Impact of growth curve and dietary energy-to-protein ratio of broiler breeders on offspring quality and performance

The impact of growth curve (GC) and dietary energy-to-protein ratio of broiler breeder hens on chick quality and broiler performance was investigated. Pullets (n = 1,536) were randomly allotted to 24 pens and assigned to 1 of 8 treatments from hatch onwards, according to a 2 × 4 factorial arrangement with 2 GC (standard growth curve = SGC or elevated growth curve = EGC, +15%) and 4 diets, differing in energy-to-protein ratio (96%, 100%, 104%, and 108% AME(n) diet). At 28 and 36 wk of age, 60 hatching eggs per maternal pen were selected for incubation and 768-day-old broilers were assigned to 32 pens according to maternal treatment. Broilers from EGC breeders were 1.9 g heavier at hatch (P < 0.001) and 36 g heavier at slaughter (P = 0.001) than broilers from SGC breeders due to a 1.0 g/d higher growth rate (P = 0.003) and 1.5 g/d higher feed intake (P = 0.006) from hatch to 32 d of age. An increase in breeder dietary energy-to-protein ratio resulted in a linear decrease in embryonic mortality in the first 3 d of incubation (β = -0.2% per % AME(n); P = 0.05). At hatch, broiler BW decreased with an increasing breeder dietary energy-to-protein ratio (β = -0.1 g per % AME(n); P = 0.001), whereas at slaughter broiler BW increased with an increasing breeder dietary energy-to-protein ratio (β = 3.2 g per % AME(n); P = 0.02). This was due to a linear increase in growth rate (β = 0.1 g/d per % AME(n); P = 0.004) and feed intake (β = 0.1 g/d per % AME(n); P = 0.02). Additionally, an increase in breeder dietary energy-to-protein ratio resulted in a linear decrease in body weight corrected feed conversion ratio (β = -0.002 per % AME(n); P = 0.002). Overall, it can be concluded that a higher GC of breeders and an increase in breeder dietary energy-to-protein ratio enhances offspring performance.