb 500 eggs. The ACRB eggs had a greater solid portion as yolk, whereas the Cobb 500 devoted more solid percentage to albumen. Percentage shell was not different between the strains, but ACRB eggs had 2.7% greater percentage moisture loss after 18 d of incubation than Cobb 500 eggs. Conductance, conductance constant, and conductance standardized to a 100 g egg weight basis were all higher for ACRB eggs than Cobb 500 eggs at 12 and 18 d of incubation. The Cobb 500 chicks hatched 6 h earlier than ACRB chicks. The Cobb 500 incubation duration was 498 h, and the ACRB incubation duration was 504 h. There was no difference between the strains for percentage infertile eggs, embryonic mortality, hatchability, or salable chicks. The ACRB chicks hatched with a smaller dried residual yolk sac as a percentage of chick weight compared with the Cobb 500. Both strains had an average relative yolk-free chick weight of 61% of average initial egg weight. Thus the Cobb 500 eggs had decreased gas exchange across the eggshell, which may have contributed to the earlier hatch and decreased yolk utilization. Modern Cobb 500 broiler embryonic metabolism appears to have either become more dependent on albumen rather than yolk or has become more efficient with yolk reserves during development. Broiler hatch performance does not appear to have changed over the past 58 yr.

Growth, livability, feed consumption, and carcass composition of the Athens Canadian Random Bred 1955 meat-type chicken versus the 2012 high-yielding Cobb 500 broiler.

A flock of the Athens Canadian Random Bred (ACRB), a 1955 meat-type chicken control strain, was raised alongside a flock of 2012 Cobb 500 fast feathering high-yielding broilers to determine selection changes over the past 57 yr. All birds were reared under management practices appropriate for the Cobb 500. Birds were weighed weekly and processed at 6, 8, and 10 wk. Whole carcass, carcass parts, and organs were weighed. Modern broilers outweighed ACRB at every age, ranging from 3.7 to 4.7 times the size of the ACRB. All parts and organs were compared as a percentage of live fasted BW. The ACRB had significantly heavier feet, wings, internal organs, and feathers. The modern Cobb broiler had double the breast and larger leg muscles and had a significantly greater fat pad. Despite the larger muscle mass, the supply organs, the heart and lungs, were significantly smaller in the Cobb broiler than the ACRB as a percentage of BW. Relative size of supply and other vital organs should be given consideration for genetic selection of the future broiler. Comparisons of ACRB weights and organ percentages with past published data indicates that the ACRB remains a consistent control strain.

No evidence of temperature-dependent sex determination or sex-biased embryo mortality in the chicken.

Skewing the sex ratio at hatch in commercial poultry would be economically beneficial to the poultry industry. The existence of temperature-dependent sex determination is uncertain in birds. This experiment investigated if incubation temperatures skew sex ratios of commercial broilers. Three incubators were each set at a hot (38.3°C), standard (37.5°C), or cool (36.7°C) single-stage incubation temperature one time over 3 trials to eliminate incubator effect as a Latin square design. Sex ratios of hatched chicks and dead embryos were monitored. In one trial, embryo weights were evaluated. The percentages of male hatched chicks did not differ based on incubation temperature (P = 0.4486; 49.5% in the hot treatment, 51.4% at standard temperature, and 49.8% in the cool treatment). The percent hatch of eggs set was lower in the hot treatment (83.6%) than the standard (93.5%) and cool (91.6%) treatments (P < 0.0001) with greater late embryonic mortality in the hot treatment (P < 0.0001); however, the sex ratio of dead embryos did not differ among treatments (P = 0.9863). Pooled data of embryo mortality found no sex-biased embryo mortality with a female/male sex ratio of 1.22:1 (χ(2) = 1.27; P = 0.2596). Embryos from the hot treatment were heavier than those from the standard treatment by d 14 of incubation and were heavier than the embryos from the cool treatment by d 9 of incubation (P < 0.0001). These data indicate that incubation temperature affects embryonic mortality and embryonic growth rate, but it does not affect the sex ratio of broiler chickens. Additionally, no evidence was found for sex-biased embryo mortality in commercial broilers even at the incubation temperatures of this study.

Impact of Skip-a-Day and Every-Day Feeding Programs for Broiler Breeder Pullets on the Recovery of Salmonella and Campylobacter following challenge.

The impact of restrictive feeding programs on Salmonella and Campylobacter colonization and persistence after challenge was investigated for broiler breeder pullets housed in an experimental rearing facility. Pullet-chicks were placed on litter in 3 feeding program rooms and each room contained 2 replicate pens. The feeding programs were: (1) Skip-a-day in trough feeders (SAD); (2) Every-day in trough feeders (EDT); (3) Every-day on the pen litter (EDL). On d 1, an additional group of hatchmate chicks were housed in a separate room and gavaged with Salmonella Typhimurium, to later serve as seeder chicks. After seeders were confirmed Salmonella-positive at wk 4, at wk 5 seeders were placed into each feeding program pen to commingle with 135 penmates. At 7, 9, 11, 17, 18, and 20 wk the litter surface in each pen was sampled using intermittently stepped-on drag-swabs. At 8, 12, 16, and 20 wk of age the ceca were sampled from 10 penmates/pen and 2 pooled spleen samples/pen were collected. SAD litter remained Salmonella-positive through 20 wk of age while EDL and EDT pens had no detectible litter Salmonella recovery by 18 and 20 wk. EDL fed pens had no direct (<102 cfu/mL) litter Salmonella recovery during the entirety of the experiment. Salmonella prevalence for ceca from SAD pullets was significantly (P < 0.05) higher at 8 wk (70%) compared to EDT (40%) and EDL (30%). At wk 12, SAD pullets for both on and off-feed sampling days had significantly higher Salmonella recovery (40%), compared to EDT and EDL (both at 5% recovery). By 16 and 20 wk, only the SAD pullets on the on-feed day (48 h without feed) had recovery of Salmonella at 20%. Salmonella recovery in pooled spleen samples did not appear associated with feeding treatments (22% positive). The remaining pullets challenged with Campylobacter at 21 wk produced similar trends as was seen for Salmonella. SAD program pullets had significantly higher Campylobacter from ceca (80 to 100%) compared to pullets on EDL (30 to 60%) or EDT (40 to 95%). These results suggest that using a Skip-a-Day feeding program for broiler breeder pullets contributes to persistently higher Salmonella and Campylobacter ceca colonization and litter prevalence.