Changes to Cobb 500 chick characteristics, bone ash, and residual yolk mineral reserves during time spent in the hatcher.

Previous work has identified an effect of hatch time on chick femur mineralization. This experiment assessed the impact of hatch time and a 24-h post-hatch unfed time period on chick bone mineralization and yolk mineral utilization. In early hatching chicks, yolk Mg, Zn, K, P, Fe, and Cu decreased by 40 to 50% over the 24-h post-hatch unfed time period, whereas yolk Ca and Na decreased by 25 to 40% (P = 0.026). Yolk Sr was intermediate, decreasing by 37%. Late hatching chicks which had been hatched for no more than 30 h had a higher femur bone ash percentage compared to early hatching chicks which had spent over a 30-hour sojourn unfed in the incubator (P = 0.013). These results indicate that removing chicks from the incubator within 30 h of their hatch is likely to benefit their femoral mineralization.

Changes to mineral levels in the yolk of meat chicken embryos during incubation.

A total of 864 settable Cobb 500 eggs were used to explore changes in yolk mineral content during incubation. Eggs were individually weighed and then placed in a commercial incubator. On embryonic day (ED) 0, 6.5, 13.5, and 17.5, 36 eggs were sampled and yolk weight and mineral content were determined. The concentration of iron (Fe), phosphorus (P), and zinc (Zn) declined (P < 0.05) from ED0 to ED17.5. The concentration of calcium (Ca), magnesium (Mg), and strontium (Sr) increased (P < 0.05) from ED0 to ED17.5. The concentration of copper (Cu), potassium (K), and sodium (Na) increased initially (ED0 to ED6.5) but declined thereafter. There was no change (P > 0.05) in the concentration of yolk manganese (Mn) from ED0 to ED17.5. Substantial changes in yolk mineral concentration occur during incubation and are presumably associated with mobilization of shell reserves and flux between albumen and yolk. These data may be useful in designing in ovo interventions, optimizing meat chicken breeder premix formulation or assembly of suitable neonatal or pre-starter diets for meat chicken chicks.

Why did severe feather pecking and cannibalism outbreaks occur? An unintended case study while investigating the effects of forage and stress on pullets during rearing.

This 2 × 2 factorial experiment aimed to investigate the effects of stimulating foraging behavior from wk 6 and imposed stress at wk 16 on the development of severe feather pecking (SFP) in chickens reared for free-range egg production. Non-beak-trimmed ISA Brown chicks were purchased at one day old and floor-reared on wood shavings. From wk 6, straw was provided daily in dispensers (Forage vs. No forage) to stimulate foraging. At wk 15, there were 16 pens of 50 pullets. "Stressors" were applied to half the pens in wk 16 via combined transport, relocation, and mixing (TRM) of pullets, simulating activities around transfer from the rearing to egg-laying farm (TRM vs. Not TRM). Range access was permitted from wk 21. Behavior, plumage damage (PD), growth, egg production, feed use, injuries, and mortalities were recorded, along with litter moisture and pH. In wk 26, an SFP outbreak commenced. By wk 34, PD was worse in south- than north-aspect pens (P < 0.001). Further, PD was more affected by side of the shed than the experimental treatments. In wk 30, an outbreak of injurious pecking (IP) commenced in the 4 TRM-treatment pens on the south side, with IP deaths almost 3 times more common in the Forage+TRM than No forage+TRM treatment. We suggest factors associated with a 13-day rainfall event that occurred in late winter predisposed the flock to SFP. While multiple factors such as winter cold, muddy ranges, damp floor litter with elevated pH, among others coincided, hens were clearly more impacted in south- than north-aspect pens. Once initiated, SFP possibly spread via social learning, and by wk 40, ∼98% of hens had PD. Interestingly, the IP outbreak was related to a combination of factors (stressors?), such as being housed in colder, damper south-aspect pens (note: southern hemisphere), having added Forage, and TRM. These unexpected relationships could help direct future research to identify the specific factors involved in the causation of SFP and IP/cannibalism outbreaks.