Effects of incubation temperature pattern on broiler performance

During incubation, development of em-bryos is affected by eggshell temperature (EST). A con-stant EST of 37.8 degrees C has been considered so far to result in most optimal embryo development. However, it can be hypothesized that a higher EST in week 2 in combination with a lower EST in week 3 stimulates embryo develop-ment and subsequent grow-out performance. In this study, 468 eggs of a 44-week-old Ross 308 breeder flock were incubated at different incubation temperature pat-terns in a 2 x 2 factorial arrangement. In week 2, EST was either 37.8 degrees C or 38.9 degrees C, and in week 3, EST was either 37.8 degrees C or 36.7 degrees C. At hatch, chick quality was determined. Thereafter, 320 broilers were grown in 32 pens (8 repli-cates/treatment) for 6 wk. Weekly BW and ADFI were determined, and at day 40, slaughter yield from 128 broilers (4 per pen) was determined. Results showed that EST in week 2 did not interact with EST in week 3 for any variable. An EST of 38.9 degrees C in week 2 resulted in a 1 mm longer chick length (P < 0.001) and 0.4 mmol/L lower blood glucose level (P = 0.04) at hatch than an EST of 37.8 degrees C. Grow-out performance was not affected by EST in week 2 of incubation. An EST of 36.7 degrees C in week 3 resulted in a 1 mm shorter chick length (P = 0.02), 1.0 mmol/L higher blood glucose level (P < 0.001), and higher relative heart (P = 0.01) and stomach weights (P = 0.03) at hatch than an EST of 37.8 degrees C. Additionally, an EST of 36.7 degrees C in week 3 resulted in lower BW, ADG, and ADFI on slaughter age (all P < 0.03) than an EST of 37.8 degrees C. In conclusion, no interaction between EST in week 2 and 3 of incubation was found for any variable. A higher EST in week 2 had minor effects at hatching and during rearing, whereas a lower EST in week 3 seemed to result in better organ development, but resulted in lower grow-out performance.